paalw

928 S4 '89 Auto

Ok, i now have a very irritating problem. As the topic says.

If i run the engine for more than 5-15 minutes and the shut it down, it will not start again(in most cases). The first time I crank it after i shut down, there is a little life like it might start(maybe 1/2 sec) then it goes back to just cranking. And every time after this it just cranks. If i come back 6-7 hours later it fires right up.

anyone have a tip where to start? i have searched the forum, but can not find a totally similar case, where it will not start right after shutdown. Battery is almost new and charged.

i have tried pressing the pedal to the metal, and halfway and everything. does not want to fire.

Lizard928

year would be very helpful.

though I would guess it you held the pedal down and got nothing then it is most likely that you are not getting enough fuel.

My first step would be to measure the resistances of the Temp II sensor and verify that it is correct.

Also try turning the key on wait 6 sec, turn off and repeat about 15 times. this will hopefully purge any air that may be trapped somewhere.

paalw

thanks. added.

it sure smells a lot fuel when i leave the car after cranking it for 4 minutes. but i will try the repeat trick next time.

Lizard928

if it smells rich of fuel, then what I would do is crank it over (about a half a turn) and then put my foot to the floor. This puts it to flood clear threshold. in other words cuts all fuel and continues to pump until it can fully ignite what it has.
Although this does sound like you may have a leaky injector or two.
It would be a good idea to hook up a fuel pressure guage and moniter the fuel pressure after shut down to confirm/expel leaking injectors.

Mrmerlin

pull the vacuum lines off of the FPR (fuel pressure regulator)and fuel dampers look for leaking fuel do this when the engines warm also test to see if they hold vacuum

RngTrtl

sounds like it is never coming out of cold start mode (i.e. more fuel in for cold starting). I say plus 1 for the temp II sensor. an AFR gauge and a FP gauge would be great here to see if you are flooding after you turn the motor off, or if you are indeed running rich after the motor warms up and as soon as you crank it up again the motor thinks it is still cold and dumps extra fuel in that floods it.

paalw

will test

nop. when this "program" starts to run, engine is not running smooth either, and fuel consumption is higher than cold mode. so i have already excluded that.

asnowsquall

Not sure if this car has a reference and speed sensor for motronics control (DME) , but my 86 BMW 535i had the same problem and it was only in the summer time. When the car got up to operating temp and you shut it off to go in shopping or something, then come back outside and it wouldn't start. Its one thing when it does it to the wife, but the mother inlaw too...
Well it did it in my driveway, and the Bently manual said to ohm out the sensors and sure enough one was bad. I replaced them both and that was the problem. I had changed the flywheel and had to pull those sensors out and I cleaned them off so its possbile just messing with them hurt them. Good luck.

John Speake

Hello Paawl
How are you getting on with this problem ?

How long does the car have to run before you get a no restart situtation ? If not very long, what is water temp at this point ?