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fuel pump woes

aarong

NAXJA Forum User
Location
Robie Creek, ID
I did a search and couldn't find an answer. I have a 89 XJ 4.0, I have been trying to nail down this intermittent starting problem that I have. It starts, runs until you release the key, then dies. Occasionally it will continue to run. I was doing some trouble shooting today on it. One thing I noticed is that the fuel pump will buzz sometimes when I turn the key to the on position, sometimes there is no buzz. I know that the fuel pump runs for a few seconds when turning the key on, if the engine doesn't start the pump shuts off.

My question is: should the pump engergize (buzz) with every attempt to start?? Or does the computer sense that there is enough fuel pressure and doesn't trigger the pump to energize occasionally??

I don't remember if I heard the pump energizing everytime that I turned the key to the on position before my start/stall condition appeared.

I also checked the voltage at the pump connector, when cranking the engine I was getting 0.40 volts, once the engine caught I was reading 12 volts at the pump. I have tried swapping out the relays but that doesn't seem to help. I also recently replaced the IAC and the problem persists.
 
bad ignition switch (electric part on the steering column) or bad ballast resistor on the fender well (white ceramic brick w/ a wire in and a wire out)

either of these can give you a start, but not run condition. If the switch were bad, you could be making contact in the start position, but not the run. If the ballast were bad, you would have power to the fuel pump when cranking (it's bypassed whencranking) and none when running.
 
Shorty, thanks for the reply, I swapped out the ballast resistor today and still no start. I actually thought about the switch when I was out for a mtn bike ride tonight. I will shoot some contact cleaner into the switch and maybe that will do the trick. Again, thanks for the reply
 
just disconnect the battery first-- you don't want to short anything out and create new problems! Don't overlook adjusting or replacing the switch either- they can go bad over time.
 
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