Need some help from all the jeep guys here please

[spence3030]

i recently bought a 94 xj with 168k on the engine. the guy i bought it from wasn't all that knowledgeable about jeeps, but swore it was dying out because of a bad fuel pump that was on it's way out. it ran good for the short test drive i took it on and then died on the way home and had it towed the few miles back.

i put the battery on a charger and let it sit until it had a good charge.

so far, i replaced the fuel pump with a bosch pump and strainer and put a new fuel filter in it. it ran great after i put the battery back in all charged up.

then i drove a few miles to get the emisssions done and then it just died. thinking it might have been the battery i grabbed a new one and threw it in. it started right up and was able to get about half way back home and then it died not ten minutes later neat the parts shop.

had it towed back to the house and pulled the alternator figuring it was probably bad (it looks original) and took it to advanced to get tested. the guy ran the test 3 times and all 3 times it passed, but i'm not that trusting of those machines.

got a re manufactured alternator and put that guy in. took the original battery back to pepboys and they tested it, it said it was bad, but it was under warranty so they gave me a brand new one.

i got everything put back together and let it idle in the driveway, it idled 25 mins with the lights on and then died again.

my guess is that it has to be something draining the battery. i'm going to grab some new battery cables, as the old ones seem pretty beat.

i'd appreciate anyone Else's input on either what the issue might be, or any suggestions for what brand of battery cables to use(that aren't the super nice and expensive cables)


thanks
chris

 

[joe_peters]

STOP.

When it won't run, WHAT ARE THE SYMPTOMS?

1. Won't crank?

2. Will crank, won't fire off?

ONE STEP AT A TIME--DON'T THROW PARTS AT IT, DON'T JUMP FROM ONE ERRONEOUS ASSUMPTION TO ANOTHER.

We can get you there, if you let us help you.

 

[spence3030]

the old battery was under warranty and pepboys traded me for a brand new battery. installed the new battery and and it start just fine. ran with a solid idle for 25 minutes and then just died.

when i tried to restart it, it felt like the battery was dead. it will crank just fine but will not fire up.

the battery cable look to be the original set from the factory. i also have a newer ignition coil that the junkyard threw in with some other body parts.

my thought was it might be a bad coil short out and possibly draining the battery by causing a screwy connection, but i'm thinking the battery cables might be bad.

any thoughts as to whether i'm thinking in the right direction?

 

[MoFo]

the old battery was under warranty and pepboys traded me for a brand new battery. installed the new battery and and it start just fine. ran with a solid idle for 25 minutes and then just died.

when i tried to restart it, it felt like the battery was dead. it will crank just fine but will not fire up.

If it "will crank just fine", the battery IS NOT DEAD and your battery cables are doing their job.

the battery cable look to be the original set from the factory. i also have a newer ignition coil that the junkyard threw in with some other body parts.

my thought was it might be a bad coil short out and possibly draining the battery by causing a screwy connection, but i'm thinking the battery cables might be bad.

any thoughts as to whether i'm thinking in the right direction?

Because your cables are old, that does not make them bad (see above). Since your battery is not dead, a "shorted coil" is not causing your problem. The coil could possibly be the cause a thermal cut out, but the probability of that is very slim. The XJ coil is pretty reliable.

By far the hardest thing your electrical system has to do is to turn over the starter motor. If that is turning up to speed you DO NOT have any problem with your battery or battery cables. If your starter motor is spinning, leave the battery and cables alone!

It sounds like you have some part failing when it gets hot. Did you do a search for thermal failures? You symptoms sure sound like a bad CKPS.

 

[joe_peters]

I agree with MoFo.

The most common thermal failure is the crank sensor.

Start it, let it run until it dies, unplug the crank sensor and measure across terminals B and C, with your meter set for ohm 1k-10k. The circuit should read OPEN--no resistance. If there is a low resistance replace the crank sensor.

Post up what you find.

Good luck.

 

[stockli]

How does the motor sound when it's running? Does it die when u put it in gear?

I'm asking because I went through this with an 89 and it turned out one of the cylinders was warped. It woul idle but it was noisy, then it would heat up to temp and die. A buddy of mine who is a mechanic put some pressure on the motor and she seized up solid after about 30 seconds.

When it gets running rev her up a little and see what happens, I spent more on chasing parts then I did popping a new motor in her, which fixed everything and she ran like a top.

 

[spence3030]

The motor sounds pretty much like the rest of my cherokees have sounded, that standard 4.0 sound.

last night i did notice that there was a vacuum hose leak from the intake manifold to the regulator on the front of the fuel rail, but i don't think that would cause the electrical to die on me.

When it was running it ran really well off a freshly charged battery, good power, good acceleration.

when it did die after idling. I waited a few minutes tried to restart it and sounds like it wants to start, but then starts having a slow turnover, like the battery doesn't have enough juice. I didn't want to try more than 3 times so i didn't kill the battery completly

 

[joe_peters]

You may have more than one problem.

1. Weak/bad battery.

2. Poor main cables.

3. Weak/bad starter.

HOWEVER--you may still have a thermal failure issue.

Start with the battery. Charge it, then have it load tested WITH A CARBON PILE tester--not the digital junk. If it passes a load test--1/2 CCA for 15 seconds, remains above 10 volts--then next are the cables.

