fuel pump groan
 

I have a 88 300e that runs great for a few minutes then dies. when it dies I can hear the fuel pump groaning. When I turn the key to activate the fuel pump it also groans but if I let the car sit for a little bit it will start and do the same thing. The car will stall out at all speeds. I just dont want to spend over $300 to replace the fuel pumps if they are not bad. Please help

There is also a fuel filter and a pressure regulator that may be causing you problems.

The filter was replaced not long ago. Isn't the groan sound caused by a dry pump? Isnt the accumulator after the pumps if so would that still cause the problem?

Similar problem on my recently reborn 1978 280CE.........got worse quite quickly to be nearly as bad as yours

Filter change should be your first step........if that makes no difference it is likely the pump or the supply of fuel to the pump

I suggest you check fuel delivery with a new filter.........mine gave good delivery at first then poor varying delivery when playing up........my problem turned out to be a choked in tank strainer screen............the groan was from sucking against the blocked screen............sitting for a while must have allowed some of the gunk to float away.....but it quickly clogged up again

When draining the tank the flow slowed to a trickle..........a blast of compressed air up the fuel outlet tube started things going again and gave me the diagnosis...........pulled the tank and couldn't believe the crud.........3 coffee mugs ~ 1/2 Kg!!

Clean tank & new in tank strainer and the problem was solved.........I still had to replace the pump as during the process it jammed with gunk that I couldn't clean

Pulling the tank in my case (w123) wasn't as bad as it sounds......the symptom of being ok when sits for a while is what makes me think it is the screen........fuel delivery is the first check.......on mine spec was > 1litre in 30 secs......crack return line fitting on fuel distributor

Link to my problems

The accumulator maintains pressure for a restart......typical symptom of accumulator problems is needing a couple of tries when restarting after sitting for a while

Dry pump would come from lack of fuel supply to it....I noted what I called 'zinging'......speeding up of pump....and the groaning as it tries to catch up

Anyway I'm sure fuel delivery measurement is the key to diagnosing your problem

You should be able to get a new fuel pump for alot less than $300 in the US.....others talked about ~$US160 in a previous thread