Wiring or electrical problem

1959 - 1978, M151, M151A1, M151A2, Technical questions and discussions, regarding anything related to the M151.
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steve1973
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Wiring or electrical problem

Post by steve1973 » Sun Apr 16, 2017 12:47 pm

Hello all,
I'm just finishing up installing a new front wire harness from Vintage Wiring of Maine. Everything seems to work but I do have one problem. When I go to start the jeep and press the foot switch and release the starter stays engaged and running. When I turn the switch off and back on the starter kicks in without pressing the foot switch. All switches have been replaced and tested. I even tried putting in the old switches with same results. I retraced all wires and are in correct locations. So here's the interesting thing. I traced back to a oil sensor switch, not the oil pressure, and not sure what it does. Two wires, number 77, and wire 77B got to this switch through a plug.

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When I unplug from the switch everything works fine. So I'm at a loss of what to do next. Is the sending unit the problem? Do I really need to have this plugged in? I need your help. One more thing. It ran fine before I changes the wiring harness but wires and connections were questionable.

Steve A.
1941 White M2A1 (90% restored)
1945 M10 ammo trailer (restored)

BeltFedBob
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Re: Wiring or electrical problem

Post by BeltFedBob » Sun Apr 16, 2017 2:55 pm

Never mind my post.
Last edited by BeltFedBob on Sun Apr 16, 2017 5:55 pm, edited 2 times in total.

steve1973
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Re: Wiring or electrical problem

Post by steve1973 » Sun Apr 16, 2017 3:49 pm

Isn't the item in front of that a mechanical fuel pump? Sure looks like it to me. If so why would I also have an electric pump? I don't think I have an electric fuel pump. By the way this is a M151A1. I think I forgot to mention that.

Steve A.
1941 White M2A1 (90% restored)
1945 M10 ammo trailer (restored)

Rickf
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Re: Wiring or electrical problem

Post by Rickf » Sun Apr 16, 2017 4:47 pm

I replied to your post on the g838 Steve so I will not get into great detail here but you did not mention the A1 over there. I assumed it was or you would not have spent that kind of money on that harness. The problem is not going to be in the switch, it sounds like you have a relay in the system somewhere. And yes, the A1 would have originally had an electric fuel pump in the tank. Um........................ what did you do with the fuel pump wire that was up top? That may be a clue. There should be a fuel pump wire coming out of the bundle in the dash and it is number 77, it will be the same length as the fuel gauge wire.
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone

Rickf
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Re: Wiring or electrical problem

Post by Rickf » Sun Apr 16, 2017 4:56 pm

Ok, I was just looking over my diagram and the only way I see that the starter can get power through that circuit assuming there are no other add ons is if either you plugged in the safety switch wrong or he wired the plug wrong and when oil pressure builds up it close the circuit between 77A and 77B instead of 77A and 77 as it ids supposed to. Did you run the other end of 77B to the starter terminal? If yes that is right.
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone


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D Pizzoferrato
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Re: Wiring or electrical problem

Post by D Pizzoferrato » Mon Apr 17, 2017 4:56 am

If you look at the Oil Pressure Safety Switch drawing in the manual, then take a meter and actually check continuity of the switch, you will find that the drawing in the manual is backwards. I had this same problem when I did my 66. As I modified an A2 harness, yet retained the electric fuel pump, I had to build an auxiliary harness to link the fuel pump, battery/ignition, and Oil Pressure Safety Switch. I used the manual drawing for a reference. It acted just as yours is. Then I checked the switch and had a WTF moment; changed a couple of pin locations in the Packard plug and all was well. Hard to believe that they put a harness together wrong based on a faulty manual picture, but I'd bet they don't make many of these and may have needed a reference. It's also easy to push the wrong pin locations when your dealing with a mirror/mated image on these connectors.

As you have a mechanical fuel pump, you don't need the safety switch harness. Lose the connection to the intermediate terminal on the switch and use it for show.
David Pizzoferrato
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steve1973
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Re: Wiring or electrical problem

Post by steve1973 » Wed Apr 19, 2017 4:35 am

Thanks to everyone's input. I learned a lot. Also from the members on the G838 forum site. Here is some photos of the gas tank. You can clearly see a cut wire that has been tied back.

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It also looks like one port is silicone over.

Steve A.
1941 White M2A1 (90% restored)
1945 M10 ammo trailer (restored)

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