I have a 1995 Mercedes 300D that I have been running on biodiesel (B100). I recently had a leaky injector. My mechanic had to pull the head (and send it out to be check for a crack - there was none) to replace it. I drove over 600 miles after I got the car back and then experienced a run on condition; while driving on the highway the engine started to race and smoke belched out the exhaust. I slowed down and the condition passed. It happened a few miles later.

I took the car back to the shop and found that fuel had leaked into the motor oil and this had gotten into the combustion chamber(s) and caused the condition above. The mechanic claimed that the work he did was not related and would not have caused this. He suspected that either the injection pump was leaking or the lift pump.

He replaced the lift pump but I have not driven much so I don't know if the problem is solved, but I suspect that the mechanic will next suggest having the injection pump rebuilt, which may cost $2,500 or so, and I'm looking for advice on what might be the cause of this problem and how to solve it.

When we drained the motor oil there was about a gallon of fuel mixed into the 7 quarts that should have been there.

Thanks,
Jerry

You experienced the beginnings of a "runaway diesel". A leaking lift pump or IP could cause this.

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RRGrassi


70's Southern Pacific #5608 Fairmont A-4 MOW car

13 VW JSW 2.0 TDI 193K, Tuned with DPF and EGR Delete.

91 W124 300D Turbo replaced, Pressure W/G actuator installed. 210K

90 Dodge D250 5.9 Cummins/5 speed. 400K

If you are getting fuel oil into your lube oil there are only 3 places where this can occur.....

#1.....the cheapest to fix......the diaphragm in the lift pump can leak fuel into the lube.....please note that your FI Pump is lubricated with engine lube....on the newer Bosch Pumps....some of the older, I think pre 1970ish pumps have their own independent sumps that need checking......

#2....the most expensive to repair.....the FI Pump elements (plunger/barrels) can become worn enough to cause leakage, and it will also enter the engine oil.....there are also some "O" rings and seals that could be leaking internally....

#3....the Fuel Injectors could be leaking into the combustion chamber, and this will wash lube from the cylinder walls causing excessive wear of the piston and liner of whichever cylinder id effected.......there may be some excessive fuel oil passing thru the exhaust on this one.....there would probably be very lousy performance here as well....

there are no other places where the fuel and the lube can come in contact.....unless you physically pour some fuel into your lube.....

SB

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Diesels:
'85 300D, "Max, Blue Benz", 155K, 27.0 MPG
'84 190D 2.2, "Eva, Brown Benz", 142K, 40.2 MPG
'77 240D (parts car)
'67 Eicher ES 202 Tractor "Otto" (2cyl, Air Cooled, 30HP)
Gassers:
'94 Ford F-150, "Henry", 170K (300 Six) 17.5 MPG
'85 190E 2.3, 148K....Parts Car
'58 Dodge W300M Powerwagon (Flat Fenders) Less than 10 MPG

Is the lift pump aka the primer pump that is mounted to the crankcase? Is it the same gizmo with the manual hand pump to prime the fuel filter?

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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

On the 1995 Mercedes there is no manual pump for priming. The device that was replaced had two ports on top for fuel and a plunger on the side that 'pumped' the fuel.

I had the lift pump replaced, rather than the diaphragm. I'm cautiously driving the car to see if the engine oil level rises.

If it is the injection pump, is there a great rebuilder that it can be sent to? The last time it was sent to a local rebuilder but I don't know their level of expertise. Also, are there seals or O-rings inside the IP that should be replaced with Viton considering I'm running Biodiesel?

Jadavis, a forum member here sells Viton o-rings. You might want to check with him.

http://www.peachparts.com/shopforum/showthread.php?t=184946&highlight=viton+o-rings

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1987 300TD 309, xxx 2.8.2014 10,000 mile OCI


Be careful of the toes you step on today, as they may be connected to the ass you have to kiss tomorrow. anonymous

“Be who you are and say what you feel, because those who mind don’t matter, and those who matter won’t mind.” Dr. Seuss

If it were my decision, I would not take your Fuel Injection Pump to any shop that is not an Official Bosch Service Center......see link....

http://www.boschservice.com/ServiceLocations/DieselServiceCenter/

My local Mercedes-Benz Dealership just changes FI Pumps with rebuilt ones, they do not service them in-house......

SB

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Diesels:
'85 300D, "Max, Blue Benz", 155K, 27.0 MPG
'84 190D 2.2, "Eva, Brown Benz", 142K, 40.2 MPG
'77 240D (parts car)
'67 Eicher ES 202 Tractor "Otto" (2cyl, Air Cooled, 30HP)
Gassers:
'94 Ford F-150, "Henry", 170K (300 Six) 17.5 MPG
'85 190E 2.3, 148K....Parts Car
'58 Dodge W300M Powerwagon (Flat Fenders) Less than 10 MPG

i would replace the lift pump right away! its only 12 dollars at max and diesel will destroy bearings in your bottom end.

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Have you ever noticed that anybody driving slower than you is an idiot, and anyone going faster than you is a maniac?

As long as they would add one additional commandment for you to keep thy religion to thyself.
George Carlin (Wonder where he is now..)

1981 240d (engine donor 1983 240d) recently rebuilt engine hurray! - No more.. fought a tree and the tree won.

pearl black 1983 240d 4speed (Converted!@$$%) atleast the tranny was rebuilt.

1984 300d turbo 147k
the small hand primer pump is $16.44 the primer pump assembly is $157.96 this site fast lane, new hand pump is install on the assembly do not remove only the right side 19 mm deep socket for input fuel, the left side is fuel out. 3 10 mm nuts on side use 3/8 10 mm deep socket on left side 2 hours diy .use oil pan under engine i change engine by metric and trans the primer pump assembly was not change , i change the fuel pump later, now have more power, no smoke, increase fuel miles

Add RAYMOND485 to your ignore list. He is a spammer that has no clue what he is talking about. His solution to every problem is to throw a lift pump or camshaft at the engine.

Was he speaking english in his post?

The 1995 E300D has the OM606 engine, which does not use a hand primer pump.

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"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970

Oh, my mistake, could it be the injection pump elements then?

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Have you ever noticed that anybody driving slower than you is an idiot, and anyone going faster than you is a maniac?

As long as they would add one additional commandment for you to keep thy religion to thyself.
George Carlin (Wonder where he is now..)

1981 240d (engine donor 1983 240d) recently rebuilt engine hurray! - No more.. fought a tree and the tree won.

pearl black 1983 240d 4speed (Converted!@$$%) atleast the tranny was rebuilt.

Gus Pfister - Pacific Coast Fuel Inj in the Bay Area rebuilds IP's for ~$1K.

I'd exhaust a lot of other avenues before pulling the the IP. Unless messed with, they just don't bad that often.

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Terry Allison
N. Calif. & Boca Chica, Panama

09' E320 Bluetec 77k (USA)
09' Hyundai Santa Fe Diesel 48k (S.A.)

1. Your reply makes no sense, nor do any of the other replies you ever make on this board.

2. Why are you resurrecting a 15 month old thread and talking about OM617s, and that has nothing to do with a W124?

3.

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91 350SD
14 F150 Eco
19 Fusion Hybrid
11 GT500