 Fuel pump runs continuously, PO rewire |
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| rjames |
 Oct 27 2008, 04:04 PM
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I'm made of metal  Group: Members Posts: 4,305 Joined: 24-July 05 From: Shoreline, WA Member No.: 4,467 Region Association: Pacific Northwest 
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When removing the gas tank for a sway bar install I noticed that the fuel pump on my '75 had a different colored wire hooked up to it, and a stray wire not going to anything. It has always worked fine, so I ignored it. Then I learned that the fuel pump is supposed to shut itself off after a few seconds with the key in the 'on' position. Mine doesn't do that, it just runs continuously. While I do want undo whatever the PO did and wire it correctly, I don't have time to do anything now. My questions is will this hurt anything assuming I actually start the car and don't just leave the ignition in the position without it running? Thanks- Robert |
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| wertygrog |
Oct 27 2008, 10:35 PM
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wertygrog Group: Members Posts: 429 Joined: 12-November 05 From: Long Beach, CA Member No.: 5,114 Region Association: Southern California |
So is there a relay that runs the pump for 2 seconds or so, or does the FI brain do this? Where is this fuel pump relay- on the engine compartment relay board I presume?
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| bperry |
Oct 30 2008, 06:45 PM
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Lurker Group: Members Posts: 477 Joined: 16-February 04 From: Dallas, Tx Member No.: 1,661 |
QUOTE(wertygrog @ Oct 27 2008, 11:35 PM)  So is there a relay that runs the pump for 2 seconds or so, or does the FI brain do this? Where is this fuel pump relay- on the engine compartment relay board I presume? There is a tech article that might help a bit: Fuel Pump for Carbs Actually it's kind of a convoluted circuit path. If you look at the relay board photo, the fuel pump relay drives +12v to the fuel pump when the coil is energized. The +12v that gets switched to the fuel pump is live all the time and comes from the red fuse in the photo; however, the coil of the fuel pump relay gets +12v from the power supply relay and the ground to the fuel pump coil comes from the FI brain/computer. The Power supply relay coil gets its +12v from the ignition switch on the same circuit as the coil. The Power supply relay coil ground is always grounded. The +12v that is switched by the power supply relay coil is live all the time and is *not* fused. So what that all means is that in order to activate the +12v to the fuel pump you must: - Have a fuse in the location where the red fuse is. - Have the power supply relay plugged in - Have the fuel pump relay plugged in - Turn on the ignition switch. - Ground pin 1 of connector T4b (normally done by FI brain) --- bill |
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Posts in this topic
rjames Fuel pump runs continuously Oct 27 2008, 04:04 PM
Mark Henry Carb or FI?
If it's been switched to carbs th... Oct 27 2008, 04:22 PM echocanyons I just went through this, maybe not the same situa... Oct 27 2008, 04:40 PM rjames The car still has it's original FI system in t... Oct 27 2008, 04:57 PM
southernmost914
The car still has it's original FI system in ... Oct 27 2008, 05:08 PM type47 you need to trace the current path through the rel... Oct 27 2008, 05:16 PM southernmost914
So is there a relay that runs the pump for 2 seco... Oct 28 2008, 05:58 AM rjames
[quote name='wertygrog' post='1095644' date='Oct ... Oct 30 2008, 03:13 PM 7275914911
74 and 75 1.8 use a dual relay mounted by the ba... Nov 9 2008, 05:54 AM rock914 Hey guys,
could use some help, I have been working... Nov 9 2008, 02:48 AM rock914 Strange you would mention not putting a relay in t... Nov 9 2008, 11:43 PM tracks914 I beleive having the fuel pump run continuously is... Nov 11 2008, 06:31 AM |
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