SM313

I HAVE A 1988 MERCEDES BENZ 420SEL THE CAR HAD BEEN SITTING FOR 3 YEARS. I HAD A ISSUE WITH THE FUEL SYSTEM FUEL PUMP WASNT COMING ON AND NO FUEL GOING TO THE FUEL DISTRIBUTOR. I CHANGED THE FUEL PUMP RELAY NOW THE FUEL PUMPS R COMING ON AND WHEN THE AIR FLOW PLATE IS DOWN I HEAR A SINGING NOISE AND FUEL DOES SHOOT UP THRU THE 8 INJECTOR LINES. I HAVE GOOD SPARK AT ALL CYLINDERS AND THE CAR DOES FEEL LIKE IT WANT TO START BUT DOESNT ALSO CHECKED COMPRESSION ON ALL CYLINDERS GOT GOOD COMPRESSION IM STUCK CAN SOMEONE PLEASE HELP ME

shkarus

Interestingly I have pretty much exactly the same scenario with my 1990 500 SEC which had been standing (Garaged) having done 400 miles in 4 years. After being told by Auto Technics in Sheffield that it required a new fuel injection distributor unit (Bosch £600-£1000 fitted) and having had a recon unit fitted (£250) IT wasn't that! I then took it to a mechanic I have reliably used in the past who has diagnosed a fuel delivery issue (Not enough pressure to the injectors over 1500 RPM) the car idles properly until warm and then starts to develop a bad intermittent idle before dying completely. He will replace the fuel pump (noisy which is not a good sign) and if this fails will also replace the fuel pump relay which is another common issue manifesting the above symptoms.

I would also strongly advise you to flush/purge the entire fuel system of any old fuel if it has been standing and change the fuel filter as it is most likely considerably contaminated by now, I would also clean the injectors and check their plastic housing for leakage which can be another issue.

You will probably also find that the fuel pipes which feed the pumps are corroded and will also need replacing.

I will now give 'Auto Technics' (Sheffield) a wide birth having diagnosed the wrong issue and having cost my serious time and money to chase my tail!