924Board.org

[steve]

ok i've done everything i can think of to my 1977 924na to solve the hot start problem. i have replaced the fuel pump, fuel accumulators, cold start valve, warm up regulator, and have wired in the doorbell thing that is in the tech section. but the car still won't start right up i have to turn the key for a good 30-45sec before it will start then i have to rev the engine to keep it from dieing. after i get it running it drives ok but the idle is rough. its like a pulse. it'll idle great for 20sec then stutter then idle great for another 20sec then stutter on on on it goes. any ideas would be of great help.

Thanks
steve

[Diesel]

Make sure all of your injection lines do not touch the head. It will heat the fuel inside the line and cause vapor lock. My $.02 worth.

[dpw928]

Steve,

Noticed you haven't replaced/checked the thermotime switch. If it is bad, it can cause the cold start injector and warmup regulator supply too much fuel on warm/hot starts. Since it is at the back of the head and very difficult to reach, simply unplug the bosch type connector. If it starts without continuous cranking the problem is the switch. Good luck.

Dennis

[red78]

dunno much about porsches..but my car has that trouble sometimes..usually when the vaccum advance comes unhooked..or the points have gotten a little to warm...check over the distributor and some vaccum lines..those are notorious problems with k-jet on my car..though i have a carburator

[Roger Hall]

Red78 may be right. I had similar problems with the hicup (and other problems Im still chasing). I visually checked the vacum lines they looked ok. After trying everything you did plus new injectors, fuel filter, air filter, coil, plugs I pulled off the vacum lines and they were trash. I could not see the cracks because the lines are covered in a material. I replaced them and the hicup seems to be gone and the car idles much better (still chasing some other problems though). Also check the rubber boots they may be cracked.

It could also be the injectors. They may leak causing hot start problems. They pull out with a pair of pliers and are real simple to check. Pull hem out one by one put them in a plastic coke bottle and crank the car over check spray pattern. After you stop cranking the injector should close and not leak. A leak will drain the fuel line and cause starting problems (check the Haynes manual for the correct procedure).

You can check the thermo time switch at the connector to the cold start switch just disconect the wires and put a voltmeter on them. When you begin to crank the car the voltage should drop to zero in 3 to 10 seconds (also chek the manual on this one).

I also read that adding a check valve to the fuel pump prevent fuel from draining back into the tank and solve some starting problems.

Let me know what happens

[Joes924]

I had a rusty gas tank that kept me out of the running for a while I was replacing injectors and went through 2 fuel distibutors untill i was told it was probably the tank I took it out and bought a reseal kit 2 of them used for motorcylcles