Hey everyone, I did a normal tune-up for my 91 XJ. Changed the fuel filter, spark plugs, and motor oil. After finishing and cleaning up I hopped inside my jeep to hear its wonderful engine, but what's that? Crank Crank Crank Dead. Crank Crank Crank Dead. It sounded very healthy cranking, but it just wouldn't start! Double checking everything I changed, the jeep was getting fuel, the plug wires were correct+secured (triple checked). I did a check engine test and only got the codes 12 and 55. I also checked if I was getting spark, which I was! So now I am stumped. Does anyone have any idea what else could prevent my jeep from starting? Any help would be wonderful.

also, i found one bad spark plug wire, but it should still start regardless of the bad wire correct?

 

Check to make sure the CPS is tight, they can become loose and that will keep it from starting. If it is tight you may want to get a new CPS. With a bad CPS (crank position sensor) it will crank all day with no start.

 

Not necessarily. So that is a possibility.

How are the gauges when you turn the key on? Do they go to normal position, or do they stay bottomed out? If the gauges don't move, then you need to test your crankshaft position sensor. You can test if with a voltmeter. There is a write-up in the write-up section. This is most likely your issue, and can be replaced in an hour or so. Need lots of extensions and wobbly adapters. There is a good write-up for this in that section as well.

 

By chance is there a coil on 91's? maybe double check that wire make sure it's hooked up. Also have you tried starting fluid? Just a spurt to see if it will hit, if it does you know it's definitely fuel related. If it doesn't hit, you know it's electrical.

 

hey all, first off, thanks for all the replies, this forum has always been great with help . I tried the starter fluid, and it still doesn't crank, I also bought a whole new set of spark plug wires to see if there was an issue, but it still would not crank. I got a buddy to crank the ignition for me while I was looking at the engine and I could smell the gas being fed into the engine, I double checked if all the wires were secure and they were.

 

If you pull one of your plugs, have it resting on your block, and have someone crank it does it spark? remember, threads have to be grounded, but if you sprayed in starting fluid, and were getting spark, you should have at least gotten some type of combustion.

 

The gauges stay bottomed out I believe. I might check this out next, I went to advance auto and they are selling CPS's for $50 (ugh).

 

I did that as well, I got a spare sparkplug and plugged it into each wire, all of them sparked. The spark plugs are champion rc12's

 

I don't know if this has to do anything with why the car will not fire, but I was using Bosch +2 Spark plugs, would the switch would have any effect?

 

Howdy;

I vote CPS.

mine went out on DC beltway going to friends house for football game party..... in teh construction zone near Alexandria...OH JOY!

jeep would crank till the cows came home....

it was raining an nasty an i got towed to friends house and next morning ripped out old one put new one in.


VROOOOOOM!!

the ol 91 beater came to life.

just a thought, good luck sir!

cpnwrench

 

There are numerous threads of people having problems with Bosch plugs with the 4.0. Enough of these to make me absolutely NOT recommend using them.

Plain old Champion copper plugs are best for your vintage.

This is probably not the cause of your no start, but keep in mind what others are experiencing with Bosch plugs. '

I like Bosch products, but not Bosch plugs for the 4.0

 

The old "trilogy" is needed. Fuel, Spark, and air (all at the right 'time')

If you have spark, then it is NOT the CPS or coil.
If it cranks over, it is NOT the nuetral safety switch.
Is it getting fuel?

You may have the plug/distributor wires connected wrong. Make sure you have them in the proper firing order.

 

Howdy! old revival, but just wanted to let the people who were helping know that it is NOT the CPS!!! I just replaced it today and the thing still won't crank! I'm running out of ideas.. could it be the starter? I double checked the wiring and it still won't start (crank, but not start)

 

If it turns over but doesn't start, the problem is definitely NOT the starter.

You mention you have spark. But is it "quality" spark. You need a strong, blue, snapping spark. Yellow/orange/white indicates a weak spark, which may not be strong enough to start the engine. For a weak spark, suspect the ignition coil.

If spark is strong and BLUE, try spraying a small amount of starting fluid or a small splash of gas into the intake. If the engine starts and runs momentarily, then your spark is just fine and you have a FUEL DELIVERY problem.

 

I would replace the cps, I replaced mine under hood in a rest area on vacation. I luckily was going down in two cars so my brother in law drove me to napa and I used a box wrench I think it was a short one, it might have been easier underneath with extensions......