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View Full Version : Delay in fuel pump/check engine light. Electrical grimlens? Need help!


Intellect
November 21st, 2017, 07:09
1995 cherokee 4.0 i6 4wd. Tittle says it all. Usually only when cold starting.. ill turn the key to acc (you expect mr pump to whuuuuur) but nope. Sometimes it takes 20 seconds to 3 minutes. Sometimes itll whuuur right away.

Side note, was just chasing bleed off issues so i KNOW the pumps good. 110%. Good. Bosch and good.

I know it is an electrical issue because know how the check engine light comes on when you turn the key to acc? Well... Whenever the fuel pump DOESNT whuuuuur, the check engine light DOESNT come on either. They are both delayed. They will come on at the same time... Wether its a 25 second delay or 5 minute delay. Sure enough, whenever the whuuur finally happens, than i see mr check engine illuminate.

Odd part, when the delay happens, the radio, headlights, abs light, ebrake light, all work fine....

I have a seperate forum open that i was informed my above issue is the ignition switch, so i tried a new ignition switch. Identical problem... So im back here

(Abs light is on cause i clipped the lines when i got rid of my turdy 35, and brake light is on cause ebrake is up, ebrake also does nothing when i swapped axles i deleted it)


Side note, anyone ever hot wired a switch to the pump? Imagine its a terrible idea.

No ballest resistor.. 1995 return style...

New fuel pressure reg, pump, injectors, filter, etc. Bosch and name brands. Warrantied multiple parts multiple times to eliminate them from possibilities. (During my bleed off issue, which is FIXED)

Back to topic at hand... I researched it for hours. Here and other forums. No direct answers. Ecm,pcm,ignition switch etc are some of the things i was told could be it. I can use a multimeter if someone can help me. It sucks cause its an intermittent issue, USUALLY when cold. (Hasnt ran within 3 hours seems to be the cap off).

MAP/IAC/TPS/ GOOD GOOD GOOD. 125% GOOD. (Replaced, tested, multimetered, GOOD)

Cps.. 85% its good, only multimetered/tested. Via bleepin jeeps tutorial.

Also , ONLY WHEN COLD usually. Florida.."cold"... If its been running i can usually recrank within an hour - three no issues...


Let me paint a picture.

(Fuel gauge hooked to rail and within view)

Get in the jeep, half turn key, no check engine light or fuel pump whuuur.... Wait 20-400 seconds... Finally! Pressure builds some. Half turn it again, 50/50 change of the check engine light/pump instantly working or waiting 20-400 seconds again, lets say it works instantly, pressure builds more and to spec (49psi ish), i go to crank. (Has full pressure), starter works, engines turning, but acts as if no fuel or something because it doesnt want to start. At this point i can forcefully hold the gas down some and cause terrible idling like a car running with no gas/bad plug/ cant even describe it/misfire ish? , For about 2 minutes, than it be fine. Or i can crank it 3-12 times and wait for the one that actually turns over and stays without stalling... I can make a video if need be.

After this though, i can highway it fine.. offroad 6 hours fine... Stop for lunch and gas and brakes just fine, as long as it isnt off TOO long, i can hop in, crank it up like oem, and head off!

1995 4.0 Cherokee 4wd i6

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Intellect
November 21st, 2017, 07:13
50/50 chance***

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Anak
November 21st, 2017, 08:32
I would wonder if this doesn't somehow relate to some of your other electrical fun under the dash. No clue, perzactly how though.

Refreshing ground connections (particularly in the area of the dash/cowl) would probably be my first step. Figure out where they are, take them apart, sand them down and reassemble. See if that makes any difference.

Intellect
November 21st, 2017, 09:28
The pervious problem is completely unrelated. I can go in depth later on how i know why.

I wish i knew what to meter to figure this out. Buddy has a $50 94 ecm i might buy as a gamble? Because what else controls BOTH the fuel pump and check engine light upon start up, besides the ecm?

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lawsoncl
November 22nd, 2017, 15:37
You tried swapping out the ASD relay? That feeds the fuel pump relay and provides power to the injectors.

Patrick S.
November 22nd, 2017, 19:09
Had exactly the same problem you describe. You need to swap your ECU.

Cheers,

Patrick
93 XJ

Intellect
November 22nd, 2017, 21:03
Had exactly the same problem you describe. You need to swap your ECU.

Cheers,

Patrick
93 XJThank you Patrick. I plan to try a part out ecm ($50) and if that works, than go new (if they even sell new ones) or buy remanufactured. Any recommendations of a good source/price?

I love the short and sweet reply too. LITERALLY the same issue? Everyone has had "a similar issue that led to ___" but the symptoms never matched mine 100%.

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Heavyopp
November 22nd, 2017, 21:39
Buddy has a $50 94 ecm i might buy as a gamble?
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Aren't you working on a 95? Why would you think a 94 ECM would be OK -- I know it mattered greatly with my 2000 -- had to find the exact match -- which I did and it was plug and play

Same thing -- $50 shipped from eBay warranty by seller which I didn't need

Why don't you post up your ECM numbers -- maybe someone has an exact match -- that would make it easier for you


I knew I saw one recently -- https://cnj.craigslist.org/pts/d/pcm-from-1995-jeep-cherokee-xj/6382791947.html

My local craigslist -- maybe contact the guy and see if he will ship -- It's an hour drive for me each way -- guess I could go get it if the guy won't ship

lawsoncl
November 23rd, 2017, 00:14
Aren't you working on a 95? Why would you think a 94 ECM would be OK

There are a handful of oem part numbers and you should ideally match the existing one. The different flavors cover things like manual versus automatic and CA versus federal emissions. The 1994 and 1995 ECMs were otherwise identical with the same oem part numbers. I don't see where it can hurt to try a spare if you have one. Worst case it through a code that you don't have the extra O2 sensors or it can't talk to a trans computer.

Search the p/n on ebay if you need one, typically $50-$100, or $224 for a Cardone branded rebuilt (ie a clean up used unit that they might have actually tested).

lawsoncl
November 23rd, 2017, 00:33
Interesting video on fixing bad caps in a YJ PCM. The symptoms described are lack of check engine light and no fuel.
https://www.youtube.com/watch?v=zYJnBobh1PA

(Side note though - don't use silicon caulk that smells like vinegar when it cures as the acid can eat the traces on the board.)

Intellect
November 23rd, 2017, 07:44
Mine says 12 of 94 so figured the ecm is same. https://uploads.tapatalk-cdn.com/20171123/415ca9f5b07a88bb42b7575b93cbe713.jpg

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Heavyopp
November 23rd, 2017, 08:40
Look at that craigslist add I linked -- exact match

certainly worth a try to see if the guy will ship

Patrick S.
November 30th, 2017, 18:20
As other said you need to match the exact number 56026948 in your case. Try junk yard, ebay or similar.