Make it run DIESEL for DUMMIES
 

OK here goes. In got the car home and I'm checking things out ('82 240D). The PO even dumber than I am by the looks of the vac system.
Vacuum system corrected and in tact.
New fuel hoses and filters before the IP
All injectors and lines were found loose at the injectors and the pump.

So I pulled each injector out for a look. Nothing realy obviously damaged;. I hooked up a battery and gave it a crank or two. It sounds normal for all I know. I have no compression tester at this time but she sound like each cylinder is there.. The thing I did notice is very little fuel coming from th IP. I kind of expected gushing amounts from each line, but only got spit.

Does it sound as if the IP died to any of you?
Second question, where can a backyard guy like me find a high pressure compression tester reasonably?

FineOlBenz,

At highway speed the engine spins at about 3,000 rpm or so, which means 1500 injections per cylinder, per minute, or 6,000 total per minute, or 360,000 per hour. In an hour at highway speeds you use roughly a gallon of fuel. So each spritz is about 1/360,000 gallon. At idle it is even less. So don't expect a gusher from the injectors.

If you have loose connections, the fuel lines will allow air to enter, especially when the engine is shut down. As the fuel leaks out, air leaks in. This can get into the pump and cause the pump to get air bound. Basically the fuel is not a compressible fluid and air is. Since the pump was designed for fuel, it does not work right on air. So, tighten the fuel lines carefully.

Good luck, Jim

Sooooo
I'm looking at a compression problem.

I won't ask "How do I adjust the compression?" I don't want the computer system to split an electron gut laughing.

It seems odd but there are several diesel engine failures in extreem cold weather. This car failed to start one cold January morning. I've been checking the posts and there have been several others also. I wonder if there is an oiling problem in cold weather. I think there are some oil knozzels directed at the wrist pin and cylinder walls, if these fail in cold weather due to oil viscosity, that would explain a lot. On several occassions the compression dropped to 50 or 60 psi on all cylinders all at once????????????????????????????????????

Then again I've noticed several at 220 to 260K miles dead due to lack of compression.

Jim Smith,

I think at highway speed you will use about 2 gallons per hour (I don't know of any MB Diesel that gett 60 MPG), so you calculations are off by 50%.

Also, the IP does not get air bound. The over flow is at the top of the IP and any air goes out there and back to the fuel tank as long as fuel is being pumped to the IP. Any air in the lines goes out the bleeder hole in the in the top of the secondary fuel filter. If the hole in the fuel line is so large that air is sucked in by the fuel pump instead of fuel, then fuel starvation to the fuel pump is the problem.

P E H

PEH,

That is right, I was off by 50% or more. I used numbers I could add and subtract, and multiply and divide late last night. The 3,000 rpm was probably wrong too but it was a nice number. Considering he probably did not see the injector squirts at anything like 3,000 rpm (more like an idle setting if he was cranking with the starter motor) the point was it is not a gusher - so don't be alarmed by the relatively wimpy spritz and suspect the injection pump is sick.

As for the air getting into the fuel lines, it really does not matter where in the line between the injection pump guts and the injector nozzle you get air. The air is compressible and the system is designed to have a non-compressible fluid so that the pressure builds and pops the injector in a predictable relationship to the rate of rotation of the shaft in the fuel injection pump. The injector is essentially a simple relief valve and once the set pressure is reached it opens, and stays open until the pressure drops. If there is air anywhere in the system, that tiny stroke of the pump will not be enough to compress an air bubble of any volume, and push the intended quantity of Diesel fuel through the injector. The net effect is the engine won't start readily or at all.

The point was that FineOlBenz reported the lines were loose and leaking and that would contribute to a hard starting condition. Given a loose connection, the fuel in the line will leak out when you shut the machine down. Air will leak in, and the pump to the injector connection is no longer "solid" resulting in a need to do crank for a long time, or use the hand pump, to re-establish a solid line of Diesel fuel between the injection pump and the injector nozzles. Makes for hard starting.

So, if I were FineOlBenz, I would fix the leaks and try to start the car again. The leaking lines surely did not improve the starting performance.

Jim

Thanks for the info on little squirts from the IP. The glow system tests out fine so all I'm lacking is compression (a new motor, win the Lotto and so on). I'm not out much on this car if any as I traded a guy steak dinner for two for the car. So this project is just to keep my sanity.

