Fuel pump not turning on till engine turns over ?

cumminatyanow

cumminatyanow

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Jan 21, 2010
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6
this mite be somthing simple i have 99 the fuel pump does not always turn on until i start cranking the engine it will crank for a while then finaly start. If i turn key on and bump engine until the fuel pump turns on truck fires rite up ? i thought it might be stock lift pump but just put new airdog on same results could it be the relay under the hood ? i am not sure .
 
your system is losing pressure after it sits. vp's don't like to start under a lot of fuel pressure. When I race my truck I have to plug my fass wiring into a key hot setup I have because my computer turns off the lift pump at 100mph. I have to crank on it for a while to start it under pressure because a vp is picky like that.
 
01quadcab said:
your system is losing pressure after it sits. vp's don't like to start under a lot of fuel pressure. When I race my truck I have to plug my fass wiring into a key hot setup I have because my computer turns off the lift pump at 100mph. I have to crank on it for a while to start it under pressure because a vp is picky like that.
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i will check all fittings again tonite mite be return leaking ? all the rest is brand new
 
Your truck should be wired such that as soon as you turn the key on, it bumps the lift pump then turns it back off until the key is turned more to crank the engine. This is because the VP doesn't like much pressure when the truck starts cranking. It bumps it to give enough pressure for the fuel to move forward, but not to pressurize the fuel too much. This is normal to my knowledge. If you wire the pump to come on and stay on when you turn the key on, you'll have hard starts from all the threads and stories I've read. So, I'm sorry, but I really don't understand the question here. Try me again.
 
how long does it take for your truck to do this? Is it in the morning or after the truck as sat for a few hours?
 
only does it after it sits for a while it started fine last nite this morning it cranked for a long time then finally started ?about the third time i tried cranking i heard the fuel pump prime up it started rite up ? i will double check wiring ?
 
4x4dually said:
Your truck should be wired such that as soon as you turn the key on, it bumps the lift pump then turns it back off until the key is turned more to crank the engine. This is because the VP doesn't like much pressure when the truck starts cranking. It bumps it to give enough pressure for the fuel to move forward, but not to pressurize the fuel too much. This is normal to my knowledge. If you wire the pump to come on and stay on when you turn the key on, you'll have hard starts from all the threads and stories I've read. So, I'm sorry, but I really don't understand the question here. Try me again.
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this is what i have been told to my truck does not do the do the bump until the third key start ? as soon as it does the bump it fires instantly that is why i am confused ? after is been started its been starting rite back up
 
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