Hot Start Problems

[kenzinger]

Hi all,

Just picked up my first Porsche, a 1983 911SC. Thanks to those of you that helped me make the decision! So far, it appears to be in great condition except for a hot start issue that it looks like the previous owner(s) have been chasing. I understand that it is usually the fuel accumulator or the check valve in the fuel pump that causes the issue but both the accumulator and the fuel pump have been replaced within the last three years.

I'm planning to get a fuel pressure gauge to start troubleshooting but want to get some input. I'm thinking it might either be bad fuel injectors or cracked vacuum lines.

Any thoughts on other potential causes? Troubleshooting methods? Can the injectors and/or CIS vacuum lines be replaced without dropping the engine?

Thanks!

[Bob Kontak]

Until you find the warm start culprit pull the air filter cover off and remove the air filter. With key in the run position - lift up on the air sensor arm to allow the fuel pump to pressurize the system. Then start it. If you have a leaking whatever your rest pressure is probably zero PSI after not much time at all. You are dead in the water. This may get you running.

Get a decent set of gauges specifically built for CIS. You can watch your rest/residual pressure drop like a stone, I betcha.

Yes, a leaking injector can dribble off rest pressure. Pull them out one at a time attached to the line. Learn how to use the search function being new here to see best how to lift them out.

Lift the sensor plate with key on to build pressure for a second or two and see if the injector leaks after releasing the arm. Best to do this on a cold engine as the injector will spray.

I doubt vacuum lines will kill your engine dead. You probably have a few leaks (you are not alone) but unless huge it should not be an issue.

Absolutely no engine removal.

[ClickClickBoom]

Tuning CIS without a CO gas tester is rough. I used s Gunson that I got off eBay and my 2.7 ran like a top fueler hot and cold, from sea level to 8000ft. Lots of CIS primers out there find and read until your eyes bleed.