Clogged injectors 1983 240D
 

In taking care of my dad before his passing, things got shoved down the line. After 5 years and an additional 13,000 miles (car has 155,000 miles on it), I have been meaning to change the fuel filters since I changed them 5 years ago, but haven't.


I want to spank myself. In any case, the car was running perfectly and also started instantly almost regardless of the weather. Also, the return lines coming off the tops of the injectors and are obviously leaking.


I replaced the fuel filters, but cannot quite start the car.


Any thoughts on a course of action?

Sounds like you didn't bleed it. It's air bound. Loosen one injector line at a time and crank it until the air bubbles stop. Have a helper watch the injectors until straight fuel is coming out with no bubbles. Also, next time you do it fill the fuel filter with diesel. It doesn't allow as much air to be introduced to the system. If there's a lot of air it may be wise to have a charger nearby.

When I say loosen, just crack the lines. Also, I'd take care of the orings that are leaking on the injectors, you will start sucking air and make it harder to start.

O rings?
 

Thanks for the input on air in the system. I will try that.


As far as I know however, there are no O-rings on a diesel 240D. There are crush washers separating the injector and the head, metal to metal. The fuel lines are also metal to metal.

I suspect it is the individual hoses on the returns of the injectors that may be leaking. More typical of the old rubber hoses on these diesels by far than any other leakage. At least in that area.


I do not know your 240ds year of manufacture. Over time components in the fuel linkage deteriorate. Any owner should periodically check to see if someone presses the pedal to the floor. That the lever on the injection pump goes as far as it should. My 1983 one has a deviish setup where there are two rubber inserts on a fork transmission universal joint. The actually rot and disentigrate with time. Allowing so much slop the lever on the injection pump is badly compromised in advancement.


As far as I know the two rubber sleeves may be the cheapest parts available for these cars at a dealer. There are no aftermarket. Around a dollar if needed for two should not put you in the poor house. Actually for the amount these engines really vibrate. To me is remarkable how long the linkage components stand up.

1983 barry12345
 

Does the leakage on the return lines cause a performance problem? Some of mine are soaked making tiny puddles in the injector sockets.


Your comments on the linkage are also interesting. I have some leaks in my door trunk gas actuators that cause run on at times. When I push the STOP lever on the linkage at the pump, I have to do so forcibly to stop the engine.


This car is in great shape, but when I started driving it regularly a number of plastic parts started to disintegrate. The linkage under the trans shifter (automatic), for example. There also is a plastic part (like a half moon on the long link (the half moon turns the up and down motion of the accelerator pedal to a circular one) coming off the fire wall and going to the injector pump. This half moon is hidden by metal, so you do not know it is there unless you unscrew its retainer off the firewall. When this gave out (after I did the rear brakes and master brake cylinder), it was a real puzzlement. How does doing the brakes keep the car from going more than 25 MPH with 0 acceleration.


You stated, "My 1983 one has a deviish setup where there are two rubber inserts on a fork transmission universal joint." What is and where is "fork transmission universal joint that these rubber inserts are located. I likely have the same issue.


I really appreciate you input.

Located beside the engine. You should see two little black pieces on the forks of that universal. It appears yours is an 83 240d as is one of mine with that joint.


So you should have it. Or you can grab each side of the linkage and hand twist one against the other section. It is an open cage rotating assembly to observe. You do not want to see excess slop.

One problem is those small sleeves rot and just fall off at times so they are no longer even present. In your mind when examining the joint they never existed in that case. So you are not expecting them to be there.


As for a driving indicator. You have no top end beyond around fifty miles per hour. Plus poor acceleration without them.

Depending on your background and what you have on hand. Heat shrink tubing might replace them if needed but it may not stand up.

Personally I really like these 616 engines. They will last a very long time if you become aware of where the issues are with them. Plus address them. Cheap to do as they demand very little really.

Not periodically checking and keeping the fuel system in good general condition. Makes a drop in available power and a noisier engine at speed. Plus a rougher idle sometimes. I still suspect it also damages the engine longer term.

Mercedes marketed their four cylinder diesel engines first. There are some small but important differences in comparison to the later five cylinder turbo engines. The lift pump for example is weaker but can be upgraded to the output pressure specifications of the later version. Simply by changing the lift pump pressure spring.

