HELP!!!!

[easttxhunter]

Hey guys I havent posted in a long time. I posted a question on the facebook page but Brasscatz suggested i post up here as well. Will a bad crank position sensor cause the fuel pump to not come on when you turn the key? Replaced what I thought was a defective fuel pump this weekend and the only way I can get the pump to come in is if I put my test light on the negative battery post and touch terminal 85 on the relay with the relay partially exposed. The other thing I noticed is the pump continues to run and if I remember right it used to prime and shut off. I'm pretty sure I don't have spark either because I rigged a jumper so that the pump would run but it still would not start. This is a 92 sport 4.0l. I didnt check the relay with a meter but I did the poor man method by jumping off the battery to connector 85 (ground) and 86 (relay power) and it clicks. also tried a couple different relays with no luck.

[nickyg]

I am by far no expert,
But Whenever I suspect the Crank postion sensor I just go ahead and change it.. If it's not bad today it will be next week.
Sorry I can't be of more help.. I'm sure by the end of the day someone will post the correct answer.

[Mudderoy]

Hey guys I havent posted in a long time. I posted a question on the facebook page but Brasscatz suggested i post up here as well. Will a bad crank position sensor cause the fuel pump to not come on when you turn the key? Replaced what I thought was a defective fuel pump this weekend and the only way I can get the pump to come in is if I put my test light on the negative battery post and touch terminal 85 on the relay with the relay partially exposed. The other thing I noticed is the pump continues to run and if I remember right it used to prime and shut off. I'm pretty sure I don't have spark either because I rigged a jumper so that the pump would run but it still would not start. This is a 92 sport 4.0l. I didnt check the relay with a meter but I did the poor man method by jumping off the battery to connector 85 (ground) and 86 (relay power) and it clicks. also tried a couple different relays with no luck.

I'll start with "I don't know" but really I'm wondering if it isn't an ECM issue. I wouldn't think a bad CPS would keep the fuel pump from running, I guess it could. Oh of course fuses, relays, wiring should all be checked prior to assuming it's a bad ECM.

[Brasscatz]

This is a tough one... Relay was where my mind was going at first but you've eliminated that possibility. The pump first kicks on when you turn your key to the ON position... could there be something wrong in your ignition?

[bluedragon436]

I know when my crank position sensor went out, the fuel pump still ran like it is supposed too, just didn't allow spark to give me engine start... And you said you did try and swap the relay for your fuel pump with one of the other similar relay's that you know are good?? IIRC there are a few other relays in teh power center that are the same relay, that run other things such as A/C or fog lights... that you could swap?? I know with the older XJ's there is a fuseable link up front and I think if it burns up it'll stop the XJ from starting as well... I know a few folks have replaced the link with a circuit breaker, since it can easily be reset when it does trip... Have you tried checking for power @ the fuel pump when you have someone try and turn on the ignition??

[easttxhunter]

Well I replaced the sensor and it didn't work. I know the fuel pump is good because as I said I can make it run by grounding the relay. I hate throwing parts at it but looks like that's where I'm at. Guess the next thing is ecu

[easttxhunter]

Brasscatz I guess that's a possibility but not sure how I would diagnose it.

[Brasscatz]

Just consulted my manual and found that on my 98 I have a fuse #19, a 15 amp fuse in my relay box under the hood that is also labeled "fuel pump". I don't know if it's the same on your 92 or not, but have you checked that fuse to see if it is blown? I don't know how it is wired or if that fuse controls the fuel pump relay, or what, but at least it's another easy thing to check.

[easttxhunter]

I verified that I have no spark as well. So no spark and no fuel pump.

[bigjim350]

do you have any signs of a aftermarket alarm system on it? Some alarm systems cut fuel and spark. If not, id lean towards the ECM. If you want we can meet up on a weekend and Ill let you use the ECM out of mine to test it, mine is also a 92

[easttxhunter]

JIIIMMMM how the hell are you man. Long time no talk. Yeah i dont see any kinda horn under the hood or box under the dash indicating it had an alarm on it. I first started having trouble with it in December at the deer lease. Coming in from a hunt it started to studder like it was running out of fuel. it eventually would clean up and run fine. every time i would drive it i noticed the studder more frequently until one day i started it up to put it on the trailer and bring it home. It ran for about 30 secs and died never to start again to this day. I thought for sure it was the fuel pump but now im scratching my head.

[easttxhunter]

it would be awesome if I could try yours out. the jeep is at my dads house in Woodbranch. You still have my number? Ill pm you just incase.

[NW99XJ]

If i'm not mistaken, the earlier XJ's have an "Automatic Shut Down" relay .....The ASD and the Fuel Pump Relays are controlled by the PCM. When you first turn the ignition on these relays should turn on for a few seconds. The PCM controls the relay ground on the control circuit. This is why you SHOULD hear the fuel pump run for a few seconds right before start up. This pressurizes the fuel system. After a short run time the PCM turns the relays off waiting for engine start. When you turn the ignition to start, the engine cranks and the PCM then reads the sensor info for start up.

If the PCM is working good you should at least have the ASD and Fuel pump relays energize. To test this, attach a test light or horn to the fuel pump power wire and to ground. Then turn the ignition to ON and see if you get any action. You can also do it at the relay by running some thin wire from the relay pin-87, out above the relay then attach the test light or horn there and to ground.
If you get no reaction, then there's a good chance you have a bad relay.
I would also verify you have spark....use a pair of insulated pliers, and when holding a disconnected spark plug wire, gap it to something with ground, and see if you can get spark to the connection point inside the boot. ( a screw driver may help get you up inside it.) If you have spark then you know you have a fuel issue.
If no spark, I would figure that out first....either coil, distributor, or possibly a bad CAM position sensor. (inside/below the distributor ----I think)


If all else fails, it may come down to the PCM...... its not uncommon for PCMs to have solder joints fail on a couple of the capacitors inside.
Here is a link to a good write up on how to fix this IF it is the case....
PCM FIX (http://www.jeepforum.com/forum/f13/fixing-lazy-pcm-new-caps-writeup-501951/)
NOTE: this is a pretty invasive procedure, that should only be done by one who is competent with soldering techniques and is willing to risk tearing into their vehicles computer system.

[easttxhunter]

I messed with it a little more today and when I had my dad turn the key to on, none of the relays click

[msmoorenburg]

Do a lite check when you turn the ing on you should see a check engine light come on. if not i have a ecu you can try and another you can have if its good

[easttxhunter]

Yeah there is no check engine light. That would be awesome if you could let me try it. Your Matt that shared the shop with Rene right?

[easttxhunter]

Well guys I popped in the new/used ecm and she fired right up. Case closed. Thanks everyone for your ideas.