Tach not working
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Senior User
Joined: Aug 2012
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nope! after reading an earlier response, I should have known the oil sensor is on top of the hpop. when I rewired the cps, I never put those wires back on. that was my own stupidity and frustration getting the best of me.
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Senior User
Joined: Aug 2012
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yes and yes. ..
two ford dealers said my truck has a tach sensor on the fuel injection pump. is the pump the hpop? I thought the psd didn't have this sensor, but the IDI engins did/do.
Lead Driver
Joined: Oct 2003
Posts: 8,476
Likes: 37
From: Madison, WI
NO tach sensor! Would the guy at the dealership have even been born when our trucks were built? I'd bet a nickel he wasn't working there when our vintage of truck was regularly serviced there.
Given everything you've had to pour into this truck, it's high time you got some device that communicates with it via the OBD-II port. That way you can see EXACTLY what it's doing (injection pressure, RPM, etc) while cranking.
Given everything you've had to pour into this truck, it's high time you got some device that communicates with it via the OBD-II port. That way you can see EXACTLY what it's doing (injection pressure, RPM, etc) while cranking.
Thread Starter
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Senior User
Joined: Aug 2012
Posts: 104
Likes: 0
NO tach sensor! Would the guy at the dealership have even been born when our trucks were built? I'd bet a nickel he wasn't working there when our vintage of truck was regularly serviced there.
Given everything you've had to pour into this truck, it's high time you got some device that communicates with it via the OBD-II port. That way you can see EXACTLY what it's doing (injection pressure, RPM, etc) while cranking.
Given everything you've had to pour into this truck, it's high time you got some device that communicates with it via the OBD-II port. That way you can see EXACTLY what it's doing (injection pressure, RPM, etc) while cranking.
i even questioned the dealers about this. their responses were, its right here...i even explained that the IDIs have them but the PSDs do not, and i explained that i don't have an injection pump; my fuel pump is mechanical and the only thing having anything with a sensor would be the HPOP. i still questioned them. they are idiots.
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Thread Starter
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Senior User
Joined: Aug 2012
Posts: 104
Likes: 0
NO tach sensor! Would the guy at the dealership have even been born when our trucks were built? I'd bet a nickel he wasn't working there when our vintage of truck was regularly serviced there.
Given everything you've had to pour into this truck, it's high time you got some device that communicates with it via the OBD-II port. That way you can see EXACTLY what it's doing (injection pressure, RPM, etc) while cranking.
Given everything you've had to pour into this truck, it's high time you got some device that communicates with it via the OBD-II port. That way you can see EXACTLY what it's doing (injection pressure, RPM, etc) while cranking.
is there a place that makes an aftermarket engine compartment wiring harness? the idea of having a fresh harness rather than one that's aobut 20 years old seems to be a nice option.
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Senior User
Joined: Aug 2012
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ok, now im getting desperate!
i pulled out my engine compartment wiring harness today, checking for the lack of continuity. my harness does not have any broken wires thereby affecting the CPS's ability to properly send a signal to the tach.
can anyone please provide me with some insight as to why my tach is not working and therefore affecting the ability of me being able to fire up my new engine?
in sum, the PCM was replaced and i put in a second new CPS. I found one broken wire. i fixed it, but still no fire.
help in this department would be so appreciative. ive even prayed for a miracle!
Postmaster
Joined: Sep 2007
Posts: 4,195
Likes: 6
From: Medford Oregon
1. Have you checked oil level in the HPOP reservoir?
2. Measure voltage on ICP wire LTBlu/Red. You need at least 1 volt while cranking to have enough pressure to fire injectors. If you are getting CPS signal then it will probably ramp above 3 volts.
Some other voltage and resistance checks can be found here ...
97-15A 7.3L DI Turbo Workshop Manual
Don't have tunnel vision as some trucks don't register tac during cranking depending on the PCM version.
2. Measure voltage on ICP wire LTBlu/Red. You need at least 1 volt while cranking to have enough pressure to fire injectors. If you are getting CPS signal then it will probably ramp above 3 volts.
Some other voltage and resistance checks can be found here ...
97-15A 7.3L DI Turbo Workshop Manual
Don't have tunnel vision as some trucks don't register tac during cranking depending on the PCM version.
Thread Starter
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Senior User
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about the scanner device: for some reason my truck will not run with my scanner plugged in it. every time i have plugged it in to the obd port to read live data, my truck dies every time.
Thread Starter
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Senior User
Joined: Aug 2012
Posts: 104
Likes: 0
1. Have you checked oil level in the HPOP reservoir?
2. Measure voltage on ICP wire LTBlu/Red. You need at least 1 volt while cranking to have enough pressure to fire injectors. If you are getting CPS signal then it will probably ramp above 3 volts.
Some other voltage and resistance checks can be found here ...
97-15A 7.3L DI Turbo Workshop Manual
Don't have tunnel vision as some trucks don't register tac during cranking depending on the PCM version.
2. Measure voltage on ICP wire LTBlu/Red. You need at least 1 volt while cranking to have enough pressure to fire injectors. If you are getting CPS signal then it will probably ramp above 3 volts.
Some other voltage and resistance checks can be found here ...
97-15A 7.3L DI Turbo Workshop Manual
Don't have tunnel vision as some trucks don't register tac during cranking depending on the PCM version.
i will check this out after i put the harness back in.
for the record however, no tunnel vision here. while cranking, my tach does in fact register about 100-200 rpm, or at least it did before the engine swap.
Last edited by drpaul311; Dec 19, 2014 at 10:50 AM. Reason: spelling
Lead Driver
Joined: Oct 2003
Posts: 8,476
Likes: 37
From: Madison, WI
What scanner are you using? A generic OBD-II scanner will do exactly what you describe.