'91 XJ Help plz

R Q

R Q

Well-Known Member
Joined
Apr 4, 2005
Location
Charlotte
Picked up a '91 XJ, 4.0, auto, 4wd. It didn't run since December. It started cutting off but started back and then finally died totally and has been parked since. No fuel, no spark. All other electrical works. Gas gauge won't register after I put 5 gallons in but the low fuel light went out after I added a couple gallons. Other gauges work. Fuel pump does not cycle when switch is turned on and there's no fuel pressure at any time. Wire to fuel pump shows 6 volts when key is in on position.
Fuel pump has been replaced for sure and other issues have been said to have been chased but there's no evidence of it. major and minor fuses are good, checked with meter. Relays have been swapped to known working systems and continue to work.
We were on the trail of the Crank Sensor being bad but ours was slightly different than what the book showed so the meter tests were not conclusive but we replaced it anyway since we had already gotten it.
Did not have time to check coil.
Am considering finding used ECM at Pull A Part to plug in and see if that helps.
I've read a LOT of stuff on forums but am overwhelmed at this point so am asking for answers and opinions.
Please tell me what you think.
 
"no fuel, no spark"...have u put gas straight down the intake and see if it runs. do that real quick to make sure u don't have spark (or did i miss a test that confirmed no spark), otherwise that is easiest way to make sure you have no spark. as far as fuel pump...do you have power to the fuel pump relay and do you hear ASD and Fuel Pump relay click...start there. if no power to those 2, check ignition switch feed going to power box
 
John Fuller said:
"no fuel, no spark"...have u put gas straight down the intake and see if it runs. do that real quick to make sure u don't have spark (or did i miss a test that confirmed no spark), otherwise that is easiest way to make sure you have no spark. as far as fuel pump...do you have power to the fuel pump relay and do you hear ASD and Fuel Pump relay click...start there. if no power to those 2, check ignition switch feed going to power box
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Thank you, I sprayed ether into throttle body, nothing. Pulled a plug, no fire. Checked coil wire from coil, no fire. Pretty sure we have no fire.

I checked for clicking at the relays and could not here or feel but I switched them out between known working ones and had no change.

I'll check Ignition switch feed to fuse box shortly. And to see if I have power to the relays also.
 
make sure ALL grounds are good, not broken or frayed and ALL positive cables have really good contact...start with the simples first..you would be surprised how simple stuff can cause all kinds of issues. let me know
 
We double checked (removed, sanded, and reattached) grounds. Already had cleaned battery cables.
We did a test and determined that we had a bad ASD relay but a new one did not make it work. Evidently tested it wrong.
We have power in the Fuse box and have been able to jump the fuel pump into working.
Pull A Part has a '91 on the yard so we are heading there to see if it has an ECM
 
hey, so when u jumped the fuel pump, did it run or still no spark?
 
No spark at that time but we have made progress since.
We determined that the PCM could be bad and there was a fresh '91 at the Pull A Part so we went there and got it and a coil.
New PCM made it start and run for a few seconds. The coil made no difference.
Spark plug gaps were at .050 and cap and rotor looked terrible so at that point I sent Jr. to get new ones. Old plugs were loose as I was taking them out. New ones installed didn't help much.
I had the bright idea to check codes at the CEL so we did that even though it was not run for more than seconds. At first MAP came up so we checked vacuum lines and although sketchy maybe they're ok. Is there a Mass Air Flow on this? There is a TPS and one other sensor on the Throttle Body so we are figuring that's it. I SHOULD have gotten all sensors off of that '91 at the yard.
We checked fuel pressure when it was trying to run and it held between 30-40. Then we had the idea to hit it with a little ether as it was dying to see if it would keep running. It did so we are thinking a MAF if it has it.
What's your thoughts now?
And thanks for your help, it's helped a lot.
 
no jeep has no MAF...map sensors are the replacement!! so when running u sprayed ether and it WOULD keep running? if so, than u have fuel issues. I've seen many fuel pumps (including my new one just recently) the fuel hose on the sending unit looses the clamp and falls off....lucky fuel pump comes out quick but check that. my brand new one after one weekend wheeling stopped and pulled it out sure enough that hose was loose. and sounds like you have spark now?
 
alright then, good to hear! ur fuel issues: pull out pump and see if your line on the housing is secure and check voltage at the pump wiring with KOEO, jeep xjs are kinda known for some fuel pump wiring issues on older Renix jeeps and some early early 90s like yours.
 
