rs2800

Hi guys, I'm having an issue that has me completely stumped. I hope you experts can help me with this. I am restoring a completely original 96 XJ. Of course the exhaust manifold was cracked and needed to be replaced. Before I started this the jeep ran great. I removed the intake and exhaust manifold. One freeze plug was weeping, so I replaced all of them. After I installed the new exhaust and reassembled everything it will crank but not start. I have fire to the plugs and good fuel pressure to the fuel rail. I pulled the fuel rail and injectors, turned the engine over and indeed I am getting fuel. It sorta tries to start, but just won’t quite do it. I have put the scanner on it and it shows no codes. It pulls the vehicle information from the PCM so that doesn’t seem to be the problem. I am almost finished with it and it looks brand new. All I need to do is get it running again and install the new headliner. I really hope some of you guys, with much more knowledge, can help me find the issue. I’ve been working on this thing for over a year and really want to get it finished and start driving it. I would greatly appreciate any help you can provide. Thank you.

awg

* triple check you plug wire order, I have heard some manuals are wrong, there is a correct diagram on this forum, search archives

* spray engine start spray while cranking

* do a vacuum check while cranking in case you made the common error of inlet manifold hung up on locating pins

* double check each sensor plug is properly connected

* harness can be damaged when flexed back

If you have fuel and spark, you should be close, check the easy things first

rs2800

Thanks so much for your response. The jeep was running great before I started the replacement, so the wiring order should be correct, as I only removed one plug. Other than that, I only touched the exhaust side. I have tried the starting fluid and it didn't do anything. It made no difference at all. I have removed a plug and it was wet and fuel came out when I cranked it. It is possible it could be in the harness as I bent it back pretty good, but everything seems to be okay as I have spark, fuel and contact with the PCM. Is there another way to check if it is in the harness? The intake appears to be installed correctly, at least it looks good, with no gaps or anything, and I am getting fuel to the plugs. Is there a way to check the vacuum without the engine running? Would one of the sensors on the throttle body cause the problem I am describing? If I'm getting spark would it be the crank position sensor? Could the spark possibly be too weak? I have checked just about everything I can think of. It almost starts and that is what is driving me crazy. It will try to hit at first for a little while and then stops and starts turning over faster like there is no compresssion. If I had any hair I would have pulled it out by now. I'm almost thinking of having it towed to a mechanic, but I've never taken anything to one before. I've always done all my own work. It's a pride thing I guess. I also do my own paint and body work. I'ts just a hobby for me, and I normally really enjoy it, but this one is really starting to exasperate me. Do you have any other ideas about what the issue could be?

exasemech

Sounds like you have plenty of fuel, have spark, are convinced no major vacuum leaks( check everything on manifold/tb again), and didn't mess with plug wires etc
Not impossible it's flooded for some reason (IAC messed up?)
Try cranking it holding accelerator pedal on floor, it's the clear flood mode

awg

I agree crank with throttle to floor, or pumping throttle

It could be IAC, or TPS

You say you have spark, with a $5 spark tester, is it a good spark, (blue and jumps almost 1/4", or a bit weak & yellow)

XJ hate starting with a low voltage, your battery must be over 12.2V

Yes you can check vacuum 2 ways when cranking, Vacuum gauge, or OBD with live data (may be hard to define results with just cranking)

An OBD2 like BAFX with Live Data may help

Finally, as you say the engine seems to crank too freely, it would be worth checking compression on at least a few plugs

No vehicle like stale fuel...how old is the fuel in the tank ?

A lack of wanting to cough hard, or fire with ether spray may be indicative that it is not a fuel issue (although it could be flooding)

Its very hard to check the harness internal wires, O2 and crank sensor are around the exhaust area

As a wild stab in the dark, disconnect your front O2 sensor plug and see if it will start

rs2800

Thanks guys, I will test out your suggestions. I may have described some of the symptoms incorrectly. When I turn the key, it comes so close to starting it's unreal, but then goes to just cranking. If I try to start it again soon, it only cranks and doesn't try to hit. Its no longer turning over faster and just cranks normally. If I wait quite a while and then try, it hits and tries to start again and then goes back to just cranking. I have used a spark tester which shows I have spark. I have also removed a plug and grounded to the block and I just saw a spark but didn't pay attention to the color or intensity of it. I was only checking for a spark. As I said, it always started immediately and ran great before I changed out the exhaust manifold. I just drove it into the shop, put it on the lift and started taking it apart. After putting it back together, it had the starting issue. I have rarely experienced such frustration (and I'm married). Could something I did have damaged the coil, causing a weak spark? Could the crank sensor have been damaged and creating an insufficient spark. All I know is I think I am getting too old for this. LOL If you have any other ideas after reading these symptoms please let me know.