E300 fuel problems, I need to talk to him tomorrow
 

First thank all of you that post and answer. Your wealth of knowledge has helped me become very familiar with my newly acquired 1996 e300. Now the problem…

The car stalled and died shortly after I purchased it. I changed the prefilter, o ring and fuel filter with no luck. I took it apart and reinstalled them and bam, it ran, for 2 miles anyway then it stalled. It started back up so I drove it home.

Since then I changed the shutoff valve and o ring, all the plastic fuel lines and the k 40 relay. No luck so I had it towed to an independent Mercedes tech.

They got it running but you could see the air flowing through the lines and it would stall quickly. They called me this evening and said it was the fuel delivery computer; the part is $1,200.00 and has to be coded to my specific car.

I’m not so sure about this and it would seem to me that I have an air leek which is the problem (don’t know where) and not a computer error (would it put out a code) but I’m not a Mercedes tech and I couldn’t get my lawnmower started because the rear bagger wasn’t latched down (I found out it has a sensor).

Any input?

Seeing air in the lines sounds like a problem; but you know this already.

Some questions: Do you see air in the line to the prefilter? If so, the leak precedes that. Otherwise, are you sure that the prefilter O-ring has sealed properly? Do you have any fuel leaking from the shut-off valve when the engine is stopped?

Will they pay for the part if it turns out it's not necessary? I had a similar problem on my 98. It was a part located at the front of the engine and very near the fuel filter. It had many fuel lines running to it. When mine failed, the dealer said he had many more in the shop for the same reason. I'm sorry I can't describe the part better or be of more help but I'd think long and hard before I spent 1200 bucks on a guess.

I agree with matt. Look for the source of air entering. The computer shouldnt cause that.

Check your pre-filter again. I had trouble getting mine sealed once after replacing the o-ring. Had to crimp the washer and put a little silicone grease on the o-ring to get it sealed.

MBDOC said in a post yesterday that stalling a few miles after cold start could also be caused by the fuel thermostat.

Fuel delivery computer? Whats that then?

How can a fuel delivery computer introduce air into the system?

Sorry for sounding cynical.

Yeah, exactly...this sounds bad.

The very first thing I'd do is check all of the lines to make sure they are all routed correctly. It's really easy to push one into the wrong side of the lift pump or shutoff valve and not notice it.

Don't take for granted it was right when you bought it, maybe someone screwed it up before you ever saw it and you just copied their routing and duplicated the problem. Then, assuming the lines were all routed right I would check each line, one by one to make sure its o-ring was sealing right, but start on the pre-filter before you get that far.

I'd bet $10 they pre-filter o-ring is at fault. This one has caused more agitation on this car than any other part. A $0.10 part that has probably lead to more people selling these cars than any other. I'd bet $100 it's not a computer problem if you are seeing air in the lines. Find another shop or fix it yourself unless this guy is so sure that he'll not charge you if it doesn't fix it I would not approve him installing a $1200 part by the "shotgun" method.

Since essentially the entire system is under vacuum from the tank through to the lift pump any seal failure in any of those fuel lines or connections will cause air to be drawn into the fuel system. In my opinion this is the worst design MB ever came up with.

Why they would design a system that has the fuel pump located under the hood, downstream of at least a half-dozen o-rings is beyond me. It's much easier to find a faulty seal under pressure than it is under vacuum but having the pump draw the fuel through all these lines is what makes it really hard to find a failed one. That's just about the only good thing about putting a fuel pump in the fuel tank is that it eliminates the possibility of drawing air from a failed seal on the "sucking" side of the pump. This system almost invites that sort of failure by its very design.

Bottom line is this...find the failed seal and you will eliminate the problem. It could even be a blocked screen in the tank, just use logic and follow the fuel path from the tank to the IP and it will get solved.

Could it be that a vacuum system would result in air drawn in, whereas a traditional system results in fuel being pumped out?

Obviously diesel on the roads is a very bad thing. Petrol in an engine bay doesn't bear thinking about.

"Mechanics" make the recommendation to replace the ECU when they have no clue about the actual problem. :rolleyes: Have the car towed to somebody who's actually worked on one of these cars.

That isn't an uncommon problem..The ECU must power up the shut-off solenoid for the car to start..if the shut-off solenoid shorts out, it can damage the output signal of the ECU..did they test & find that problem???

Thanks, you guys confirmed my skepticism. I did have the car towed to another place this morning. When I described the problem he knew exactly what I was talking about and said mine is the third car in a month that had this problem. He said it may have to do something with a reformulation of diesel.

MB Doc. The first shop said they tested the voltage at the shut off valve and found it not within spec. They said they bypassed the computer and had the car running without stalling. Based on that, they came to the conclusion that the computer was bad. ($311.00 diagnosis). They still could not give me a good reason why the lines where filled with air.

I will of course keep all you posted.
Thanks Again

No way that air in the lines is caused by a bad computer. Don't forget the lift pump. Simple and easy to replace, and can cause weird problems. My car was stalling and acting badly in general. Solved by a new one.

Rgds,
Chris W.
'95 E300D

Update!!
 

Well I got got my car back today but I'm a bit uneasy. When my wife drove the car home it bucked five or six times (lossed rpm then bounced back up)

I do have to say the guy who worked on it was great. He replaced a few things I missed for the air in the lines (crush washers on IP pump, fuel pre-heater) and took the car for a drive and it ran great but then it died on him. He traced it down to a bad connection to the shut-off valve. He took the computer out and recrimped some connector, fixed a ground wire and we are off and running.

I still have a check engine light on PO380 glow plug malfunction...? I'm wondering if a bad computer would be responsable for all these issues (besides the air in the lines).

I'l let you know if I'm still running in a few days

My car threw a P0380 code after I cranked it dead trying to prime the fuel system. As soon as the battery was charged and the code was cleared from memory it never came back so it can come just from low voltage. Clear it and see if it recurrs.

Code PO380 is telling you there was a malufucntion in the circut to the GP's(ie: they didnt get hot). Typical cause is someone started up on cold plugs.

If that was the case you can clear it or wait for 3 cold starts and it will clear itself.

thanks, I am going to charge up the battery and see how that goes. Also, I found a broken wire on the EGR valve. I soldered it and I'll keep my fingers crossed.