Sam928

John,

You're right. A failing fuel pump relay could be the problem. Unfortunately, mine is almost new. After my car died in the middle of the night on country road with no cell phone service I replaced all of the engine-critical relays and bought some spares to keep in the glove box.

Sam

dprantl

No problem starting when cold vs. not wanting to start when hot is usually the engine running too lean when hot. An easy way to get it started is with a shot of starter fluid into the air filter.

Dan
'91 928GT S/C 475hp/460lb.ft

Stephencs601

Have the same problem currently. I was not hearing the fuel pump when I turned the key. I jumped the fuel relay and heard the pump. Replaced relay and pump is running again. I believe that may have fixed my problem. Will see the next time I hot start it over the weekend

jpitman2

You should NOT hear the pump with ignition on alone - it must be cranking for the relay to pull the pump in. SOME cars run the pump for 5-10 secs at turn on, but NOT 928s. Usually hot start failures are related to vapour locks (check valve issue) or similar, or less frequently, electrical issues that are heat related. I think more common with CIS cars also - I have had a couple of them.
jp 83 Euro S AT 52k

dprantl

It is very very easy to jumper the fuel pump to at least hear whether it works or not. You should pull the fuel pump relay and jumper pins 30 and 87 with a jumper wire, then listen for the pump. If you hear it, try and start the car with the wire in place. If it starts, you found your problem.

Dan
'91 928GT S/C 475hp/460lb.ft

SimonC

I had the same problem on my 1980 S. After spending lots on new injectors and pressure tests, it turned out to be the fuel mixture plate. It was far too high, causing big mixture problems.

Exactly the same symptoms. No hot start, but a 10 minute wait would get it going.

I wish I had started with that and saved myself $1500.
I also learned that its worth buying my own pressure testing kit. They are not expensive and I have overcome my initial fear of working with petrol injectors.

BTW - the recommended book is now unavailable. Have been waiting for Amazon to source it, but they gave up. Would welcome a scan, if anybody has one.

Have attached the Bosch troubleshoot for k-jetronic from the manual. Happy hunting.

SimonC

Range Rover

My GTS had a similar problem and it turned out to be a sensor in the fuel pump.

The relay for the fuel pump may also be getting a poor connection.