Intermittent Hesitation and Stalling - Varnished Fuel Tank and Clogged Fuel Pump Sock

Fuel Systemintermediate✓ OP Confirmed

Problem

7M-GE had intermittent hesitation on throttle that occurred randomly at different RPMs. The issue would temporarily go away after turning the car off and back on. Eventually progressed to the car dying while driving - sometimes a slow loss of power, sometimes stumbling and dying when braking to a stop. The car had sat for 10 years before the previous owner sold it.

Random hesitation on throttle at varying RPMsIssue temporarily cleared by turning car off and restartingIntermittent misfiring under loadCar dying while driving - sometimes gradual power loss, sometimes sudden stalling at red lightsDifficulty restarting after stalling - had to let car sit before it would idle againProblems worse when fuel level dropped below half tankIssues appeared on trips longer than 15 miles

Root Cause

The car had sat for approximately 10 years before the current owner purchased it. The old gasoline had turned to varnish inside the fuel tank, contaminating the fuel system. The fuel pump sock (inlet filter) had become rock hard from the varnish buildup, restricting fuel flow to the pump. The fuel exiting the filter was orange-colored, indicating severe contamination throughout the fuel delivery system.

Confidence

High confidence — Original poster confirmed this resolved the issue

View Original Thread →Posted January 2023 on SupraForums.com