This is on my '91 300D 2.5t which has 389k miles. We had it since 190k miles on the odometer. A few months back the car started to miss and stumble. At that time I thought it was because of some bad fuel from Murphy USA station. Changed fuel filters but no effect. P/S pump made some noises so I figure the pump must have failed at this many miles causing too much load on the belt drive system. Replaced P/S pump and water pump (had noisy bearing as well and at least 200k miles on it) still no changes.

Just had the injectors serviced by a fellow lister on the forum (balanced within 25 psi between each other). Installed them and the car actually ran worse like a couple of cylinder not firing, letting out huge amount of smoke. If I rev up the engine and let off the accelerator then the car would die and could not even stay at idle.

Thinking of a bad head gasket, I started to tear the engine down to get to the head gasket. In the process of removing the exhaust manifold I noticed one stud was missing and another one was replaced with a regular bolt. The upper slide rail pin had grip marks on it. So this indicates to me that the previous owner/mechanic had gotten here before. There is no obvious signs of the OM602 head gasket failure syndromes - the head/block mating area is clean (especially at the #1 cylinder below the chain tensioner), no cold pressurized upper radiator hose, no oil in exhaust manifold.

I checked timing on it this morning, the chain stretch is at 3.5 degrees and injection pump timing is at 8.5 ATDC (compared to specs 14.5+/- 0.5 degrees)! So the valve timing (retarded 3.5 degrees due to chain stretch) and IP timing (advanced by 6 degrees) combined are about 9.5 degrees off the specs if I am understanding this correctly. Don't ask me how we could have driven the car like this for almost 200k miles withnot knowing this. The car ran fine all these years except for boost issues until just recently started with this miss/stumble problem.

So here are my questions and where I need your collective wisdom:
1. Could 9.5 degree off IP timing be the culprit for the miss/stumble?
2. What would be the best option at this point? - Should I go on and remove the head and inspect/replace the head gasket or just correct the IP timing and put everything together to see if it fix the problem? I seriously think PO had already replaced the head gasket from the missing exhaust manifold stud and damaged slide rail pin. Replacing the head gasket is a can of worm to me so I don't want to touch it unless you guys think I absolutely need to.
3. If I reset IP timing, where should I set it at? Should I set it at 14.5 ATDC or retard it by a degree (15.5 ATDC) to match the retarded valve timing?

Additional info - I replaced the delivery valve seals about 100k miles ago. I guess I could redo them again if you think they may be the cause.

Your collective wisdom is much appreciated.


Tan

'87 190Dt
'87 300TDT
'91 300D

Lots of accumulated miles on that engine and injection pump. I make your injection pump timing currently retarded. Either retime the injection pump but get an accurate check of the chain stretch first to see if it is still serviceable.

On the otherhand much of what you are experiencing could just be air leaking into the fuel system. To test for that I would put the return hose from the injection pump in a glass jar. Keep the hose end under the fluid level and watch for air coming out of the injection pump with the return fuel.

Another way would be to put a good clear section of fuel hose in so you could visually watch for air. The front of the engine may also need attention but probably is not the cause of what you are experiencing.

I re-timed IP last night to 14.5 degree ATDC. Checked chain stretch again and it appears to be between 3 to 3.5 degrees range. Due to the scored line on the camshaft being really thin while the mark on the cam towers being thick, exactly stretch seems impossible.

I will check the cylinder compressions later this week when I get time. Has anybody used the cheap compression test kit from Harbor Freight - 12 Piece Diesel Engine Compression Tester . Will it do the job?

I have the cheap kit, and it's junk, but will give adequate indication of compression. best is to go the coolant pressure route, and see if coolant seeps into any cylinders, then switch to the leak down test to see if there are leaks you can find.

__________________
John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

It has been a year since I last posted on this. Since then I have tried to tackle this problem from all angles but it still does not run. Things I have tried include:
- Checked cylinder compression using Harbor Freight cheap compression testing tool and all cylinders except #4 (can't get to it due to obstructions) were above 360 psi.
- Replaced head gasket. Old one wasn't bad at all. Checked the head and block - all flat and no cracks.
- Checked turbo, spins freely
- Injectors serviced by forum member Greaser (Mark Blevin) and supposedly balanced really well and set a few bars higher than spec
- Checked IP shutoff valve and it works as it should
- Redone delivery valve seals and seal rings (at least once)
- Re-checked/re-timed IP timing at least 3 times using the IP Locking screw.
- Checked vacuum pump. normal (minimal) wear on the pump roller and IP timer curve surface.
- Re-check chain stretch. Was within 1/2 degree which is excellent considering it has 388K miles.
- Replaced IP overflow valve
- Replaced IP feed pump
- Replaced water pump
- Replaced P/S pump
- Replaced all fuel hoses including the ones to fuel preheater.

