Mechanics

94 SECURITY, WONT STAY RUNNING

1994 Jeep Grand Cherokee • 150,000 miles

I was haveing a problem with an electrical drain and I found that fuse #8 was causing the problem, so I pulled it out and it set the security.

How do I reset the security?
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J.stieg
January 6, 2012.



Close all doors, hood and trunk and use the key to lock and unlock the door to disarm the system.

KHLow2008
Jan 6, 2012.
I closed the doors and hood and unlocked the driver side door with the key and the security is disabled. Jeep starts fine.

Every time I disconnect the battery the security will set. It did not do that before. Not a big deal but seems abnormal. Any ideas, thanks

Tiny
J.stieg
Jan 7, 2012.
No, that is normal. It happens to us all the time when working on a vehicle.

Wrenchtech
Jan 7, 2012.
Once the battery is disconnected, the security would reset when reconnecting. The only way it will not set is wile reconnecting the battery, the ignition switch is turned to ON, which is not advisable as it can fry the engine computer if there are any current surge.

KHLow2008
Jan 7, 2012.
Now it does not fire up right away. The security lights are NOT flashing so that side seems normal.

Need some expertise.
It takes 4 or 5 crank attempts before it starts. I can not hear any activity at power distribution box for the first few cranks.
Also there is no spark on initial crank.

In detail: The coil has positive feed in run position, but not any ground pulse from PCM (on first 5 cranks). Also the fuel injectors are the same way no grounding pulse(on first 5 cranks)

I suspect Ignition switch, PCM, ASD relay, or possibly crank sensor.

I appreciate your help, thanks!

Tiny
J.stieg
Jan 16, 2012.
If difficulty in starting is only after angine is stopped for a while, the most likely cause would be drop in fuel pressure.

If there is not sparks, you need to test if battery voltage is available at the ignition coil while cranking, if yes, it is not likely to be the ignition switch or ASD relay. The PCM is a likely cause but PCM seldoms fails and allow you to start.

The most likely cause would be the crank or cam sensor depending on what is missing, fuel or sparks.

KHLow2008
Jan 16, 2012.
Ok here is where I'm at. The Jeep will not start in the first ten cranks, or the first 2 min of trying roughly.

1 The fuel pump does not come on.
2 The coil has 12v cranking but no PCM pulse and "NO SPARK"
3 Injectors also have 12v cranking but no PCM ground pulse.
4 Security/theft activated when battery is disconnected.

The first three problems go away after a minuet of cranking or so.

Tiny
J.stieg
Jan 18, 2012.
Presence of battery voltage at the ignition coil and injectors indicates the ASD relay is being energised and should also energise the fuel pump relay.

Which engine do you have?

KHLow2008
Jan 18, 2012.
I have the 5.2l

I found whats going on, When I turn the key to the run position, I leave it there for 15 seconds then I hear the fuel pump come on and then I crank and it starts.

There is a delay in the ignition. Not sure why

Tiny
J.stieg
Jan 18, 2012.
The fuel pump relay is being energised late.

Attach a test light to the ignition coil power supply wire and turn ignition on. Note if battery voltage is present then or delayed as well.

If it is present, check the fuel pump relay. It could be failing.

If battery voltage is also delayed, you have a fault with the PCM. Check for bad ground circuit connections.

KHLow2008
Jan 18, 2012.
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