no13

after the temp warms up, it works.

Here's a real head scratcher.

I live in Utah. With the weather starting to get colder, I'm back to the problem I first experienced last fall (1 year ago)

I have a 1991 cherokee sport. It's the 4.0 w/manual trans.

If it's cold, I can go out and turn the key to the on position and normally, in warm weather, you'll hear the pump prime. When it has gotten colder, you won't hear this.

When cold, during cranking, nothing happens. You can't even hear the pump going. After a moment, you'll start to hear the pump going intermittently while cranking but it still will not prime when turning off the key then back to on. 5 minutes could go by, then you can turn it to the on position and the pump will prime.

At this point, the engine will almost start. A few tries and it does start but runs rough, pops, etc... until some mystical event happens and it begins running smoothly.

This is a well maintained vehicle. Distributor, plugs, wires are new.

The starter relays are new

The pump is new (I replaced it last year thinking that would be the problem, but same results.

Connections are all good.

After taking it to a repair shop to have them look at it, 3 days later, still same issue. Evidently they can't listen to my description because I said it has to be COLD. Not sitting in their shop overnight. Idiots. All computer codes come back normal, it runs fine, never skips, doesn't die... nothing.

This morning, after reading a bit, I decided to just go out and try wiggling the relays, wires, whatever. I pulled the relays, reseated them and waited.

With the key on & the hood up, nothing happens still. Then, for the first time, I start hearing a faint clicking noise. It's coming from the fuse / relay area. I notice it starting to get louder... then it stopped... and the PUMP PRIMED.

What is my problem? I don't get it. This shouldn't be so hard.

Thanks for looking, if this post sucks just delete it.

Kelly Wood
"Real off-roaders don't have shiny wheels"

mwdouglas

sounds like a bad relay to me its over heating and isnt functioning if you know what relay was making the noise replace it and let us know if that fixes the issue

no13

I know which one it was, it was the fuel pump relay. But it's not when it's overheating. It's just when cold.

I've tried replacing them and it gives the same results.

I'm goin to a junkyard today to see if I can find a computer for the heck of it.

pump is new, wiring is good, connections good, relays good, works fine when warm, no priming when cold...

mwdouglas

im stumped then if you replaced the relay and it still does it i think you got a good idea with getting a spare ecu and trying that

no13

More to the story now that winter is here and it's cold...

On a whim... knowing this thing starts when warm, I thought that I'd take an electric space heater outside one morning. It's super cold and the jeep will crank over, but there's no sound from the pump.

I put the heater on top of the ECU face down, lower the hood and go back inside to get ready for work. About 20 minutes and I"m ready for work... and guess what... it starts.

Computer?

I think I"ll punt and just buy a new computer and see what happens.

98jeepsrt6

Hello, im would suggest maybe the battery.. On my older cars with smaller batteries i have the problem with cold starts and i live in Miami,Fl.. Once i upgraded the battery i didnt have the problem as much..

I say this because theres water inside your battery and im sure in Utah its ****ing cold compared to here, so it may be freezing up.. How are your interior lights and such when you turn the key to on position?
This will give you a good indication if you have good battery strenght. If your lights seem dim then theres your culprit.

no13

Battery is great, lights are all full, everything works fine when cold.

daurwid

Replace the ECU relay in the relay block under the hood and any fuses that run to the fuel pump/ignition. Just because they look good and you've "re-seated" them does not mean they are good.

I have 1991 Jeep Cherokee Limited. I just had to do this on mine. Replaced a 40AMP fuse and the ECU relay and a couple small 20AMP relays in regards to the ignition system and so far have not had the same problem.

Wiring to the pump could be bad and after power has "heated" the wiring up it will work properly.

cwill

I have a 1994 cherokee that has the exact problem. I live in East TN.here the weather has been very cold lately.I can't hear the pump running either. The first time this happened I sprayed starting fluid into the engine and it started but ran very eratic like there was a firing issue. Then when I worked the throttle trying to keep it running it would suddenly rev up perfectly and then sputter again, finaly it leveled out .
The next time I turned the key on for a couple of minutes before trying to start it, I did this a couple of times and it finally started. It had a new crank sensor installed recently.
Did you ever find a solution for your problem? I was hoping to share some of the info. if you had any luck.

Charlie

thorguy57

What part of Utah? I live around tooele.

no13

Salt Lake. I get out to the Tooele valley often however, we race Go Karts at Millers.

no13

I replied to your PM, but for anyone here looking, here's what I found.

As I stated in a prior message:

On a whim... knowing this thing starts when warm, I thought that I'd take an electric space heater outside one morning. It's super cold and the jeep will crank over, but there's no sound from the pump.

I put the heater on top of the ECU face down, lower the hood and go back inside to get ready for work. About 20 minutes and I"m ready for work... and guess what... it starts.

Put a heater next to, or on top of your computer. Wait about 10 min. If the pump starts working, get a new computer.

ezab

Try checking the wires at the Ballast Resistor.

no13

What's that look like?

no13

Just a little update for anyone wanting to know.

I was right. I finally went to a junkyard after calling THE dealer.

From the horses mouth. For the 1991 Jeep Cherokee with the 4.0 and manual trans, there were three computers used. No other computer will work. They are: Canadian Emissions, California Emissions and Federal. Mine's federal and I found a 1991 with 4.0 & manual, pulled the computer and in the parking lot, plugged it into my baby. Still frozen cold from sitting in the donor for half the winter... It worked first try and continues to do so.

A 50 dollar job and a whole 5 minutes.

Later!