cherokee90

1990 jeep cherokee 4.0, a4, 4x4. the jeep ran about 4 months ago, i went to start it and the fuel pump wont kick on. i checked the fuel rail and nothing... yall have any ideas. is there anything that will just go bad that controls the fuel pump?

dennis461

Battery is dead 50%
Fuel pump is dead 25%
Key switch is dead 20%
PCM is dead 3?
Relay is dead 1%
Chipmunk ate wires 1%

Caish

Start at the fuel pump with a test light, then move to the fuel pump relay on the right inner fender. I think there is a fuse for it too, but I have not had to trouble shoot the fuel pump yet.

Solomon7

Mine did that. Check the Crankshaft Position Sensor about 11 o'clock on the trans bell housing viewed from the front.
If it doesn't work, the pump won't prime. Cheap, easy r and r.

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96 ex USFS rig, BDS 3" SP lift,Aussie locker in rear with ZJ disc brake conversion, 31" KM2s, JKS quicker disconnects, poly everything, Banks header, T&J/Barnett Performance mount block brackets, MORE mounts, Flowmaster 40, ZJ HD fan, Iron Rock Offroad TB and double shear bracket, Ecode 90/100w H4 conversion with harness, CB soon.

"Difficult takes a day, impossible takes a week"

Throttle Jockey

mine did the same thing after sitting for a while. i hit it with starting fluid and it has started fine every since. not sayin this will help but just puttin it out there. make sure the grounds are good. the fuel pump is grounded to the tank/body. if you dont have a good ground from the battery to the body or the engine to the body. (been there too)

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Well, Sometimes you'll have that.

cherokee90

battery is good had a charger hooked up to it. wish this was the problem.
good grounds
all wires good
gonna check relay and fuse next.
and pcm bad??? hows this happen and how offten. do they just self destruct or what?

whats the omh's suppose to be on the cps when you check it?

dennis461

The PCM runs the pump for threee seconds after turning ignition key to ON. PCMs rarely fail, but it happens.

cherokee90

put the pump on a switch? bad idea?

Caish

CPS should be 200 +/-75 Ohms.

JeepCoMJ

check your spark.

if you have spark, but no fuel, then you could have;

bad relay
bad fuel pump


most likely culprit on a '90 is a bad ballast resistor. it's white, made of ceramic, long with an offset bolt holding it to the inner fender wall. either located toward the drivers side of the air box, or farther back, same side, near the firewall.


make a jumper wire using two male spade connectors. bypass the resistor, and goop up the ends with some dialectirc grease. then tape over the ends, and never look back.

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Project 3800
1986 MJ - 3800 camaro powered, 5 speed 4wd
Utility MJ
1987 Comanche 4.0 w/ .030 bore, cam, '01 intake, borla header, 62mmTB. auto, full H.O. '99 conversion, 4" lift, d30/d44, 3.55's, 31x10.50 dayton timberline a/t's

cherokee90

ballast good, already tryed bypassing it still nothing

JeepCoMJ

take two wires attatched to a 12v battery, climb under the jeep, disconnect the fuel pump, connect negative to black, and positive to the other large wire (green, purple, or orange...can't remember lol). if that makes the pump come on, your issue is elsewhere...try replacing the relays near the battery, then start checking the fusible links with a test light.

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Project 3800
1986 MJ - 3800 camaro powered, 5 speed 4wd
Utility MJ
1987 Comanche 4.0 w/ .030 bore, cam, '01 intake, borla header, 62mmTB. auto, full H.O. '99 conversion, 4" lift, d30/d44, 3.55's, 31x10.50 dayton timberline a/t's

cherokee90

fuel pumps bad. i put to wires to it and nothing.... so i pulled it were can i get a cheap one

JeepCoMJ

they're between $80 and $100.


"cheap" and "fuel pump" don't belong together. going "cheap" is a sure way to be replacing it sooner rather than later.

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Project 3800
1986 MJ - 3800 camaro powered, 5 speed 4wd
Utility MJ
1987 Comanche 4.0 w/ .030 bore, cam, '01 intake, borla header, 62mmTB. auto, full H.O. '99 conversion, 4" lift, d30/d44, 3.55's, 31x10.50 dayton timberline a/t's

RebelRed

Did a new pump make the fix? I'm having nearly an identical problem but after 2 new pumps, and trying to make them run by wiring them direct..still not running.
Going to take the latest new one out and bench test it. Been two months dicking with this problem.....grr...