It is a very reliable type of fuel pump as well. Yet they are so old now. They should be rebuilt with a ten dollar or so kit. Or their output pressure gauge checked. Just to maintain if needed the reliability and pressure function they originally had. Adding the pressure spring from a turbo diesel lift pump at the same time to upgrade them. Is better than not doing it. Reduces the impact or resistance to flow of the secondary filter restriction as it contaminates.

Another area that I have been thinking about. Is stay on top of oil changes. I thought it always was a good ideal because of the rapid soot buildup in the oil.

Now to add to the list. The viscosity improvers in our multi grade oils wear out. So the running viscosity of oil not changed often enough falls. At the time these engines where marketed only single grade oils where available.

I have been looking for anything that may be other than running low fuel pressure. As the reason or a contributing reason to the eventual failure of the first rod bearing for a long time now on the 616 engines. Running multii grade oils too long without changing them may also be a factor.

Single grade oils may get really contaminated if left in too long as well. I suspect that they will still hold a better viscosity than the multi grades do. The multi grade enabler is a plastic additive that does wear out. Apparently the molecules increase in size as the temperature rises.

So my guess is that if two engines were operated for seven thousand miles. One with normal single grade oil and one with a multi grade. If you pulled a sample and checked the oil sample. Plus heated it for a viscosity reading. There may be lower viscosity left in the multi grade in comparison to the single grade oil. Just a suspicion at this point.

Yet we still have people suggesting that we can run multi grade oils for longer intervals if they are synthetic. Without a clue of what viscosity is still present at say 300 degrees F. As they get older. They both employ the same plastic viscosity additive I suspect.


Oil labs do this test I suppose. Reporting the viscosity of the oil is still okay. What is okay and what is it in comparison to the single grade oils? Okay is not a lab test result.


Perhaps the viscosity has dropped back to say 30 at high test temperatures. Thirty while adaquate or okay for most older engines is not enough for these engines.

Again just remember that the additive to make oils multi grade. Does wear out. So the oil will not thicken or declines too much at high operational temperatures as that additive deteriorates. Reducing the increased viscosity protection.

The lower engine blocks are built strong and operate at far less rpm than they could. Yet there are certain failures that Mercedes would have corrected if they were a design flaw existing.

So I am going to add that overdue oil changes may also be a small contributor. Yet still not the primary cause of the number one rod bearing failures on 616 engines.

I as an old guy want to pass one 240d down in our family. So it is important for me to keep it in good shape. I have one good spare engine on hand. These engines are not cheap to rebuild properly and good used ones will become really scarce all too soon.

No sense in not replacing the short leaking lines between the injectors anyways. In general you probably have a small accumulated pile of minor things you can easily do yourself cheaply.


It sounds like an example that is still well worth keeping up. I am an old guy now and remember when my dad told me. I should find a way to keep many of the odd older cars that were passing through my hands when really young. He was right.

As for the brakes jack each wheel off the ground and make sure you can turn the wheels fairly easily. You might have some semi seized calipers to deal with if the car sat around too much. Also if you encounter serious resistance to turning on a rear wheel you might have a seized emergency brake. Or did not put the transmission in neutral rather than park. Most times it will be the caliper though.

Generally whatever is found is not that hard to address with brakes. A test I do often that accomplished the same end. Is to drive the car for a distance of a mile or so and let it coast to a stop. No wheel should be hotter than any other. I use a temperature reader but saliva on a finger is good enough. In your case you may even smell a hot wheel.

Weeping fuel return hose is common. My new "Made In Germany" woven rubber hose started weeping after ~4 yrs. I replaced w/ 1/8" Viton hose on ebay, advertised for M-B and VW diesels. No leaks in ~2 yrs, so apparently authentic Viton (from China). Tygon hose works for some, but probably temporary. Silicon hose swells in a week. I mostly use Diesel HPR fuel, which is bio-derived so probably taxes hoses more than D2.

Still there jake12tech?
 

I did a diesel purge, but I had to pump the pedal to start the car. In minutes, it was running great with very little smoke out the tail pipe. I put the lines back on and it would not start. It was idling ok, but probably about 50-100 RPM less.

