Great Lakes 4x4. The largest offroad forum in the Midwest banner
1 - 20 of 25 Posts

· Registered
5,080 Posts
Discussion Starter · #1 ·

now that I got that out of the way.

92 Cherokee, 4.0, Auto

Starter's good and is cranking hard, no issue there.

Distributor is fine, all the plugs and wires are fine.

The rotor is spinning and is fine.

There's no spark at the main wire coming from the coil.

Could it be the ignition coil?

Some of my searches said to clean the CPS contacts, but how the hell do you get to the CPS, I can hardly see it, much less get my arms in there to do something with it?

I don't have the money to be throwing money at parts to figure out what's bad, I need to know what's wrong and I need to fix it.

Any ideas?

· Registered
5,080 Posts
Discussion Starter · #7 ·
Okay, so I unbolted the front driveshaft to give myself some working room, and I can get the socket and ratchet up there, but there's no room to turn it. The only way I can see to get those bolts out is with an air/electric ratchet or impact. Both of which would need serious extensions and a universal to even be able to go up there. Unfortunately all my extensions are in Gladwin with my dad right now. Guess that's what I get for trying to save space in my Jeep.

Any ideas on how to do anything up there?

· Registered
9,047 Posts
The start (cranking) signal from starter relay signals PCM
when starter is engaged. When PCM determines starter is engaged, it
begins to monitor inputs from crankshaft position sensor and camshaft
position sensor.
The PCM uses these signals to determine spark timing and
whether the first fuel injection should occur at cylinder No. 4 or 1
(4-cylinder) or cylinder No. 3 or 4 (6-cylinder). Once synchronization
has been established, the PCM energizes the proper injector and
provides the ignition output needed to start the engine.

The Automatic Shutdown (ASD) relay is located in power
distribution center near the battery or next to radiator coolant
recovery bottle.
The ASD relay is used by the PCM to supply voltage to fuel
pump, fuel injectors and ignition coil. The relay contacts are
normally open.
Power is supplied to relay coil when the ignition switch is
turned on. The PCM controls the ground circuit, which energizes the
coil and closes the relay contacts.
The PCM will only ground the relay when ignition switch is in
the RUN or START positions and activity is sensed through the
crankshaft position sensor and the camshaft position sensor in the
distributor. If the PCM senses the RPM signal has stopped, it will
remove the ground from relay coil, which will cause the contacts to
open and remove power from the circuit.
Ballast Resistor (Cherokee)
A ballast resistor, located between fuel pump relay and the
fuel pump, is used to reduce voltage to the fuel pump. This reduces
fuel pump noise during operation. Ballast resistor is mounted on
fender panel, next to washer fluid reservoir.
When fuel pump relay is energized, voltage is supplied to
fuel pump through the ballast resistor. During start and wide open
throttle conditions, ballast resistor is by-passed and fuel pump
receives its voltage from ballast resistor by-pass relay.
NOTE: Wrangler DOES NOT use a ballast resistor or ballast resistor
by-pass relay in the fuel pump circuit. The PCM operates
fuel pump through the fuel pump relay during all operating
Ballast Resistor By-Pass Relay (Cherokee)
A ballast resistor by-pass relay is located on a bracket next
to power distribution center (next to coolant recovery bottle). By
switching the ground circuit on or off, the PCM can control fuel pump
(power) feed. The ballast resistor by-pass relay receives its voltage
from fuel pump relay.
Normally, voltage is supplied to fuel pump through a ballast resistor. At wide open throttle, fuel pump receives voltage through
the ballast resistor by-pass relay, which speeds up fuel pump to
compensate for higher fuel demand.

· Premium Member
4,555 Posts
Aren't they also the symptoms of coil failure as well though?

What would be involved in PCM replacement?
a coil is a possible cause but pcm failure is kinda common for offroad xj's. for the replacement of the pcm you just bolt it in and go if you get it remanufactured or used. id check used options first.

if you want to check the coil just go get one from autozone and plug it in, ground it and see what happens. if it dont fix it then just return the part.
1 - 20 of 25 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.