dirt5track

Can anyone tel me if the fuel pump should come on a for a few seconds when I turn on the key before I start to crank it over. I have a 1992 xj 4.0 aw4. I am having an issue with the fuel pump not getting power in the mornings. I have replaced all the relays including the auto shut down and the problem is still here. Good for a day then bad for a day, literally every other day it won't start. I cobalt put it in the shop and was told the fuel pump won't get power till the cps sees the motor turn over. I seem to remember that the pump would prime the system when the key was turned but the shop says that is wrong.
Any response would be appreciated.
Thanks

Byro

It should kick on with "key on" to prime the system for a few seconds then kick off until you crank it over.

tjwalker

Yes, by design.....turn the key to the on position and fuel pump should energize and run for approximately 2 seconds. Then turn off and not come back on until the engine is cranking over and is getting input from crankshaft position sensor, etc.

notop46

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I read between the lines and removed some extra characters to shorten your initial problem statement^. You need a new shop!! You already know more than those fools.

The fuel pump will run while the key is in the on position for 2 seconds without RPM signal (CPS). This allows it to build pressure prior to start. If you stall the engine, it will run for 2 seconds after RPM ->0. This stops the pump in case you have a crash to prevent a gasoline fed fire in the engine bay or to prevent hydro-locking the engine if you have a leaky injector.

dirt5track

Thanks for the replys. I thought I was right. I have found the problem. The computer has gone bad and is not sending power to the auto shutdown system.

Coach

my fuel pump runs all the time, never shuts off, I wonder why? Coach

Slick761

What year? I've seen that with a bad starter relay.

Coach

It's a '91 and I actually have the fuel pump relay jumpered, I have an issue inside the fuse block where the relay won't work.