1987 300TDT cranks but doesn't start and other fuel system questions
 

I changed the large canister fuel filter on my 1987 300TDT, and now the engine will not start up. The engine cranks over, and it seems as though it wants to catch but it doesn't run. I have tried cranking the engine for over ten 20 second periods (with 5 minutes breaks in between), but it never catches. I have tried cranking the engine to the point that the battery is now drained. I'm charging the battery up so I can try starting the engine again, but I am worried about draining the battery again without being able to start the engine.

In order to minimize the cranking time and lessen the air in the fuel system, I poured the fuel from the old filter into the new filter. According to the Mercedes shop manual the OM603 engine is self priming. So how long is it supposed to take for the fuel system to prime itself? Is there anything else I can do to get it to start up? :confused:

I also have a couple other fuel system questions:

There is a diesel fuel heater/thermostat after the prefilter on the OM603. On my 300TDT, the previous owner bypassed the fuel heater/thermostat. I'm not sure what is wrong with them. The price of the fuel thermostat seems to be over $130. I'm not sure what typically goes wrong with the diesel fuel heater/thermostat. Is there a common failure mode for either the fuel heater or thermostat? Is there a way to repair the thermostat? I also live in California, so I was wondering how important the fuel heater is in warmer climate?

Finally, before I changed the fuel filter, the engine seemed to smoke on a cold starts and run rough for a minute or two after which it seemed to smooth out. What would cause this? My first instinct is that the glow plugs are not all working, but a mechanic that worked on my 300TDT for the previous owner supposedly replaced the glow plugs. Any ideas? It happens regardless of the ambient temperature.

Thanks in advance,

-Steve

Pausing 5 minutes between 20 second tires is a little long. Whatever progress you make will be negated by time. Try 10 second tries 10 seconds apart. The manual says to crank continuously for a minute or something like that. I can't see how that's not asking for trouble.

You might help your injection pump along. Crack the the lines into the injectors while you crank. When fuel leaks from a fitting, tighten it and crank again. It'll probably catch before you get fuel out of all 6 fittings but I find that if I don't help the priming along for each cylinder it can take a while of rough idling before it smoothens.

Oddly enough my 2 SDs never needed priming after replacing the fuel filters.

I was tempted to bypass the fuel thermostat when it sprung a leak. In my case either the plastic end piece cum fitting or the o-ring cracked when I replaced all the fuel lines. Turns out there's an inexpensive repair kit available at the dealer that includes both pieces. I needed it ASAP so I didn't check FastLane.

My SDL is that way when it's cold. I find that going through a couple of glow cycles, leaving the key in the on position for 10 seconds after the glow light goes off, works wonders. The glow plugs are pretty new and resistance checks out. Could be any of a number of things causing the cold start roughness. Lazy glow plug, lazy delivery valve, low compression in one cylinder, etc. Check the resistance through the glow plugs and consider new delivery valve seals if they're original. Otherwise, live with it.

Sixto
95 S420
87 300SDL

There was quite a discussion about someone having difficulty getting one of these engines re-primed awhile ago and it should be in the archives. Also by dumping the old filter oil into the new filter I wonder about some junk in the filter being transfered like water in the bottom of the old filter etc. It might have dosed your pump. Should really only put clean fresh fuel oil into the new filter. Hopefully you got it running before reading this note or the archives help.

Or Diesel Purge.

Sixto
95 S420
87 300SDL

Just a note of interest. I got the idea of pouring the fuel from the old filter into the new filter from the "Mercedes-Benz E-Class Owner's Bible". The "Mercedes-Benz E-Class Owner's Bible" is written by Stu Ritter who is technical editor for the Star Magazine, as well as 25 year MBZ repair shop owner/technician. At the time I thought the idea was good, but I seem to be getting a different opinion from everyone else.

Thanks for the replies so far though.

-Steve

What model?
 

What exactly is a 300TDT? is this a Turbo Diesel Wagon? Or is it just an '87 300D? I have seen the TD designation, and the DT designation, but never used in conjunction.

SteveM.

- PS - let 'er crank. Get a good jump start and crank for 30-45 seconds.

Jetmugg,

A 300TDT is a turbdiesel wagon. The 300DT is the turbodiesel sedan. The "T" tacked onto the end stands for Turbo. Mercedes-Benz uses this nomenclature when referring to the different models.

-Steve

Thanks.
 

I did a little searching and saw others using the "TDT" designation for turbo wagons as well. I guess I just hadn't seen this before. Do the letters 300TDT appear on the back of the car somewhere?

My 190D 2.5 Turbo reads "190D" on the left of the trunk lid, and "2.5 Turbo" on the right.

