PLEASE HELP! - PeachParts Mercedes-Benz Forum

mattmeier · #1 10-17-2009, 11:18 PM

Hi all I have a 2001 ml55 amg with the 5.5l that has a no start problem that I can't figure out. It just quit on me due to the fuel pump burning out so I replaced it. Since I replaced the fuel pump now have a no start problem at first I thought it might have been the crank position sensor but replaced it today and still won't run. The motor turns over and fires however as soon as you let go of the key it dies and after every two to three attemps of trying to start it the motor backfires. Any ideas or suggestions would be greatly appreciated. Thanks Matt

long-gone · #2 10-18-2009, 02:42 AM

Sounds like it MIGHT be a wiring problem. At least that's where I'd start looking first. Perhaps when your pump "burnt out" it took some wiring with it. Maybe the pump didn't burn out at all but rather a link supplying juice to it did. Sounds like your primary ignition wiring is good to fire it up but when you let the key drop back to position 2 there's no juice there (either to the ignition or to the fuel delivery system) to keep it running. The backfire may be just a build up of unburnt gas from the previous starts and sudden shut-off's.

All just conjecture of course on my [very amateur] part, but I'd start by investigating the fuel pump relay and wiring associated with fuel delivery and ignition, particularly the fuel pump circuit.
Get the old pump if you still have it and connect it to a car battery and see if it actually is bad. If it still works that would indicate the original problem was something else. But even if it doesn't work, and having been replaced, there may be another fault in the fuel delivery or ignition circuit that was part of the original problem. Check the fuses particularly for the fuel pump. Even if it looks good, spin it in place to clean the contacts, then see if it starts. If not, maybe someone else here has other ideas or could help you with checking the pump relay and/or testing the circuit and wiring to the pump.

Of course I could be totally off base, but from your brief description, that's where I'd start investigating.

mattmeier · #3 10-18-2009, 09:01 AM

Thanks for the input however i tried the fuse thing already with the fuel pump, I even put a jumper wire on the fuel pump to make sure it was running when i tried to start it but still got the same result. I am going to start looking at the wiring today see what i can find. Thanks for the import I'll report back on my fidings.

Shaun McCarren · #4 10-18-2009, 10:42 AM

Hey fellow ML55er
Well, what caused the fuel pump to fail? Some type of blockage? I haven't heard much of fuel pump issues on the 163 chassis. However, the wiring harness seems to be an issue on many 163's http://www.peachparts.com/shopforum/showthread.php?t=156415&highlight=163+fuel+pump

How many miles and what year on the ML?

mattmeier · #5 10-18-2009, 11:11 AM

It is a 2001, just over 100k miles. Not sure why the fuel pump burned out but it had a wire connection burned up, looks like it shorted out. thanks for the link, I have the same problem as described in that posting.

tonylaker71 · #6 10-19-2009, 12:33 AM

did you check for any codes? it sounds like you might have a das problem. as in drive authorization. have you tried using a different key. they go bad all the time. you will need access to a star diagnosis machine to check codes. you can also check the key with it. did you make sre you have fuel pressure at the rail? hope this helps

mattmeier · #7 10-21-2009, 09:11 PM

I have good fuel pressure at rail but was wonderin were i can get a star code machine?

Shaun McCarren · #8 10-23-2009, 01:33 PM

Your looking at a few hundred dollars to get a knock off multiplexer and software (CarSoft) to be able to check the various systems and make changes. The authentic MB system is very pricey (maybe $10k).

So the harness is ok? I'd recommend you get a MB tech to take a look at the car. This forum is a great resource.

Tony's comment about a DAS or key problem (DAS reads the key and authorizes the car to start or not...a bad key will allow the car to start but it will stall in a few seconds).

I'd still go back to the fuel pump as that is the most recent issue...unless some type of power spike damaged other components. I didn't want to bring up other ideas to throw you off track...but could also be the ignition or a DAS/Key issue. Again, the odds of that at the same time as replacing the fuel pump seems unlikely. You have the fuel pump plumbed and wired correctly. How's your battery? Checked it under load?

Did the fuel pump just die or was there some precursor?

mattmeier · #9 10-27-2009, 07:12 PM

still working the issue, as for as for the fuel pump it went all at once and the harness was good but the pump wires that run from the sending unit to the pump look like they shorted out. I am working on ordering the key to see if that fixes it. Will keep you all updated but if you have any more ideas please let me know. Thanks for all the help so far.