injector pulse
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Joined: Dec 2007
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injector pulse
I have a 92 f-150, 302, 170,000 mi. The truck randomly starts, it carries 37psi on the rail and has good spark. I tested the injectors and they are not pulsing. I've looked for broken wires and haven't found anything, tested the ICM, swapped out ignition switch and still no luck. What tells the injectors to pulse? Checked relays and fuses that pertain to the fuel system and the're good. One weird thing is when I turn the key on if the fuel pump primes for 2 seconds or so and stops the truck will start, but sometimes it runs constantly and it won't start.
FTE Legend
Joined: Jun 2006
Posts: 31,930
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From: Ottawa, Ontario
The constant running fuel pump is a bad sign, it could mean a bad computer but could also be a sticking fuel pump relay. If the computer doesn't see a pulse from the TFI module it won't fire the injectors, and the TFI module gets it's signal from the pickup inside the distributor.
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yeah I had hoped it would be a cheap fix. The thing I don't understand is that sometimes the pump runs constantly and sometimes it cycles how its supposed to. Would the computer mess up intermitently if it was on its way out, or would it do it every time?