The E-class wagon with a turbo 603 engine should be a very good running car. Sounds like a nice one.

SteveM.

Well, I finally was able to get the engine to start after cranking it 3 times for 45 seconds with a minute or two rest intervals. I also had to to floor the accelerator to get the IP to purge the air out of the injectors and to get the engine to run initially because it wanted to die. The engine coughed and sputtered and ran rough for a minute or so until the air was out of the lines.

Once the engine was running I discovered a new noise, the tapping sound of a valve. I'm not sure, but I think one of my cam followers may be going out. Does anyone know how long the cam followers last on the OM603? The engine has 185000 miles.

Jetmugg,

The 300TDT E-class wagon with the OM603 is a nice combo. It will be even better once I finish fixing all of the broken items on it. :) (The previous owner was a cheapskate.) The 1987 300TDT was the last diesel powered wagon MBNA imported to the US. It would have been nice if MBNA imported some W210 chassis wagons with the OM606 turbo motor, but they chose not to for some reason. A W211 chassis wagon with the CDI motor would have been really nice, but unaffordable by me.

Thanks for all of the replies,

-Steve

The lash adjusters can last forever. They seem to like Mobil 1. Mobil 1 has the right detergents or whatever ingredients to clean the lash adjusters and the passages that feed them to get rid of tapping. It takes a few thousand miles of Mobil 1 to get results. I don't know if the lash adjusters become addicted on it from that point.

There's a procedure to test lash adjusters. I'm not sure if it involves pulling the cam which is a PITA in the 603. If you're going through all that trouble you might as well replace all the lash adjusters ($300?). Check the new ones before installing because the defect rate is surprisingly high regardless of source.

Sixto
95 S420
87 300SDL

"Is there a common failure mode for either the fuel heater or thermostat? Is there a way to repair the thermostat? I also live in California, so I was wondering how important the fuel heater is in warmer climate?"

The failure in the fuel heater is usually corrosion from the hot coolant that runs thru it, allowing water to get into the fuel (nasty!) and is the same reason its recommended to change antifreeze every year or 18 months religiously in these engines.

Every time I change filters in my 87 300D it takes a lot of 30 second starter motor turns before it starts to fire off and then runs rough. While it's running rough, I hear tapping and it takes a while for them to go away. The taps in my case is "nailing" injectors after having disturbed the fuel system. Injectors seem to be very sensitive from my experience and may be what you are hearing!

Thanks for all of the good posts so far.

I have had the 1987 300TDT for about 1 year now, but I figure that I have only put maybe a 1000 miles on it since I bought it. I have been running Mobil 1 Truck and SUV (aka Delvac 1) for only about 650 miles or so. When I first got the 300TDT I noticed it made a metallic knocking sound that was not the usual diesel knock. More recently before I changed the fuel filter I noticed a tapping noise at idle that has been fairly consistent. After getting the 300TDT started today, I listened for the tapping noise and it seemed to be coming from under the valve cover. In order to rule out the injectors I think I will drive the vehicle for a few hundred more miles and see if things quiet down. I did a search on lifter replacement, and I think the procedure according to GSXR is to warm the engine up, pull the valve cover and then press on on the lifters one by one. If they squish down, then they are bad. I would rather not replace the lifters, so I will give it some time and see what happens.

As for the fuel heater/thermostat, I guess I will need to investigate the parts further. Since the whole fuel heater assembly is bypassed, I have no idea what is bad and what works. I was hoping any heat exchanger/thermostat failures would be something obvious since I don't feel like hooking it back up and taking a chance.

-Steve

I just replaced all my lifters. You'll likely have to test each lifter when the lobe on the cam is in the relaxed position for each lifter. They will all squish down at some point, but a bad one will have little resistance to squishing down. It's not difficult to remove the cam properly, and a magnet will extract lifters with ease! It took me a couple of hours from start to finish, I had fun doing it!

When the belt tensioner shock Heim ends wear out it can cause alarming sounds like rod knock. With the engine idling, press on the shock with a stick and see if that clears the noise.

