i just repaced the fuel accumulator to solve a intermittent hot start problem. the car starts perfectly every time now. A side benefit, it seems to have solved some intermittent idle problems as well. I'm guessing the CIS needs a steady fuel pressure that accumulator helps to provide.

 

well I spoke too soon. for a few days of no problems, my 90 300sl just did a hot start failure again. she started to start, then died, then after cranking for about 10 seconds she started and ran fine. before, she always started after a period of cranking from 6 to 15 seconds if I had this intermittent problem. I have never had a cold start problem so far. most of the time she starts right up and runs good. the pump and back flow valve were replaced about 20 thousand miles ago. I resently replaced the injectors for a hard & rough idle start problem after she had set for over a half hour or so. That problem was solved. I don't know how replacing injectors could be related to this intermittent problem. the only things on this engine I haven't replaced is the fuel distributor, throttle valve, and the air flow meter. the hotter the engine, the worse the problem. even though the back-flow isn't that old, I'll replace it again tomorrow. I've got to be losing fuel pressure. what else is there between the pump and the injectors that could leak off? other than the accumulator.

 

well back to the drawing board, the check valve didn't do it. out of 30 perfect starts, 2 were hard starts. she starts to start then dies, then after cranking for a short time she always starts on the second try. and only when hot. go figure.

 

Ahoy, Brookings,

I have a '90 300SL which experiences start problems after it has been stopped for a while when warm. It will start/stop, and then re-start OK. If I depress the throttle during such 'warm' start, it goes OK immediately.

I have just assumed that it has a fuel dribble which somewhat floods it, and the part throttle start clears it -- just like an old carburetor car.

????????????

Enjoy /s/ Bob

 

for me, If I push down on the the gas she won't start at all. only if I keep cranking with the accelerator up will she start. I wish it would just break down period. intermittent problems are the pits, to say the least. most of the time she runs and starts perfect. do you ever have a cold start problem? does it ever cut out on a hard acceleration?

 

Ahoy, Brookings,

No cold start problems, and no cut-out on acceleration. Must be different problems. Good luck!!!

Enjoy /s/ Bob

 

Ahoy, Brookings,

A furthur thought: The cis fuel injection system on my 300SL is much like a VW which I had. The VW included a 'start' injector which fired a shot directly into the intake manifold, the magnitude of which was related to temperature. Does this feature such also, and if so, is it working???

Enjoy /s/ Bob

 

May not be in your system but I had a start relay go bad. It was the one that controlled the fuel cutoff solenoid. Sometimes it would start right up other times you could crank till the battery went dead. Found the bad relay by tapping on it when it would not start.

 

rhbelter you are so right on. one can assUme a lot on these cars. my biggest mistake was thinking I had a fuel pressure issue. I had the classic hot start symptoms. After replacing injectors, backflow, Accumulator and temperature sensor and still have a hot start issue. I broke down and got a code reader and found faults 3,11,28,29. They all pointed to the temperature sensor as a possibility. but it couldn't be that cause I just replaced it a couple months ago. So I went through checking all the contacts and did continuity tests on the related wires. So as a last resort I checked the opposing contacts on the sensor for the same resistance and sure enough one side was open. I put my old one back in last night and cleared all the faults. And today, no fault codes 3,28,29. So yes, it was a temperature issue. I still have an intermittent low idle issue probably within fault code 11 someplace, but I've had that minor problem awhile. But knock on wood, the hot start problem is over. gee, I'm within fault code 11 of engine perfection. that's a sweet thought. Moral of this story "if you're going to work on your car you have to get the diagnostic reader that is needed for your car." Otherwise you'll just drive yourself nutz. Guess work sucks!

 

Ahoy, Brookings,

Please advise info on a source and model of a code reader which will work on my '90 300SL, plus a source for code definitions.

I do have the Star Classic Service Manual Library Model 129 which I bought directly from our local MBZ dealer. It is NOT easy to make headway / use.

Thanks /s/ Bob