Ok, I did some reading here but didn't find what I was looking for. This is not my vehicle btw, I'm helping a friend diagnose it.

95 E300, 210,000 miles, running mostly biodiesel for the past 100k or so.

Basically, the crankcase fills with fuel pretty fast, can't drive more than 20 or 30 miles without having a brief runaway diesel issue. The lift pump, the injection pump, and the injectors have been replaced per the mechanic's instructions to no avail. This has been an ongoing saga for a couple years and he's ready to give up.

Is there anywhere else the fuel can be coming from that wasn't covered? The car is in great shape otherwise and would an a shame get rid of.

Thanks!

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Once I left an injector line hanging over an open prechamber and fuel dripped into the combustion chamber, past the rings and into the sump. Does your friend note a lumpy engine as if an injector were stuck open? I suppose fuel can leak inside the IP and drain with lubricating oil into the sump.

[Edit] Fuel is more likely leaking through an injector if it's causing a runaway situation.

Sixto
87 300D^2

If it was a bad Injector dumping raw Fuel into the Engine that would cause the Engine to run poorly.

When I looked in the Manual I noticed the Injectors go through the Valve Cover. I cannot tell from the Pics how the Injector is separated from the innards of the Engine.

If there was an Injector Return Line leak or a Injector Nut leak Fuel might be getting by what ever O-rings or Gaskets seal it from the inside of the Engine.

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84 300D, 82 Volvo 244Gl Diesel

There are a lot of o-rings and such that must be changed to Viton for use with biodiesel; it's possible that the owner missed one -- it's easy enough to do on the OM606NA engine. The little return hoses are usually one of the first things that one changes for biodiesel but they are also hidden from view by the black plastic cover.

The injector hard lines are also hidden from view by the cover. A leak from a split or damaged hard line might then cause the o-ring in the valve cover to deteriorate and send fuel into the camshaft housing and thence to the crankcase via the oil returns. Try running the engine without the cover so topside leaks can be seen. A leak big enough to put significant amounts of fuel into the crankcase should be visible with the car idling in the driveway.

Jeremy

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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

An Injector Return line or leak around the swedged area of the Injector Nipple would not show up as a difference in Engine performance.

A leaking Hard line ought to have some effect on Engine performance because all of the Fuel for that Cylinder would not be getting injected.

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84 300D, 82 Volvo 244Gl Diesel

First off, if your crankcase oil is being diluted with fuel that quickly, and for the last 2 years, I am surprised that he hasn't spun a bearing yet, or just plain seized up the motor due to lack of lubrication.

Better define "the crankcase fills with fuel pretty fast". Are you taking about a quart, or a couple gallons, in 20 to 30 miles?

The only place I can think of where fuel could get into the crankcase that fast is the "wells" in the valve cover for the injectors. If the seals have failed and the injector "well" is filling with fuel due to a leaking return line (most likely) or a leaking injector body or hard line fitting (not likely at the quantity you are taking about) that could allow fuel to flow into the crankcase.

Try removing the plastic cover on top of the valve cover and run it while looking for leaks.

I cannot think of any other interface between the crankcase and the fuel system.
The fuel heater interfaces with the cooling system.
The IP has been replaced, so assume that it is not leaking out of the front shaft into the crankcase.
???

Good luck.

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Greg
2012 S350 BlueTEC 4Matic
2007 ML 320 CDI
2007 Leisure Travel Serenity
2006 Sprinter 432k
2005 E320 CDI
1998 SLK230 (teal)
1998 SLK230 (silver)
1996 E300D 99k, 30k on WVO
Previous:
1983 240D, on WVO
1982 300D, on WVO
1983 300CD, on WVO
1986 300SDL 237k, 25k on WVO (Deerslayer)
1991 350SDL 249k, 56k on WVO - Retired to a car spa in Phoenix
1983 380 SEC w/603 diesel, 8k on WVO
1996 E300D 351k, 177k on WVO

Thanks for all your replies, it looks like we need to take a serious look at those return lines. I know he replaced a number of things with Viton, but we'll have to double check everything when I see him tomorrow.

@GregMN - He hasn't driven it much since the problem has gotten worse and I know he changed the oil recently, but yes, diluting the oil with biodiesel is something that might not be good for the engine.

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we'd need to know EXACTLY what was replaced, and how it was replaced, to know if it's from the IP, the mount, the injectors, the lines, etc.
20 miles to runaway is a LOT of fuel! it's got to be either inside the IP, or on the fuel return side... no way that much fuel is going past the pistons, unless there is a HOLE in one of them...

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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!

There is no way of fuel going past the injector seats, the overflow pipes leaking from the injectors is plausible but enough to actually get into the crankcase via the breather grommet would also mean that the engine actually is taking a bath in diesel fuel too.

I think the only way is the injection pump itself.

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2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)

Does the 95 have that strange shut off/fuel recirc device? It might be possible that it is leaking fuel into CC.

that device is on top of the fuel filter and just blocks flow of fuel into the secondary filter (big one)

it is nowhere connected to the engine. I think that the fuel section in the IP is leaking into the crankcase, If it would be dribbling from the injector spill pipes the engine should be bathing in diesel on both sides.

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2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)

I'm referring to the shut off/ recirc device found on top of IP from mid 95-98 E300D. http://www.*********.com/assets/rep/thumb/1012180.jpg

But yes, that would not cause it, it is simply mounted to the pump and not ported to it internally.

I thought I heard something about it being oil psi sensitive (shuts car off with low oil psi) but this is not so. Sorry, been a long time...

that part is the control module for the rack on Electronic IFI found on the W210 diesels with the 606 engine, The car in question is a W124 which has a mechanical injection pump. The w124 diesel pump is very similar to the old 60x pumps - they have linkage to accelerate and vacuum shut off valve.

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2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)

I took a look at the car today and there is a lot of melting rubber everywhere. He told his mechanic to replace everything with viton but it is obvious that very little if anything was done. Looks like a big red flag to me that his mechanic was not paying enough attention.

Another interesting thing he said was that the problem went away temporarily when he replaced the IP, only to return 2k miles later.

He's selling it for $1,000. If anybody is interested PM me. I just don't have the time and garage space to take on this project.

Thanks for your help!

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pics?


I could find a buyer for the car down here, and fix it for them.

send me a PM!
thanks.

__________________
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!