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Old 06-02-2020, 07:33 PM   #1
kglowacky
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ocm fuel pump wire

I am wiring my fuel in tank fuel pump thru a relay . Is the wire from the engine harness a ground or a power wire? need to know what side of the relay to hooks up to. I am assuming it is a power wire
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Old 06-02-2020, 08:39 PM   #2
LS short box
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Re: ocm fuel pump wire

On the after market LS harnesses I've used they supplied a 12 volt wire to the fuel pump. The LS ecm supplies the ground to the fuel pump relay I believe.
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Old 06-05-2020, 04:58 AM   #3
ls1nova71
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Re: ocm fuel pump wire

The PCM supplies 12v to the fuel pump relay to turn it on.
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Old 06-05-2020, 04:25 PM   #4
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Re: ocm fuel pump wire

I think the older LS computers like before 2006 supplied the ground to the relay. After 2006 when they went to the 58 tooth crank the computer supplies the 12 volt.
I may be wrong. I'd ask the question over on LS1tech.com. Those guys over there are pretty good.
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Old 06-05-2020, 08:51 PM   #5
dayj1
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Re: ocm fuel pump wire

ls1nova71 is correct. The PCM provides 12v to the fuel pump relay. That is true for both the 24x and 58x systems.
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Old 06-05-2020, 10:43 PM   #6
rodstored-72
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Re: ocm fuel pump wire

are you asking about on the factory harness? I have a '13 4.8 LS with all the factory "x" connectors (underhood fuse box). the fuel pump conn. wire is grey and same gauge as the pink wire from my '86 truck. I think these 2 wires will splice together & then go back to the pump? ... I think?? LOL!! If you have a aftermarket harness I think the directions will tell you how to connect the wire.... hope this helps....

....good luck!!
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Old 06-07-2020, 11:26 PM   #7
solidaxel
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Re: ocm fuel pump wire

Quote:
Originally Posted by dayj1 View Post
ls1nova71 is correct. The PCM provides 12v to the fuel pump relay. That is true for both the 24x and 58x systems.
So on the relay pin 86 supplies the 12vdc and 85 is always a ground
So when the key is turned on (switched) the fuel pump becomes (relayed) hot with 30 and 87 to the pump

So I am to believe that the ECM supplies the 12vdc with the key on
or does it just get a switched 12vdc with the key on
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