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Re: Concern about the fuel pump not stopping in a wreck
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Posted by kansas (more from kansas) on Thu, 7 Sep 2006 10:47:32 Share Post by Email
In Reply to: Concern about the fuel pump not stopping in a wreck?, Brian, Thu, 7 Sep 2006 03:33:16
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Having the fuel pump continue to run after an accident with the engine off is definitely a concern. It was of course never a concern with mechanical pumps, and it is not a concern on contemporary vehicles because the fuel pump is controlled by the computer, which will only operate the pump for a couple of seconds when the key is first turned on, and when the engine is rotating.

How to accomplish this purpose on a vintage retrofit is a little beyond me technically, but is in principle fairly simple. The negative terminal of the ignition coil has a signal that will switch high(~12V) to low (~0V) with each spark impulse as the engine rotates. The signal will be either high or low, depending on engine position, with key on engine off--but it will be steady, not switching. So what is needed is a circuit that can detect the switching signal and distinguish it from steady high or low, and actuate a relay to operate the fuel pump, ONLY when the signal is switching indicating that the engine is running.

Some of the vintage enthusiasts who have called this problem to your attention may have devised a solution. Please post if you find one.

posted by 198.69.250...
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