Starts and stalls, starts and stalls
 

Hi I have a 90 300SEL and it will start up great stumble and stall. It might do this two maybe three times then its fine. Only when cold. Also if I feather the fuel pedal I can keep it going and avoid the stall. Any suggestions? 120,000 klm and just had a complete tune up with plugs,wire,button and cap. New Voltage Prot. Relay and other than that works good.

The cause is partially clogged fuel injectors.

Buy a bottle of redline fuel additive (nothing else works). If that doesn't resolve the problem, then replace the injectors.

Had the same issue on my 300E and 420SEL, injectors helped overall fuel economy and performance/idle quality. But the starting and stalling issue is generally the fuel pressure accumulator down by the fuel pumps. When it gets weak it causes a pressure fluctuation when starting after sitting, (especially when warm) causing the stall.

I believe I changed the regulator a year ago, I will try the red line and see what gives. I have a fuel pressure tester but not sure of where to connect it on this car.

Somebody can chime in for certain but I believe there are two plugs on the side of the fuel distributer. You can test from there.

Redline is good stuff.

Subscribed.

The 1989 SE does the exact same thing, however, on a hot restart within 15 minutes, it does not have an issue.

The more time elapses, the more likely it is to have the problem.

Redline had absolutely no effect and I'm doubtful that new injectors can cure a problem that appears to be dependent on fuel pressure. If the problem was present under all conditions, I'd be inclined to go toward the injectors.

I'm going to investigate this fuel accumulator...............

Anybody have a photo of the fuel distributor and where the connection ports are?

The fuel distributor is the assembly that feeds the 6 injector lines.

Yup, know that part but where does the f pressure tester connect? what line/port ? what kind of connector do I need?