Electric Pump Power

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Electric Pump Power

Unread post by Surveyor » August 20th, 2018, 10:46 pm

Electric Fuel pump is working great... as long as I have it running off of a jumper to battery. Engine runs no problem but...

Knowing that I wanted to eventually go back to in-tank, I swear I checked about a year ago to see if I had 24v to what I thought was the fuel pump wire and I had power then but not now. Wire is tagged three times as 87,106,38. Manual says it should be 77. ??? Now voltage ranges from 0 to 5v at most.

I checked for 24v to 77a on oil pressure safety with ignition switch on - good.
Checked for 24v to 77B on oil pressure safety when depressing starter - good.
Tried to jump all three on oil pressure safety, no power to pump with ignition off. When I try and turn ignition on, the starter engages and jumpers couldn't take the current, no sparks but they heated up pretty good. Quickly turned off ignition and did not try that again. Is this test with it on or off? Manual not clear.

Just read old post. Will try and jump 77 and 77A tomorrow and see if that gets it ticking.
1960 M151 Run #1
"There is one nut on a M151 that is very difficult to remove....." - K8icu
"She ain't a Cadillac and she ain't a Rolls, But there ain't nothin' wrong with the radio" - Aaron Tippin
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Re: Electric Pump Power

Unread post by rickf » August 21st, 2018, 10:13 am

77 is the fuel pump and 77A is the supply wire to the safety switch. They are two you want to jump to run the pump directly off of the switch. 77B is the wire to the starter which runs the pump while cranking, if you jump 77A and 77B you are putting power straight from the breaker to the starter on a 14 gauge wire. "Technically" the breaker should pop before the wire burns but I would not trust a 40-50 year old breaker to do it's job.
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone

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Re: Electric Pump Power

Unread post by Surveyor » August 21st, 2018, 9:54 pm

Second wire at tank has no tag numbers. Just took a day away from it to think about it but at some point I must have mixed them. m151 working as it should now, brain not so much. :? Fuel gauge was not hooked up at panel so I don't think I caused any other problems there. This means the fuel level sending unit would be hooked to 87,106,38 wire instead which should be marked 28 instead, if I read the manual right :?: :?: :?: Weird.
1960 M151 Run #1
"There is one nut on a M151 that is very difficult to remove....." - K8icu
"She ain't a Cadillac and she ain't a Rolls, But there ain't nothin' wrong with the radio" - Aaron Tippin
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rickf
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Re: Electric Pump Power

Unread post by rickf » August 21st, 2018, 10:08 pm

Gas gauge is #28
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone

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