Did you replace the fuel filter on the rail?
 
John Fuller said:
alright then, good to hear! ur fuel issues: pull out pump and see if your line on the housing is secure and check voltage at the pump wiring with KOEO, jeep xjs are kinda known for some fuel pump wiring issues on older Renix jeeps and some early early 90s like yours.
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Will do. If that's good then how do I check injectors? (I haven't looked into it yet, it may even be in the manual)

And Ghost, the filter is new.
 
well injectors are quite that common issue. they usually leak around the housing when they go bad but even then, injectors wouldn't not run..not in my 16yrs of working with these. DO THIS: since you know how to hot wire the fuel pump at the relay, hot wire it, then start it...if it runs just fine with the jumper wire at the fuel pump relay than either you have bad pump, wiring issue to the pump, or possible fuel pressure regulator but again, regulators i've had go bad to where it would only do 18psi of fuel or so but jeep still would run, just kinda crappy. i gotta feeling it's in the pump, the housing/sending unit rubber line but let me know how it goes. i'm not saying to not rule out injectors but that's kinda the last on the list since it's not very common at all for them to go.
 
What about the ground at the back for the fuel pump? It is on the left or drivers side and part of the tail light harness. Attaches to the unibody under that back rear panel.
 
ghost said:
What about the ground at the back for the fuel pump? It is on the left or drivers side and part of the tail light harness. Attaches to the unibody under that back rear panel.
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yep. that would be fist place i would start if he has fuel pump wiring issues...if it's not the pump itself
 
John Fuller said:
yep. that would be fist place i would start if he has fuel pump wiring issues...if it's not the pump itself
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When I chopped mine I left that ground off and it would run for a while then shut off like the fuel pump was dying. I was at DurhamTown Tellico and it almost ended my day.
 
richard, I have an extra brand new fuel pump i got double shipped from rockauto, its yours if you need/want it. from a 95 IIRC
 
72Rockcruiser said:
richard, I have an extra brand new fuel pump i got double shipped from rockauto, its yours if you need/want it. from a 95 IIRC
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Thanks Kyle, We took a day off so as not to piss off each other too bad (and for me to set the agenda for how it's going to go) so the wheels will be moving forward again shortly. Will be back soon.
 
Update: Checked fuel pump issues and its all good. We have great fuel pressure and fire. Took IAC off last night and it's not functioning. They are $100 so for now we are going to pull one at the pull a part and go from there. We need a few more misc. items anyway. We did put new injectors in it also. It wants to run and its almost there.
 
glad to hear things are going good. keep it up. been gone last 3days so was away from computer.
 
Installed the Pull A Part IAC today and no change. The Distributor that I picked up is a later model and doesn't match so I'm not going to install it.
SO, I'm going to go over everything again myself to make sure Jr didn't skip anything. (I'm thinking he did)
 
can u give me quick update as far as what ur still having issues with completely: u have spark, u have fuel i think i've understood but i've gotten lost as where ur at running wise....then hopefully i can guide u in right direction
 
We have spark and fuel. We had nothing before replacing the ECM. It will start and run for 2-4 seconds and die. We've replaced ECM, crank sensor, IAC with a used unit, new plugs, wires, rotor, cap, and new injectors. New fuel filter also. We have good fuel pressure.
I'm going to start over and check everything myself now just to be sure something hasn't been overlooked.
 
so far with what u described, sounds like TPS sensor bad...that's common with issue ur describing
 
I replaced the TPS today with a new unit. It didn't help or at least not much. It seems to run for an extra second or two.
Is the IAC supposed to move freely or is it somewhat rigid? We put in a used unit from junk yard.
Will start over tomorrow and recheck everything we have already done or thought we did.;):shaking:
 
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