what tells the fuel pump to shut off and turn on?

 

If your talkin lift pump here, the ECM actually controls the trigger wire but it runs the whole time your truck runs plus approximately 40 seconds before start up during the wait to start cycle.

 

so could it be a problem with my ecm that is cutting off the fuel pump. everything else is working great but like i said there is no power to my lift pump once i loose fuel pressure?

 

mine doesn't run till you actually bump the starter. Well thats what it did and now I have the fass and same thing.

 

That's funny.
When I turn my key on the electric lift pump runs for about 1 second then shuts off,if I bump the starter it will run for a little while (could be 40 seconds I suppose)

 

To test your pump just hotwire it right to the battery and drive around for a while to see if the pump shuts off. Coming off the battery your pump will run all the time so if it shuts off like this you know the pump is bad.

 

ok to day i went out and got the code 1689. turned the key heard aftermarket fuel pump kick on turned the key and of course it fired up and ran like a champ for about 5 min. then the fuel pump shut off no power to the fuel pump. disconected the batteries for about thirty and reconnected them turned key on fuel pump kicked on fired it up she ran for about a min then i lost power to my fuel pump. if i put a jumper cable to my fuel pump it will kick right on. i am going crazy i don't know what else to do any opinions?????

 

Yer gonna have to run it for a while hooked to the battery to see if keeps runnin like that before your gonna know anything more.

 

sorry code was 1693 not 1689

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so i went out and hooked a jumper wire strait to the lift pump and would only get 6 lbs fuel pressure as soon as i would start the truck the pressure would drop down to between 0 and 1 so i shut it off then i hooked it up to both the lift pump and the carter 21 lbs of pressure and i started the truck she ran like a champ and held a constant 21 lbs for at least 15 min with no problems. does this mean my ecu is bad. i have all ready checked the relay and replaced it.

 

read the codes today one was

p1689

and

p0382

what are they