Good morning all,

I have a 1999 Mercedes E300 with 214,000 miles on it. I was driving home yesterday on the highway and noticed the car felt as if the cruise control had engaged. I was traveling along at 80 mph when I noticed the speed. After taping the accelerator, a couple of time the cruise seemed to disengage. after a few minutes, the car began picking up speed again and I tapper the accelerator again and disengaged the cruise control. The car began slowing down and I noticed lots of grey smoking behind me.

When attempting to speed up, the car had a sluggish feel. I also noticed the clanking from the diesel engine appeared louder for a short time. I could coast to the nearest exit and pull into a parking lot. Once I got in the lot, the car cut off. I feared the engine was locked up. The engine did turn over when cranked, but did not start. It appeared the glow plugs didn't glow. The engine has a more labored feel as it turned over. I also checked the oil and the car does have a good level of oil in it.

After having the car towed home, I am puzzled as to where to start in sorting out this issue. I am assuming the engine is in good shape since it did turn over and has oil? A friend of mine mentioned that the transmission modulator may have ruptured and transmission fluid may have gotten into the cylinders?

Can anyone shine some light on this issue that is more familiar with the E300? Thank you for taking the time to read my post, and for any assistance you may offer.

Ron
Richmond, VA

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This car has an electronically controlled transmission. There is no vacuum modulator, so that is not a possibility.

Also the cruise on these engines is strictly controlled by the ECU directly operating the injection pump. No mechanical connection between your foot and the injection pump here. When you push down you are turning a potentiometer in the engine compartment. This is reported to the ECU and the ECU in turn sends a request to the actuator in the injection pump for more fuel. There is no cruise actuator on the linkage, the cruise is derived in the ECU and just alters the rack position to maintain speed and ignores your foot (unless you accelerate past the setpoint or hit the brakes).

What is more likely the cause is the crankcase breather puck diaphragm has ruptured and is causing engine oil to be ingested into the intake via the breather duct (this is the tube coming off the passenger side of the valve cover into the intake just ahead of the turbo past the air filter). The engine is taking the oil and burning it as extra fuel.

Fortunately this is very easy to change, it is right under the decorative cover. It is the black saucer over cylinder #5.

Get on this quickly, if it totally fails, the engine will go into a runaway condition and self destruct by sucking the lube oil dry. It will be a death race between overspeed and oil starvation until something fails, and you will only be able to stop it by choking off the air supply.

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The OM 642/722.9 powered family
Still going strong
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech

Thank you Jay Bod for the quick response and the detailed explanation. I feel like I can breath a sigh of relief.

I did try to start the car this evening and it is still labored and not starting? Should I just replace the crankcase ventilation pod? Or is there something else I should do?.

Thank you

Ron

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As stated the transmission modulator is a moot point. Not only does your car have an electronic transmission, but on the diesels that use a modulator the vacuum source is a vacuum pump, not the intake manifold so there is no path for the trans fluid to aspirate into the cylinders like there is on a gas engine.

What you didn't mention is what the oil pressure was doing during this event. Did you by any chance have a warning light on the dash that went ignored? I don't think this generation has an oil pressure gauge like the earlier cars did.

Even if you did blow the crankcase breather puck, I wouldn't expect the engine to be "laboring" to try to start.

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Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Dieseasel 3009

There were no warning light on the dash when I was having my issue. When I say labored when starting, it is much like the engine turning over when I forget to glow the plugs properly. I don't think the glow plugs are glowing as they should?

Thanks

Ron

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I would pull the inlet manifold to look for sludge build up, my n/a 606 with 126k was nearly a third blocked by EGR soot.

Once you have this off pull one of the glows to see if working or not, be super careful when removing as they break off fairly easily.

Also, check manifold for signs of black oil, turbos have been know to feed oil under some circumstances similar to Jay's post.

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David


1996 Mercedes S124 E300TD - 129k - rolling restoration project -

1998 Mercedes W210 300TD - 118k (assimilated into above vehicle)

Spock

Thank you for the excellent information. I will be sure to check the items identified. I suspect I will need new glow plugs.

Thanks

Ron

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Update to my issue....

The car has been at my mechanics house for many months (he is very slow) and he completed the glow plug change. He also changed the oil separator mentioned to change. After getting the car put back together, it will not start. When he cracks the fuel lines at the injectors, the fuel is very slowly dripping.

I got call this morning and he said he checked the fuel pressure , and it is very low. I would love some suggestions of what to check next. He also said he now doesn't believe the oil issue was the problem. He said the injector definitely needed changing. He questioned the fuel distributor may be the issue. (I don;t think a diesel has a fuel distributor. To his defense I own four Mercedes. Two are gas and two are diesels.

Thanks in advance...

Ron
(Richmond, VA)

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Slow is an understatement. 10 months and he's still working on it?

Diesels have an injection pump, not a distributor. The K-Jet gas cars DID use a part called a fuel distributor, but it was a completely different principle.

Low fuel pressure can be due to an air leak, a failed lift pump, a failed shutdown solenoid, clogged filters, etc.

I'd suggest finding a new mechanic...

__________________
Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Fuel distributor? He means injection pump.

I would work from the least invasive route possible first, injectors, lift pump, delivery valves etc, before going straight to pointing the finger at the injection pump.

Do a compression test to see if it's engine or fuel related.
Have a shop that can run tests on the pump and injectors, diesel injection shops and the like.

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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.

Grey smoke and loss of power - sounds like lack of fuel.

The glow plugs didnt glow in the parking lot when you pulled over because the engine was hot and did not need them.

Check tank strainer and replace filters and o rings on the fuel lines

I'd find another mechanic.

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Jim

When the fuel lines are loosened at the injectors, and the engine is cranked over, just a dribble of fuel is normal unless one can force the injection pump to full throttle. I have no experience at all with your electronic fuel injection pump, so I don't know if it is possible to force the injection pump to fuel throttle (which is simple on older cars with mechanical injection pump).

Normally the injection pumps are very robust and last the life of the car. They may require service as o-rings and gaskets leak, and using poor quality fuel can damage them, but none of those problems would cause a "no-start" condition.

My suspicion is that your car has sat for so long that the fuel injection system has lost its prime, air has leaked in, and your mechanic will have a difficult time if he is not familiar with starting a diesel engine in this condition.

I would recommend that he loosen all the fuel lines at the injectors, crank until fuel leaking at the joint is observed, and then tighten up that line and continue until fuel is at all injectors. Plugging in the block heater for an hour or more before doing this will help the engine start. I'm sure he will also need to hook up a charger to the battery and boost it while cranking, as the amount of cranking required would easily drain a good battery, let alone a battery that is probably weak from sitting so long.

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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

Last note - the starter is a heavy-duty Bosch unit that can handle cranking for extended periods of time (like 60 seconds straight) with a minute or two of rest in between cranking. Once fuel is at all injectors and all the lines are tightened down, crank crank crank and don't give up easily. Smell for raw fuel at the tail pipe to make sure the injectors are injecting fuel.

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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

Thank you to everyone that took the time to respond to my post. I will be taking your advice and moving forward with the car. Any further details on the process will be helpful.

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