Re:Why do they still make car alarms? (2015)
by hathawsh on Tuesday January 19, 2021 @06:23PM
(#25840358)
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?
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Re:Why do they still make car alarms? (2015)
by dkdk8283 on Tuesday January 19, 2021 @06:36PM
(#25840483)
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.
Re:Why do they still make car alarms? (2015)
by spiritplumber on Tuesday January 19, 2021 @07:34PM
(#25841057)
Oh, this thing was made in 1975. The motor is a mopar 440.
Re:Why do they still make car alarms? (2015)
by technothrasher on Tuesday January 19, 2021 @07:50PM
(#25841181)
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.
Re:Why do they still make car alarms? (2015)
by throwaway0a5e on Wednesday January 20, 2021 @07:07AM
(#25845436)
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).
Re:Why do they still make car alarms? (2015)
by throwaway189262 on Wednesday January 20, 2021 @12:53AM
(#25842980)
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.