I loosened the fuel line at the large fuel filter (the one that comes from the fuel pump to large filter), and the small fuel filter is still about 1/3 air inside after pumping the primer pump like crazy.


I removed the #4 injector line and almost nothing was coming out and I still couldn't get all the air out of the small plastic fuel filter no matter which way I tried to orient it. How much fuel should be coming out of the injector line? I had about zero. Makes me think it could be the IP fuel pump gone bad or could a loss of vacuum cause the problem. My car has 155,000 miles, so when do the IP fuel pumps go bad if ever?


Any further thoughts any one?

Everyone has a air bubble in the plastic filter. As long as you don't see bubbles flowing on down the line that is normal.

Crack one line at the injection pump and crank with a helper. It's probably extremely air bound, so you may not see fuel for awhile. Crank for 10 seconds of time with a 20 second rest so you don't burn the starter. It will start again, have faith. The IPs barely ever go bad unless you pump WVO thru them.

hey rick - what fuel primer pump do you have on there? it could be leaking air if it's the old style that has a white top and you have to unscrew to pump it.

If it ran well on the purge. This might eliminate some issues. To me although I might be wrong. The lift pump was working and the primer pump was not letting air get in.


You might disconnect the fuel line just after the lift pump. Crank the engine and watch for fuel coming out the lift pump. There is also a chance you have really bad fuel in the tank. That is a real long shot though.

Fuel tank strainer clogged maybe??

I know that the IPs hardly ever go bad, but I was referring to the fuel pump on the side of the IP that the primer pump is screwed into. I don't have a clue how the fuel pumps actual function, but I assume they can go bad also. I went to the dealer, and that little unit (fuel pump) the primer pump is sitting on cost a little over $300.


When I visually inspect my IP, I cannot tell which pump I have, and I may have to go to the dealer to see which IP I have. Each IP (there are three different models) has a different Bosch designation fuel pump, and each varies with the engine model (617 or 616). 07.1-145 (entitled, checking fuel pump and overflow valve) of the manual shows the test method for each, and while the part is called a "fuel pump" in the manual, I am not sure it is actually a pump in the traditional sense. I say this because to test "the pump" you are measuring vacuum and delivery pressure in different places. Keep in mind this is all new to me, and even when I read the procedures in this part of the manual, I do not thoroughly understand them.


My primer pump looks original with the white nylon handle on top. ************** sells a primer pump made by Monarch that he calls the best pump he has seen. I will probably buy it to see if that fixes things. It may take a while to get the part and put it in (car is outside and the condo building officially states no working on cars; a bunch of busy bodies here.) Any thoughts after seeing this?

Well, as far as the Condo issue, my only advice would be tow the car to a friends or somewhere you can work on it. As far as fixing it, here is what I would do first. Look at what you know so far......it ran fine on diesel purge, but not when the cars fuel system was hooked up. That tells you the problem is most likely between the tank and the IP (since by running it off of Diesel purge you isolated the cars fuel system).

That said, I would definitely order and replace the old white handled primer pump you have. I would also change both fuel filters (be sure to pre-fill the spin on filter with fresh diesel or Diesel purge). Lastly, I would replace the leaking rubber return lines between the injectors.

When that is all done, I would crack all four injector lines at the injectors and crank (put some rags under the lines to catch the dripping fuel.) Crank for 10-15 seconds at a time then rest the starter for 30 seconds. You should see fuel coming out of the lines you cracked once the air is all bled out. Once the air is bled out, re-attache the lines and the car should start and run. Drive the car until the fuel tank is almost empty, then pull the fuel strainer out of the bottom of the fuel tank, clean and re-install. Fill with fresh fuel and you should be good to go from there.

If someone has not mentioned it already you can test for a clogged fuel tank screen by swapping the position of the Fuel Inlet Hose (the one that goes to the plastic filter) and the fuel return hose (the cigar hose) where the tubings are at the fender well.

You need to have at least 1/2 tank of fuel because doing that draws fuel from a higher positon in the fuel tank (note that it also means you would run out of fuel before the fuel gauge shows empty) so if you are not willing to keep the tank filled above 1/2 tank just swap the hoses for the test.

