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Amedee
Amedee, Jeep Technician
Category: Jeep
Satisfied Customers: 25037
Experience:  ASE certified Technician advanced level specialist. Wisconsin certified emissions state inspector
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1998 jeep grand cherokee: liter engine..it wont start, engine cranks

Customer Question

i have a 1998 jeep grand cherokee 4.0 liter engine and it wont start,

engine cranks fine, replaced the coil and the crank case position switch, and still no fire, stuck a screwdriver in the coil wire and checked for fire nothing, what would you suggest next, i also removed all fuses and reinstalled them just to make sure, no blown fuses
Submitted: 7 years ago.
Category: Jeep
Expert:  Amedee replied 7 years ago.

Greetings!

 

I would rec to check for power at the ignition coil and injectors when cranking the engine over. The Auto Shut Down relay supplies power to the ignition coil and injectors. If there is no power, there will be no injector pulse and there will be no spark from th ignition coil. The asd relay could be bad. Or the computer may not be energizing the relay. IF that is the case, the inputs to the computer may be bad (possible bad cam or crankshaft position sensor)

 

AUTOMATIC SHUTDOWN (ASD) RELAY

As one of its functions, the Automatic Shutdown (ASD) relay will supply battery voltage to the ignition coil. The ground circuit for the ASD relay is controlled by the Powertrain Control Module (PCM) . The PCM regulates ASD relay operation by switching the ground circuit on-and-off.

Customer: replied 7 years ago.

where is this asd located and can you send a picture, also is there a cam sensor as well as a crank case position sensor, and i am assuming that the pcm is located on the fire wall on the passager side is this correct

Expert:  Amedee replied 7 years ago.

That is correct!

Here is a picture of both the ecm and the asd relay.

 

graphic

graphic

Customer: replied 7 years ago.

ok i am satisfied with that,

where is the cam sensor?

Expert:  Amedee replied 7 years ago.
The Camshaft Position (CMP) Sensor is mounted in the distributor housing.

 

 

graphic

Customer: replied 7 years ago.
so this cam sensor could cause there to be no spark from the coil? i have changed the asd fuses around a bit but no difference there so i am leaning toward the cam sensor, what you think
Expert:  Amedee replied 7 years ago.

Well, yes... if the cam sensor is bad the computer will not recognize the engine rpm and there for it will not activate the ASD relay.

 

Just be sure to test it before replacing it.

Customer: replied 7 years ago.
sorry to keep asking questions, if i do not have a ohms meter is there a way to test the cam sensor
Expert:  Amedee replied 7 years ago.

You can use a voltmeter or a lab scope.

 

If you use a voltmeter, you can only check the voltage coming out of this sensor with the engine off not with the engine running. THis is recuse the voltmeter is simply not fast enough to check the output of the sensor. But you could still check for power and ground going into the sensor with the key on with your voltmeter.

Expert:  Amedee replied 7 years ago.

Hello!

 

Did you have any further questions?