450 SL in Denmark

Hi Peter,

looking at spark plugs, your injectors in 2, 5, 8 are from 3 different groups. So it cannot be ECU. Pressure loss test was done. That should exclude valve shafts and oil rings as well. Have you done a cleaning test of injectors and have you verified ground connections of injectors?

Thanks, Volker.

The wiring harness is new, but I will check the grounding connections to be on the safe side. I will also try to find someone in DK who can clean the injectors professionally.

Have you any experience with the solonoid in the injectors going bad, so that the injector does not close fast enough? - meaning that it continues to spray even if the signal is no longer there?

Best, Peter

Hi Peter,

well injectors can clog and normally that blocks them. But sometimes needle is fixed in a way that it cannot close and leaks permanently.

and if it is the injector, the problem should wander to next cylinder if you swap injectors.

Hi Volker,

With the compression test done and showing encouraging results I couldn't leave the uncertainty about manifold vacuum. I have purchased a proper vacuum gauge with glycerin and it now shows 560 mBar at hot idle. That gives me peace of mind. The engine still runs rich and somewhat uneven, so next up are the injectors.
 


Best, Peter

Hi there,

Well, I have now changed the three injectors associated with the three fouled spark plugs and also changed all the spark plugs with new NGK BP5ES. The engine is however still not behaving and is sputtering/misfiring in idle and at low speeds/load and it has problems getting up to speed. It smells of fuel in idle and when I changed the oil today the oil also smelled of fuel.

I have pulled the ECU out and measured according to Norbert's (I believe) check list. Please see enclosed table (measured at ambient and warm temperatures). To me it looks as if the values are within spec. although I am a bit doubtful about the coolant temp. sensor value when the engine is warm.

Since changing the spark plugs I have driven 100-125 km. and I also pulled them out today and they look even. There are no apparent signs of rich running, but perhaps that would not show itself in just 100-125 km. of driving? I don't know myself.

The idle mixture potentiometer is turn all the way counter-clock wise (lean) and it seems still to run rich.

I am really beginning to doubt if I will ever get this car to run right, but I am also not known to be a quitter. I need all the help I can get.

Best, Peter