If power returns to normal then you fuel tank screen is restricting the fuel flow.

Another issue can be a plugged fuel tank vent. To test for that drive without the Fuel Fill Cap on. Doing that allows the tank to vent though the fuel fill. If your performance returns you need to clean the Fuel Tank Vent.
Note that the above can be a little messy if your fuel tank is full or near full.

If the above tests don't locate the problem you likely have an issue with the Lift Pump, Hand Primer and or the Fuel Pressure Relief Valve.
There is cheap rebuild kits for the Fuel Supply/Lift Pump. No one has mentioned it on Mercedes but on other Bosch Fuel Injection Pumps I have seen the Fuel Supply/Lift Pump Poston return Spring break. But, that has happend to no one I know of on this forum.

LOVE THE GERMANS
 

Having driven new Mercedes from 1980 to the late nineties, every car I ever had one or two killer problems. Every three to four years I would lease a new car, and all but the first, was a diesel. Mercedes fixes their problems after they put the cars on the street, thus making changes after the sale that may not apply to all like models.


Everything on my car is like new from the tank to the fuel pump, see photo. The screen in the tank will be the last thing I check. The front of the car is to the left.


I would like this to be a learning experience, and while I might be slow on input, I hope you will tag along.


"A" is a clear plastic tube that I intend to replace. The manual states that you should loosen the hollow nut on the large fuel filter this tube goes to, and start pumping. Close the hollow nut when no more bubbles are visible. This nut only needs to be loosened a little as fuel spurts everywhere with each pump. I believe the part barely visible under nut "A" is the Fuel Pump check valve. I say this because it is threaded on both ends and the "A" nut needs threads. Does this check valve have two little ball bearings and a spring in it? One of the two valves (I am guessing only two valves in the pump) has the bearings and spring. If you don't know or know for sure, please respond. It is shown in Pelican parts as # 000-090-01-10-MBZ.


"B" is my lovely original primer pump that I now see is leaking as we speak, I intend to replace it with one manufactured by Monarch in Germany (same company that does injection nozzles). While it may be the only problem, it may not, and I want to learn from this if possible.


Step two in the manual states that both of the two IP pumps that apply to my 616 have either (1) a bleeder screw on top to loosen (it is to the right of the four fuel lines to injectors) or (2) there should be a similar one way valve (perhaps in its place) that should hiss or bleed the air out of the IP. If there is a bleeder up there, you continue to pump until no more air. Then again, the car may have neither. It is a Mercedes after all, so refer to my first paragraph.


"C" is the feed from the plastic main fuel filter, which assuredly has a brass nipple on top. I am guessing that under the nipple, the nut looking part is another check valve. Can any one confirm this?


Who knows what part "D" is? If I remember, Mercedes only stocks the fuel pump, the primer pump and only one of the valves and gaskets. No springs and no ball bearings, and I don't remember seeing this on the parts diagrams at the dealer.


One other thing that I would mention is that in testing the fuel pump, the manual says you are measuring vacuum. Given that, a weak or faulty vacuum pump on the front of the engine may also be involved. On the other hand, since it is German, they perhaps meant to say suction, although this makes no sense as the measurement is in "bar," .6-.8 bar.


I also saw one posting on the forum mentioning clogged up valves in the pump. Perhaps after 34 years, and sometimes sitting idle for periods, perhaps the fuel pump should also be replaced. My screen in the fuel tank looked like dirt, so why not where check valves are located. Doesn't hurt to take it apart first, however. Anyone in attendance do this? I assume that none of the fuel pump extends into the IP. Anyone?

DIESEL911
 

I now note you mentioned the venting in the fuel tank. When I pulled the tank 4-5 years ago, it was like new, inside and out, and clean as a whistle (after I power washed the inside with a cleaner), so I am OK there.

Did you try and do the bleeding procedure and do the simple thing I said first before throwing parts at it??? :confused::confused:

These cars don't self prime like an om606. If it starts up for a second when the fuel lines are connected up like normal and stalls, it's cause there's air in the system!

It has taken me 2 hours to bleed an om616 before after replacing 3 different fuel components. I had to recharge a battery from cranking it!

