i have a 95d with the same problem, drained 4 gallons out of the sump after 30-40 miles. overhauled lift pump twice thinking that was it. nope. thinking now its the ip. i figured that about 30% of the fuel is going into the block. i find it hard to believe that that amount of fuel can bypass the injector pump and still have the pressure necessary to open the injectors. the engine runs well. thanks, joe hunt

Okay, I'm trying to think outside the box on this one because lots of money has been thrown at this with no results.

Here is what I came up with: Vacuum pump sucking in fuel from somewhere, like a shut off valve? Hopefully someone who knows more than me can chime in here. Is this possible?

Also, anybody have a fuel system diagram for this engine with the various parts identified? I've been searching all morning, and I just keep finding links to that Russian site that doesn't work anymore. It would be very helpful for me.

Thanks!

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The fuel system diagram is pretty much simple if you look at the fuel filter.

The main fuel line goes into the top prefilter, it exits from the bottom of the prefilter cavity to the lift pump, the lift pump then "pushes" fuel into the secondary filter from its other pipe, the pumped fuel is then pushed into the delivery valve area of the pump, and finally the last bit is the exit from the injection pump which joins the rest of the return lines on the fuel filter.

If you are assuming that the vacuum pump is sucking in fuel then I can assure you that the system would have no vacuum - hard shift, no shut off etc. if that were the case.

For your testing sake - make the engine run off a gallon of fuel in a bucket in the engine room, with all vacuum disconnected. Take the vacuum out of the equation. The pump itself has some seals that separate the oil part of the pump from the fuel part. Those need to be checked

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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)

Fuel system & vacuum diagrams will be in Group 7 in the FSM:
Model 124 Maintenance Manual Index

There's pretty much no way that fuel can get into the crankcase except through the injection pump.

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Dave
Boise, ID
Check out my website photos, documents, and movies!

I think that tells the whole story right there.

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Dave
Boise, ID
Check out my website photos, documents, and movies!

I have attached a pic from underneath the plastic cover on a car that has been running 100% biod for the past couple years or so. The biod will turn some of the seals to mush. It seems hard to imagine getting enough fuel from this source to fill the crankcase but it would not surprise me.

Have you removed the plastic cover? I'd do that and see what is going on. Keep in mind the crankcase should be pressurized during operation.

I'm wondering if there is a vacuum line hooked to a fuel line with that much fuel getting in there. Was any work done to the car just before it started doing this?

Oh yea, change all the plastic elbows and connectors on the crankcase vent system part of which is shown.

Attached Thumbnails

 

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Jim

Is your friend running commercial biodiesel or home-brewed stuff?

Run the IP on a test bench to see if fuel is leaking from the fuel system to the lubrication system. You might have an upset tech but at least you'll know.

Sixto
87 300D

That sounds interesting. I have his old ip, where can I get it bench tested? Truck repair shop?

He has been running it on home-brew.

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Any Diesel repair facility should be able to do it or recommend a place.

Bosch has a clumsy website but I found this:

A-1 All German Car Corp.
400 W 219th St.
10034 New York
New York / United States of America

Sixto
87 300D

Update:

I called H & R FUEL INJECTION in Long Island to discuss the issue and possibly rebuild the ip, but he indicated that the only way it could happen that fast is through bad injectors. Last week we removed and sent them to him and just got the word back. One is completely shot and two were pretty bad. Looks like we solved the mystery. I'm just shocked that it could purr so sweetly with at least one injector uncontrollably pissing fuel.

By the way, the previous owner told me he thought his mechanic already checked the injectors, but by the look of the return lines I knew you couldn't even look at 'em sideways without breaking them.

Anyway, we should have the car back together again in a few days, and I'm looking forward to a celebratory drive.

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I'm not convinced this will solve the problem, but hopefully I'm wrong...! Please keep us posted on what happens after you drive through a few tanks of fuel.

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Dave
Boise, ID
Check out my website photos, documents, and movies!

Ok, maybe it's too soon to celebrate and I'm getting ahead of myself.

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The only place LARGE volumes of fuel can enter the crankcase from is
(wait for it)

the lift pump seal has failed...
This is the fuel piston seal that should prevent leakage into the injection pump oil sump.

Old truckers called it making oil.
The issue is covered in this thread.

Run away diesel, why does it happen?


.

I told him that the lift pump has been replaced twice to no avail, so perhaps I should have said "Only OTHER way..."

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Out of curiosity, how much time/miles elapses between replacement of the lift pump and next re-appearance of the problem?

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."
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