No spark problem
11-12-2018, 10:29 PM
#17
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Location: Las Vegas
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Year: 1987
Model: Cherokee (XJ)
Engine: 4.0
Sorry for the delay, had a pool pump break, and had to fix that before the water turned green...
Today cleaned up the C101 some more, got a hint of a start, but not really much.
Pulled the ECU and tried back-probing to check the voltage getting from the CPS to the ECU. The probes on my multimeter were kind of fat, had to work to get a good connection. Was all set to get the reading while cranking, and the dang thing started! Ran on high speed idle for a minute or two, would not slow down to normal idle. I had noticed that both the wires on the ECU had a little movement in and out. Pulled gently on the white wire, nothing, pulled in and out on the violet wire, and the Jeep kicked down to normal idle. Not sure if that was a coincidence or not... Pulled gently on both wires again, and no change. Started 5-6 times afterwards just to make sure, and no problem any time. In fact, it now starts more quickly than before this incident.
Almost willing to call it fixed, but want some more time and starts on it first.
The only thing I haven't done is replace the grommet/ cover plate that the CPS fits through, it was getting in the way of the CPS working correctly. Is that important to have in place? It's obviously not a dirt free seal anyway...
Today cleaned up the C101 some more, got a hint of a start, but not really much.
Pulled the ECU and tried back-probing to check the voltage getting from the CPS to the ECU. The probes on my multimeter were kind of fat, had to work to get a good connection. Was all set to get the reading while cranking, and the dang thing started! Ran on high speed idle for a minute or two, would not slow down to normal idle. I had noticed that both the wires on the ECU had a little movement in and out. Pulled gently on the white wire, nothing, pulled in and out on the violet wire, and the Jeep kicked down to normal idle. Not sure if that was a coincidence or not... Pulled gently on both wires again, and no change. Started 5-6 times afterwards just to make sure, and no problem any time. In fact, it now starts more quickly than before this incident.
Almost willing to call it fixed, but want some more time and starts on it first.
The only thing I haven't done is replace the grommet/ cover plate that the CPS fits through, it was getting in the way of the CPS working correctly. Is that important to have in place? It's obviously not a dirt free seal anyway...
11-13-2018, 07:07 AM
#18
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Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
Leave the grommet out.
Here's something:CRUISER'S MOSTLY RENIX TIPS
Many times, when other fixes have failed, it becomes necessary to eliminate the ECU to harness connections as a cause. This requires removing the ECU. Up under the dash, to the right of the steering column is the ECU mounted to a black bracket. The bracket is held in place by two 10mm nuts to the underside of the dash. It’s most easily removed using a ratcheting wrench but a socket will work.
Once you get the ECU down, unplug the two harness connectors from it. Visually inspect the connectors and pins.
Using a good quality electronics cleaner, liberally spray both of the harness ends and the ECU pin area.
Now, take a small pick or a dental tool and go to the harness connectors. Using the tool, tweak each female receptacle in the harness plugs so they will grasp the ECU pins more tightly.
Plug the harnesses back on to the ECU and reinstall it.
Revised 1-31-2016
Here's something:CRUISER'S MOSTLY RENIX TIPS
RENIX ECU CONNECTOR REFRESHING
OCTOBER 30, 2015 SALAD 14 COMMENTS
Many times, when other fixes have failed, it becomes necessary to eliminate the ECU to harness connections as a cause. This requires removing the ECU. Up under the dash, to the right of the steering column is the ECU mounted to a black bracket. The bracket is held in place by two 10mm nuts to the underside of the dash. It’s most easily removed using a ratcheting wrench but a socket will work.
Once you get the ECU down, unplug the two harness connectors from it. Visually inspect the connectors and pins.
Using a good quality electronics cleaner, liberally spray both of the harness ends and the ECU pin area.
Now, take a small pick or a dental tool and go to the harness connectors. Using the tool, tweak each female receptacle in the harness plugs so they will grasp the ECU pins more tightly.
Plug the harnesses back on to the ECU and reinstall it.
Revised 1-31-2016
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