This is the first time I've heard of intentionally running a fuel pump backwards and I wonder whether you're right. The fuel pump in modern vehicles is normally submerged in the fuel tank. My guess is that air drawn in by the pump would just make harmless bubbles; the pump would still be fully lubricated. Does anyone know for sure?
Fuel pumps on EFI motors have a supply and return. Return is significantly smaller in diameter and will probably allow the engine to barely run at all. It would probably start and shut off giving the thief the impression the car is junk instead of being disabled.
Oh, this thing was made in 1975. The motor is a mopar 440.
Not all EFI systems use a return line. Some use a PWM controlled pump, rather than a pressure relief valve, to keep the fuel rail pressure constant and so forego the return line.
You're forgetting the part where the fuel pump is a vane pump and will pump in reverse just very poorly (assuming directional rotor, which most have).
It's likely old and carbeurated. Running pump in reverse may serve to empty the carbs fuel "bowl".
Some cars can run a good while off the bowl. Enough to get a mile maybe.
A little plastic impeller isn't going to care about a couple minutes of cavitation.
It's not some fancy high pressure vane pump.
Compared to losing the RV it seems like a negligible cost for what the commenter describes as “older RV”.
Sure, but there are several options that would be zero cost.
Older RVs can fairly readily be acquired at zero cost if you don't mind wasting time on title issues.
When his neighbors house burns down, the insurance company isn't going to pay out after finding this post. Not a negligible cost.