cmp,ipr trouble shooting
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cmp,ipr trouble shooting
1.On my 94 7.3 Turbo if the CMP goes open will this effect the circuit that cycles the gp relay or turns the "wait to start" light on?
2. Could a bad IPR cause engine to shut down instantly and disable the gp relay or "wait to start light"?
3. Does anyone know how to test a cmp if it is disconnected and what the ohm readings would look like? My truck just quit (just like I turned the key off) while driving to town. It would not fire but the "wait to start" engine light would not illuminate. I waited 15 min. while cycling the key several times and the light came on, engine cranked ran fine for 100 yards and quit again. Hasn't worked since. I read the voltage at the cmp with the key on and had 12v on the ref. voltage & about 12.27 on the cmp signal. I am in a rural area and hard to get to mech. that could work on it. Any help is much appreciated.
2. Could a bad IPR cause engine to shut down instantly and disable the gp relay or "wait to start light"?
3. Does anyone know how to test a cmp if it is disconnected and what the ohm readings would look like? My truck just quit (just like I turned the key off) while driving to town. It would not fire but the "wait to start" engine light would not illuminate. I waited 15 min. while cycling the key several times and the light came on, engine cranked ran fine for 100 yards and quit again. Hasn't worked since. I read the voltage at the cmp with the key on and had 12v on the ref. voltage & about 12.27 on the cmp signal. I am in a rural area and hard to get to mech. that could work on it. Any help is much appreciated.
Last edited by bobreid; Jan 25, 2005 at 07:54 PM.
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From: Northern IL
I will assume you have a PSD engine since you are asking about CMP and IPR. If you do not have a PSD but rather a 7.3 IDI turbo which was offered in 94 then you do not have a CMP or IPR.
To answer question #2, no. The symptoms you describe are consistent with a bad CMP.
I did at one time have the Ohm readings but that computer has since crashed. I do remember the old one had different ohm readings if it was hot as opposed to room temp. The new one stayed consistent regardless of temperature. Anyway a CMP is a hall effect sensor, it needs a metal object to pass in front of it to work. It is not a open / closed type "switch".
Usually, but not always a CMP will act up on a hot engine. Let the engine cool off & it will start and run till it warms up again. Besides the WTS light not working, if while you are cranking the tach does not register any PRM 's it is the CMP.
To answer question #2, no. The symptoms you describe are consistent with a bad CMP.
I did at one time have the Ohm readings but that computer has since crashed. I do remember the old one had different ohm readings if it was hot as opposed to room temp. The new one stayed consistent regardless of temperature. Anyway a CMP is a hall effect sensor, it needs a metal object to pass in front of it to work. It is not a open / closed type "switch".
Usually, but not always a CMP will act up on a hot engine. Let the engine cool off & it will start and run till it warms up again. Besides the WTS light not working, if while you are cranking the tach does not register any PRM 's it is the CMP.
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Ggg6, I finally got some time to trble shoot and found that my tach did work. I turned on my key and as before had no response from glow plug relay. As I was checking volts & trying to locate sensors I unplugged the ( what I think is) ICP and the GP relay operated. The engine started and ran perfect. When I plug the ICP back in it kills the engine just as if I turned the key off. I really do appreciate your help, it pionted me away from the CMP and I stumbled across this. Thanks agian!
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