Newcomers - and some older owners don't know exactly what a Lift Pump (LP) is, what it does, and what makes it tick - hopefully this will help towards a better understanding. Here's what a LP looks like:
This is approximately what the LP (Lift Pump) looks like as installed at the driver-side rear area of the Cummins in our trucks. 3 bolts attach the pump to a bracket on the engine, there is an in and out fuel line, and either a plug for power attachment to power the pump like this one, or on older styles, the wiring was attached to posts on the bottom of the motor. That style was eventually discontinued due to salt and other contaminents damaging connections and causing LP failures.
Below we see the internals of the actual pump section with the cover removed. You can see the vanes - this is a vane-type pump, and the rotor that holds them as they rotate inside the walls of the pump housing. This is the ONLY part of the pump that can be disassembled for any sort of cleaning or service.
Here below, is a closer look at the disassembled pump rotor, with the vanes laying in front - those vanes simply float in their respective slots, and press against the walls of the pump by the rotational force of the pump rotor. Occasionally, those vanes might become sticky and not float freely in their slots, reducing or stopping fuel flow.
Inside the pump housing can be seen the end of the pump motor shaft with the milled end that engages the matching slot of the nylon insert pressed into the pump rotor. Occasionally, the nylon shaft coupling will fail, and fuel flow will stop, even though the motor will still spin. No known means or replacements are available to replace a damaged one - so the pump usually must be replaced when this occurs.
Also seen, is the fine stainless steel mesh filter strip formed around the outside of the pump cavity to provide filtering of any coarser trash that might enter that housing
(MORE below.)
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White '02 Quad cab, NV5600, GAUGES! Comp, Walbro, DTT SS intake, Rip's 4 in. exhaust, Don M's 1.6's, DSS, Frantz oil bypass & fuel filters, Amsoil air filter, MOBILE Ham Radio-IC-706, 600 watt amp, '88 Kit 24 ft. 5er, 418 HP/978 Tq., 24 ft KIT 5er.