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Ex- 6BT Square Body Man
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Discussion Starter · #181 ·
I just talked to John, cool guy !! 👍

Said to run without lift pump and check return rates on injectors and see if that changes anything.
 

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Is the Fuel Rail Pressure gauge attached to the CP3 or is it separate? Just a thought but maybe the gauge itself is causing issues. Any way to ohm it out?
 

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Ex- 6BT Square Body Man
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Discussion Starter · #183 ·
Is the Fuel Rail Pressure gauge attached to the CP3 or is it separate? Just a thought but maybe the gauge itself is causing issues. Any way to ohm it out?
Fuel pressure sensor is on the right end fuel rail.
Fuel pressure regulator is on the CP3
 

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Ex- 6BT Square Body Man
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Discussion Starter · #184 ·
Tell me if I am out in left field.

Right now rail pressure is around 9k
If I unplug the FPR there is no change, its like the ECM thinks there is no FPR connected.
I have seen posts where unplugging the FPR defaults to full pressure.
One common thing is everytime I work on it I move the harness around and it's ok for awhile.
So I started checking wires. Put a different connect piece that goes from the FRP to the main harness and no change.
Bypassed the lift pump, no change.
I clear the FPR code and it comes right back.
Fuel rail pressure stays at 9k even when I clear code.
I don't suspect the new FPR that came on the new CP3 because it did the same thing with a new FPR on the original CP3.
I am now starting to suspect a wiring issue.

Edit: I also pulled the fuel rail pressure sensor, found some gunk on it, clean it with carb clean, blew it out with air and put it back on.
 
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Tell me if I am out in left field.

Right now rail pressure is around 9k
If I unplug the FPR there is no change, its like the ECM thinks there is no FPR connected.
I have seen posts where unplugging the FPR defaults to full pressure.
One common thing is everytime I work on it I move the harness around and it's ok for awhile.
So I started checking wires. Put a different connect piece that goes from the FRP to the main harness and no change.
Bypassed the lift pump, no change.
I clear the FPR code and it comes right back.
Fuel rail pressure stays at 9k even when I clear code.
I don't suspect the new FPR that came on the new CP3 because it did the same thing with a new FPR on the original CP3.
I am now starting to suspect a wiring issue.

Edit: I also pulled the fuel rail pressure sensor, found some gunk on it, clean it with carb clean, blew it out with air and put it back on.

I think you're on the right track (y)
 

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Tell me if I am out in left field.

Right now rail pressure is around 9k
If I unplug the FPR there is no change, its like the ECM thinks there is no FPR connected.
I have seen posts where unplugging the FPR defaults to full pressure.
One common thing is everytime I work on it I move the harness around and it's ok for awhile.
So I started checking wires. Put a different connect piece that goes from the FRP to the main harness and no change.
Bypassed the lift pump, no change.
I clear the FPR code and it comes right back.
Fuel rail pressure stays at 9k even when I clear code.
I don't suspect the new FPR that came on the new CP3 because it did the same thing with a new FPR on the original CP3.
I am now starting to suspect a wiring issue.

Edit: I also pulled the fuel rail pressure sensor, found some gunk on it, clean it with carb clean, blew it out with air and put it back on.
I think you are on the right track also. You’ve replaced so much on the truck it seems to me like the ECM is not seeing fuel pressure properly. Does the truck see Fuel Rail Pressure Not running with the ignition ON? Just wondering if you could plug sensor in and press the end to see if values change with a scanner hooked up?
 

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Ex- 6BT Square Body Man
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Discussion Starter · #187 · (Edited)
I happened to have a spare fuel pressure sensor from a parts engine, so I swapped it before work this morning. Now the FPR code is gone but now I get a low voltage P1092 code for that sensor.

Also shows no rail pressure in the data grid.
I will check voltages after work today.

Edit: I also unhooked the batteries, this is the one thing I have always done while working on the truck.
I will let them sit unhooked while at work.
 

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Ex- 6BT Square Body Man
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Discussion Starter · #188 ·
I grabbed a pic of the fuel pressure sensor when I pulled it last night.
This is what was on it. Look at that gunk.

Brown Wood Tin can Household hardware Fastener
 
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so hope this get you info on wiring

YMMS:2004 Chevrolet Cab & Chassis Silverado 3500Oct 29, 2021
Engine:6.6L EngLicense:
VIN:Odometer:

Fuel System,Rail Pressure Solenoid,Engine
Operation
ECM controls fuel rail pressure by commanding the FRP (fuel rail pressure) regulator open or closed on inlet of fuel injection pump. A FRP (fuel rail pressure) sensor gives the ECM an indication of fuel rail pressure. ECM uses this information to regulate fuel rail pressure by PWM Control of FRP regulator.
Location
Best Test Location:
At FRP regulator connector or at C107 (38 pin) connector. Note: C107 is at left center of Engine above valve cover. C107 is the lower one of two connectors.
Component Location:
On fuel injection pump.
Connector
VIEW: HARNESS SIDE, BACKPROBING AT FRP.

