Troubleshoot Your AirDog® Fuel System

With the engine OFF, and key in the ON/RUN position, the AirDog® will run quieter very soon after purging the air out of the system.

It is normal for your AirDog® system to make some intermittently varying noises, due to a varying amount of air being drawn from the fuel tank and through the system. As fuel gets warmer, the foaming effect of diesel fuel worsens, which will also cause an increase in pump noise. An effective test, which will help determine how much air is coming from the fuel tank, is the Bucket Test (see below for instructions).

If excessive noise is absent while performing the Bucket Test, this could indicate that the problem or restriction is in the connection at the tank, or inside the tank. Inspect the connections and tank as necessary. The issue could be as simple as a loose connection, crack in a suction tube, or clogged tank vent.

  • Verify the power and ground leads are properly connected, are connected well, and are tight.
  • Verify the trigger wire to the control relay is properly connected.
  • Verify the fuse is good in the wiring harness.
  • Verify the appropriate fuse is good in the vehicle fuse panel.
  • If all connections and fuses are good, verify that you have power going into the lead to the AirDog®. (Test light suggested).
  • If all connections and fuses are good, and a test light is not available, remove the relay from the wiring harness socket. Using an insulated jumper wire, jump the red and yellow wires in the relay base, female spade side. Do not start the engine.
  • If the unit starts running, the relay trigger connection is in question. Verify the relay trigger wire is properly connected.
  • If the unit does not run with direct power, we will need to verify that there is nothing lodged in the Gerotor Assembly. CONTACT US to discuss.
  • If the relay trigger wire is properly connected, the relay is in question. For testing, a standard 5-blade relay from under the hood can be used. Plug in the relay and turn ignition key “ON” to activate the relay and unit.
  • If your unit runs, replace the relay.
  • If the unit does not run, the relay trigger wire/connection is in question. Verify the relay trigger wire connection again.
  • If the relay trigger wire connection is good, remove the relay from the wiring harness and check the continuity of the trigger wire in the wiring harness.
  • No continuity: Replace wiring harness.
  • Continuity found: Verify power is available at the power source being utilized with a test light. Fuse and/or connection are suspected.
  • If the unit does not start with the jump wire in the relay socket, using a test light, verify the power is to the yellow wire in the relay socket.
  • If the yellow wire in the relay socket shows power, go back to the fuse (between the relay socket and power connection), remove the fuse, and test for power to the red wire into the fuse holder.
  • Initial question: Do you have fuel flow from the AirDog® unit?
    • If the answer is yes, where is the location of the gauge port being used?
  • The gauge port in the filter housing will not work when the fuel is routed around the stock fuel filter housing.
  • The gauge port utilized may not be in the pressure stream of fuel.
  • The pressure gauge is not reading pressure.
    • The vehicle is receiving fuel; however, the pressure relief for the pump (ex: VP-44 / CP-3) is open and allowing fuel to return to the tank through this pump.
    • Pinch the line going to the pressure pump to stop the flow of fuel after the pressure gauge. Remove the relay from the unit’s wiring harness. Place a jump wire between the red and yellow wires in the relay socket. Read the pressure in the dead head mode.
    • If the pressure goes up to the desired pre-set pressure, the problem is indicated to be with the pressure pump relief mechanism.
    • If the pressure does not show on the gauge, the problem is indicated at the unit or gauge. Check to another gauge.
  • Check the line connections to ensure tight connections and fittings, and no breaks or cuts in lines: Tank to AirDog®, and AirDog® to Engine.
  • If the electric motor is running, but sounds like it is running slowly (quieter than normal), check the voltage to the motor. Low voltage will reduce the motor RPM’s; hence, reduce or stop pressurized flow.
    • If low voltage, check the wiring connections and voltage regulator.
  • Pump Won’t Prime: Loosen the fuel filter (not water separator) while the AirDog® unit only (not the engine) is running. This will allow the air to be released. The tone of the motor will change as fuel enters the gerotor.
  • Immediately after hearing the tone change: Tighten the filter back up, preventing spillage.
  • Still Not Priming: Remove water separator. Turn the PureFlow™ product on. Place your thumb under the water separator nipple. Ensure there is suction at the water separator nipple.
  • Add 3-4 gallons of diesel fuel to a CLEAN 5-gallon bucket.
  • Remove the suction line from the top of the tank and drop into the bucket of fuel.
  • Place the return line from the AirDog® unit in to the bucket.
  • Ensure correct voltage is at the AirDog® unit.
  • Turn the AirDog® unit on and view the output to engine fuel pressure and/or volume.

Only an obstruction in the suction line or a clogged water separator can affect the performance of this test.