Subject: Hot Starting Problem
Sent: 01/20 2:23 AM
Received: 01/22 6:15 AM
From: Chase Clark, [email protected]
To: [email protected]
CC: dmcnews, [email protected]
In reference to your problem starting your car, I have a Porsche 924 and a DeLorean. Last summer the Porsche had problems starting when hot and I was told it was a sign that the fuel pump was going bad and a vapor lock was being created. Porsche 924s also use a Bosch K-Jetronic Fuel Injection system like in the DeLorean.
In the case of your problem, a Tech Tip from Performance Products Porsche parts catalog may help the investigation:
HARD STARTING WHEN HOT "If your engine cranks for a long time before it fires up when hot, but starts fine when it's cold, you may have a leaking check valve in the fuel pump. In order to start immediately, fuel needs to remain in the fuel lines. A faulty fuel pump check valve will allow the fuel to flow back into the gas tank leaving the air in the fuel lines. When you attempt to start the car, all the fuel lines need to be filled first to build up enough pressure to start injecting. This takes especially long when the engine is hot since the injection system runs leaner when hot. Find out if the fuel pump check valve is the problem by getting someone to clamp the rubber fuel line to stop the flow of fuel on the engine side of the fuel pump right when you turn off the engine. Wait 20 minutes, have your friend remove the clamp and immediately try to start your car. If it starts up right away, it's the check valve and time for a new pump."
The Performance Products catalog (1-800-423-3173) also has a troubleshooting section for the Bosch K-Jetronic and L-Jetronic Fuel Injection systems. I would reprint it for everyone, however, it is copyrighted by the Robert Bosch Corporation.
Well, I hope that helps you in your search for answers.