can i hook the fuel pump up to a switch?
Thread Starter
TECH Addict
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From: Springfield IL
can i hook the fuel pump up to a switch? i need to know whether or not i can hook my 255 up to a switch or if the computer has to run it. someone told me the pumps turn on and off as fuel is needed. is this true?
No. The only time the pump turns back off is when
you first hit the ignition, to charge the rail. Once the
engine is running the pump runs full time.
If you want to cut or assert power independent of
the PCM, do it in the coil line, not the power feed.
The power feed is too wimpy to begin with and draws
a lot of current.
If you took a SPST, center-off toggle switch and put
center pole to relay coil, one pole to PCM coil drive
and one pole to IGN you'd have all the options (cut
out, always-on w/ key, and PCM-controlled.
you first hit the ignition, to charge the rail. Once the
engine is running the pump runs full time.
If you want to cut or assert power independent of
the PCM, do it in the coil line, not the power feed.
The power feed is too wimpy to begin with and draws
a lot of current.
If you took a SPST, center-off toggle switch and put
center pole to relay coil, one pole to PCM coil drive
and one pole to IGN you'd have all the options (cut
out, always-on w/ key, and PCM-controlled.
Thread Starter
TECH Addict
iTrader: (70)
Joined: Sep 2003
Posts: 2,525
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From: Springfield IL
does the pcm need to know its running?
i have a rear mounted battery and plan on doing dual 255's intank. i was going to run 2 skinny wires up to a switch and at the back have a 30-40 amp relay and alot larger wires running the pump/ pumps in the future
i have a rear mounted battery and plan on doing dual 255's intank. i was going to run 2 skinny wires up to a switch and at the back have a 30-40 amp relay and alot larger wires running the pump/ pumps in the future
Originally Posted by ramairstyle00
does the pcm need to know its running?
i have a rear mounted battery and plan on doing dual 255's intank. i was going to run 2 skinny wires up to a switch and at the back have a 30-40 amp relay and alot larger wires running the pump/ pumps in the future
i have a rear mounted battery and plan on doing dual 255's intank. i was going to run 2 skinny wires up to a switch and at the back have a 30-40 amp relay and alot larger wires running the pump/ pumps in the future
the PCM only cuts the fuel pumps off if the engine is not running.
when you turn the key on, it kicks the pump on for a set time(couple seconds), then, because the engine is not running it cuts it off.
if i were you, i would keep your rear mounted relay idea....... but trigger the relay to be flipped on by the PCM... just like stock.
thats how 99% of the LS1 conversion guys do it too...
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Joined: Dec 2003
Posts: 342
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From: Houston
The fuel pump is wired this way for your saftey. If you get into an accident and cut the fuel line the engine will die and with no ignition pulse the pcm will cut the power to the fuel pump.
If you wire it direct the fuel pump will run and continue to feed a possible fire if you are unable to cut the switch.
Alan
If you wire it direct the fuel pump will run and continue to feed a possible fire if you are unable to cut the switch.
Alan