It should not take 2 hours to bleed a 616 to start if there are no air leaks or restrictions in the fuel system.

1. fill the secondary fuel filter with fuel

2. pump the primer pump till restriction is felt and you hear the rattling of the ove-flow valve

3. crack one injector line nut (ONLY ONE!) 1/4 turn and put a rag around it

4. glow the glow plugs then crank the engine till it starts, which should take no more than 5 to 15 seconds of cranking.

6. The idle will be rough since the injector with the cracked line nut is not firing, it was used to bleed the air out of the other 3 injector lines and injectors. Wear goggles while tightening the cracked injector line nut and the idle will smooth out as the remaining air in the system bleeds off to the tank.

What you call the fuel pump check valve (aka over-flow valve) is on the side of IP facing the engine block. It has 2 hexes which takes a 17 mm and 14 mm wrench. Do not touch "D" unless you have the lift pump off for a rebuild. If the engine ran well while doing a diesel purge, your problems are either air leaks in the supply line that you disconnected all the way back to the tank or a clogged tank strainer. The metal line often develop pin hole leaks under the clamps.

your right it shouldn't take that long. this car was an exception, it had been sitting with air in the lines for quite sometime. read a thread from a member "goldeneagle" with a 300cd that had a lot of air in the system after removing the IP and some other work done to it. it took him a couple hours to get any fuel at the injectors. it can happen!

I see this repeated all the time regarding W123 tanks and it is simply FALSE! The return line to the tank is not half way up in the tank. It will not run out of fuell if the tank is less than 1/2 full if you swap the return and supply lines. The return line is less than 1 " off the bottom of the tank. I know because I have cut open a W123 tank and studied its construction.

jake12tech, right now, the engine turns, but shows no hope of starting. Further, the primer pump is original and is dripping at the bottom at about 1 drop per second. It would seem this could introduce air into the system. I have ordered the Monarch primer pump. I haven't had this much trouble before.


funola, I would like to clarify terminology with you. The Mercedes manual refers to the whole unit that the hand pump is attached to as a "fuel pump." It includes the hand pump and the iron body it is attached to, and is sold as a unit, even today. Mercedes does not sell the hand pump alone. You have used two terms, "primer pump" and "lift pump." When you refer to primer pump, that is obvious to me, but when you shift to the words "have the lift pump off for a rebuild," are you referring to removing the cast iron body the primer pump is mounted to and rebuilding it?


Other than clearing air from the system, does the "fuel pump," as defined by Mercedes (above) do anything else, other than prime? Is the IP the only thing pulling fuel from the tank, or does the "fuel pump" assist in doing that?


funola, I also checked the back side of the IP, and in my case, there are no hex nuts back there (engine side of the IP), so no over-flow valve in that location. So, I guess, if there is an "over-flow valve," it must be elsewhere. Maybe, I do not have one.

lift pump aka fuel pump aka cast iron body pump and is engine driven. It "lifts" the fuel from the tank and provides pressurized fuel to the IP.

Primer pump aka hand pump. Pump it by hand to prime the fuel system when there is air in it in order to start the engine. How else? If you have a drip at the base of the primer pump. You need to fix it! There should be no wetness from fuel anywhere! It should be totally dry!

I'd suggest replacing the cigar hose with a temporary clear PVC line in place of the cigar hose (highest point of the fuel system, returns fuel to the tank) to look for air. It should have solid fuel in it at all times, running or shut down overnight. Should not have any bubbles in the clear line.

The overflow valve is a special Banjo bolt where the clear line on the left side of this pic connects to on the IP.

http://i31.photobucket.com/albums/c3...530_195531.jpg

I was balled out today FUNOLA
 

The acting President of the condo board told me that some people complained about me revving my engine and working on the car (diesel purge at that time). I can hardly wait to get out of this place, buy another home and have my own garage.


My car came from Florida 5 years ago, and the engine compartment was as clean as your or better. Now, after 5 years in the Chicago area, that nasty salt is corroding my hard lines. Oh, well. I assume you are in a salt free state.


Thank you for your input. I obviously have to replace the primer pump, and if that doesn't work, I guess I have to look at the fuel pump. Everything from the tank to the fuel pump and large fuel filter is fine.


