 Fuel pump question |
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| 914itis |
 Feb 24 2012, 10:14 PM
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#1
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Advanced Member  Group: Members Posts: 2,892 Joined: 9-October 10 From: New York City Member No.: 12,256 Region Association: North East States  |
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 ?
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Replies(1 - 6)
| jonferns |
Feb 24 2012, 10:38 PM
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#2
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Advanced Member Group: Members Posts: 2,081 Joined: 29-March 07 From: New Jersey Member No.: 7,631 Region Association: North East States 
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Did you check to see if there's power at the pump when the key is turned on?
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| 914itis |
Feb 24 2012, 10:41 PM
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#3
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Advanced Member Group: Members Posts: 2,892 Joined: 9-October 10 From: New York City Member No.: 12,256 Region Association: North East States |
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 |
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| underthetire |
Feb 24 2012, 10:47 PM
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#4
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914 Guru Group: Members Posts: 5,062 Joined: 7-October 08 From: Brentwood Member No.: 9,623 Region Association: Northern California |
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.
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| 76-914 |
Feb 25 2012, 08:41 AM
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#5
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Repeat Offender & Resident Subaru Antagonist Group: Members Posts: 13,502 Joined: 23-January 09 From: Temecula, CA Member No.: 9,964 Region Association: Southern California
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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. (IMG:style_emoticons/default/beerchug.gif)
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| Prospectfarms |
Feb 25 2012, 09:28 AM
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#6
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Member Group: Members Posts: 495 Joined: 7-March 11 From: Louisville, KY Member No.: 12,801 Region Association: Upper MidWest |
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.
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| underthetire |
Feb 25 2012, 11:01 AM
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#7
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914 Guru Group: Members Posts: 5,062 Joined: 7-October 08 From: Brentwood Member No.: 9,623 Region Association: Northern California |
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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