Sixto
95 S420
87 300SDL

Suddenly fuel primers (the newer ones...not the air leaking old ones) seem like nice things to have. :)

Here i am again. Kind of sorry if I sounded offensive about putting the contents of your old fuel filter into your new one and realised I had heard the folklore you mentioned before as well from some source or other. Just never made any common sense to me but I could be wrong in what I think. Just seen some pretty bad things come out of fuel filters like water and dirt before and for all I really know mercedes fuel filters may be different. But really cannot see how. As for the engine noise if it is a lifter mechanics used to add a little automatic transmission fluid to the base oil to devarnish them (sticky lifter) I suppose. I would wait and see if anyone else chimes in before considering it. Of course it will not deal with real wear in a lifter. Or perhaps check around. May save you a job or perhaps it is discouraged today. Mobil I may have the same action as I believe someone mentioned. Anyways glad you got the pump bled down. :)

barry123400,

Don't worry about it. I kind of wondered about dirt coming out of the old filter myself when I transferred the contents over. I may try filling the filter with Diesel Purge like sixto suggested next time so the the cranking time is decreased.

sixto,

I haven't noticed the metallic knocking sound recently, but I just replaced the belt tensioner lever, pulley, shock, and spring about a month ago.

The only noticable engine sound at this point is the ticking sound which seems to come from the valve cover. I figured the metallic knocking might have been a precursor to the ticking noise from the valves, but perhaps not.

Thank for all of the helpful ideas.

-Steve

All this proves U shouldn't replace the fuel filters until necessary.

P E H

Next time you change the oil, change the two little O-rings on the center shaft. Yes, those "hard plastic" rings are actually rubber O-rings!

The noisy lifter is probably just flat from all that cranking with no oil pressure.

I only change fuel filters with a hot engine, it cranks faster. Fill the new filter with diesel purge or clean fuel on the outside holes and you will be fine. Better to slop some fuel around than to crank forever....

With a hot engine and the fuel filter full, it should actually start right up instantly, and purge the air out before the engine quits.

Peter

It looks like it may be time for new lifters. :( At least I hope that is the main cause of noise. I started my 300TDT up again yesterday, and let it idle for a few minutes to see if the tapping noise would go away. No such luck. I then decided to drive the 300TDT to the gym, and after about going half a mile the noise from the engine bothered me enough that I turned around and I went home.

I listened to the noise intently at idle, and it seems to be coming from the valve cover area towards the front of engine around the number 2 cyclinder. Originally the noise was a faint ticking/tapping sound, but now it is a definite loud tapping noise. The noise almost seems to get slightly louder when I open the oil filler cap, but it hard to tell.

I am almost worried that it may be some other valve problem since the noise seems louder than what I remember to be a bad lifter noise, but maybe the lifter is totally flat.

Is there anything else I should look for when I pull the valve cover off?

Maybe all the cranking of the engine finished off the bad lifter?

Has anyone heard of FEBI brand camfollowers (lifters)? Are they decent as compared to the OE ones?

Thanks,

-Steve

Another source of noise is leaky delivery valve seals. My SDL lost a lot of what I thought was valve tapping when I replaced the delivery valve seals.

Sixto
95 S420
87 300SDL

I replaced the delivery valve seals on a 1987 300TD this weekend. The idle is noticeably smoother now. Keep in mind that after changing these seals, it takes a heck of a lot of cranking to get the engine started.

speedy, do you mean that it took a lot of cranking the first time after the IP went back together or every start since?

Sixto
95 S420
87 300SDL

Sixto,

The IP would lose prime after the car has been run and shut off. The result would be excessive cranking needed to get the engine started after sitting overnight for example. After the delivery valve O-rings and washers were replaced, it took a lot of cranking to get it going, but so far the IP holds prime and is completely dry around the delivery valves and hold-down plates.

Crack an injector line open
 

If you feel that you have a noise from an injector open the lines as the engine is running. Do this one at a time. When the noise goes away it is related to the injector line you just opened.

Thanks for all of the replies.

I think the noise is from the valves, since it has a somewhat metallic sound. It is also fairly loud. In addition, the engine starts right up when I crank it over now. The engine runs rough and smokes right after startup, but it smooths out fairly quickly. I also seem to recall the tapping noise was fainter before I changed out the fuel filter and then after cranking it many times, and flooring the accelerator (which revved the engine) I was finally able to get the engine to run.

If the delivery valve seals are leaking, would I be correct in assuming that the top of injection pump would have diesel fuel seepage from around the injector lines? I don't believe the top of the IP has diesel fuel on it, but I will double check. I'll probably change the delivery seals when I seal the oil leaks in IP.

Does anyone know if the "FEBI" brand of lifters (camfollowers) is as good as Mercedes OE?

Thanks,

-Steve

A bad tappet will make a harsh metallic snapping noise, just like a bad tappet or loose valve adjust on any other engine.

Check that the belt tensioner shock isn't bad first, it sounds almost exactly the same (metallic clank or snap) because the metal eye is banging on the metal bolt....

Unless you unscrewed the pressure valve holders for some reason, the seals aren't leaking, they don't fail in service. If one was leaking, it would cause both injector knock (sounds like someone driving a large nail into a solid oak slab) and seriously rough running below 1500 rpm. Shaking and some white smoke stone cold right after startup is typical of these engines. You can eliminate some of it by running the glow plugs 10-15 sec after the light goes on before cranking, or by replacing all the glow plugs ($18 or so each).