Rectangle Font Symmetry Pattern Symbol



1=FRP REGULATOR CONTROL​
"Yellow"​
2=FRP REG SUPPLY VOLTAGE​
" PPL-WHT "​

at connector of harness of ECM
VIEW: HARNESS SIDE, BACKPROBING AT C107

Product Rectangle Font Parallel Pattern



C9 =FRP REG SUPPLY VOLTAGE​
"Yellow"​
C10=FRP REGULATOR CONTROL​
" PPL-WHT "​


Tests
Duty Cycle Test
Connect test leads:
Yellow=FRP regulator Control (Yellow = test lead from Scope +)
Black=known good ground (Black = Ground from Scope -)
KOEO, Duty cycle should be about 26%. KOER at idle, Duty cycle should be about 38% and vary with Engine load. Snap throttle Duty cycle should increase to about 42%.

Out Of Range No Signal Test
If voltage is out of Range or no voltage signal appears, turn Key off and disconnect FRP regulator.
Connect test leads:
Yellow=FRP REG supply
Black=known good ground
Key on, voltage should be about 12V.

Signature Test
Connect test leads:
Yellow=FRP regulator Control
Black=known good ground
Lab Scope should be used to check waveform signature integrity.

Rectangle Plant Font Parallel Electric blue


As Engine load changes, frequency will change.
Rectangle Plant Font Parallel Electric blue
 

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Ex- 6BT Square Body Man
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Discussion Starter · #190 ·
So to the fuel pressure regulator I get 16-17 volts.
To the fuel pressure sensor I get 7 volts.

No change after having the batteries unhooked, so that rules that out.

With my spare fuel pressure sensor rail pressure goes to zero while running
With the original fuel pressure sensor it is at 9k while running

KOEO with original sensor fuel rail pressure is bouncing between 178 and 200 psi
 

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Discussion Starter · #191 ·
Rebuilt the filter head with a Nick Tane kit and replaced the fuels to the filter head.
No change.
Buy hey, preventive maintenance, right :ROFLMAO: Old line were all weather checked on the outside anyway.
I think tomorrow I am going to change the FPR.....again, even though it's a new one that
came on the CP3.
 
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So shouldn't you have 12V going to the sensor as supply side voltage.

Seems as if 16-17V is too high.


did you do the Duty Cycle test on it?
 

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Discussion Starter · #193 · (Edited)
So shouldn't you have 12V going to the sensor as supply side voltage.

Seems as if 16-17V is too high.


did you do the Duty Cycle test on it?
Thought it was high myself, somebody else told me my alternator might be hosed. Also said sensor supply voltage should be 5 volts.
Have to do some more testing, but might be on to something.
Batteries are maybe a year old.
 

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Ex- 6BT Square Body Man
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Discussion Starter · #194 ·
It's my junk multimeter, voltage shows correct with another multimeter and in my code reader.
The troubleshooting continues.
 
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Discussion Starter · #195 ·
Checked voltages at certain points and they seem to be good
For giggles I put the brand new Bosch fuel pressure regulator on and it would barely run.
Took a long time cranking to fire up.
Put the fuel pressure regulator the came with the new CP3 and it runs better but throws code for regulator.
Discussing with others they say another sensor issue might be the cause of the fuel regulator code.
I ordered a new Bosch fuel pressure.
Original one had some gunk and it's been suggested to replace it.
One of my parts engine doesn't do anything, I have no history on it so I gotta think it's bad.
This is a nightmare.
 

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Ex- 6BT Square Body Man
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Discussion Starter · #196 ·
New fuel pressure sensor is in and no change, that leaves ECM or wiring as being the issue.
 

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Check wiring 1st before you spring for the ECM
 
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Ex- 6BT Square Body Man
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Discussion Starter · #198 ·
Check wiring 1st before you spring for the ECM
Been all over the wiring, can't find any issues and checked all fuses.
Testing last night, voltage on FPR would drop as I increased throttle.
I think it's working as intended.
All sensors are getting correct voltage, there is no change when I swap ECMs, even though I can't start it with the ECM from my parts engine.
The guy I got the parts engine from never got it running, and I can't get it to do a vats relearn.
I think it's hosed.
When I put the other FPR on it took a lot of cranking and would barely run when it did start, so
I think this tells me wiring is ok.
I found a used stock ECM from a 2005 on farcebook for $280, I am going to get it tonight.
 

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Been all over the wiring, can't find any issues and checked all fuses.
Testing last night, voltage on FPR would drop as I increased throttle.
I think it's working as intended.
All sensors are getting correct voltage, there is no change when I swap ECMs, even though I can't start it with the ECM from my parts engine.
The guy I got the parts engine from never got it running, and I can't get it to do a vats relearn.
I think it's hosed.
When I put the other FPR on it took a lot of cranking and would barely run when it did start, so
I think this tells me wiring is ok.
I found a used stock ECM from a 2005 on farcebook for $280, I am going to get it tonight.
Did you inspect the wiring running out of the fuse block? There have been some rub through issues coming from the fuse block
 
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Ex- 6BT Square Body Man
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Discussion Starter · #200 ·
No dice with the other ECM, did the VATS relearn got it running and same code.
I am going to rip apart the whole harness from the FRP back to the ECM, only thing left I can think of.
 
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