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Failure mode - Ford 6.7L Power Stroke Diesel (Scorpion)

Low-pressure fuel supply weakness (lift pump, filters, water-in-fuel)

Reliability tier: verified - verify before ordering, see /disclosure/

Symptoms

Compare with the other causes of the same sign on this engine: hard start, long crank or no-start (4 causes) · loss of power, limp mode or derate (5 causes) · misfire, rough idle, hesitation or surging (5 causes)

Root cause

The low-pressure supply side (in-tank or frame-mounted lift pump, primary/secondary filtration, water separator) feeds the CP4.2 high-pressure pump; starvation or contamination on this side is exactly what stresses the CP4 into the contamination-cascade mode (CP4.2 high-pressure fuel pump contamination cascade). This record covers the low-pressure-side failure itself - lift pump weakness, filter restriction, and water intrusion - as distinct from the high-pressure pump's own catastrophic failure mode, per the same low-pressure-vs-high-pressure split already used on cummins-6_7 (Lift pump / fuel delivery weakness vs the pump/injector modes). A separately-sourced mechanism worth naming on its own: the factory fuel filter housing is plastic, and aftermarket vendors (S&S Diesel Motorsport, per its product listing on Dave's Auto Center) document it cracking/leaking with age - the OEM housing holds 4-micron/99%-efficiency filtration at a 12-gram dirt capacity; aftermarket billet-aluminum replacement housings roughly double that capacity while addressing the cracking risk. This is a housing-integrity issue, distinct from filter-element restriction or water intrusion.

Diagnosis

Fixes

replace the lift pump on confirmed low-pressure-side failure ()

replace fuel filters on schedule (both filters, shortened interval under hard use per the vendor source) and inspect for metallic debris at every change ()

upgrade fuel filtration (e.g. an aftermarket lift-pump/filtration system) as a preventive measure protecting the CP4 from contamination exposure ()

replace a cracked/leaking OEM plastic housing with a billet-aluminum housing kit rather than a like-for-like OEM reorder, if leaking has already started (billet aftermarket housing vs OEM plastic reorder) - billet housing costs more upfront ($300 per Dave's Auto Center) but addresses the cracking failure mode at the root and nearly doubles dirt-holding capacity; OEM reorder is cheaper but carries the same long-term cracking risk

Prevalence

common

Parts for this repair run about $300.00: see them next to the other repairs on this engine in repair costs.

Affected configurations (108)