Fuel starvation problem

JEFF RENNA

MEMBER
1984 GMC S15
4.3L
V6
4WD
AUTOMATIC
196,000 MILES

My vehicle has an engine swap to a v6 4.3l with TBI injection. It starts and runs fine I can only drive it for about ten minutes then is sputters and finally stalls out. If I give it fifteen to twenty. I can start it and drive it again until it repeats. Change out injectors has new clean tank, fuel pump, filter. Can a clog or inoperable charcoal canister and or gas cap be causing this issue? Never seem to have any pressure when I remove the gas cap. The computer does not show any codes other than the code 12.

Thanks

1 Reply

CARADIODOC

MECHANIC
33,916 POSTS

There are two common things to start with. The first is you described exactly how the symptoms act when the pickup screen inside the tank is plugged or is collapsing. It typically takes about ten miles before it fully collapses, then it has to sit for about five to ten minutes before it will stretch out enough to allow fuel to pass. This has happened to me four times with three cars.

The next thing to look at is the fuel tank straps. I know this is a problem with the smaller 1990's Blazers. Not sure if it applies to yours. The fuel pump is grounded through the tank straps, not a wire. If the tank and / or straps are rusty, you will get a crank/no-start or an intermittent stalling problem due to loss of ground. To solve that, drill a small hole in the tank's flange, outside the welded seam. Drill another small hole in the frame. Run a self-tapping screw into each hole and attach a wire between them.

The next time this occurs, check for spark right away, before the engine will start again. If it is missing, you do not have a fuel problem. You have a loss of spark and fuel problem. Most commonly that is due to a failing crankshaft position sensor or camshaft position sensor. Either of those commonly fail by becoming heat-sensitive, then they work again after they cool down, often for as much as an hour.