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Thread: FUEL CONTROL ACTUATOR Cummins CP3 Diagnosis

  1. Top Of Page | #1
    Old & Grumpy! Polaraco's Avatar

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    Question FUEL CONTROL ACTUATOR Cummins CP3 Diagnosis

    03 5.9 Quadzilla, +50 HP injectors FASS 95

    My fuel pressure from my FASS does a dramatic drop at exactly 1400 RPM. This happens driving or sitting still. I've gone over the entire FASS install. I was suffering from some fuel starvation through the tank module. I have a draw tube now.

    My pressure holds at 16 to 17 PSI sitting still, and 15 to 17 driving under 1400 RPM. Actually it barely changes. As soon as i break the 1400 RPM mark, the pressure can fall down to 8 or 9 PSI. I'm thinking the actuator is opening too much at that RPM threshold.

    I'm not getting any white smoke or erratic idle. It's not hard to start. I'm not getting any symptoms typical of a bad FCA. But it's weird the feed pressure drops so dramatically at 1400 RPM. I turn the tuner off and nothing has changed much, But that doesn't mean the Rail Pressure fooler in the Quad is not still active.

    I have to find the solution to this soon. 8 PSI is too low

    @Canadiandiesel @AccurateDiesel

    Does this sound like something the actuator can cause? What is the diagnosis?

    Tim Do you have these?


    2003- 3500 RWD Automatic.
    S & B intake, BD Intercooler, Pusher Air Horn, MM3 Double R Tuning, Turbo Timer, electric Flex-a-lite fans, FASS 95,
    50 HP tips, upgrade to 351 turbo, 3.42 gears, Twin air compressors, air bags, Remote dual oil filters, Hellwig sway bar, Front Winch. Home made Fuel Heater, BD Exhaust brake with Torque Lock. Tons of TLC

  2. Top Of Page | #2
    Old & Grumpy! Polaraco's Avatar

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    I found this

    03-16-2008, 07:38 PM

    P0251-CP3 PUMP REGULATOR CONTROL
    For a complete wiring diagram Refer to Section 8W.

    When Monitored:
    When the ignition is on.

    Set Condition:
    The ECM detects a discrepancy between the PWM supplied to the Electronic Fuel Control Actuator and the PWM returned from the Electronic Fuel Control Actuator.

    Possible Causes
    FUEL PUMP
    (K604) FUEL CONTROL ACTUATOR DRIVER OPEN
    (K65) RETURN CIRCUIT OPEN FROM FCA TO ECM
    (K604) FUEL CONTROL ACTUATOR DRIVER CIRCUIT SHORTED TO EXTERNAL VOLTAGE
    (K65) FUEL CONTROL ACTUATOR RETURN CIRCUIT SHORTED TO EXTERNAL VOLTAGE
    (K65) FCA RETURN CIRCUIT SHORTED TO (K604) FCA DRIVER CIRCUIT
    (K604) FUEL CONTROL ACTUATOR DRIVER CIRCUIT SHORTED TO GROUND
    (K604) FUEL CONTROL ACTUATOR DRIVER CIRCUIT SHORTED TO ANOTHER CIRCUIT
    (K65) FUEL CONTROL ACTUATOR RETURN CIRCUIT SHORTED TO ANOTHER CIRCUIT
    INTERMITTENT CONDITION
    ECM


    Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING)




    Diagnostic Test
    1. FUEL PUMP

    --------------------------------------------------------------------------------

    Ignition on, engine not running.
    Disconnect the Fuel Control Actuator (FCA) harness connector.
    Connect an incandescent test light across the Fuel Control Actuator driver circuit and the Fuel Control Actuator return circuit at the fuel control actuator harness connector.
    Observe the test light.
    The ECM will perform a self test of the circuit which should momentarily flash the test light brightly, one time, approximately 20 seconds after being connected.

    note: Check connectors - Clean/repair as necessary.



    note: Compare test light brightness to that of a direct connection to the battery.



    Did the light flash brightly?

    Yes
    Replace the Fuel Pump.
    Perform POWERTRAIN VERIFICATION TEST (DIESEL). (Refer to 9 - ENGINE - STANDARD PROCEDURE)

    No
    Go To 2


    2. (K604) FUEL CONTROL ACTUATOR DRIVER OPEN

    --------------------------------------------------------------------------------

    Turn the ignition off.
    Disconnect the ECM harness connectors.

    note: Check connectors - Clean/repair as necessary.


    Measure the resistance of the FCA driver circuit between the electronic fuel control actuator harness connector and the ECM harness connector.

    Is the resistance less than 10 Ohms?