When I was doing the diesel purge, I drove the car, and the brakes seemed a little hard to push. It maybe that I had that feeling since the car has sat there for the last few months, and have been driving our Nissan Versa which is easy braking. It makes me ask the question; is the fuel pump fully mechanical or does vacuum come into play in any way?

While I get my work done
 

I like to share something that has worked quite well.


When I bought the car about five years ago, one of its many issues was that the rubber breather hose coming off the valve cover was melting away from the heat.


I replaced the breather tube, and I also ordered a spark plug protector from Amazon to enshroud the breather tube and keep the heat away.


After five years, it has done its job nicely, and looks pretty much like the day I put it on the car. if you like the idea, please let me know.

Have you gotten it running yet? Have you stopped the return lines from leaking? I've found that NAPA has rolls of 1/8" fuel line that is diesel compatible for ~ $1.20/ft. Buy 3' or 6 and store some in the trunk with fuel filters, tools to change them and a set of used but still serviceable belts.

No, J Man, I have to do this in the wee morning WEEK END hours before the condo police wake up.

I will check under the clamps that hold the two fuel lines later. It is hard for me to work under the car at my current residence, but I doubt my fuel lines are the problem barring any rock damage that may have happened. I am going to replace the clear hose connections (at the fuel pump, the IP and the large filter) and hand pump first to see if I can get it going. Funola outlined what seem to be a good procedure for bleeding the air out of the system, and I will do that once the hand pump is replaced plus the return lines going from injector to injector to fuel filter.

Thx

I was referring to the return fuel lines that run between the injectors. NAPA line at $1.20, not $20.

BUBBLES
 

I am getting a solid stream of bubbles coming out of the overflow valve on the back of the IP and thru the clear line back to the large fuel filter. I have checked all the fittings, replaced the primer pump again and cannot find any leaks. I ran the engine for fifteen minutes, and still bubbles.


The clear fuel line on the lift pump (left side of the primer pump) is a compression fitting, no added "O" rings or anything else to seal it, CORRECT?


Haven't been able to see how that much air can continue to run through the overflow valve.


Any additional thoughts, yes or no?

It's a flare fitting, not compression. No o-rings on flare fittings.

Have you tried running out out a gallon tank of fuel in the engine compartment as if you were doing a diesel purge? If no bubbles by doing that, you have rusty pin hole leaks in the supply line under the car or a leaky short rubber supply line at the tank. If you still have bubbles with the gallon tank, you still have a leak some where letting air in.

Do you have a clear line in place of the cigar hose (return to tank). That is the best place (the only place IMO) to look for presence/ absence of bubbles.

I can see pin hole leaks, but
 

if air entered the hard lines from the rear, why don't I see bubble coming into the small primary filter?


Does it matter which end of the primary filter is higher than the other?


I have replaced all the rubber fuel hoses only 5 years ago.


I also am not seeing a reason to temporarily replacing the cigar hose with a clear line. I am getting bubbles from the overflow valve thru that clear line to the top of the secondary filter which feeds right into the cigar. If there are bubbles in the clear line, I would assume that they would be in the cigar line also.

Some people just don't want to listen. The clear hose in place of the cigar hose IS the single most useful diagnostic aid for air in fuel in a Mercedes diesel, that I have a permanent one on my 85 (look at my pic above, there's a 1/2" long clear line at the filter head before the cigar hose). That banjo bolt where the 3 lines meet has a small orifice which goes into the fuel filter. Any air that gets into the fuel system ends up in that short clear line. The clear line is what you should have installed before doing anything else. Of course you can replace parts by trial and error, one by one, till the problem is fixed.

I do listen
 

Funola, I sincerely appreciate the help you have given, but please remember that this is a blog, and not everyone is a Mercedes mechanic. One needs to sort out the good and maybe not so good or maybe the terrible.


Did you also replace the soft braided line coming off cylinder #1 with the clear line? See photo where X is planted.

I am not a mechanic but that clear line is THE most important tool to diagnose air in fuel issues from my 25 years of driving diesels. Any diesel mechanic that's any good will use that tool, unless he charges by the hour plus parts and replace them one by one by trial and error.

Yes I did replace the braided lines with polyurethane lines. They were clear when new but turned brown after a year.

