M104 Starts then falters when dropping to idle

[bh13coupe]

Hi Guys

I have some serious issues with my M104 maintaining tickover.
I can get the car started no problems and the car goes to the immediate higher RPM (approx 1100 RPM). What I am experiencing next is the RPM then drops down to tickover 600RPM as normal and then the car conks out. It cant hold the tickover RPM. I am also hearing a loud whine the fuel pump that would signify its running out of fuel. the tank is third full.

My initial thoughts are the fuel pump is knackered but if that was the case the engine wouldnt start at all? Can I discount the fuel filter for the same reasons?
So the next option i would guess is the Fuel Pump relay or the OVP relay?
What I am also experiencing is all the warning lights are not clearing down when the cars starts, I dont know if this is related.

Background on the car is that it is my 3rd car and has had very little use and it hasnt been driven for several months which is not a good thing. Up to this point its fired up up like clockwork without issues. I want to get it exercised again as I know old cars need running and not rotting in the garage.

Has anyone experienced this sort of problem and can they point me to the source of the issue and how it was fixed?

 

[RichardF]

Start with reading the codes. Cleaning all the fuses may sort the warning lights, which ones are staying on, is the battery good?

 

[bh13coupe]

Thanks Richard
battery is very strong its brand new, its a full house on the lights, I have never seen that before in 15 years of ownership. only the hand brake light goes off when the brake is released. all the fuses are ok, i have put a complete refresh in there. I dont have a code reader to hand but my indie is local and I will try to pinch his tomorrow, I doubt he uses one that old too often.
Electrically everything works as intended, lights, seats, gauges, stereo, sunroof, windows etc. it seems the fuel reserve light is staying on which ties in with the other lights.
I forgot to mention that the wiring loom was replaced when the car was 10 years old.

 

[RichardF]

It sounds like 2 separate problems, have you tried disconnecting the MAF? Does it drive okay? Is this car a 3.2HFM or 3.0 24v?

 

[hotrodder]

It won't be the only cause but both times i've experienced all the preflight* warning lights (including reserve fuel) on the dash coming on and/or staying lit the cause was a dead alternator. First time the alternator was properly FUBARed, all the warning lights were brightly lit and there was a massive current drain with the ign off. The rebuilt alternator lasted 7 years or so and died about a month ago, this time the warning lights would get dimmer as the rpm increased while trying to get home before running out of leccy

As Richard have you driven it or kept the engine alive with the throttle until it warmed up. If so did it idle better once warm? In either case does it hunt (fluctuating rpm) before stalling or just die? A couple of times i've lived with a vacuum leak while waiting for parts and usually that = low/stumbling idle and stalling when cold and a high rpm with hunting when warmed up. A fuel evap purge valve that's stuck open can cause this as can loads of other things

I take it you traced the loud whine to the fuel pump as from the drivers seat that noise could be the exhaust air pump doing it's thing (not fitted to all cars, runs for a couple minutes after a cold start)?

Always worth looking at/reseating the OVP relay and the fuse(s) in it

* i.e. not parking brake or mainbeam tell tales

 

[MB-tex]

Hey Paul

Just had similar issues - could help? See this thread now solved as of today:
http://www.mbclub.co.uk/forums/engine/221109-w124-m104-idle-issues.html

Changed the fuel pressure regulator valve and car would idle again. This part failing may also be detrimental to the fuel pump, making it overwork to compensate for lack of pressure regulation. Could be your problem?