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FPC Hardwire Kit Troubleshooting Notes

FPC Hardwire Kit Troubleshooting Notes

Testing Tools

There should be very few tools needed to test, but below are some that may be helpful.

Multimeter

FPC Diagnosis Jumper

Pump Doesn’t Prime ( no power to the pump)

Symptoms

  • The car cranks, and confirmed there is no fuel

  • Can’t hear the fuel pump prime

Fuel Pump Controller Failure (most common)

The fuel pump controller provides the ground for the fuel pump and may fail from time to time. The easiest test is to take a known working unit and swap it out to see if there is a change.

More FPC information and diagnosis.

 Additional Checks if FPC is Good

  • Check the add-a-fuse to ensure there are 2 fuses in it

  • Confirm the location of the add-a-fuse

    • Check your vehicle install guide for this location

  • Ensure the 30-amp fuse in the relay box is installed and in the correct location.

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  • Check the ground location

  • Verify power going into the fusebox/relay

  • Verify 12V on the red wire and ground on the black wire for the relay triggers.

    • If this works, they should hear a click from the fusebox/relay when the key goes from off to on.

  • Verify 12V on the white wire at the fuel pump with ground to the chassis, NOT the blue wire

Multimeter Help

Vehicle Runs But After Awhile the Car Shuts Off

Sometimes, after sitting for awhile the car will restart and run for a bit, then shut off again.

Fuel Pump Controller Failure (most common)

The fuel pump controller provides the ground for the fuel pump and may fail from time to time. The easiest test is to take a known working unit and swap it out to see if there is a change.

More FPC information and diagnosis.

If this is not the cause, then refer to Circuit Breaker Troubleshooting

Weird But Normal Behavior - Pump Primes Without Fuse in Engine Bay

When the fuse in the engine bay is pulled, the pump will still prime due to the power to the pump being pulled from the battery. You will have issues once started (See Below ), but if they don’t want fuel to flow, they need to disconnect the power to the hardwire kit either by disconnecting the battery feed or pulling the fuse in the fusebox.

Circuit Breaker - General Information

The circuit breaker’s job is to protect the battery from damage/shorting caused by the large-gauge red cable running from the battery to the back of the car. This could include situations where the cable could be pinched during a seat install, at a door, or even in an accident.

The circuit breaker is manually resettable, so if it trips due to overload, it can be pressed to reset.

Circuit Breaker - Troubleshooting

Symptoms

  • Intermittent popping (disconnecting) of the breaker

  • Random power loss (breaker beginning to fail)

  • No power across the circuit breaker at all

 Testing

  • Put both cables on the same post to drive the car, and eliminate the breaker to see if the problem goes away. If it does, please contact iWire for a replacement.

The Vehicle Runs and then Stops

Symptoms

  • The car starts and runs for around 30 seconds, then stops.

  • It generally happens at the same time the engine is built because the fuse gets pulled during that process, so the car can crank to build oil pressure without starting.

 Solutions

  • Fuse in the engine bay for the fuel pump relay

Battery Draw

Symptoms

  • The vehicle has a draw (draining) of the battery while the car is off

 Solution

  • The add-a-fuse is in the wrong fuse location.

  • Confirm fuse location and move.

Pump Primes on Accessory (vehicle sometimes doesn’t start)

Symptoms

  • The vehicle doesn’t start or starts randomly

 Solutions

  • Move the add-a-fuse to the “key on” fuse position so it continues to prime while cranking

Main 30-AMP Fuse in the Fuse/Relay Box Blows

The most likely cause is a short to ground on the power side, the white wire. Most commonly, this is due to the stud passing through a metal hanger, and the insulation sleeve has failed, allowing the stud to come into contact with the metal hanger. Test the stud for continuity to the hanger itself.

image-20250822-170053.png

Fuel Pump Runs All the Time

This is most likely caused by the blue ground wire grounding out somewhere. Commonly, with metal hangers, this is because the ground stud has broken through the insulation and is touching the metal hanger, therefore grounding the pump all of the time instead of the fuel pump controller.

Testing

  • Unplug the fuel pump controller to see if the pump continues to run. If so, the stud is grounding out.

  • Measure for continuity with a multimeter between the ground stud and the hanger