Engine - Poor Performance/Hesitation/Stumble
85ford22Article No. 85-22-29
PERFORMANCE POOR/HESITATION/STUMBLE (5.0L) DUAL FUEL TANK SWITCHING PROCEDURE
LIGHT TRUCK 1986 F SERIES
If the driver switches from an empty fuel tank to a fuel tank with any amount of usable fuel, and then inadvertently switches back to the empty fuel tank, the vehicle will continue to run with fuel from the fueled tank.
With the switch in the empty tank position, the fuel pump in the empty tank will operate. However, the vehicle will continue to draw fuel through the high pressure fuel pump from the fueled tank.
This is due to the unique operation of the fuel tank switching mechanism, which consists of switching valves located in the frame-mounted fuel reservoir, that are activated by hydraulic pressure. With no fuel pressure from the empty fuel tank, the valves will not switch and the high pressure fuel pump will continue to draw fuel from the fueled tank pump which is not shut off.
This can result in poor performance, stumbles, stalls, etc., due to reduced fuel pressure and volume. The life of the in-tank fuel pump of the empty fuel tank may be reduced.
Refer to Section 24-35 of the 1986 Light Truck Engine Shop Manual, Volume B for diagnosis and repair procedures.
OTHER APPLICABLE ARTICLES: None
WARRANTY STATUS: "INFORMATION ONLY"