Short version in second post
Hello everyone. Recently acquired a 91 300d. I will tell the full story of how I acquired the car and current state its in. What I'm looking for is advice on what to do next to solve its horrible running issue. I bought the car in April when my truck broke down near LA. I bought this Mercedes at an auction for 300 bucks and with 193k on the clock. ( once I received the title I learned it had passed 200k back in 07 so it's far greater than that) the car ran rough already but drove. The main issue at that point was way to much black smoke after about 2000rpm and it wouldn't shut off right away. Anyways I replaced a few tires and headed home to Seattle. I stopped at a friends in Medford Oregon at his shop and did some diagnosing on why there was some much black smoke. Checked for boost pressure and there was none. The impeller on the turbo was completely seized. Anyways I couldn't find any good turbos nearby so I headed home as before. Closely watched water temps kept it from being too smokey and it actually did good on fuel consumption. When I got home I replaced the turbo with a working one from a 190d so it was the non vacuum controlled turbo. After that it was still running like crap. I had heard of diesel purge and I decided to try it to maybe fix the rough running. I followed the procedure 3 times replacing the filters each time and running an extraordinary inline filter. On the diesel purge it ran absolutely perfect. And there was barely any black smoke at boost either. Only issue was still running for an extra 10 sec after I would turn the key off. When I got it back on diesel it was smoking white very excessively and started to run so bad. I decided I might have clogged the injectors so I ordered a set of. Monarks. Rebuilt them. Set the pop pressure (all at 135 bar and one at 137 I couldn't get it any better ) put them back in and same thing. White smoke and runs really rough for the first ten minutes then idle cleans out but still smokes white. I have since deleted egr completely with no changed. At this point the fact that the car runs for extra few seconds after I shut the key off makes me think the ip has been messed with or its burning oil and that is causing it to run but i would prefer the ip is the issue. Any ideas??

I realize it's a bit long of a post so short version:
Purchased with seized turbo- symptoms were black smoke above 2000 rpm and wouldn't shut off right away after turning ignition off.
Drove home 1200 miles.
Replaced turbo still smokes black and doesn't shut off right away.
Ran 3 bottles of diesel purge through the system.
Started to smoke white and won't stop after warming up
Rebuilt injectors and pop tested. Set at 135 + or - 2 bar
Still smokes white. Some black on WOT. Still won't shut off for about 10 sec after ignition is off

Check injection timing. There's a 17mm bolt on the side of the IP. It looks like this, but in this picture the bolt isn't there. That's also where the tang should be in position. Use an inspection mirror to see timing.


If your timing is out of whack, your chain stretch is as well. When the chain stretches, it throws off the timing since the pump is chain-driven.

If it was burning oil, it'd be smoking blue.

What color does the white smoke smell like? If it smells like fuel, it's a fuel issue.

If it's white and smells sweet, it's coolant. Your rough idle could be related to a head gasket, but I DON'T want to say that yet until I know more. Head gaskets are known issues on the om602 & om603s. We'll look into that later after examining the fuel system. How's the power? Is it responsive, does it feel like it misses at all?

Your shutoff issue is vacuum related.. Likely a leak on the driver side of the engine vacuum nest. It's wise at this age to replace all the vacuum lines everywhere in the engine bay they're all worn and cracked likely.

Driving from LA to Seattle I didn't have to add oil once. It dropped a smidge in the level but not enough to even worry about. It definetly feels like it misses for the first 5 min to ten min. The white smoke is fuel. Doesn't smell like burnt oil or coolant. Also replaced oil and did motor flush. Nothing in the oil. Coolant is clean and level also hasn't dropped. I'll get to check the timing with the ip.

Also, it's worth checking the resistance of the glow plugs. If you aren't getting adequate heat to the cylinders, your cylinders will miss and run rough until up to temperature. That will cause raw unburnt fuel and white smoke at a start. Check your glow plugs and make sure they're functioning. If it continues after warming up its likely your timing is retarded from chain stretch.

These cars are really simple to diagnose and fix. About your oil leak... Common leak points on these engines are the vacuum pump and front crank seal. The front crank seal is common on engines with more blowby and have higher combustion pressures.

Rough idle don't forget your engine mounts too!

Actually, that's not the case. Even with bad glow plugs, idle on a 602 will smooth out LONG before getting up to temp.

__________________
14 E250 Bluetec "Sinclair", Palladium Silver on Black, 153k miles
06 E320 CDI "Rutherford", Black on Tan, 171k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver, 142k mi, wastegate conversion

19 Honda CR-V EX 61k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

I will probably replace motor mounts either way. Injection pump seams to be leaking heavily from the bottom cover. Front of the engine is surprising dry. But oil on the driver side is spring across the rear of the oil pan so can't tell if rear seal is leaking yet. It does have some blow by but not excessive I would say.

Engine still smokes after warming up so glow plugs also are issue but not the main issue I believe as idle evens out but smoke continues.

I did not mean operating temperature of the engine. The cylinders will catch heat in 30 seconds or less with bad glow plugs provided you have good cylinder compression.

Just because the engine smokes as it starts up like you say doesn't mean its the glow plugs. Check them anyway. It's probably retarded injection timing.

Is the top of the IP damp? If so, you need to freshen the delivery valve seals.

Have you don't a compression check?

Crack each injector line until fuel flows: if the cylinder is missing, there will be no change in running, otherwise it will slow down and get rough.

Make sure the fuel clamps on the primary filter are tight and the rubber joints are healthy.

You probably have a vacuum leak, that's why it takes a while to shut down. And probably why your turbo wasn't producing boost. if you don't have one, pick up a Mityvac, it's the best tool for locating vacuum problems.

IP is dry in the top. Have not done compressions check, bought a kit from harbor freight but the dummy injector was too long so I gave up on that and won't buy a kit until I mess with the ip timing

There might be a vacuum leak but so far I have everything sealed off good. Where the rubbing is cracked I've put some electrical tape on it

So yesterday I started it up let it run for a few minutes and proceeded to crack the injectors lines open to see if there was any change. On the first injector there was no change. when I cracked the rest of the injectors engine would start shaking more and slow down. So I presume at this point either blown headgasket or burn valve in cylinder one. I swapped 1 and 2 cylinder injectors to rule out any injector issue fault there might have been. I will begin the process to remove the head today.

NOoooo! Don't pull the head yet!

__________________
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

Very long read here, but the bottom line is that a problem with a delivery valve (they are located in the top of the injection pump) can cause exactly what you have.

Delivery valve internal leak as a cause of nailing? Yes? No? Maybe???

Get the special socket and all the o-rings and copper washers, and rebuild all your delivery valves. Research the procedure to make sure you understand, ask questions here if you don't.

Closely inspect each delivery valve for scoring or rough sealing surfaces, and be ready to replace any that are questionable. #1 is your prime suspect right now.

__________________
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

You could do a leakdown tester to be 100% positive before removing the cylinder head.

However removing the head is probably the most straight forward way if you don't have an air compressor and leakdown tester.

However removing the head is one hell of job, something I'd do only if I knew 100% what the problem was.

I'll be lurking to see your results when the time comes.

__________________
1998 Ford Escort ZX2 5 speed - 279,000 miles My Daily

1992 Mercedes 300D 2.5 202,000 - Pure junk
2000 Mercedes E320 Black - 136,000 miles - Needs repair

Don't forget to grease the screw and threads on the spring compressor.

This test definitely points to a fuel problem, NOT a head gasket problem.

__________________
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