So, I'm chasing a no start issue in my 95 F250 7.3 Powerstroke after reassembly. One thing I've noticed is that when the truck is turning over, the tach is not bouncing at all. Which would initially make me think the CPS is an issue.

My question is, if the CPS is good, should it bounce regardless if the PCM is good or not? Or does the CPS require a good, working CPU before one would see the tach bounce?

Thank you for your assistance!!

 

The CPS connects ONLY to the PCM; the PCM thus feeds the tach. So yes, a bad PCM could cause a tach failure.

Are you getting a WTS light? Is the GP relay closing?

 

weak batteries can make it not bounce too from lack of RPM

 

Yes. I am getting a WTS light. How would I know if the GP relay is closing?

 

Listen for it. Also check for voltage at the terminal that leads to the GPs.

Do you have a device that can read real-time data, do PCM-driven diagnostic tests and obtain codes?

 

These two batteries are only about 6 months old and I had a fresh charge on both of them.

Something odd (or maybe not) after turning the engine over for a bit the "Service Engine" light comes on.

 

corroded terminals can make good batteries not perform at 100%


scanner to monitor your engine
Torque Pro
https://play.google.com/store/apps/d...g.prowl.torque
Use the communication in the profile
SAE J1850-PWM
make sure you add in Ford PIDs
https://play.google.com/store/apps/d...ch.CarGaugePro
people like it cause it will pull codes, buzz test and CCT
Warning, Some OLD PCM's have to be flashed before you can pull codes

 

I can hear it click off once the wait to start light goes off.

I don't have anything that can read real-time data, unfortunately.

 

My terminals are brand new military spec terminals and the terminals on the battery were cleaned once I placed them back in the truck from charging.

 

if you don't have a spare Ford CPS, you should get one and keep it along with a 10 mm wrench in glove box


I would change that before the PCM and check the wiring down there for chaffing

 

Ok. I've got a spare CPS in the glove box. I just bought this one a few months ago, so I didn't suspect it. However, I know they are notorious for going belly up.

 

and did it make a difference?

 

and is the spare a motorcraft or IH?