NOT SO CLEAR TUBING ANY MORE
 

The polyurethane tubing likely is suffering from the heat. May I suggest clear silicone? Silicone tubing has a high temp range of 400-550f depending on the type. Low end is -30 to -40f.


Go to Aliexpress com and search "clear silicone tubing"


Starts at about 60 cents a foot to a little over a dollar, many with free shipping to your home, 1-5 meter minimums.


I would look at many of the food grade as many of these can be exceptionally smooth on the inside, up to 40 time smoother than stainless, which gives me an idea. It may be a replacement for the long stainless lines, although it would need many attachments (hose is very flexible) or a channel to support it. It would defy the corrosive salts here in the Midwest.


I will get some temporary tubing to try to get the car going.

Before getting more out of control with diagnosing your air in fuel issues, stay with what works. I have no issues with those Polyurethane return lines other than them turning brown, those lines has been on the car for 3 years now with no leaks. The other clear lines is Nylon and they've been also on the car for 3 years and they stay water clear. Is polyurethane the best? No, it is listed as fair in resistance to diesel fuel. Polyurethane eventually harden at the barbs and start to crack and leak, but my experience is that won't happen for 4 to 5 years. Those return lines should be replaced every few years as preventive maintenance anyway. I'll replace them soon. Viton and Nylon is best, Silicone is POOR! Nylon is not possible for the short return lines because it is too stiff and needs clamps, Viton tubing is usually too thin for my taste. Polyurethane is tough but only rated as fair. The factory braided lines is fine if you get quality ones. They're probably Nitrile.

My engine is so strong that it wanted to start with all four hard fuel lines loosened. BUT, I put the clear line in just as you have it.


Once I tightened all four fuel lines at the injectors, the car started right away. Even though I ran it for about 15 minutes, I was still getting bubbles coming thru the line from the overflow valve into the secondary fuel filter, and then thru the clear tubing you had me install between the secondary fuel filter and the cigar hose. All four injector lines had fuel coming out of them.


Logic tells me that air seems to be getting into the system, as opposed to just having a need to clear it out. If that is happening, it seems that there are three main culprits since they are coming out of the IP. The primer pump which I put another one in. The feed from the primary filter, which is as tight as a drum and third, the clear line on the left side of the lift pump and going to the secondary filter. Attached is a photo of the connection of this line at the lift pump. Isn't this a compression fitting, as it goes face to face, as opposed to a flare fitting having a flared end squeezed around a receiver?


Since the primer pump and fuel feed seem fine, it seems that I need to check out this connection. I don't know what else to do.

If you do not believe me that's a flare fitting, you'll have to research for yourself the difference between a flare vs a compression fitting.

Do you smell diesel in the engine compartment? Is there wetness anywhere from fuel? I think I've already asked these questions.

Take some toilet paper and go around the fittings and wipe around them. If you find any wetness, fix it till it's dry.

Yes, a flare fitting
 

as I took a closer look at the brass fitting. It is smooth on the inside edges, and should not be leaking


I have checked for leaks and see none.


The car started right up, and for a little bit, there where bubbles running from overflow to large fuel filter and thru the short clear tube you suggested installing. I had primed and opened all four injector lines and got fuel from each.


For the first time, my primary fuel filter had zero air inside, and after 5 minutes of no bubbles, the bubbles started again (same path), and the car ran roughly another ten minutes. This is getting frustrating.


After seeing the bubbles running the same path as I thought they would (back thru the cigar hose), I am not understanding how adding the clear tube helps to figure things out. I should naturally suspect the lines from the tank, BUT, with the primary fuel filter being totally filled with fuel, I am not seeing any bubbles coming thru the filter, not one.


Don't get it

That clear line is the only place to see all air that is in the system since it is the return to tank, i.e. if there is air in the secondary filter (the big one), you will see it in that short clear line and may not see it in the other lines because of the orifice on the banjo bolt mentioned earlier. WHEN YOU SEE NO MORE BUBBLES IN THE SHORT CLEAR LINE, THEN THERE IS NO MORE AIR IN THE SYSTEM!

