95 4.0 RHD (UK) crank no start

[ahyland]

I've done a ton of searching and tried about two dozen things and still can't get my 95 4.0 xj Cherokee (66k miles ) to start, starting to think the pcm might be toasty

It cranks but won't start, I have spark and good fuel pressure and it doesn't drop off too quickly, reset distributor to tdc on compression stroke but it just won't go

Crankshaft sensor is good
Camshaft sensor is good
New coil plugs and leads
New rotor and cap
Drained tank and put 20L of premium petrol in
Spark looks good (although not bright blue)
Battery charged to 13 volts
Also replaced map, iac and TPS sensors
New starter motor
Checked injectors with noid lights (old and new injectors)

Checked the grounds about 100 times

Compression is 140 psi (+-10 on all cylinders)

Anything else to check because this is driving me crazy

It wants to start and gets very close just doesn't quite get there

Any help would be appreciated

Pcm part number is 56026950 (yes really)

 

[ahyland]

When I search the pcm part number the ONLY result I get is for a grand Cherokee and not a Cherokee, has a previous owner put the pcm from a grand in a non grand? Is this my problem?

 

[ahyland]

Extra info

I currently have no cooling system installed, waiting to see if it will run first in case it's all got to come out to make it do so

I also have no brakes, I've put 3 new lines in just waiting on some bits to arrive to do the last one, is there some kind of safety system where I need to have brake pressure for it start?

I have no (except the ones that should) warning lights on the dash, the only flash codes I get are 12 and 55, I get ones for cam and crank if I unplug them, their voltage readings look okay too

Could the timing chain be a tooth off or something?

 

[Natesgtojudge]

Was it running fine before you replaced everything? Hindsight being 20/20, and all that good stuff, but your vehicle has crazy low miles to begin with to start throwing all those parts at it and changing everything. Rather than going one step at a time now you've got a whole bunch of extra variables it could be.

Have you tried getting it to start and run for a few seconds on starting fluid? If it starts and runs fine for those few seconds after a few blasts of starting fluid it would tell you whether or not its a fuel issue.

Are you absolutely sure you have the spark plug wires going to the correct cylinder with their position on the distributor cap? I would also take a look around the engine bay for any loose pigtails or something that might've gotten disconnected and not plugged back in. MAF, throttle body, etc. Just take a few minutes and confirm all the plugs are in and secure.

 

[ahyland]

Was it running fine before you replaced everything? Hindsight being 20/20, and all that good stuff, but your vehicle has crazy low miles to begin with to start throwing all those parts at it and changing everything. Rather than going one step at a time now you've got a whole bunch of extra variables it could be.

Have you tried getting it to start and run for a few seconds on starting fluid? If it starts and runs fine for those few seconds after a few blasts of starting fluid it would tell you whether or not its a fuel issue.

Are you absolutely sure you have the spark plug wires going to the correct cylinder with their position on the distributor cap? I would also take a look around the engine bay for any loose pigtails or something that might've gotten disconnected and not plugged back in. MAF, throttle body, etc. Just take a few minutes and confirm all the plugs are in and secure.

I bought it with the engine in the boot so I'm not sure how it ran beforehand. I was missing most of the stuff I've replaced. It had sat for 11 years so I've done a medium rebuild on the engine etc.

I did try starting spray, didn't really make a difference

However I have just borrowed the neighbours jump pack (topdon 3000 or something) and put it in boost mode and it fired up after about 10 seconds of cranking Think it supplies it with around 16 volts in boost mode.

Ran it for around 20 seconds as I dont want to warp anything with no coolant but it sounded great, no misses or backfiring.

Could this point towards high resistance in some of the wires and boosting the voltage overcomes any possible wiring issues?

When it was cranking it sounded much faster then on the battery alone, possibly bad wires to starter or the (new) starter itself?

I will have to take another look tomorrow as it's got no exhaust currently and is almost 9pm

 

[ahyland]

Update

So I connected jump leads to the body and terminal on the starter and it fired right up, which is odd because I did a voltage drop test on the starter wire and got like 0.1 volt, idk.

Iv attached the exhaust so it's a bit quieter and noticed it's missing on 1 cylinder and won't idle without a little bit of throttle, haven't figured out which one yet, will have to put a stick on the pedal or something to keep it at 1000 and unplug either spark plug wire or injector and figure out which one and go from there

I'm going to buy some 2 awg wire for the starter and 4/6 stuff for grounds ect, I may even put a dedicated ground for the body on the starter.


At least I'm getting somewhere with it


Still got bits to do, need to put new tank in but waiting on one from Germany and the brakes need finishing, may post some pictures later in the week, I have an eent right at the end of April I'd like to take it to so sort of have a deadline

 

[Rob Mayercik]

Update

So I connected jump leads to the body and terminal on the starter and it fired right up, which is odd because I did a voltage drop test on the starter wire and got like 0.1 volt, idk.

Iv attached the exhaust so it's a bit quieter and noticed it's missing on 1 cylinder and won't idle without a little bit of throttle, haven't figured out which one yet, will have to put a stick on the pedal or something to keep it at 1000 and unplug either spark plug wire or injector and figure out which one and go from there

I'm going to buy some 2 awg wire for the starter and 4/6 stuff for grounds ect, I may even put a dedicated ground for the body on the starter.


At least I'm getting somewhere with it


Still got bits to do, need to put new tank in but waiting on one from Germany and the brakes need finishing, may post some pictures later in the week, I have an eent right at the end of April I'd like to take it to so sort of have a deadline

If you have an expired credit card or hotel key card, you can open the throttle by hand at the throttle body and slip the card in between the bit you rotate and the stop it sits against for idle, will yield a similar result.

Saw someone do that years ago with his work badge (which is also the same size/thickness as a credit card) to keep the idle up on my '92 while we were trying to jumpstart another XJ whose battery had gone dead due to a wonky alternator. I think of it as the "redneck high idle switch"...

 

[Anak]

Not cranking over fast enough is certainly an issue. See Rob Dahm's challenges with his 12 rotor.

The battery cables are a good place to start. If they have not been replaced already then they are probably due.

If battery cables don't solve the problem the the starter and solenoid are the next most likely suspects. Note that the brushes on the starter are relatively easy to replace if you want to try going that route. See post #8 here: Starter Rebuild

 

[ahyland]

Update #2

Not sure if it just needed to "burn" off the assembly lube after the rebuild but I used a large socket to hold the throttle body open slightly so it would run at 1000 rpm for a few minutes without me needing to hold the pedal down but when I start it now it's like everything has eased offa and it fires right up. No idea could be a gremlin that comes back.

I had already ordered the new cables so will fit them anyway onc they arrive

I've also fixed the misfire / strange idle issue, turned out to be a bad new map sensor, gone back to the old one but have to use cable ties to hold the connector on.

Both issues possibly related to the map sensor but it was staring to start easier before I replaced it

Slowly getting there

Brake parts and fuel tank should be arriving tomorrow, will fit Tuesday/Wednesday when off work

 

[ahyland]

Fitted new cables for the starter and ran extra grounds from near the pcm to the battery did t bother with a ground for the starter as it seems perfect the way it is now

Also ended up replacing the caps in th pcm and it's running like brand new. Still need to sort the brakes, windows horn and front bumper out but that's it