CPS - SOLVED
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Tuned
Joined: Nov 2016
Posts: 385
Likes: 116
From: Full time RVer
CPS - SOLVED
No start and tach is not moving. Replaced CPS with a new spare from RiffRaff (black). Much to my surprise, no start and no tach movement. Well?
Is there a test procedure for the CPS? I haven't run across one. What about one for the harness? It's been a bad fall for rodents here in the woods. Anything that sits outside, needs a trap in the glove box. At least I haven't noticed any magic smoke under the hood.
At least it didn't happen while we are boondocking in the west.
Is there a test procedure for the CPS? I haven't run across one. What about one for the harness? It's been a bad fall for rodents here in the woods. Anything that sits outside, needs a trap in the glove box. At least I haven't noticed any magic smoke under the hood.
At least it didn't happen while we are boondocking in the west.
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Tuned
Joined: Nov 2016
Posts: 385
Likes: 116
From: Full time RVer
I was hoping someone had tested the harness by checking the pin voltages at the CPS plug? I do have a electrical schematic, so I can see there is a DK Green 795 (pin 49 PCM) cam pos sense, a LT Blu 796 (pin 65 PCM) cmp r tn and BRN/WHT 351 (pin 90 PCM). Is the CPS a 5 volt sensor?
Lead Driver
Joined: May 2009
Posts: 6,815
Likes: 708
From: Tobyhanma, PA
I believe it is a 5 volt sensor. I just visually checked my harness when I was having a no start issue.
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Lead Driver
Joined: Sep 2002
Posts: 9,554
Likes: 2,034
From: North Texas
Try 49 and 65 on VAC, just crank the motor at the solenoid. Should put out some voltage on a DVOM. Pin 90 is probably a ground that is shielded. At least other sensors like this I have tested are like that. Input. Output. Shield.
What voltage you should see, I could not tell you. I know what to look for on the BMWs I own that use something similar. Depends on cranking speed, teeth on the sensor, etc. I have one reference pin on the flywheel of a BMW that is 0.4 VAC and the teeth on it show 4.0 VAC. There are well over 100 teeth there.
Either way, try it and you will see if you have the voltage flowing at the square connector. If so, clean it with Deoxit. Reconnect. Check at PCM plug next.
What voltage you should see, I could not tell you. I know what to look for on the BMWs I own that use something similar. Depends on cranking speed, teeth on the sensor, etc. I have one reference pin on the flywheel of a BMW that is 0.4 VAC and the teeth on it show 4.0 VAC. There are well over 100 teeth there.
Either way, try it and you will see if you have the voltage flowing at the square connector. If so, clean it with Deoxit. Reconnect. Check at PCM plug next.
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Tuned
Joined: Nov 2016
Posts: 385
Likes: 116
From: Full time RVer
It's running! WooHoo!
I checked the harness and it's intact. The rodents are off the hook.
I disconnected the CPS plug and reconnected it 5 times. It started right up. This indicates too me that their was an issue with the contacts in the plug or their is an issue with the a wire/wires at the plug? I cleaned the contacts well, pinched the plug contacts slightly tighter and put some dielectric grease in it. I'm going to try starting it a few times a day for the next week and see how reliable it is?
I would like to thank everyone for your time. Its IPA thirty.
I checked the harness and it's intact. The rodents are off the hook.
I disconnected the CPS plug and reconnected it 5 times. It started right up. This indicates too me that their was an issue with the contacts in the plug or their is an issue with the a wire/wires at the plug? I cleaned the contacts well, pinched the plug contacts slightly tighter and put some dielectric grease in it. I'm going to try starting it a few times a day for the next week and see how reliable it is?
I would like to thank everyone for your time. Its IPA thirty.
Tuned
Joined: Nov 2020
Posts: 403
Likes: 171
From: Greenville, SC
Thread Starter
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Tuned
Joined: Nov 2016
Posts: 385
Likes: 116
From: Full time RVer
Thread Starter
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Tuned
Joined: Nov 2016
Posts: 385
Likes: 116
From: Full time RVer
WELL, it's no start and no tach needle movement again. I checked the continuity on the three wires from the CPS plug to the PCM plug and their fine. I turned the buzzer on my Fluke DVOM and wiggled the harness along it's entire length and no loss of continuity.
I also verified the 5 VREF and 12 volt dc return signal, all good. Still no tach needle movement. PCM???
I'm wondering if the new (spare) Motorcraft CPS from RiffRaf is defective? Could be a fluke. Another new unit should be here tomorrow. This is starting to look like a trip to the stealership. That would be a 16 mile tow bill also.
I also verified the 5 VREF and 12 volt dc return signal, all good. Still no tach needle movement. PCM???
I'm wondering if the new (spare) Motorcraft CPS from RiffRaf is defective? Could be a fluke. Another new unit should be here tomorrow. This is starting to look like a trip to the stealership. That would be a 16 mile tow bill also.
Lead Driver
Joined: May 2009
Posts: 6,815
Likes: 708
From: Tobyhanma, PA
I had the same issue. I had gotten a junk parts store replacement, it wiggled the tach a bit but apparently not enough. I tried everything for days, finally pulled the "spare" cps I had out if the glove box. It was literally the oem 20+ year old one, no oring, just gobs of rtv stuck around it. I cleaned it up, gave it a new oring and sheet you not, the truck fired up as soon as I hit the key
Trying a different sensor is always worth a shot to me.
Trying a different sensor is always worth a shot to me.