Hey everyone, just wanted to say i've been lurking the forums for a while and it's been a great resource for all things XJ. I came to ask for suggestions on where to start for an issue I have.

I've got a 1997 XJ Sport that will turn over but will not fire. It's got 215,xxx miles and unknown maintenance history so I went through and changed the spark plugs, ignition wires, cap, and rotor but the issue still persists. This leads me to believe there is a fuel issue. It sounds like it WANTS to fire as it cranks.

I'm just looking for ideas on places to start.

potentially relevant info:
-It threw an O2 code a few days before not starting
-It has always taken 3-4 seconds of cranking to fire before starting (as long as I've owned it anyway)

I rented a fuel pressure tester to check pressure at the rail but the weather and my work schedule has prevented me from touching it yet.

Thanks in advance!

 

when i first got my xj it was doing the same thing for the longest time. after a buddy cameover we ended finding out i had a bad crank sensor. maybe start there?

 

Check your fuel pressure with a fuel pressure gauge.Also pull a spark plug wire off of the sparkplug.Then put another sparkplug in the wire,have someone crank it over to see if the plug sparks.That should narrow down whether its a spark or a fuel problem.hope this helps.

 

Rather than taking shots in the dark waiting to hear "ouch!" Isolate each system...

1. Ignition, spark to coil, spark to distributor. Should be strong blue spark. If not, could be multiple things ( a manual will come in handy)


2. Fuel, You seem to have this covered, if fuel pressure is ok you may want to check the spray pattern of the injectors, it should be a cone shaped fog not a stream.

3. When all else checks out do a compression check.

All the while triple checking all connections

 

i have spent months trying to solve this odd hesitation issue i have. ive spent plenty of moneey chasing this gremlin, only to find out that it could be my down stream o2 sensor. either way, in an effort to get it running better i have changed the cap and rotor, plugs and wires, new TPS and IAC valve, (on yours i think it the CPS and MAP sensor, a little diff. than my 99) the only things left are the o2's and the coil. and for the first time it threw a code saying the o2 was bad. literally never has thrown a code before, so i was happy. like was stated, it really sucks shooting in the dark... long story short, be methodical and dont waste money till your sure... coulda saved myself like 200+...

 

Verify spark as mentioned above.

If you have a strong, blue, snapping spark (not yellow/orange/white), then try spraying a small amount of starting fluid into the intake. If the engine starts and runs momentarily using this technique, you have confirmed a FUEL DELIVERY problem.

Test your way to a solution. No guesswork.

 

OK guys I've got the fuel pressure tester hooked on to the rail and she reads a steady 49psi when I turn the key and prime the pump and the pressure holds there while cranking. I'm going to tentatively rule out fuel delivery as an issue.

I've got a fellow Jeep jockey on his way over to help me verify the ignition components are sound (which I think they should be).

For the sake of my sanity let's say compression is good for now; what else goes bad on these 4.0 motors? I keep reading about the CPS, is there a way to test this unit? The only thing I'm thinking that could be left is some kind of sensor or other electronics.

cliffs:
-Fuel pressure is nominal
-Spark is ok (probably, working on it)
-She cranks (and sounds like she REALLY wants to start, especially when cranking for a long time)

What's left?

 

1. Pull a spark plug, keep it attached to the plug wire

2. Place the plug electrode near a good engine ground

3. Have a buddy crank the engine while you watch.

You are looking for a strong, blue, snapping spark. Yellow/orange/white indicates a weak spark which may not be strong enough to start the engine.

You really need to verify if you HAVE GOOD spark, HAVE WEAK spark, or HAVE NO spark. The results of the above test will tell you this and will dictate the next logical step in diagnosing this. This test only takes a few minutes.

Report back what you find.

 

Really sounds like the CPS. Pretty common on these trucks.

 

I just wanted to say thank you for the help you guys have given me really quick; I'm sitting inside waiting for an extra set of helping hands to show up.

 

Spark is verified, fuel is verified, it cranks, still won't fire.

Is there anything else you guys can think of to check beside compression? I don't want to prematurely draw the conclusion that it's the CPS.

 

your timing might be off, try loosening the bolt on your distributor, and while a buddy tries to start it, turn it to either side and see what happens. If it tries to start at some point during that, you're a tooth or two off on your distributor, and you'll have to go through all the painful steps of setting your timing right.

 

If you have spark, it is almost assuredly not the crank sensor. If that is bad, you have NO spark.

Are you SURE that it is a strong, blue spark? Anything less and you've got troubles. Quality spark is absolutely essential. A weak ignition coil can leave you with weak spark.

Assuming a good spark, I'd test the camshaft position sensor, located inside the distributor. It isn't common, but if it fails in a certain way, it can create a no-start.

Base timing is controlled by the distributor, but unless you have had it out, I'd leave it alone.

 

I shilled out the cash for a new CPS sensor and installed it with the help of a friend. We were pretty optimistic after seeing so many threads mentioning a bad CPS that this might help. It didn't. I'm still having the same issue.

Other than checking the timing and compression now I don't know what else is left.

I just don't understand how I can come home from work one day and pull it in the driveway, and then go to leave the next day and it's brain dead.

 

Things work until they don't. That is the nature of anything electrical or mechanical.

As I mentioned, check your cam sensor. I've seen it before. Certainly no guarantee, but testing to a solution is the only strategy here.