No spark 4.0 1997

[drueg]

Greetings, over the past couple of weeks I've had an occasional hard to start after running issue. It happened after that car had run for 10 minutes and then sat for an hour (at the gym) then when I would try and start and it would just crank for 2-3 minutes and finally would catch and run fine.

Now it has no spark on any cylinder. Fuel pressure is 37 lbs with just turning the key. I checked every fuse on the truck and all appear fine.

I don't want to just start throwing parts at it; my searches find that I might have a bad coil pack or cam position sensor.

Tomorrow, after my back quits screaming at me, I plan to check that voltage at the coil pack and then use my VOM to look for unusual resistance in the three coils on the pack.

FYI, everything else electric on the truck works fine and the battery is fresh charged in good condition.

Ideas???

Dan

 

[Rowdy Fitzgerald]

Check all your connections, clean them and apply dielectric grease, make sure the grounds are all sanded clean and reattached. Then try it again. Then get a electrical tester and test the cps, coil packs, etc.


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[RonD]

In 1995 the spark control was moved into the computer.

The CKP(crank position) sensor behind the crank pulley is what starts and times the spark system.

Assuming you have checked the coil pack's connector, and you have 12volts on the red wire at the coil pack with the key on, then it is either a CKP sensor or computer problem.

CKP sensor is on passenger side of crank pulley, it's wires run up past the water pump to the lower intake and join the wiring harness just below throttle body

 

[drueg]

In 1995 the spark control was moved into the computer.

The CKP(crank position) sensor behind the crank pulley is what starts and times the spark system.

Assuming you have checked the coil pack's connector, and you have 12volts on the red wire at the coil pack with the key on, then it is either a CKP sensor or computer problem.

CKP sensor is on passenger side of crank pulley, it's wires run up past the water pump to the lower intake and join the wiring harness just below throttle body

It was the crank sensor.
Changed it and it fired right up.

Thanks
Dan

 

[RonD]

Good work

Those rarely fail, did it look like something hit it?

 

[drueg]

Nope, it has no exterior signs of damage.
What puzzles me is that it was first intermittent and then suddenly terminal.

 

[RonD]

Yes, that is also odd, almost like a bad or dirty connector.

It should also set a code P0335 to P0339 are CKP sensor codes