Speaking of the secondary filter I see this in your 1st post:

"I want to spank myself. In any case, the car was running perfectly and also started instantly almost regardless of the weather. Also, the return lines coming off the tops of the injectors and are obviously leaking.


I replaced the fuel filters, but cannot quite start the car."

Assuming you've replaced the leaking return lines, maybe the act of replacing the secondary filter started your problems?

rickmay,

Your problem started when you replaced the fuel filters, that's where I would look to find your remedy.

With an 83 240D, I assume you have a "01" fuel filter head (6150920108).
Did you replace the crush washer and o-ring on the fuel filter bolt when you changed the secondary filter?

Does your primary fuel filter have bronze inserts?
This feature can prevent the filter nipples from deforming when you tighten the fuel hose clamps.

Did you replace the short fuel hoses attached to the primary fuel filter?
The hoses get dry, conform to the old primary fuel filter, and then don't seal properly on the new filter when they are re-used.

Are you using original hose clamps on your primary fuel filter hoses?
The original hose clamp bands are not very wide and the adjustment screw can bottom out.
I have wider fuel hose clamps on my setup that you can see in the second photo of the first post on my Fuel filter upgrade thread.

Many people (myself included) use 5/16 fuel hose which is slghtly oversize and can leak unless you really tighten the hose clamps so that the hose can't rotate on the fittings.
IIRC the correct metric hose size is 7mm, but 5/16 hose will work if you tighten it well.
You should not be able to rotate the hose on the fitting, even if you use a fuel line clamp (or vise grip with a rag) to grasp and twist the fuel hose.

Hope this helps.:)

Hoses and filters
 

Alec300SD, it sounds like you are describing the earlier filter. Mine has no number on it and epc.net does not show a part number for my filter head.


I have a screw on filter with an "O" ring, picture attached.


I will check or replace the secondary filter now and fill it either with fuel or with diesel purge. I will also replace the fuel lines with 7mm (search: IAP Performance AC133107 Fuel Hose (7.0 x 2.5mm; 1 Meter; Made in Germany for VW Beetle)


Funola, you said; Assuming you've replaced the leaking return lines, maybe the act of replacing the secondary filter started your problems?


I don't know since I replaced return lines, clear lines and filters.

If the car was running perfectly before you did any kind of parts replacement, then whatever you did is suspect.

IIRC, if the center bolt of the filter housing takes a 24 mm wrench, it is the later style and it needs 2 rubber o-rings and no copper washer. If it takes a 22 mm wrench, it is the earlier style and it needs a copper washer only, no rubber o-rings. That copper washer is not a common size thus hard to find unless from the dealer if still available. Someone found a replacement home plumbing fiber washer that supposedly works. You'll have to search for it.

If you had installed the short clear line before replacing any of the fuel system parts, and saw that there was no bubbles in the clear line, then install the first part, start the engine and look at the clear line before replacing the next part, you'd know if you had installed the parts correctly.

Next time you work on your fuel system, remember to install the clear line first.

REPLY TO FUNOLA
 

If you remember, you suggested adding the clear line between the filter and cigar hose. As I said in my prior post, I am not understanding how you are using this short clear line to diagnose anything. My hunch, many posts ago, was if bubbles were coming to the secondary filter via the clear line attached to the overflow valve, they would logically exit the cigar hose. Now, that I put the clear hose in the chain, it confirms my thinking about where the bubbles go; it is back to the fuel tank.


I also have not opened the 24mm nut on top of the secondary fuel filter, and have no reason to assume it is the problem. What's is it for any way? I ask, as I said in my prior post, I have a screw on filter.


In the beginning the car stopped running. I have somewhat of a vacuum leak from the door openers, and at times, I would drive somewhere, exit the car with key, and let it run. It would sooner or later stop. I changed the two fuel filters, and I could not get it started. After getting it towed home, I did a diesel purge, as I said early on in this thread, and the engine was running fine, EXCEPT AS I NOTED, the idle was a little rough, something new. LOL

The big bolt in the top of the fuel filter housing is what you loosen to remove the fuel filter. If you just spun the fuel filter on, it's probably loose! The filter doesn't "spin on" (or "spin off" for that matter), you hold it in place and snug down the bolt on top! The idea being to prevent making a mess and sloshing fuel everywhere.