 Fuel Pump 2 seconds, Fuel Pump voltage |
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| thompson-mfr |
 Mar 14 2014, 12:40 PM
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#1
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Thompson, Ryan  Group: Members Posts: 198 Joined: 30-September 08 From: Silverton, OR Member No.: 9,598 Region Association: Pacific Northwest  |
I have a 74 2.0L original FI and the fuel pump has been moved to the front trunk. I converted to the in and out style (75-76).
My fuel pump used to go on for 2 seconds to prime, then off until cranking or running. I know this is how it is supposed to work. Mine now is on constant with the key in aux position (before starting/cranking or running) What controls this? The computer? I also have only 7 volts to the pump and 9 volts at the fuse on the relay board that pump power goes through. Good 12+ volts at battery. Finally to the question: Does the computer control this 2 second prime? |
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| SirAndy |
Mar 14 2014, 01:15 PM
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#2
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Resident German Group: Admin Posts: 41,679 Joined: 21-January 03 From: Oakland, Kalifornia Member No.: 179 Region Association: Northern California |
QUOTE(thompson-mfr @ Mar 14 2014, 11:40 AM)  Finally to the question: Does the computer control this 2 second prime? Yes, the brain controls the ground for the pump relay to do the 2 second prime ... (IMG:style_emoticons/default/smile.gif) |
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| thompson-mfr |
Mar 14 2014, 04:36 PM
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#3
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Thompson, Ryan Group: Members Posts: 198 Joined: 30-September 08 From: Silverton, OR Member No.: 9,598 Region Association: Pacific Northwest |
QUOTE(SirAndy @ Mar 14 2014, 12:15 PM) QUOTE(thompson-mfr @ Mar 14 2014, 11:40 AM) Finally to the question: Does the computer control this 2 second prime? Yes, the brain controls the ground for the pump relay to do the 2 second prime ... (IMG:style_emoticons/default/smile.gif) So, can I deduct if that is not happening there is a problem with my brain ecu? Do you know the wiring (battery to fuel pump)? I traced it from the fuel pump to the main harness coming through the firewall to the relay board. Guessing the brain interacts with the relay board to control the FP relay? |
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| Dave_Darling |
Mar 14 2014, 06:28 PM
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#4
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914 Idiot Group: Members Posts: 14,991 Joined: 9-January 03 From: Silicon Valley / Kailua-Kona Member No.: 121 Region Association: Northern California 
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QUOTE(thompson-mfr @ Mar 14 2014, 03:36 PM) So, can I deduct if that is not happening there is a problem with my brain ecu? Not necessarily--it is more likely that when you moved the pump you didn't hook into the original wiring. The original wiring goes: Battery to relay board, through fuse on board, through relay to pump. And pump directly to ground, because that's also important. The relay is controlled by the FI brain, and also by the relay that powers the FI. --DD |
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| thompson-mfr |
Mar 15 2014, 12:44 PM
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#5
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Thompson, Ryan Group: Members Posts: 198 Joined: 30-September 08 From: Silverton, OR Member No.: 9,598 Region Association: Pacific Northwest |
QUOTE(Dave_Darling @ Mar 14 2014, 05:28 PM) QUOTE(thompson-mfr @ Mar 14 2014, 03:36 PM) So, can I deduct if that is not happening there is a problem with my brain ecu? Not necessarily--it is more likely that when you moved the pump you didn't hook into the original wiring. The original wiring goes: Battery to relay board, through fuse on board, through relay to pump. And pump directly to ground, because that's also important. The relay is controlled by the FI brain, and also by the relay that powers the FI. --DD I didnt move the pump the po did. It has worked for years. The 2 seconds has worked for years. Now all the sudden it doesn't. I know the ecu is robust and rarely the cause of anything, but if it controls the 2 seconds and now that is stuck on. What else could this be? Thanks for your suggestions. |
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Posts in this topic
thompson-mfr Fuel Pump 2 seconds Mar 14 2014, 12:40 PM
SirAndy So, can I deduct if that is not happening there is... Mar 14 2014, 06:23 PM Cap'n Krusty Yes. If you want that to happen, you need to powe... Mar 14 2014, 01:15 PM 76-914 What size wire did you run to the pump? That's... Mar 14 2014, 02:19 PM Spoke
I also have only 7 volts to the pump and 9 volts ... Mar 14 2014, 03:18 PM
thompson-mfr
I also have only 7 volts to the pump and 9 volts... Mar 14 2014, 04:39 PM Dave_Darling Ah, if it has worked for a while then my assumptio... Mar 15 2014, 06:38 PM Tom 86 is the controlled ground for the fuel pump rela... Mar 16 2014, 07:57 AM thompson-mfr Thank you everyone that chimed in here! I am ... Mar 16 2014, 09:18 AM |
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