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92' Cherokee with a hangover? No fuel pump unless its sunny....

It's a little nippier than usual (I live on top of a mountain) so it took a little longer to get warmed up, but it started.

When I clicked on the key, no fuel pump or check engine light at first, then slowly (as I turned the key multiple times) I could hear, barely at first, a low purring noise coming from around the direction of the relay box/pdc thing. At the same time, I left the key on, the check engine dummylight in the dash started to fade in & out, and the 'purring' sound got louder, the fuel pump and check engine light, woke up at the same time. Primed the pump by turning the key few more times and it started up.

WHATEVER this is, the check engine light in the dash and the fuel pump are related as these are the only things that don't work when the cherokee is cold. Does the check engine thing have some type of sensor somewhere and could this be the problem that doesn't allow the fuel pump to engage? I don't know I am not a mechanic.....also, again, there is no fuel at the schrader valve at the rail while this is going on.
Where is the temp sensor? Is it on that side of the motor? THANX in advance for all the suggestions.... :)
 
A common hair drier is great to PRE-HEAT one area at a time when tracking temp problems.
Warm up an area like say PDC or (?) and test - if trouble pops up, (or goes away), faster you are getting close!
 
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Ok, lets take a breath, have a cold beer, and contemplate things for a minute.

Ok, I feel better now.

Key, lock cylinder, remote rod, ignition switch.

I suggest you check the ignition switch/remote rod. The ignition switch is mounted on the steering column. They wear, they shake loose, and when you turn the key the remote rod can't act on the switch for it to make proper connections, and the connector likes to melt too.

Ignition switch:
getimage.php

Note the slotted mounting holes for switch adjustment.

So, I recommend you make sure the switch is in good condition and adjusted properly.

Do that, post up results.
 
I have had a similar issue with a 96 Caravan and a 94 ZJ. Ended up replacing the PCM and all was well. For whatever reason the PCM wasn't sending a signal to run the fuel pump when the key was turned. I could pressure up the rail by jumping the pins, but still no start. Swapped in the new (salvage) PCM and it fired right up. Worked for both vehicles. You probably have a corroded connection in the PCM that happens to be at that location and overnight it builds moisture and shorts the connection. Once the sun dries out the moisture the short goes away.
 
Wow, this thread sounds all too familiar. Your on the right track with the hair dryer idea. I used a industrial paint remover after gutting my wiring harness looking for loose grounds. (Remember that every wire has two ends). I'd cut the shrink warped ground connections out, re soldier and shrink wrap back together, ect. Pretend you own a renix, and just go threw every wire coming and going out of those two relays, pull your pdc, get a cold twelve pack, take notes. (light tester, jumper wires, multimeter)

This is what I pretty much had to do on all my weekends and spare time and i just got to a satisfiable conclusion this morning, happened to be digging around and saw this post. still don't know for sure if mine is totally fixed but it sure fired up in a convincing way.

I would rule out the computer as culprit seeing how it magically fixes itself every morning. I completely scrubbed and bathed my ignition switch in dielectric grease, and had no luck. I have noticed that unplugging and re connecting my cam position sensor would help some times to jolt something back to life but ultimately found that the problem lies in the wiring. (Although some would argue that its on the top left corner of the sticker on the drivers side fire wall). Best of luck.
 
UPDATE It rained last night and has been nippy here and mostly shady. I don't have a blow dryer but I do have a contractor heat gun. So, after heating up different things(the relay box, the computer thing, wiring etc) I've narrowed it down to the can thing in the back, at the left/passenger side of the motor. I had my bf push it back so it's in total shade. When I heat up the area at the top of the canister, while leaving the key on, after about a minute or so, the relays start clicking and then the fuel pump kicks on. I've done this over a half dozen times to make sure, letting it cool down each time. what does the canister have to do with any of this? is there some sort of sensor in it? :)
 
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Ok, the evap canister..... can this thing be cleaned or do I need to get another one? I've hit this thing close to 20 times now with the heat gun, key left in the on position, and the clicking starts and fuel pump starts buzzing after about a minute or so. I let it cool down every time in between.
 
Note: keep temps controlled by distance and direction of hot air flow. Do NOT go hotter than -"you can hold your hand on the part(s) more than 10 seconds". Watch out for adjecent parts.

Try Gently massaging the harness nearest and any connections nearby. (May not be the actual canister itself!)
Disconnnect and reconnect connectors in area.

Wrap approx 5 x 8 inch piece of cardboard with a layer or two of aluminum foil. This is a insulating tool used to shield,
**Cut, bend, replace,size, etc. to fit as needed.**
Shield off canister from other nearby anythings and heat cycle. Note effect. Try another angle/shielding as needed to isolate. The time delay, to see effect, is time to travel inside to the problem thru insulation, plastic or ? and is a good clue.
Need to isolate the problem as much as possiable.

There are wire splices INSIDE the harnessing that are iffy at times on some XJ's + plain old age of wiring = sometimes not so good connections. (Rare but it happens.)
-----------------

I have No info on that year XJ so hoping some others join in on this.

Regards-
 
It's a '92 cherokee/laredo straight 6 HO automatic. Power windows, locks, cruise etc,188K, no other issues with it other than this and the cig lighter that won't work. I am aiming the heat gun right around the canister, and leaving the key on at the same time after warming that part up for a few minutes the clicking starts up slowly at first then the fuel pump buzzes. While heating up the canister thing, I move the two connectors from the harness away from there.
 
Heat goes UP. Whats ABOVE test area, OR downwind?
ANY wiring is suspect.

Shield off areas from heat to locate.

Gently pull, push on harnesses, may be a rubbed thru insulation or broken wire in harness. (Large harness bundle running across at top of firewall is suspect too!)

Connectors may have a broken wire as it enters crimped connector pin.
--------
Maintain battery volts at rest and starting. XJ's do not like low voltage in the electronics.

Regards-
 
My 92 is still having issues as well. as soon as I think I've narrowed it down to one thing, it fires up all day long and into the night, but no matter what i do it has yet to work in the morning. I re soldiered half a dozen wire connections inside the harness itself, traced as many wires as I could find to as many connections or splices I could shake a meter at and still no luck.
I agree however that its probably not the canister, but the connections around it, but again nothing has been consistent with mine other than the pain in the a**. I've been trying the heat gun on several different theories and leads but still nothing has been consistent. Soo my plan is to just keep cleaning, checking, cutting, soldiering, tracing, shrinking, and grounding as many connections as possible.
I would have to say that it is definatly something under the hood and not the dash, and most likely a connection and not a individual part. (please keep in mind I'm assuming here) My FSM is on a boat some where in the pacific so if any one else happens to have some 92 lyrics on hand to any wiring songs they might wanna share, I'd sure love to hear any advice as well on this.....
 
Well, while I have been wrong way more times than I care to admit, it sure sounds to me like a wiring connection is getting warmed up in that general area and closing an open circuit.
 
-

***Be extra careful with aluminum foil around open terminals like the battery and starter.***

***** FOIL IS NOT NEEDED FOR THIS TYPE WORK*****

-----------------------------------------------------------------
---Plain cardboard will work fine for this range of temperatures. (Foil is NOT needed until much higher temps)

Regards
 
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