K 2500 Truck 4WD V8-393 6.5L DSL Turbo (1992)
The two circuits powering the lift pump are shown in Figure 1; both circuits need to be checked. Intermittent supply circuit problems may require
monitoring the voltage at the lift pump during vehicle operation. This can be accomplished on vehicles equipped with Data Link Connectors (DLC) by
probing for voltage at terminal G while the engine is running (charging system functioning properly and batteries fully charged). A difference of more
than 1.5 volts between terminal G and battery voltage indicates a problem in the oil pressure switch circuit.
Once diagnosed, the problem is resolved by either replacing the faulty oil pressure sender/switch, the faulty lift pump, or repairing the wiring.
