I'm in serious need of help. I dont want to dump new parts into this thing trying to figure out why she's not starting only to have her still not start.

Long story short engine blew on '99 4.0L XJ and been replaced with '96 4.0L engine by old owner. It cranks but wont start.

What needs to be done??

 

Start with checking your distributor cap, wires and spark plugs. Replace all if bad. Check fuel pressure. Clean up all your ground wires. New gas etc.

What does it do when you try and turn it over?

 

Also did it run before you got it from the previous owner?
Your 1999 computer might not be compatible with an older engine like a 1996 and earlier.

 

Crank position sensor check to see if you got spark if not I am very Cretan that's the problem. The old owner probably damaged it installing the new motor but check all your grounds first that could also be the problem other wise the motors from 96 and up too 99 are the 100% the same and 2000 - 2006 are the same just a different head then the 96-99 to make up for a coil on plug set up . so no matter what year if the wiring was set up right it will run

 

You need; Air, Fuel, Spark and Compression to fire an engine, your lacking one of those items!

Check to see if you have injector pulse. Use a noid light at one of the injector plugs while cranking to see if you are getting fire. If so then you have to move on to a spark issue and you have eliminated the CPS. It would have to be either no fuel pressure or the distributor is indexed improperly.

Was the distributor ever removed then installed incorrectly? If the distributor has been out you need to make sure it is indexed properly.

The rotor should point to or just past #1 plug wire terminal on the cap. To do this you MUST have #1 piston at Top Dead Center, compression stroke.

With #1 TDC compression stroke, pull the distributor out and drop it back in with the rotor pointed to the #1 plug wire terminal

I'll bet money its out 180 and set on the exhaust stroke.

 

I have fuel but no spark. And to me it seems like its turning over slower then my other Jeep XJ. And all that is ok. only thing that might not be is the grounds and the gas. its got a full tank from the last owner lol.

I've read that from alot of threads, so i removed it and its not damaged to the eye at all. We're going to put it back in and test it with a meter going off what the Haynes manual says.

I've tested the fuel pressure and got 40 lbs like its suppose to. and I've done the whole TDC and rotor check. And the spark plugs smell like they have fuel on them. So its spark or compression. As far as i've researched i should have an average of around 110 lbs. Right? And I have weak orange spark but speratically. Like it wont when we fist try starting it then it will randomly have spark later on when checking it.

 

Have you checked your coil for some odd reason I have changer over 40 of them on jeeps and dodge at my shop this summer all of them had a weak orange spark and if you took the coil off and looked at it the case was split

 

I'll be sure to look at it next time. It's just stumping me because sometimes it fires and sometimes it wont.

I know the CPS reads notches in the flex plate and we had to bolt that to the TC earlier. If the flexplates are different between the two years that would throw off timing and injector pulse. Right? But are the flexplates different? I wouldn't see why they would be. Or could we have put it in wrong? The older models could only be bolted on one way i know that, but I'm pretty sure the newer ones can be bolted straight on.

 

So it starts sometimes and then it wont it's got to be the CPS and the the flex plates from 87 - 06 are the same on the 4 L try this next time it dose not start get someone to tap the CPS well u crank it if it starts that's her and the CPS is a magnet so it could still be damaged even if it dose not look like it

 

Sorry about the confusion. but no it hasn't started at all. I meant sometimes ill have spark and some times i wont. And are the flexplates the same for the 99 and 96? or different? I'll try that too though. thanks.

 

Yes the flex plates are the same but I bet it is the CPS

 

Im glad to hear that. I'll try tapping the CPS tomorrow when i reinstall it and let you know how it goes.

 

Check the all grounds there is one for the coil that attaches to the coil mounting studs, that was the problem on a buddys jeep last month. Check CPS per manual, also wanna check the Cam Position Sensor (disc under Dist. Rotor w/ 2 wires).Make sure battery has a full charge the computer needs to see 300 RPM before it will trigger spark IIRC.

 

I know that the ground wire is definately attached. And I just removed the CPS and its got no visible damage at all and I also probed it with a meter when i connected it back. It tested like it should. But the Cam Position Sensor (Stator) was my next suspect. So ill probably be replacing it. And the battery is extremely weak it seams. After about ten cranks its already dead. Ill have to try a different one because it does seem to be turning over slower than it should.

 

Bump please!!

I hope my post is still alive cause ive still got the problem. Today i put in a 99 Camshaft Position Sensor(Stator). And same problem! Although it did fix the random spark. Now its firing like it should but it still has a weak orange spark. We cant even get a sputter or anything with a good dose of starting fluid. So please any one with an answer...? Im debating on putting in a 96 computer.