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Andy
Andy, Truck Diagnostic Technician
Category: Medium and Heavy Trucks
Satisfied Customers: 1675
Experience:  International and Isuzu trucks , International, Maxxforce, Cummins and Isuzu engines, Diagnostic and electrical troubleshooting specialist , Hvac and truck /trailer refrigeration troubleshooter
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2014 perebilt Isl 9, px9, 4726 and 2372 codes, fuel filters

Customer Question

2014 perebilt Isl 9, px9, 4726 and 2372 codes, fuel filters have been replaced and no visible fuel leaks. lines to water separator are clear other potential faults?
Submitted: 2 months ago.
Category: Medium and Heavy Trucks
Expert:  Andy replied 2 months ago.

Hi there ! My name is Andy ! I'm a little confused . Is this a cummins engine ? If so , I can likely help but I will need the engine serial number please? It is an 8 digit number located on the valve cover label or on the front cover of the engine on the driver's side. Thanks

Customer: replied 2 months ago.
it's listed as a paccar px9, but it's an isl9 Cummins. 73635348
Expert:  Andy replied 2 months ago.

Ok thanks for the info

Expert:  Andy replied 2 months ago.

Sorry for the delay ! will look up now and send description and troubleshooting for both codes.

Expert:  Andy replied 2 months ago.

We need to chase 2372 first . If it starts , we need to check fuel inlet restriction .

Verification:

Conditions

  • Turn keyswitch ON.

Actions

  • Start the engine. measure the fuel gear pump for inlet restriction.


Note. Air in fuel will result in long crank times. Air is typically trapped in the pressure side fuel filter.

Specification

  • If the fuel gear pump inlet restriction is above the threshold called out in the procedure, then a malfunctioning low pressure fuel system component has been detected.
Expert:  Andy replied 2 months ago.

If restriction is in spec, then follow this step :

Verification:

Condition

  • Turn the keyswitch to the ON position
  • Listen for the fuel lift pump operation.

Action

  • If the fuel lift pump does not operate after turning the keyswitch ON, then measure the lift pump voltage.
  • If the lift pump operates when the keyswitch is turned ON, measure either the lift pump pressure or the lift pump flow.

Specifications

  • Voltage at fuel lift pump must be within 1-VDC of battery voltage.
  • Fuel lift pump Flow or Pressure must be within the specifications listed in procedure
Expert:  Andy replied 2 months ago.

If you get to this and all checks out , let me know and i'll send further instructions

Customer: replied 2 months ago.
Vacuum at gear pump inlet is 4inhg
Psi at high pressure filter outlet is 100 at idle with orifice
Transfer pump is 14psi
Customer: replied 2 months ago.
The truck won't throw the code working or under throttle without a load, I have to run the truck almost wide open to get the fuel filter restriction code to come on, high fuel leakage code comes on about 5 minutes into driving
Expert:  Andy replied 2 months ago.
Do you have insite program to be able to run high pressure leak tests ?
Customer: replied 2 months ago.
No, but my scanner can run that test, I tried that yesterday, and saw no leaks
Expert:  Andy replied 2 months ago.
I would try it again and see if the fuel rail relief valve return line gets hot to the touch
Customer: replied 2 months ago.
The line is about 130 degrees roughly after being brough up to temp and running high pressure for 3 minutes
I noticed the high pressure stays around 15k today but was around 6k yesterday after 3 minutes of idling, not sure what minimum high pressure rating should be at idle
Expert:  Andy replied 2 months ago.

you are using the measured orifice line for all your fuel testing .. right ?

Customer: replied 2 months ago.
Yeah, .047 or close to that, it's the Cummins orifice coupling
Customer: replied 2 months ago.
I noticed when I run it at 23k psi for the test the light goes off and makes the code inactive, any idea if that could hint towards the fault?
Expert:  Andy replied 2 months ago.

We just need to continue the troubleshooting steps til we find the problem

Expert:  Andy replied 2 months ago.

Have you checked fuel inlet restriction at high idle ?

Customer: replied 2 months ago.
at high idle it is at 6inches
Expert:  Andy replied 2 months ago.

Thanks . That is within spec .

Expert:  Andy replied 2 months ago.

Verification:

Conditions

  • Engine running
  • Engine coolant temperature is greater than 80 degrees C [176 degrees F]

Action

  • Disconnect the fuel line from the fuel rail pressure relief valve.
  • Measure the fuel rail return flow at the fuel rail pressure relief valve, not at the fuel drain manifold.

Specification

  • If the fuel rail return flow does not meet the specification at the fuel rail pressure relief valve, then a malfunctioning fuel rail relief valve has been detected.

Note: Monitoring the fuel pressure after a relief valve leakage check is necessary to ensure stable operating pressure.

Customer: replied 2 months ago.
What is the spec for the flow, is it 30 drops in a minute?
Expert:  Andy replied 2 months ago.

30 drops in 60 sec

Expert:  Andy replied 2 months ago.

correct

Expert:  Andy replied 2 months ago.

This must be checked while running the high pressure leakage test so that rail pressure is high while counting drops

Expert:  Andy replied 2 months ago.

If this is within spec , the next step will be injector return flow test

Expert:  Andy replied 2 months ago.

Hi there . Just looking for an update on this

Customer: replied 2 months ago.
Averaged it out between 3 minutes and was about 26. What's needed for injector return?
Expert:  Andy replied 2 months ago.

Return fuel is routed from the injectors, the fuel rail pressure relief valve, and the fuel pump head through three different drain lines. The measurement of fuel injector leakage requires use of a fuel return flow hose, Part Number(###) ###-#### This tool is used to isolate the leakage from the injectors, so the leakage can be measured in a graduated beaker.

Expert:  Andy replied 2 months ago.

Obtain a graduated beaker that is marked in cubic centimeters or milliliters, Part Number(###) ###-#### or equivalent.