Cables: clean both ends of both cables. Run a voltage drop test on both cables--Google or youtube it.

Run a static voltage test between the battery terminals--s/b 12.5 volts. Check between the terminals with the engine running--s/b 13.5 to 15.5 volts. If you get those numbers your alternator is charging the system.

If the battery passes, and voltage drop across the cables are good, then slow cranking means a poor starter.

However, a poor starter won't cause a warm engine to die.

Post up what you find.

 

[techno1154]

When my XJ did that it turned out to be the O2 sensor. It always ran perfect at startup especially when cold, run about 30 minutes +/- then shutdown. Leave it be for 30 minutes and it would start right back up and run perfect again for a few minutes. This may not be the problem with your XJ and neither is the battery if the engine will crank.

I too throw parts at my XJ's usual suspects one part at a time for several days even though they all tested good until I wised up and realized the PCM ignored the O2 sensor until the engine was hot and that a (real) bad O2 sensor will kill the engine. It is all about pollution in the atmosphere.

 

[spence3030]

here are my new findings from today. the car sat overnight, and i had a buddy bring over a multimeter. just sitting the battery showed 12+ volts. we checked the wires for continuity and they passed fine. we checked the cables to make sure they were good and they were.

disconnected the battery to reset the computer and connected it back and it started up. i doubled checked the distributor cap just for good measure and it and the rotor were corroded, so i replaced those just because it needed it and couldn't hurt.

started it up with the new cap and rotor and it ran fine for about 12 mins and then just died. we had the meter on the battery while it was idling and it was running at 14.05 volts (so the alternator was working fine) and then it just died again.

so the thinking that it was a thermal failure has to be correct at this point, right?

 

[lazyxj]

It definitely sounds thermal. Now get your buddy and his multimeter over again and repeat, this time following Joe's suggestion and test the CPS. It's a very common item to fail when hot.
Why bother asking advice if you do not intend to listen to a very experienced mechanic who knows a lot about XJs and is trying to pass some hard earned knowledge along to you.

 

[spence3030]

i definitely appreciate any and all help from the people. im not trying to sound stubborn and i'm definitely not trying to throw parts at the situation. the parts i've put on so far were things i was going to fix anyways.

i'll test the CPK and post the results.

 

[smokinu]

i had this same problem on my 91 xj, i bought a new fuel pump relay and replaced all the fuses on the passenger side fender that had anything to do with fuel and my problem went away.

My jeep would run great until it was warm if you turned it off it wouldn't start until it got cold again. now i have no problems! could be worth looking into?

 

[spence3030]

started the jeep up and let it run until it died again. unplugged the crank sensor and tested the B and C leads, there was resistance on them, so it looks like it was bad.

i've been reading differing opinions on this forum and other jeep forums as to whether it's fine to use aftermarket or OEM only.

thoughts one way or another?

 

[scottmcneal]

OEM only. Have you removed it to see how dirty it is? Mine did this and i had a friend tell me to pull it an clean it.That was 2.5 years ago.Still running strong to this day.Yes it tested bad.

Just thinking out loud

 

[yossarian19]

OEM vs off-brand... off brand parts have been getting worse and worse. You might get a perfectly good one. You might replace 3 of them and get bad-from-the-box crapola every time. OEM you can trust. So you gotta ask what is your time worth? If it's an easy repair it might be worth it to try and save a few bucks because you are only out a half hour if the part is bad. For other things... better to just do it once and be sure.

 

[joe_peters]

OEM vs off-brand... off brand parts have been getting worse and worse. You might get a perfectly good one. You might replace 3 of them and get bad-from-the-box crapola every time. OEM you can trust. So you gotta ask what is your time worth? If it's an easy repair it might be worth it to try and save a few bucks because you are only out a half hour if the part is bad. For other things... better to just do it once and be sure.

As Yossarian19 and others have said, the crank sensor is one of those OEM- preferred parts around our shop.

 

[spence3030]

thanks again for all the advice guys. i got it up and running today. went the OEM route, but by way of the junkyard.

ran the test on the CPS and it was bad. the sensor was a righteous pain to get out.

let the jeep idle for about 45 mins to make sure it was working properly and then drove from denver to morrison and back (30 miles give or take roundtrip) it ran pretty good.

i did notice that when coming to a stop that the the engine seemed to rev a little low, like it wanted to die out, but when i came to a full stop it was back and normal idle.

it had a cracked exhaust manifold when i bought(on the back tube where they meet almost towards to the flange at the bottom) I'm planning on replace it with another manifold that i have with the "accordion" style pipes on the front and back.

But i wanted to know if you guys think that could be the cause of a a somewhat rough idle while coming to a stop(also i've noticed that there is a faint "whistle" type sound when the jeep idles long enough to get hot, does that also sound like the exhaust manifold or possibly a vacuum leak)


thanks

 

[joe_peters]

I would look for an intake leak with the "whistle".

Piece of hose--I prefer vinyl tubing--about 3' long and then just move it around the engine with one end in your ear listening for the "whistle".

ALWAYS BE CAREFUL OF MOVING ENGINE PARTS.