Has spark, has fuel, cranks but wont start...I'm desperate

[Digger87xj]

have you ruled out all mechanical problems?

Compression?

timing chain properly installed?

cam sensor indexed correctly?


I know you said it ran before but...

 

[nicpaige]

have you ruled out all mechanical problems?

Compression?

timing chain properly installed?

cam sensor indexed correctly?


I know you said it ran before but...

I haven't checked compression since it stopped running. But it cannot be dismissed. Timing chain is properly installed, valve events were checked before buttoning up. Cam sensor has been checked, rechecked, changed and rechecked again.

 

[nicpaige]

the COP 4.0's are pretty tolerant of low voltage. i've cranked mine over with 10V in the battery and it fired.

put a timing light on it, verify that your base timing is correct and that it's not slipped.

disconnect the fuel pump power and attempt to fire it on ether.

I was not aware the timing could be checked with a light on this year engine?
Good idea on the fuel disconnect and starting fluid, will def, try.

 

[87manche]

the ECM controls all timing, but it's nice to verify that the ECM is jiving with the mechanical timing.

you need an inductive timing light, the one with a clamp for a lead.

Have you looked at what the ECM is saying regarding cam/crank signals? It's likely that they're in sync since it's firing injectors, but you never know until you ask it.

 

[AKghandi]

twice i had an issue like this, once was a knock sensor that i had hit with something and once was a coolant temp sensor.

HTH

 

[nicpaige]

I am fairly certain the 2000 XJ does not have a knock sensor. The coolant temp sensor is on my list of things to test.

 

[Digger87xj]

If it's flooding, the cylinders may be washed out and need to be oiled to created appreciable compression to start.

 

[crofoot]

just a thought,have you checked the fuel for water?With the alcohol that is in most fuel these days it doesn't take long for some to collect.We see it often in the shop I work in.You can pump a small amount in a glass jar and let it settle for a while for a visual or there are meters for that.

 

[nicpaige]

Okay, luckily a friend of mine has a 99 XJ 4.0 automatic federal emmisions as his daily driver. He allowed me to swap my PCM into his car. Unlike my XJ his started but ran like it was firing on 3 cylinders...nasty. Swapped his PCM back in and purred like a kitten. Im not sure this is 100% valid or even 50% but I'm thinking my PCM may be jacked up. Opinions?

 

[Tim_MN]

If it's flooding, the cylinders may be washed out and need to be oiled to created appreciable compression to start.

Creative thinking, but not very likely.

 

[nicpaige]

Okay, luckily a friend of mine has a 99 XJ 4.0 automatic federal emmisions as his daily driver. He allowed me to swap my PCM into his car. Unlike my XJ his started but ran like it was firing on 3 cylinders...nasty. Swapped his PCM back in and purred like a kitten. Im not sure this is 100% valid or even 50% but I'm thinking my PCM may be jacked up. Opinions?

Well I was just informed 99's had a distributor. I didnt even look when I switched PCM's out. DUH. Totally invalid test. Now to search for a 2000 XJ willing to let me test my PCM. DAMN

 

[nicpaige]

Update....matching year-part number computer from salvage tried in car and exact same results. Have fuel, spark, but will not fire and run. Back to searching for shorted wires.

 

[Green Mesa XJ]

This is so weird. There are so many of this era Cherokee that go through no start symptoms.

You've done everything and then some. If everything else is good then it has to be a short or a grounding issue.

 

[Dvlman333]

Ok I'm new here but have been working on vehicles and jeeps for years. I ran into this exact same problem on my 2004 ranger. It stayed in a grocery store parking lot for days because I was so frustrated with it. Well long story long I ended up taking a shot in the dark and cut the exhaust right before the converters and it fired right up. The cats were so stopped up that it wasn't letting enough air to flow thru and kept it from starting at all. Just my two cents but may be worth a try.

 

[TRAILREADYXJ]

Have you managed to do a compression check yet? Be good to be able to rule that one out just in case.

 

[Ecomike]

Did you adjust the throttle body for the higher air demand at idle for the larger displacement and injectors?

If it flooded, it may need oil on the rings to get compression back?

Are the spark plug wires (if it has them?) and the injector connectors all on the correct cylinders, or are they criss-crossed?

 

[Ecomike]

Ok I'm new here but have been working on vehicles and jeeps for years. I ran into this exact same problem on my 2004 ranger. It stayed in a grocery store parking lot for days because I was so frustrated with it. Well long story long I ended up taking a shot in the dark and cut the exhaust right before the converters and it fired right up. The cats were so stopped up that it wasn't letting enough air to flow thru and kept it from starting at all. Just my two cents but may be worth a try.

Not a bad idea, have had three give me headaches, but they never got to the no start.

 

[Ecomike]

Tried a Noid light on the injector wires to confirm power to fire the injectors?

 

[nicpaige]

New Cat already on XJ, Noid light checked today. Here comes the gut wrenching part. AFter going over all sensors, battery, timing, etc we tried some starting fluid down the TB. We got a few very large backfires but did not run. SO then it seemed logical to check compression.....not good on all cylinders. Added some oil into cylinders and retested....better but still only 100. Went straight to leak down test and had 85%. Looks like the rings are shot. Blow by coming from crank evac, dipstick. None out exhaust or radiator. I am baffled how this happened the damn thing was running fine, never once did it blow smoke or foul plugs or even run rough. Im going to run a scope in the cylinders just for giggles but it's a foregone conclusion that its coming back out of the Jeep.

 

[Green Mesa XJ]

Oh that sucks. I'm sorry for your trouble, it's a gut wrenching feeling too many of us know well.