GOWjeep23

I have a 91 jeep cherokee limited. I6-4.0L
Its starting having trouble starting at time like the morning, humidity, rain ect to get it to start i had to crank and crank and crank it and eventually it would sputter and start then run great. after it started once i could shut it off and start it right up again. drive around a bit, shut it off and start it right up again. thought it was moisture in the cap and rotor. as time went the problem just got worse and worse.

I have no spark right now.
12v to the coil.
The cap, rotor, plugs, wires and coil are all fairly new.
I also have no fuel pressure.
The pump doesn't kick on when i turn the key forward like it should.
I have 12v at the relay for the fuel pump.
I have just replaced the crank position sensor and still nothing.
After i've been playing with the car checking things and trying things randomly it will start with powerful spark and the fuel pump working perfectly.

could the fuel pump be bad causing the pcm to not trigger a spark? or is my brainbox toast? what should i be checking for?

GOWjeep23

i just went and jumped the fuel pump relay and my fuel pump kicked right on.

what triggers these to turn on?

tjwalker

Spark: 12 volts from ignition switch to the ASD relay; when the key is first turned on the PCM provides a ground to the ASD relay to energize it, then the ASD relay passes 12 volts to the coil primary side. If no crank sensor signal is generated after a couple of seconds the PCM cuts the ground to the ASD relay (and fuel pump relay too) and that cuts power to the coil (and fuel pump). Key to START and once again the PCM energizes the ASD relay. Now, a critical element is the crank sensor--no signal from the crank sensor and the PCM won't trigger the coil to provide spark.

GOWjeep23

i was told to check out my ignition switch because when i turn the key to the ON position nothing happens and i should hear the fuel pump kick on for a second or two. and i have already replaced the crank position sensor and nothing changed.

GOWjeep23

if i wiggle the wires under my dash my fuel pump will kick on and i can start it. so i put a new ignition switch it in and so far seems to be working. idk if thats because it was bad or because i happen to wiggle something else while i was down there.

where is the ASD relay located?

and my new crank position sensor that i put in seems to make her misfire and run really rough till it just dies and i have NO power. hard time coming up the driveway and its really not a steep driveway.

tjwalker

[QUOTE=GOWjeep23;1046450where is the ASD relay located? And my new crank position sensor that i put in seems to make her misfire and run really rough till it just dies and i have NO power. hard time coming up the driveway and its really not a steep driveway.[/QUOTE]

The ASD relay is located inside of the power distribution center, the black box under the hood on the passenger side.

As for your crank sensor, if you purchased an aftermarket crank sensor and your symptom began IMMEDIATELY after that install, buy one directly from Jeep and try that. There is no lack of threads about a whole host of issues with aftermarket crankshaft position sensors.

I buy plenty of aftermarket parts, but the crankshaft position sensor is always purchased directly from Jeep. They cost more, but worth every penny.

GOWjeep23

Could it be a problem with my security system? Is there a way to completely bypass the security system if that is the problem?
And ill have to check the asd as well when I get home tonight.
Might try putting the old CPS back in since that didn't seem to be the problem, I'm short on cash right now.

GOWjeep23

ok so i put the old crank sensor back in and shes smooth when i do get her started. did some research and found out that i had to unplug the trasmission control unit to get the lower dash part out to get at the steering column so i have power too.

i still have a problem where when i turn the key to the start position the fuel pump isnt kicking on and im not getting the usual check engine light and when i crank it no spark either. when i wiggle things under the dash i seem to get the check engine light, i hear my fuel pump and i get spark and she starts right up. once shes running she runs fine. no power loss and shes never died on me and everything is fine. what is it that would stop the fuel and the spark where i get no check engine light as well? security system?