No Start
#1
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Year: 1994...mostly...
Model: Cherokee (XJ)
Engine: 4.0L I6 HO, Lot's of Bolt Ons
No Start
Well I purchased a 99 Grand Cherokee with a 4.0L on Friday.
It'll crank all day but won't start.
Started by replacing the fuel filter(has built in pressure regulator).
Next Used a fuel pressure gauge to verify pressure, 49 PSI on the rail.
Drops to 30ish when cranking?
Moved on to checking for spark, replaced all spark plugs and did a compression test.
130-140psi across the board between the cylinders.
Not sure what to do next?
It'll crank all day but won't start.
Started by replacing the fuel filter(has built in pressure regulator).
Next Used a fuel pressure gauge to verify pressure, 49 PSI on the rail.
Drops to 30ish when cranking?
Moved on to checking for spark, replaced all spark plugs and did a compression test.
130-140psi across the board between the cylinders.
Not sure what to do next?
#3
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Year: 1999
Model: Cherokee
Engine: 4.0
You need a strong, BLUE, snapping spark. Yellow/orange/white indicates a weak spark, which is usually related to a failing ignition coil.
What color is your spark? Ignition coils can be tested for primary and secondary resistances with a manual and a meter.
What color is your spark? Ignition coils can be tested for primary and secondary resistances with a manual and a meter.
#5
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Year: 1994...mostly...
Model: Cherokee (XJ)
Engine: 4.0L I6 HO, Lot's of Bolt Ons
At this point I'm thinking the pressure drop was too high on the fuel rail.
I've ordered a new pump module and also a set of 784 injectors.
I've ordered a new pump module and also a set of 784 injectors.
#6
Old fart with a wrench
Are you getting electrical signals to the injectors? Not power, on-cycle pulses? If you're getting spark, that's about the only thing left. If the CPS was shot, you wouldn't be getting spark.
#7
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Year: 1994...mostly...
Model: Cherokee (XJ)
Engine: 4.0L I6 HO, Lot's of Bolt Ons
Yeah, actually the PO thought it was the CPS so that's brand new.
I unplugged it to verify along the way.
Also pulled the fuel injector fuse at one point to verify its function.
But I have not individually checked each injector for a signal.
I unplugged it to verify along the way.
Also pulled the fuel injector fuse at one point to verify its function.
But I have not individually checked each injector for a signal.
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#8
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Year: 1994...mostly...
Model: Cherokee (XJ)
Engine: 4.0L I6 HO, Lot's of Bolt Ons
Replaced, the fuel pump and injectors
Still same issue...
Threw a P0320 code...
But again just replaced the CPS and the coil pack is firing
Tps, map, iac?
Cam shaft position sensor?
Still same issue...
Threw a P0320 code...
But again just replaced the CPS and the coil pack is firing
Tps, map, iac?
Cam shaft position sensor?
#9
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Year: 1994...mostly...
Model: Cherokee (XJ)
Engine: 4.0L I6 HO, Lot's of Bolt Ons
Posted up the issues on the Cherokee Forum FB page.
Got some great feedback that it's likely an intermittent CPS failure (defective sensor) or the PCM is throwing the wrong code and its really a CMS failure (common on 1997+ computers)
I'll be swapping both and see if it resolves.
Got some great feedback that it's likely an intermittent CPS failure (defective sensor) or the PCM is throwing the wrong code and its really a CMS failure (common on 1997+ computers)
I'll be swapping both and see if it resolves.
#10
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Year: 1994...mostly...
Model: Cherokee (XJ)
Engine: 4.0L I6 HO, Lot's of Bolt Ons
I've swapped the CMS and another CPS same problems still
Need the pin out for a 99 Grand Cherokee PCM connector
Need the pin out for a 99 Grand Cherokee PCM connector
#15
Old fart with a wrench
Did you check the PCM wiring plugs? Your codes are for intermittent signals from the CPS and cam sensor.