Engineer Owned and Operated
  • Lift Pump Relay Harness

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    Lift Pump Relay Harness for all Diesel Hummer / H1 trucks with the 6.2 L and 6.5 L engines.  Highly recommended, particularly for trucks with upgraded lift pumps like the WHLP from Mod Mafia.  All OEM safety features related to lift pump operation are preserved.

    The Lift Pump Relay Harness provides these benefits:

    • Manual Operation of Lift Pump

    • Full Electrical Power to Lift Pump

    • Preserves Oil Pressure Switch (1992 – 1998)

    • Wait To Start Priming (1992 – 1995) (optional)

    • Plug & Play Installation

    Manual Operation of Lift Pump  Weatherproof inline switch allows manual activation of the lift pump.  Very useful for priming after a fuel filter change, and for testing lift pump function.

    Full Electrical Power to Lift Pump  Feeds full battery power to the lift pump via a sealed relay.

    Preserves Oil Pressure Switch  In the 1992 through 1998 model years, the lift pump is powered directly from the oil pressure switch once oil pressure builds up.  The high current requirements of the pump cause the switch to fail prematurely, making the lift pump inoperative.  This can lead to premature wear in the injection pump.

    Wait To Start Priming  Running the lift pump during glow plug operation (Wait To Start Priming) was first added to the Hummer / H1 in 1996.  The ECU powers the lift pump and glow plugs for about 20 seconds after the ignition key is turned On.  This helps prime the injection pump for easier starting.  With the optional Wait To Start Priming option, this feature can be simulated in the 1992 – 1995 Hummers -- the lift pump will be powered while the “Wait” light is on.  (Does not affect glow plug operation.)

    Plug & Play Installation  Relay Harness installation is simple.  No need to modify any existing wiring.  Simple connections to power, ground, lift pump, engine harness, and optionally the glow plug controller (for Wait To Start Priming feature).  Power wire is fused for protection.

    *Free shipping on all products in the lower 48 United States.  All others will be billed separately.