    Yes
    Go To 3

    No
    Repair the (K604) Fuel Control Actuator Driver circuit OPEN.
    Perform POWERTRAIN VERIFICATION TEST (DIESEL). (Refer to 9 - ENGINE - STANDARD PROCEDURE)


    3. (K65) RETURN CIRCUIT OPEN

    --------------------------------------------------------------------------------

    Measure the resistance of the (K65) return circuit between the FCA harness connector and the ECM harness connector.

    Is the resistance less than 10 Ohms?

    Yes
    Go To 4

    No
    Repair or replace the engine wiring harness.
    Perform POWERTRAIN VERIFICATION TEST (DIESEL). (Refer to 9 - ENGINE - STANDARD PROCEDURE)


    4. (K604) FUEL CONTROL ACTUATOR DRIVER CIRCUIT SHORTED TO EXTERNAL VOLTAGE

    --------------------------------------------------------------------------------

    Measure the voltage between the (K604) FCA driver circuit in the FCA harness connector and battery negative.

    Is the voltage greater than 1 volts?

    Yes
    Repair the (K604) FCA driver circuit shorted to external voltage.
    Perform POWERTRAIN VERIFICATION TEST (DIESEL). (Refer to 9 - ENGINE - STANDARD PROCEDURE)

    No
    Go To 5


    5. (K65) FUEL CONTROL ACTUATOR RETURN CIRCUIT SHORTED TO EXTERNAL VOLTAGE

    --------------------------------------------------------------------------------

    Measure the voltage between the (K65) FCA return circuit in the FCA harness connector and battery negative.

    Is the voltage greater than 1 volts?

    Yes
    Repair the (K65) FCA return circuit shorted to external voltage.
    Perform POWERTRAIN VERIFICATION TEST (DIESEL). (Refer to 9 - ENGINE - STANDARD PROCEDURE)

    No
    Go To 6


    6. (K65) FCA RETURN CIRCUIT SHORTED TO (K604) FCA DRIVER CIRCUIT

    --------------------------------------------------------------------------------

    Measure the Resistance between the return circuit in the FCA harness connector and Driver circuit.

    Is the resistance less than 10 Ohms?

    Yes
    Repair the (K65) FCA Return circuit shorted to (K604) FCA Driver circuit.
    Perform POWERTRAIN VERIFICATION TEST (DIESEL). (Refer to 9 - ENGINE - STANDARD PROCEDURE)

    No
    Go To 7


    7. (K604) FUEL CONTROL ACTUATOR DRIVER CIRCUIT SHORTED TO GROUND

    --------------------------------------------------------------------------------

    Measure the resistance between the (K604) FCA driver circuit in the FCA harness connector and battery negative.

    Is the resistance less than 10 Ohms?

    Yes
    Repair the (K604) FCA driver circuit shorted to ground.
    Perform POWERTRAIN VERIFICATION TEST (DIESEL). (Refer to 9 - ENGINE - STANDARD PROCEDURE)

    No
    Go To 8


    8. (K604) FUEL CONTROL ACTUATOR DRIVER CIRCUIT SHORTED TO ANOTHER CIRCUIT

    --------------------------------------------------------------------------------

    Measure the resistance between the (K604) FCA driver circuit in the ECM harness connector and all other circuits in the ECM connectors.

    Is the resistance less than 10 Ohms?

    No
    Go To 9

    Yes
    Repair the (K604) FCA driver circuit shorted to another circuit.
    Perform POWERTRAIN VERIFICATION TEST (DIESEL). (Refer to 9 - ENGINE - STANDARD PROCEDURE)


    9. (K65) FUEL CONTROL ACTUATOR RETURN CIRCUIT SHORTED TO ANOTHER CIRCUIT

    --------------------------------------------------------------------------------

    Measure the resistance between the (K65) FCA Return circuit in the ECM harness connector and all other circuits in the ECM connectors.`

    Is the resistance less than 10 Ohms?

    No
    Go To 10

    Yes
    Repair the (K65) FCA Return circuit shorted to another circuit.
    Perform POWERTRAIN VERIFICATION TEST (DIESEL). (Refer to 9 - ENGINE - STANDARD PROCEDURE)


    10. ECM

    --------------------------------------------------------------------------------

    Reconnect the ECM harness connectors.
    Ignition on, engine not running.
    Disconnect the Electronic Fuel Control Actuator connector.
    Connect an incandescent test light across the Fuel Control Actuator driver pin and the Fuel Control Actuator return wire at the fuel control actuator connector.
    Observe the test light.
    The ECM will perform a self test of the circuit which should momentarily flash the test light brightly, one time, approximately 20 seconds after being connected.

    note: Compare test light brightness to that of a direct connection to the battery.



    Did the light flash brightly?

