914itis
Feb 24 2012, 10:14 PM
Fuel pump question on 74 djet. Does the brain operates the fuel pump ? I connected all grounds and the relay board, fuses and relays are good , the engine is not yet in the car, when I turn the key on, the fuel pump is not powered. Is it because the brain is not attached ?
jonferns
Feb 24 2012, 10:38 PM
Did you check to see if there's power at the pump when the key is turned on?
914itis
Feb 24 2012, 10:41 PM
QUOTE(Jon Fernandes @ Feb 24 2012, 11:38 PM)
Did you check to see if there's power at the pump when the key is turned on?
I did and there is no power
underthetire
Feb 24 2012, 10:47 PM
The "brain" does turn the pump on. It switches the ground on the fuel pump relay. It times for 1 second with key on, then turns the pump on when the ecu sees the trigger points trigger. At least that's how I understand the circuit. My megasquirt is tied in the same way.
76-914
Feb 25 2012, 08:41 AM
Yep. I chased that cat on my 1st 914. IIRC, it was a ground leg that switched it. #19 sticks in my mind but don't hold me to it.
Prospectfarms
Feb 25 2012, 09:28 AM
Unless I was certain the pump is operational, if I had any concerns about my FP or its circuit I'd first try to energize the pump directly from a 12 volt source with sufficient current. Might save time later speculating about it.
underthetire
Feb 25 2012, 11:01 AM
All you need to do is ground III on the relay board. I can't upload pics from my iPad, but it's on the pelican site.
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