Hello,
I just purchased a 2000 Cherokee with the 4.0. The motor does not start. It cranks.
there is no spark and no injector.
the fuel pump is running.
The previous owner changed the crank position sensor, the coil pack, tried several ECU (one from a Grand Cherokee 4.0, I found a second set of key with the car and a immobiliser which is not the correct one (with a 90° angle)...

What I did was to put back the ECU that I think is the original and the immobiliser which is "straight" with the original key.
When I put the key in the ignition position, the key lamp on the dash flashes for 2 or 3 seconds and then disappears. With the other ECU, the key lamp on the dash stays on.

I checked the Fuel pump relay: OK.
12V on the coil and injectors.
But I have no spark nor injector signal.
The crank position sensor is making the signal(checked with the oscilloscope. the Fuel-pump starts when I turn the key on ignition position for a few seconds, then stops. And starts again when I crank. But no injector nor coil signal...

What could cause this problem?
Is there a way to check that I have the correct ECU and correct immobilizer + key? (I tried to read the VIN on the ECU with HP-tuners but it says no VIN (on all ECUs)..)
What could cause this behavior of no coil and no injector signal when it is cranking? (could this be a problem of camshaft sensor?) I have not tested the signal yet.

Would you have any idea about how to troubleshoot this?
Thanks in advance
Guillaume

 

I just found this morning that the camshaft sensor does not work: the output is always at 5V, I can see it is broken inside.
I ordered a new one.
Could you please confirm me that the camshaft sensor default prevents spark and injectors?

Thanks in advance
Guillaume

 

I believe on the later models that is correct, no cam sensor input no spark.

 

OK, Thank you.
I was thinking that the ECU would switch to batch mode when the camshaft signal is absent. But if it is not the case, it would explain why it does not start.
The previous owner changed everything but this part...

 

Yes it behaves similar for CPS and CAM
ECU wont default to anything with these- that's the purpose: no sensor input, no spark/injectors.

 

After changing the camshaft sensor, there is spark again.
the car starts and idles good but when I accelerate, it begins to shake and finishes stopping.

Now that I know the ECU is right and everything seems OK, I will remove the transmission to rethread the crankshaft sensor holes. (it is currently held with wood screws and wood dowel as both holes were stripped...

I saw that the fuel pressure is 70psi, little less than 5 bar. is this normal? and as soon as the fuel pump stops, the fuel pressure drops to 0 again: I feel like the non return valve is dead and the pressure regulator might be too. Could you tell me your thoughts?