Fuel Transfer Between Fuel Tanks
| Subject: | Fuel Transfer Between Dual Fuel Tanks |
| Models: | 1993-98 Chevrolet and GMC 6-7H MD Conventional Models |
| 1997-98 Chevrolet and GMC 6-7F T-Series MD Models |
| Equipped with 50 Gallon Dual RH and LH Fuel Tanks (RPO NL5) and Diesel Engines (RPOs LG4, LG5, LN4, LX0) |
For the above listed vehicles with dual fuel tanks, the following should be observed in order to prevent the engine from stalling or running out of fuel.
When the right secondary tank becomes extremely low on fuel, or dry, the fuel module goes into a 4 minute pump-out mode. It then transfers all of the remaining fuel into the left primary tank. When this happens, the module goes into a lock-out mode. This lock-out mode prevents fuel from being transferred from the right tank to the left tank while the engine is running. Fuel will not transfer, even if the right tank is refilled, unless the ignition is re-cycled by turning the key to the ON and OFF positions. When the ignition is re-cycled, the lock-out mode is defeated.
When the above circumstances occur, the left primary tank may be run dry without any fuel being transferred into the tank. This may cause the engine to stall. When the ignition is re-cycled, the fuel will transfer but if the engine was run dry and taken in air, the engine will not re re-primed. At this point, because the engine is not primed, the engine will not start again until the engine is totally re-primed.
In order to prevent the above circumstances from happening, the operator MUST turn off the engine when refueling the vehicle and leave the ignition key in the OFF position.
