start up my 911

[bunks911]

I just recently took my 83 911sc on a road trip out to Las Vegas, from SD and it started to give me really rough starts. Upon start up, the engine does not crank up right away and when it finally does after a few tries, it idles really weak and sometimes it shuts down and it seems really rough until I press the gas, at which point it seems to idle at normal RPM. Does anyone know of what this might be?

[Steve Grosekemper]

If you are having these problems on hot start after the car sits 5-40 minutes you are loosing residual fuel presure. This usually happens when the fuel pump check valve fails. A new check valve can be installed with out replacing the entire fuel pump.

What is happening is that the fuel in the injector lines is boiling when hot and the poor running occurs while the engine slowly purges the air out of the lines.

There could be other items causing the fuel presure loss but the fuel pump check valve is the most common failure.