I have now removed injectors and lines in preperation for the compression test. I also put some auto trans fluid down each hole to free up any ring problems. I'll let this set for the time being then flush each hole out and re oil. Heck I may even get up the energy to run the valves too.:rolleyes:

take the glow plugs out, reducing compression and allowing the starter to spin the engine over fast. crank until you get a good cloud of diesel out of each gow pug, or if you don't, you know the fue delivery system is bad.

I have had a situation where the IP had air in it, and despite operating the primer pump more than 100 times, and cranking for extended periods, could not get it to fire. I loosened the banjo bolt at the IP "fuel in" line and operated the priming pump until air stopped coming out (about 5 - 10 times IIRC). I then tightened the banjo bolt and the engine started normally.
I called this "air bound", as fuel was not being delivered to the injectors because of the air in the IP. It may have a more correct name, but this was caused by air getting into the IP, nothing else.
I know several 300D drivers who also state that when air gets into the IP, you then need to bleed it manually.

Phil here at fastlane has a gauge for....
 

Hello... Call Phil here at Fastlane. They are selling a diesel gauge for $67.50 including one adapter. I chose the injector adapter.

Tony,

What you have is a bad primer pump (PP). If the PP is working correctly, it wll push the air out of the IP but you need enough pressure to overcome the IP overflow valve.

I have had completely empty IP and pumping the PP is all it took to prime the IP. By releaseing the banjo fitting, you eliminated the need for the pressure to force open the IP overflow valve because your PP is defective even though it will pump fuel if there is no restriction.

P E H

Well, in some cases, 3,000 rpm is a highway speed. On a turbocharged 78-84 OM617, that equates to about 70mph. I guess you're saying that 3,000 was not a nice number for highway speeds. Or else, I completly misunderstood your post and typed all of this just to feel important.:p

-Joe

I thought 3000 RPM for a highway speed was about right.

P E H

PEH,
On my wagon with an turbo OM617 3,000 rpm is about 70mph. My guess is you need to wind a 240D a bit tighter to get to and maintain that speed.

H-townbenzoboy,

I was not using numbers to be specific, so 3,000 rpm along with a few other numbers for the exercise were used to make the math simple. The point was to show the amount of Diesel fuel squirted out the injector nozzle each time it squirts is very small. In my haste at 3:25 a.m., I made an error in my simplifying effort that equated to the car getting 60 mpg instead of 30 mpg. The point should still have been made - there was probably not anything wrong with the injection pump, once it was primed, since 1/180,000 of a gallon is still a little bit. In my statement about the 3,000 rpm I was just noting I picked it to do the math and keep it simple, and 3,000 rpm may or may not be a typical highway engine speed, when you are getting 30 miles per gallon.

Jim

Before test:
 

If you pulled injectors. Hopefully you took a magnet and got the little metal washers that are under the injectors. Called heat shields. If not when you crank it over it will launch them and your'll never find them. Ask me how I know. Charlie

Thanks Charlie, but I found all four after the fact of course. I have looked over the other posts that reccomend replacing the heat shields. The online catolag shows 7.5 and 10 MM orifice, what's up with that?

injector air lock
 

A bit off subject, but here goes.

Driving home at 5:00 pm air temp around 100 degrees. Engine temp started climbing at long stop light. Moderate increase in engine speed and temperature droppen to normal.

Stopped car for a few minutes and it would not restart. I popped lines off, primed pump and waited almost an hour. When I cranked it sounded like it wanted to run so I kept cranking for a long time. It did light up and run fine.

Similar symptoms persisted for a couple of years in my Ford 7.3. (1993, mechanical injection pump, no turbo) finally it wouldn't start when cool. Replaced injector pump for $1,100 and it runs like a new truck.

At least the Mercedes 240D looks accessable. I'm not afraid to R&R the pump if I need to.

Should I have to depress the fuel pedal when starting. It does not start unless I give it some fuel.

1980 240D was bargain priced, and runs like a real sweethart most of the time. I've only had it a few weeks.

up date, 123 STEAK FOR 2
 

I oiled the cylinders, let them soak for a good week. Hooked up a battery and turned her over to kick out any remaining oil. I haven't kicked out for the compression tester just yet. She sounds like there is plenty of wind in each hole. I replaced all the injectors an ran new line, except the end plug on #4. I then pumped the primer pump till fuel was flowing from #4 then capped it off. The starter sounds very week, or maybe week cylinders.

Bottom line the starter is not spinning fast enough to make 123 STEAK FOR 2 fire up.

