random fuel pump problems on startup

[rburns6462]

I have a 1996 ls400. Two weeks ago after driving the car for about 1/2 hour and letting it sit for about 2 hours, the car sputtered a bit on startup and then would not start. The engine turned over, but not getting fuel. Tried to start it two hours later. It then started no problem and ran fine for about 1 week. Same problem then occured in a parking lot, but it started five minutes later. I replaced the fuel pump relay, but 4 days later, same problem. I then had the car towed to the mechanic, but they couldn't check it for about 4 hours. The car then turned over fine, so they couldn't diagnose it. Any ideas?

 

[BigKriss]

This is an old problems on the Alfa Romeos as well. New fuel pump I'm afraid.

 

[gloverman]

Have you tried the FP pump bypass to see if it fires up?

 

[rburns6462]

Thank you for your response. Have not tried the fp bypass. How do you do that? I have however replaced the FP relay switch and had the same problem 4 days later. Tthe start up problem seems to be random. Today car is running like nothing is wrong. No problems so far when the car has completely cooled down, I don't know if that is related or not.

 

[gloverman]

under the bonnet in the diagnostic box you use a jump wire to bridge the FP and B+ terminals. This will deliver 12Volts directly to the fuel pump. Cheers

 

[BigKriss]

Thank you for your response. Have not tried the fp bypass. How do you do that? I have however replaced the FP relay switch and had the same problem 4 days later. Tthe start up problem seems to be random. Today car is running like nothing is wrong. No problems so far when the car has completely cooled down, I don't know if that is related or not.

It definitely is related. While all is cool , no probs.. Soon as you have heat soak, the outside temps are scorching etc, problems.
Save your self a lot of hassle and also the annoyance of breaking down away from home/garage and replace it. Been there, done that.

I at one stage, fitted a Porsche aux. cooling fan to blow across the fuel rail and injectors in my persuet of the problem. How about a bottle of water and regularly stopping to wet a rag that I had tied around the fuel pump.

Put in a new, save yourself endless drama.