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Intermittent no start/electrical

chameleo78

NAXJA Forum User
So a couple weeks ago my Cherokee (94/4.0/AW4) wouldn't start. It was very cold and the fuel that was in the tank was several months old so I chalked it up to condensation. I did think to check for fuel pressure and I had none. Since then I've gotten it to start by fiddling with the key but what I know is that I am not getting good power to the fuel pump. It will not always prime until I fiddle with the key and or gas pedal. I've read the "No start" write-up and am looking for some additional info on where the ballast resistor is; maybe a picture. Also where the fuel pump relay is located. Today I was going to check on some voltages and couldn't find the resistor so... However I was sitting in the Jeep and had left the key in the on position and after a few minutes I heard the pump prime. I thought it was weird that it primed all of a sudden. The only other symptom I can think of is that when the pump primes the first time it sounds rough; like it's clicking. If I turn the key off and then back on it will sound normal when it primes from then on; until the next time it doesn't prime immediately and needs played with. Once it starts it seems to run fine. I'm open to suggestions on what the problem might be and would love to have some more info on the items I mentioned above.
 
When you turn the key to the ON position, the fuel pump by design should energize and run for approx 2 seconds, then turn off. It will turn back on again when the computer receives the proper input signals and asks for fuel.

I would first try swapping out the fuel pump relay. Should be in the PDC (power distribution center under the hood). You can swap it with another relay in that box, as they are of the same part number.

I think the last year for ballast resistors was 93, so you most likely do not have one.

If you don't stumble onto this, you may have either an intermittent wiring or connection problem at the pump or the pump is about to give it up......If it is an old pump, you may want to consider a new one. They aren't too expensive. Stay away from Airtex pumps.
 
I always thought 93 was the last year of the ballast resistor, however, my 95 FSM states 94 was the last year.
 
^^ as did I and confirmed with my latest project:

'94 with early '94 build date-- she's "resistorless" and still uses the valve cover gasket from a '93 (2.5L in this case)
 
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Thanks for the help guys. I swapped relays and got the same results. I guess I need to jump power straight to the pump to see how it reacts then. If it runs good then I need to track down my power leak and if it runs the same then I guess it is time for a new pump. Sound right? Any other suggestions?
 
So I know I said I was going to power the pump directly but I haven't had the time to check that out. What I have found is that if I leave the key in the on position for about a minute the pump will run with the clicking sound and then will run normal if I turn the key off and then on again. Is there anything in the electronics that would cause the delay I am experiencing? I know, I know I need to put the tester on some things and start eliminating what might be the problem so I can determine what the problem actually is. Was just hoping for some more insight. Thanks.
 
Could it be an ignition switch problem? You could check for the correct voltages from the switch.

Or perhaps wiring/grounding contacts for the pump?

The fact that you were sitting for a several minutes with the key in the "on" position and then suddenly heard the prime sounds suspiciously like a contact issue with the switch to me.
 
i was having a somewhat similar problem. For my jeep (99xj) to startup id need to "prime" it by leaving the key on for a bit and then cranking it.

After checking all the fuel stuff out and determining i had no leak back or other fuel pump problems I traced it to a crappy main ground. The end was fairly corroded and after removing the wire i found the whole thing was covered in a powdery corrosion.

This wound up fixing my "fuel" problem along with some others I was having (random starter clicking, voltage gauge showing 17+V, random light flicker etc).

The main ground is really short running from the battery to right under the coil, I also went from the negative terminal to the fender. Took no time to do and made everything so much better.

Not saying its definitely a fix for your problem, but figured I'd toss it up in case you feel like checking it out. As a sidenote I ohmed out the corroded ground wire and it showed almost no resistance, once you tried to pass power thru the wire however the voltage loss was huge.
 
i was having a somewhat similar problem. For my jeep (99xj) to startup id need to "prime" it by leaving the key on for a bit and then cranking it.

After checking all the fuel stuff out and determining i had no leak back or other fuel pump problems I traced it to a crappy main ground. The end was fairly corroded and after removing the wire i found the whole thing was covered in a powdery corrosion.

This wound up fixing my "fuel" problem along with some others I was having (random starter clicking, voltage gauge showing 17+V, random light flicker etc).

The main ground is really short running from the battery to right under the coil, I also went from the negative terminal to the fender. Took no time to do and made everything so much better.

Not saying its definitely a fix for your problem, but figured I'd toss it up in case you feel like checking it out. As a sidenote I ohmed out the corroded ground wire and it showed almost no resistance, once you tried to pass power thru the wire however the voltage loss was huge.


x2 check your grounds. Check for loose nuts /shot wires etc. Give the grounds under the coil a good wiggle and check them for dirt /corrosion.
 
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