Still it cranks, starts and tries to run (when I keep the gas pedal depressed) but stumbles and will not stay running and it makes loud knocking sound. I have recorded a short video clip and uploaded on Youtube - 1991 Mercedes 300D 2.5 turbo cranks, no start and knocks - YouTube Maybe experienced forum member can let me know if it sounds like engine knock or injector knock.

At this point I am sicken and tired of this thing as you can imagine. I never ran oil low on this car and have been using Mobil 1 5W40 for the last approx. 200k miles so I doubt the engine had a catastrophic failure. With less than 1/2 degree chain wear this does not seem to be possible. The only thing I can think at this point is that the IP is worn out and would not sufficiently pop open the newly serviced injectors. However I don't have a spare IP to test this out. If any list members in Central FL area who has a spare good IP can let me rent it to verify this that would be greatly appreciated.

Alternatively I am also open to let it go for a reasonable price to any list member who may have more patience and time than I have to get this thing back running. At 388k miles, the paint condition is not attractive but I have kept up with mechanical aspects of the car - it has been used for a 130 miles daily commute for all these years. A/C is cold and does not leak (I resealed the entire system a few years back and it has not need any topoff). Suspension systems have updated for the most parts.


Tan

'91 300D (frustrated with it at this time)
'87 190D 2.5turbo
'87 300TDT

Where do you live? I've got a 92 or 93 300D 2.5 in that the customer wants to sell. It is showing under 200k miles, is rust free and just got new glow plugs. Starts and runs out good. Needs a new owner that knows how to take care of them. He is only asking $3k.

__________________
Jim

Are you absolutely sure you have the cam timing correct?

__________________

All Diesel Fleet
1985 R107 300SLD TURBODIESEL
2005 E320 CDI (daily)

LOTS of parts for sale!


EGR block kit
http://www.peachparts.com/shopforum/diesel-discussion/355250-sale-egr-delete-block-off-plate-kit.html

1985 CA emissions 617 owners- You Need This!
Sanden style A/C Compressor Mounting Kit for your 616/ 617 For Sale + Install Inst.

Sanden Instalation Guide (post 11):
http://www.peachparts.com/shopforum/diesel-discussion/367883-sanden-retrofit-installation-guide.html

I think so but I will verify it one more time and take some pictures this time.

Tan

Jim,
I will keep that in mind. Thank you for sharing.

Tan

You may have a plugged exhaust system. Only a small opening is needed to allow enough air flow for the engine to at least idle properly. Open up the exhaust system, perhaps right after the turbo, and try to start the engine. I know of at least two cases of MB diesel exhaust systems plugging up and doing exactly what you describe.

I'm also suspicious of your IP timing and valve (camshaft) timing. Marker on the crankshaft balancer pointed at TDC and cylinder number one at TDC, the jury mark (slot) on the inside of the camshaft gear should line up with the marks on the camshaft bearing caps. Note that all the caps have the mark, if you lay a 12" ruler on them with the end close to the gear, you get the most accurate reading. Marks should line up within 5 degrees of TDC. Once that is correct, then confirm IP timing is between 14 deg and 14.5 deg ATDC, locking tool method works fine.

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Respectfully,
/s/
M. Dillon
'87 124.193 (300TD) "White Whale", ~392k miles, 3.5l IP fitted
'95 124.131 (E300) "Sapphire", 380k miles
'73 Balboa 20 "Sanctification"
Charleston SC

We seem to share similar problems. I am working through mine very slowly and also getting frustrated. Wondering if yours has been sorted out yet?

I just watched your video and there are some loud mechanical noise while cranking (concentrate at the end of the video) that do not sound normal. There was no hint of fuel igniting to my ears. It's unfortunate you replaced the head gasket when it appeared it was not needed. Was it making the same noise before the head gasket replacement? Does it make the same noise if you shut off fuel to the IP and disable the glow plugs?

__________________
85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

Pull the cams and inspect your tappets. Press down on each...if one of them sinks without resistance, it's bad.

Some of the 1991 602 engines had issues with their timing chains and sprockets prematurely wearing, there is a TSB about it.