Peter

If cracking each injector line while idling doesn't isolate the tapping then it's not a problem with the fuel system.

Sixto
95 S420
87 300SDL

The belt tensioner shock I just replaced a month ago, so that pretty much leaves the lifters.

It looks like I will be replacing the lifters next weekend. I'll let everyone know if the problems is solved.

Thanks,

-Steve

noise
 

if you didnt have the noise before you did the things i think i heard yoiu say you did, it sounds to me as if nothing you have done would cause any mechanical damage... so worrying along those lines i think is unproductive.

did you do anything with the injectors? i had lots of horrible sounding noises with my 350 that turned out to be first missing seals at the base of the injectors and then loose injectors.

i have not experienced any noise with the hydraulic tappit adjusters on my diesel but on my 500sec i have one that makes noise with fresh oil if it is 15w40. if i use mobil one it makes no noise. this is a tapping that is annoying but not scarily loud.

I did not touch the fuel injectors or lines. Before I changed the fuel filter the tapping sound was not as loud, but I think revving the engine while I was trying to get the engine to start may have hastened the demise of the bad lifter(s). The noise was always there, just not as loud. The noise seems to be more metallic in nature, and it is the loudest around cylinder 2 at the valve cover.

I typically don't like driving a vehicle when something doesn't sound right.

-Steve

Update:

I decided to let the my 1987 300TDT (w/ OM603.960 engine) sit for a few days, and then I drove it around for a few miles at freeway speeds. The loud tapping noise went away so I guess that noise must have been air in the injectors which occurred after I replaced the large fuel filter? Would air in the injector lines cause a loud tapping?

After the loud tapping noise went away, there was still a faint tapping noise audible at idle even after the engine warmed up. I already had ordered the lifters, so I went ahead and replaced all 12 lifters and the faint tapping noise is still there. Before I replaced the lifters, I didn't find any squishy ones, but since the engine has 185K on it I went ahead and replaced the lifters. I guess I'm all out of ideas now on what could be causing the noise. It's not really loud, but it is noticeable. I am assuming that normally there is just the diesel knocking sound when the engine runs, and no tapping.

Do the injectors make any sort of faint tapping/ticking during normal operation?

Thanks,

-Steve

Injectors themselves shouldn't make any noticeable clicking noises, but the IP can, in one of my 617's it has a tiny click but I never noticed that sound on my 603 engine (even without the hood insulation).
Using a listening device like this might help:
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&rd=1,1&item=4563669349&sspagename=STRK%3AMEWA%3AIT

PS I just ordered a set of lifters for my '87 (not the daily driver, another project car) with 260K miles on them, I'd be gambling if not replacing them while the head is apart.

yeah
 

it may be a normal sound. i think that the vac pump makes a sound or perhaps the ac comp. after having a scare we all tend to listen more intently. perhaps this is what you are doing.

tom w

i know this sounds confusing....but I imagine you are suggesting that the fitting where the line attaches to the injector be loosened allowing air to escape.
I must ask though, how many of you guys do this alone? Do you have a remote starter button and if so, where do you feel is best to connect?



Fuel T-stat? What does it look like? Does anyone remove this?
And what is a Cum Fitting?



I am diagnosing a 'no start' condition with an 87 300TD. Ran fine, parked on the flat, week later, no start. I get a 'pop' maybe from one cylinder trying, but thats it. Was hoping to see priming procedure here. No luck yet. Will try opening lines while helper cranks.

Battery is fully charged.

there is a junction block right in front of the battery, follow the positive cable, it connects to it.
jump the positive cable with the wire next to it, and you will get a crank.
if you have a remote starter switch, connect it there, (like 7.00 at autozoo)

I do it alone. No remote starter. Loosen all the lines, crank for 10 seconds, tighten the fittings that are wet, lather, rinse, repeat. When at least 4 lines are wet and tight, the engine will stay running on its own.

It's an aluminum cylinder sitting on the driver side engine mount arms. Follow the fuel line from the small filter to the plastic end piece of the thermostat that's also the fuel inlet fitting for the fuel thermostat.

Other no start suspects include stuck IP fuel return check valve and clogged oxidation catalyst. To check the fuel return check valve, pinch the line from the big fuel filter back to the tank. If the engine starts, the check valve is stuck open. To check for a clogged cat, remove the plug on the #1 exhaust runner that takes a 17mm socket. If the engine starts, the cat is probably clogged.

Sixto
87 300D