CPS drama - SOLVED
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Tuned
Joined: Nov 2016
Posts: 385
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From: Full time RVer
CPS drama - SOLVED
I posted a thread in the OBS section and have run out of options. So I thought I would give you guys a go. This is where I'm currently at:
I installed a new CPS from RiffRaff 4 days ago because of a no start and no tach needle movement issue. 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 installed a new CPS from RiffRaff 4 days ago because of a no start and no tach needle movement issue. 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.
Lead Driver
Joined: Oct 2005
Posts: 6,129
Likes: 1,919
From: Ponca City, OK
I assume you've gone through all the fuses w/ the mulimeter. How about the PCM, IDM, and fuel pump relays, are they all powering up and getting voltage in and out?Does forscan work w/ the OBS rigs?
Lead Driver
Joined: Jul 2017
Posts: 6,853
Likes: 2,330
From: WV
Personally I’d check fuses while waiting then try the new CPS before digging any deeper. Especially if the sensor change fixed the same issue for a few days. New parts do fail.
Lead Driver
Joined: Oct 2005
Posts: 6,129
Likes: 1,919
From: Ponca City, OK
Ah, that's right. I'd forget my pants if not for the breeze sometimes.
Hotshot
Joined: Dec 2012
Posts: 11,267
Likes: 1,651
From: Las Cruces New Mexico
Also check for moisture, my 00 7.3 stalled on me when I went thru a puddle, turns out moisture somehow got into the CPS causing the truck to stall, bought a new pig tail and all was good. Worth a shot replacing the pig tail as the gasket could be allowing moisture to get into the connector.
Thread Starter
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Tuned
Joined: Nov 2016
Posts: 385
Likes: 116
From: Full time RVer
Also check for moisture, my 00 7.3 stalled on me when I went thru a puddle, turns out moisture somehow got into the CPS causing the truck to stall, bought a new pig tail and all was good. Worth a shot replacing the pig tail as the gasket could be allowing moisture to get into the connector.
The PCM fuse is good. But, if the PCM doesn't detect engine rotation (no tach needle movement (OBS)), it will not signal the IDM to fire the injectors.
I do have efuel, clearly some haven't read my signature. I also have a digital fuel pressure gauge in the cab, 64.7 psi.
In two weeks this thing usually pulls the cargo trailer to Arizona. I hope it's up to the task?
Thanks for taking the time.
Tuned
Joined: Oct 2020
Posts: 467
Likes: 158
All good advice above. Keep us posted I’d like to know what you find. This wouldn’t be the first sensor that was bad right out of the box..
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Tuned
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Lead Driver
Joined: Jul 2017
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From: WV
Have to go out of the way to see them on the phone. Didn’t seem relevant in this case. Obviously I was wrong. 
Lead Driver
Joined: Oct 2005
Posts: 6,129
Likes: 1,919
From: Ponca City, OK
Yeah there's quite a bit of instructional info in the tech sticky, and truthfully it's fairly plug and play. I've got AE and forscan and haven't touched AE in nearly a year now. Even mounted a tablet to the dash and have forscan running any time the truck is.
Cargo Master
Joined: Oct 2007
Posts: 2,712
Likes: 107
From: BoCoMo
I am not sure about the about the tach needle movement, but if your heating element in the fuel bowl burns up, it will arch and and blow fuse #30. this will cause a no start situation until the fuse is replaced. Check that fuse. if blown... Unplug the connection behind the fuel bowl first, so the heating element will not arch again and blow the fuse again. you do not need the "fuel bowl heating element/ and water in the bowl censor", so leave unplugged.
Water/moisture in the CPS connections area will shut the truck off and or not let it start. Take out CPS and clean area and CPS and reinstall with Dialectic grease.
Water/moisture in the CPS connections area will shut the truck off and or not let it start. Take out CPS and clean area and CPS and reinstall with Dialectic grease.
Lead Driver
Joined: Oct 2005
Posts: 6,129
Likes: 1,919
From: Ponca City, OK
So you've verified power to the PCM and the 5vref signal out to all the engine control sensors? If power is getting where it's supposed to when it's supposed to then PCM or IDM would be suspect. These guys are who's top of the recommendation list for any PCM/IDM stuff. Haven't heard a bad review to date.
https://www.dieseltechchatt.com/
https://www.dieseltechchatt.com/
Thread Starter
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Tuned
Joined: Nov 2016
Posts: 385
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From: Full time RVer
Thanks for taking the time for the replies.
I have checked the 5 vref, B+, continuity (including wiggling the harness) and all checked out fine. The exterior of the harness is also intact. Three years ago I rebuilt the engine and rebuilt the harness also.
Since I went to efuel with a regulated return, I have no fuel bowl (there evil) or anything else in the valley other than a HPOP. The glow plug relay is on the fender. The fuses are good, WTS is working as is the glow plug relay. ALL is functioning except no tach needle moment, which is essential on an OBS. I do question why their are no error codes?
Today I'm going to solder in a new CPS pigtail and a length of 3/18 SO cord to replace the existing CPS wires to the PCM plug. I know that's rather drastic. But after today the high temps will only be in the low 40s and my truck does not fit in any of my sheds.
I have checked the 5 vref, B+, continuity (including wiggling the harness) and all checked out fine. The exterior of the harness is also intact. Three years ago I rebuilt the engine and rebuilt the harness also.
Since I went to efuel with a regulated return, I have no fuel bowl (there evil) or anything else in the valley other than a HPOP. The glow plug relay is on the fender. The fuses are good, WTS is working as is the glow plug relay. ALL is functioning except no tach needle moment, which is essential on an OBS. I do question why their are no error codes?
Today I'm going to solder in a new CPS pigtail and a length of 3/18 SO cord to replace the existing CPS wires to the PCM plug. I know that's rather drastic. But after today the high temps will only be in the low 40s and my truck does not fit in any of my sheds.
Lead Driver
Joined: Oct 2005
Posts: 6,129
Likes: 1,919
From: Ponca City, OK
If it's worth doing then it's worth over doing, right.