Car difficult to start after a long run

[7783911]

i ve recently noticed that my 83 sc sometimes hesitates to start after a long run. Engine temp around 200 so not excessive. It takes some cranking (3 seconds) and stumbles so a bit of gas and then in 20 seconds the idle smooths out fine. If i dont give a bit og gas it will likely stall

any ideas?

[walt]

Are we talking immediately after a long run or some time between? This might help narrow the causes down.

[JonT]

isn't this symptomatic of bad starter solenoid? others will chime in

[7783911]

usually after it sits for 30 minutes after a long run and its warmed up. If its the next day, starts with no issues. I havnt noticed if it also occurs immediately, i will have to take for a long run, get it hot and then turn off and try to start, then report back on this thread

PS idle is good once started

[walt]

Probably need to run a fuel pressure decay test, sounds like an accumulator or check valve issue to name a few. Hopefully you have a set or can borrow a test gauge.

[garment]

I had a similar issue. It’s likely that your fuel is boiling in the lines when you shut down after a long run, and therefore creating a hard start issue. Do you have the trombone cooler or have you upgraded to a Carrera cooler? I had the fan on my Carrera cooler kick in at 180 degrees on my adjustable temp sensor, and that seems to have solved it. Fuel formulations are different from 38 years ago, and if you’ve not redone the engine yet, the bearing and ring tolerances are much higher than when the car left the factory, so I bet you’re burning a bunch of oil, leading to higher engine temps.

[7783911]

I have upgraded from the trombone to a carrera cooler and do have a fan which I usually only turn on when it hits 200 degrees, and it rarely goes above that temp unless stop and go in 90 degree weather but the fan quickly reduces that The engine had a full top end done and I have no leaks after 2 years. so..back to square one. I may phone my local porsche shop and see what they think too but with all the experience on this forum..i have faith someone has a good idea what it is. At least the car does start, albeit with a little coaxing and it runs fine once its over the initial stumble

[fanaudical]

Originally Posted by walt

Probably need to run a fuel pressure decay test, sounds like an accumulator or check valve issue to name a few. Hopefully you have a set or can borrow a test gauge.

^^^Start here.

[boyt911sc]

Check your residual fuel pressure. There should be at least 1 bar (14.5 psi.) after 20 mins. from turning off the motor or fuel pump.

Tony