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88 Comanche stalling

Hi, I have a 88 Jeep Comanche, six cylinder, automatic transmission, fuel injection, 4WD with approximately 88,000 original miles. Up to last week, it started and ran like a champ. My son (maybe the problem) took it to work one day last week. When he came out of work, it would start and then die. Start/Die Start/Die Start/Die. I had it towed to my mechanic. He told me that it was not getting any pressure from the fuel pump. Installed one and now it gets 40lbs pressure. Still won't run. He says if he sprays starting fluid into the intake hose, it will continue to run. After doing this for a a little while, it would continue to run without the starting fluid. After shutting it off, and leaving it set for a few minutes, it won't restart without the starting fluid. He says he is 99% sure it is the computer. I can get one from the junk yard for $75. When I talked to the guy at the junk yard (a junk yard that didn't have one ) he said that he'd never sold a computer for a Jeep. He said they just don't go bad. My mechanic is pretty good, but I'd like to get some input from you guys before buying the computer. Please ....any ideas?? Thanks.......Ed

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Ed
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Reply to
L.W.(ßill)

Before changing the computer, first try switching the fuel pump relay. Had the same problem, which was fixed for 6 euro's. Standing on the passengers side it is the second form the right. Try switching it with the most left one which is the A/C Clutch Relay. It will probably start immediately.

Good Luck,

Rodger from Holland.

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attnews

This is an update to my stalling problem. I got a computer from a junk yard, installed, same symptom. It really seems like it should be something simple. I am getting 40 lbs of fuel pressure. It stays running as long as you spray carb cleaner into the intake hose. As soon as you stop, the engine dies. It doesn't sputter or cough, it just stops dead. My mechanic says it just looks like the injectors are not firing. Since it runs as long as you put carb cleaner into the input hose, I am guessing it's not electrical. This truck was running fine before this happened, and it happened so suddenly, it just seems that it's something simple. Thanks for all help..........Ed

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Ed

Reply to
L.W.(ßill)

What was the result switching the fuel pump relay. Cause it seems your pump isn't pumping at all.

Rod

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Thanks.......Ed

Reply to
news.quicknet.nl

There is a balllast resistor on the fuel pump power on my 88.

It is a white ceramic one out near the rad on the drivers side.

The pump also relies on the body for ground, so if the ground strap is bad it will up and cut out.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's

Ed wrote:

Reply to
Mike Romain

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L.W.(ßill)

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L.W.(ßill)

Reply to
Will Honea

The ballast resistor also controls the injectors I believe. If the fuel pump isn't getting a clean power signal, I think the injectors shut down too.

Mike

"L.W.(ßill) Hughes III" wrote:

Reply to
Mike Romain

One of the main ground tags for the electronics is on the passenger side at the rear of the engine block. The other one is inside on the firewall above the gas pedal.

Mike

Will H>

Reply to
Mike Romain

I've been looking for that inside sucker and still haven't found it - it's gotta be there somewhere! I even had the whole dash off a while back and still didn't see it - must be under the soundproofing somewhere. I'd sure like to finally get my hands on it, tho - when I have the blower on High, I get a 3 volt drop between the battery and the fan motor ground and a good 2 volt drop in the instrument panel ground. That plays hell with the radio so I can imagine that it does the computer no good either. It also limits the output of the heater to about what I would get in the medium speed position. I've got a max 150 mv drop at the firewall metal and the stud where the strap from the engine connects, so that part is good. About what you would expect - the easy to reach point is just fine...

Reply to
Will Honea

On some of the YJ's the inside ground tag is on the emergency brake bracket, but that is with the foot powered e-brake. I figure the Comanche has the hand brake right?

I have also seen bad corrosion on the resistor pack plug. That is way down under the heater box on the passenger side.

Mike

Will H>

Reply to
Mike Romain

My '94 GC 4.0L cut out too until I had the crank position sensor replaced.. not sure if the '88 Comanche has one of these, but as nothing else has worked, would consider this possibility..

-- History is only the past if we choose to do nothing about it..

Reply to
Mike Hall

The ballast is only there for the fuel pump. The computer pulses B+ to the injectors.

Reply to
bllsht

Reply to
Will Honea

Hi Ed,

Mine is an 87 Comanche.

I had the same thing happen to me...drove out to get gas, ironically, and when I stopped at a light afterwards, the truck died. Restarted fine, died two seconds later...repeat. It ended up being the ballast resistor. It's a white, elongated kinda-trapezoidal thing bolted to the driver-side fender. There are two wires (orange w/blk on my truck) running to it.

If you bypass the ballast resistor, connecting the two wires directly, and switch the key to ON, the fuel pump will run forever instead of cutting out when it builds up the correct system pressure. Probably not good to run like this but it at least verifies that all is working properly and that it is the ballast resistor.

This happened a while ago, so I can't remember the exact details. There is one pin in the diagnostic connector which indicates fuel pump power. You can connect a 12 volt test lamp to that pin, grounding it somewhere convenient. With a bad ballast resistor, you switch the key to ON, the lamp goes on then cuts out after a few seconds, if I remember correctly. With a good ballast resistor, the lamp should stay lit as long as power is on.

It's only, like, $11 or something for a new one, so you should try that.

Cheers, /tom

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Tom Dobrowolsky

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