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HELP 94 CHEROKEE....FUEL PROBLEM


 
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oleshifty
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Joined: 13 Oct 2006

PostPosted: Fri Oct 13, 2006 4:48 pm    Post subject: HELP 94 CHEROKEE....FUEL PROBLEM Reply with quote

ok, my buddy has a 94 cherokee. It was having signs of the common fuel pump going out. Randomly wouldn't crank over. When it did start it would shutter first 20 seconds or so of driving, etc. Finally got to the point, where it was too much of a nuisance. I check the fuel pressure at the rail, there was nothing. Turned key on/off about 20 times, still nothing, next day--tried it, and there was pressure, car started but was stuttering.

I just ripped down the tank, and replaced the pump, put it all back, and the car still wont start. I don't hear the pump working, no pressure in the line, etc. I disconnected line going into pump, and I don't see anything going on there.


I tried the fuel pump relay, and the top prong hole has constant power, and the left prong SOMETIMES has power (when keys on). There was some goofy ghetto rig relay thrown in their, but I'm not sure what prong the wire went to (other wires are ran to other relays on the fuse block). BUT the car has started with this after market relay disconnected.

Is this a common problem with these jeeps? Is there anything im missing? Any help would be much appreciated.
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oleshifty
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PostPosted: Fri Oct 13, 2006 11:53 pm    Post subject: Reply with quote

ok, i tried manually grounding and adding power to the block where it should have it....and the pump works. HOWEVER the computer isn't controlling it like it should. How can I fix this? I read something about a autoshutdown. I'm not familiar with this system, does it control fuel or spark?
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Code3TJ
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PostPosted: Sat Oct 14, 2006 12:00 am    Post subject: Reply with quote

The sticky at the top of this section has a bit on diagnosing fuel pump problems. http://www.jeephorizons.com/phpbb/viewtopic.php?t=62
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oleshifty
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PostPosted: Sat Oct 14, 2006 12:25 am    Post subject: Reply with quote

thanks, but i already got the pump done....the car just isn't putting power to the relay when it should.
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Code3TJ
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PostPosted: Sat Oct 14, 2006 1:40 am    Post subject: Reply with quote

Missed that part, thought you were still trying to figure out what the problem is. The auto shutdown relay is in the power distribution center which is next to the battery. There should be a label on the cover (might have to open it) that shows which relay it is. The ASD supplies power to the fuel pump, injectors, coil, etc. The fuel pump relay is controlled through the same circuit. So, for the cost of the relay, I'd figure out which one it is and replace it. Also, I'd trace the wiring as best you can to make sure there aren't any loose (or corroded - not sure where you live) connections. Also, does it have a security system that might keep the pump from getting power if it malfunctions?
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oleshifty
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PostPosted: Sat Oct 14, 2006 10:16 am    Post subject: Reply with quote

alright, I'll dig into this ASD thing more. I read somewhere it was purely an ignition cut circuit...but if it controls fuel too, its a possibility. I know the relay for the fuel pump is good, cuz i switched it out with a new one, but i think the ASD is 5 bucks, so i'll try that b4 i start tearing apart the relay block and try to rewire everything (yes there's some corrosion in the holes for the relay...but i scraped it best i could, and even tried putting wire leads in the hole, and pluggin the relay externally---still didn't work.
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oleshifty
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Joined: 13 Oct 2006

PostPosted: Sat Oct 14, 2006 1:31 pm    Post subject: Reply with quote

ok... took apart relay box, cleaned up all corrosion, put all the femal connectors back into the slots (a couple were starting to come out). checked ground on everything.

STILL NOTHING

the output for the fuel pump relay = dead, but if i jump the relay, fuel pump works, but jeep still wont start.


I swapped the relays around for AC and ASD, and still nothing. I'm trying to find a way to actually test relays, but them im lost.
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oleshifty
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PostPosted: Sat Oct 14, 2006 3:19 pm    Post subject: Reply with quote

put a screwdriver in the spark plug boot....cranked it....no sparks pull hair
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Code3TJ
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PostPosted: Sat Oct 14, 2006 6:37 pm    Post subject: Reply with quote

Does it have a security system?
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oleshifty
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PostPosted: Sat Oct 14, 2006 11:07 pm    Post subject: Reply with quote

not to my knowledge....theres no remote on the keys i have. It doesn't even have fog lamps, so im assuming its the base model with no security system.
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RyanLodge
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Joined: 15 Oct 2006
Location: Ontario, Canada

PostPosted: Sun Oct 15, 2006 5:51 pm    Post subject: Reply with quote

Hey, I'm a newb to the forum, but I had a fuel problem before that left me stranded and twice recently an electrical problem. For the fuel problem I believe mine was just the fuel pump, was expensive though (94 grand cherokee limited), then the crank sensor went, another 120 dollars and after that the problem still hasn't been discovered. After my jeep warms up and does a highway run, it will stall when it cools. I replaced wires, distributor cap and rotor and it hasn't done it since. Anyone ever had these problems?
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swamp boy
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Joined: 01 Jan 2004
Location: New Orleans LA.

PostPosted: Sun Oct 15, 2006 7:24 pm    Post subject: Reply with quote

Pull out the ASD relay and get your tester out.. You should have power to one leg constantly. Then you should have power coming on to another leg when you turn on the key. if you dont get that you may have a bad ignition (the key switch itself ) This could also kill your coil power .. ( you can also check the coil with a tester .. Power should come one when you are turing over the engine.. (no power in means no signal from the computer)

I wish you where closer so I could look at it myself.. Test those things and let me know what you find out..Then I will tell you how to check the ignition .

Then I will tell you what the next step is after that.. Mr. Green
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oleshifty
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Joined: 13 Oct 2006

PostPosted: Tue Oct 17, 2006 9:08 pm    Post subject: Reply with quote

the ASD has constant power, and then the switch terminal of the relay comes on when the key is on. The same is true for the fuel pump relay, but no output ever comes out of the relay (i added a wire in the terminal, and used test light.


If i put ASD in, and jump wire from output of fuel pump relay to + on battery, the pump fires right up (but doesn't have the 2 second run then off feature) I haven't tried jumping the ASD relay, but that might be my next try.

I talked to the guy who owned the vehicle before (a mechanic) and he said the vehicle has had electrical type problems for a while, that he would just bypass the ASD and see if the thing will run. Can I just run a wire from top hole of relay (the constant power) to the bottom hole? (the switched output) I wouldn't even mind mounting a switch in the car if need be. This thing only has to last til about winter time.
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swamp boy
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Joined: 01 Jan 2004
Location: New Orleans LA.

PostPosted: Sun Oct 22, 2006 4:14 pm    Post subject: Reply with quote

GIve it a try and see what happens..
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