Signed,
I'm still PISSED at the RICER that smacked my other MBZ:mad:

123 STEAK FOR2 Over cooked!!!!
 

The idea of Diesel for dummies was a way to find the quick tips to see if you can make a runner. In this case there is no hope. But every day is a learning experience, so I will share this with you.


#1 Check for fuel, take off a return line bleed it good replace it with a new one.

#2 Check glow plugs. Interesting, I checked for continuity and for voltage and had both. But further testing with #1 glow plug removed and jumper cables attached it did not work, and no spark when hooking up to power. All the others gave a decent little spark and heated up. Next time I'll check with a jumper wire to the glow plug directly, with the timer disconnected of course.

#3 Easy compression test. If you cranking the engine pull off the crank case vent. In this case you could see the blow by from each cylinder in order. Yes the rings are shot.


Hense 123 STEAK FOR 2 IS DEAD.

FineOlBenz,

Checking blowby is not a very certain means for measuring the effectiveness of the piston to ring seal, or for quantifying the compression. With a 22:1 compression ratio there is always blowby, and, unless you somehow kept track of it over the life of the engine I don't see how you can make a good call on whether it is good, bad or meaningless.

I do not recall what model you are working on, but if its a 240D with a manual you can push start the vehicle. That way you can be assured you have enough rpm to actually start the engine. A Diesel needs a substantial startig rpm or the heat of compression is lost to the block, and, if it is really slow, the normally acceptable rate of leakage past the piston rings becomes too much. With a slow starter, by the time the piston gets to TDC you have lost most of the pressure because too much time has expired, not because the rate of leakage is too high.

I believe the manual also describes a method for pulling an automatic to get it started. As I recall the procedure involves towing the car to a speed of 20 mph (if it is very cold out and the transmission is cold) to 30 mph (preferred speed if the transmission is warm or near normal operating temps) with the transmission selector in "N" and the starting switch (the item the key goes into) in the run position (the position you normally put in to make the glow plugs light, then, after twisting it to engage the starter motor, the spring load returns it to when you let go of the key). Once you reach the desired speed, you stay at that speed for about two minutes to ensure the transmission fluid reaches the necessary pressure. Then you move the shift lever to "L" or "S" depending the vehicle and the letters on the shift lever gate. The car should start virtually instantly, especially if you give the glow plugs a run just before dropping the transmission into "L" but be careful as you have to cycle the key if you "wasted" the glow cycle at the beginning (only turn the key far enough to unlock the steering, then in the 30 seconds or so before you put the shift lever into "L", put the key in the glow plug cycle start, and run position). If it fails to start after about 5 to 10 second, move the shift lever back to "N" to avoid damaging the transmission. A follow on attempt can be made after running at the previously identified speed with the transmission in "N" if desired. This can also be attempted if you have a long hill to run down, which I thought was pretty ludicrous to include in the instructions in the manual - 2 minutes at 25 mph is a pretty long hill. I suppose you could be that lucky.

I have never attempted this with an automatic but have done it with a manual 240D hundreds of times. No need to let it coast and, for what it is worth, I usually run the glow plugs just before I drop the clutch with the car in 2nd gear and moving a little faster than walking speed. A small hill helps a lot. My daughter learned to do this at school, and routinely parked on a hill, facing down (for a number of reasons) and just "pop" started it as she called it.

I would not "give-up" based on what you have described so far. You apparently had a combination of problems, any which might have prevented starting - air in the lines, bad glow plug(s), and a tired starter. Good luck and keep us posted. Jim

Don't give up
 

My 76 240d had been sitting for almost two year at the state DUI impound lot when I bought it at auction.
Got it home and it spun over easily, no compression. Soaked the cylinders for a week or so in auto trans fluid (chevy of course), added fresh fuel and several batteries and alternated wd-40 and a gas soaked rag held very tightly over the intake so it would not be sucked in, finally coaxed it into starting after two days, always stopping to let the starter cool between tries.
Took it for a test drive and have not slowed down or looked back since.
Of course I had to rebuild the starter shortly afterward, not to mention the alternater, all four calipers, pads,etc., shocks, exhaust, front and rear bushings and misc. other things I try to forget especially if you ask about the new windsheild and seal and all new door and trunk seals and rubbers.

Hind sight now tells me you are better off getting the best example that you can afford of the car you want to drive but this has certainly been a cheap education and great hobby, and I have a car I enjoy drivng more than anything new I have driven in years.
Is it worth it? Without a doubt. Give it a fair try before quitting.