    Yes
    Refer to the INTERMITTENT CONDITION Symptom (Diagnostic Procedure). (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING)

    No
    Replace the ECM.
    Perform POWERTRAIN VERIFICATION TEST (DIESEL). (Refer to 9 - ENGINE - STANDARD PROCEDURE)



    2003- 3500 RWD Automatic.
    S & B intake, BD Intercooler, Pusher Air Horn, MM3 Double R Tuning, Turbo Timer, electric Flex-a-lite fans, FASS 95,
    50 HP tips, upgrade to 351 turbo, 3.42 gears, Twin air compressors, air bags, Remote dual oil filters, Hellwig sway bar, Front Winch. Home made Fuel Heater, BD Exhaust brake with Torque Lock. Tons of TLC

  3. Top Of Page | #3
    guru of all things diesel Canadiandiesel's Avatar

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    Yea sometimes the actuator opens up to much which will drop fuel pressure, it's a quick simple fix


  4. Top Of Page | #4
    Old & Grumpy! Polaraco's Avatar

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    Quote Originally Posted by Canadiandiesel View Post
    Yea sometimes the actuator opens up to much which will drop fuel pressure, it's a quick simple fix
    It's been doing this for a long time. Year and a half actually. But it never dropped off this much. I thought I had pump issues. FASS has stayed with me all the way, but we've drawn a blank.

    I ran out and did the diagnostics as I saw them above and came up with nothing. Your reply is the most logical and confirmed my suspicions. It's the only other thing it can be.

    The situation with the fuel tank was a different issue. It was a recent problem and lowered the pressure even more. The filter in the tank was definitely clogged and the screen was pretty full of junk. I blew some air through it a few weeks ago which told the story. the low pressure jumped up from 5 as a low to 9 and 10.

    I see Geno's has them for 108.00+ and eGay for 119 shipped. Cummins OE replacements. I'll wait to see what Tim has to say. He's my first choice.

    FYI I ran over a couple of threads that said the trucks reacted differently with different actuators. I find that hard to believe. They were saying the trucks idled bad, idled higher, stuff like that. You have any thing on that? It doesn't sound right

    Once again, Thank You Spencer. I knew you would know.


    2003- 3500 RWD Automatic.
    S & B intake, BD Intercooler, Pusher Air Horn, MM3 Double R Tuning, Turbo Timer, electric Flex-a-lite fans, FASS 95,
    50 HP tips, upgrade to 351 turbo, 3.42 gears, Twin air compressors, air bags, Remote dual oil filters, Hellwig sway bar, Front Winch. Home made Fuel Heater, BD Exhaust brake with Torque Lock. Tons of TLC

  5. Top Of Page | #5
    guru of all things diesel Canadiandiesel's Avatar

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    Done for a long time is 1.5 years.

    So what does that make me? Ancient?


  6. Top Of Page | #6
    Old & Grumpy! Polaraco's Avatar

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    Quote Originally Posted by Canadiandiesel View Post
    Done for a long time is 1.5 years.

    So what does that make me? Ancient?
    Well you're no spring Chicken!


    2003- 3500 RWD Automatic.
    S & B intake, BD Intercooler, Pusher Air Horn, MM3 Double R Tuning, Turbo Timer, electric Flex-a-lite fans, FASS 95,
    50 HP tips, upgrade to 351 turbo, 3.42 gears, Twin air compressors, air bags, Remote dual oil filters, Hellwig sway bar, Front Winch. Home made Fuel Heater, BD Exhaust brake with Torque Lock. Tons of TLC

  7. Top Of Page | #7
    Permanent Vacation AccurateDiesel's Avatar

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    Testing....

    Hi!

    My first thought would be to monitor the FCA command using a scan tool when crossing that RPM point. If there is a big change in command, then I would not blame the FCA itself - the question would then become, "Wwhy the drastic change in command at that point?" While the scan tool was connected, I would also monitor both desired and actual rail pressure PIDs, again while crossing 1400 RPM. Do either or both change drastically?

    If a scan tool is not available (or even if it is) one could monitor actual command at the FCA using either a DVOM, or a scope - again I would look for a drastic change in command at that RPM.

    We do have FCA's on the shelf if needed.


  8. Thanks IGOTACUMMINS thanked for this post
  9. Top Of Page | #8
    Old & Grumpy! Polaraco's Avatar

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    Ran the scan tool last night. It was not jumping like you are thinking. I'm doing more today


    2003- 3500 RWD Automatic.
    S & B intake, BD Intercooler, Pusher Air Horn, MM3 Double R Tuning, Turbo Timer, electric Flex-a-lite fans, FASS 95,
    50 HP tips, upgrade to 351 turbo, 3.42 gears, Twin air compressors, air bags, Remote dual oil filters, Hellwig sway bar, Front Winch. Home made Fuel Heater, BD Exhaust brake with Torque Lock. Tons of TLC

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