Electric fuel pump question

This is the place to get help with technical matters concerning your M151 jeep

Moderators: rickf, raymond, Mr. Recovery

Sundawg3
Corporal
Corporal
Posts: 49
Joined: November 18th, 2023, 11:26 am

Electric fuel pump question

Unread post by Sundawg3 » November 27th, 2023, 1:28 am

Mine has a switch on the instrument panel to turn on and off the fuel pump. Since there's a red wire (with fuse) at the battery running under the dash to the switch and under the seat to the fuel pump I take it that was added. Why would someone install this and where was the original power to the fuel pump supplied? I've checked the IPC multiple times with no luck.

Hambone
Brigadier General
Brigadier General
Posts: 2486
Joined: October 1st, 2010, 12:19 am
Location: El Dorado, Arkansas

Re: Electric fuel pump question

Unread post by Hambone » November 27th, 2023, 4:52 am

That was added, I believe original wiring went from circuit breaker to oil pressure safety switch to fuel pump, PO may have had wiring problem or problem with safety switch, hard to say.

User avatar
svramselaar
Captain
Captain
Posts: 1099
Joined: December 30th, 2007, 6:48 am
Location: holland

Re: Electric fuel pump question

Unread post by svramselaar » November 27th, 2023, 8:24 am

hi

if the original wiring for the pump works
i can only think they made it for priming the carb ??
the best is to take it out and use the safety switch wiring

george

User avatar
rickf
General
General
Posts: 19707
Joined: November 26th, 2007, 1:28 pm
Location: Pemberton, NJ.

Re: Electric fuel pump question

Unread post by rickf » November 27th, 2023, 9:03 am

The original wiring is the #77 circuit in the wiring diagram. You say you have checked the IPC multiple times? What is the IPC you are referring to? Is the vehicle using the factory pump in the tank or an aftermarket electric pump?
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone

Sundawg3
Corporal
Corporal
Posts: 49
Joined: November 18th, 2023, 11:26 am

Re: Electric fuel pump question

Unread post by Sundawg3 » November 27th, 2023, 12:11 pm

Illustrated parts catalogue. The "safety switch" many refer to is the forward oil pressure switch next to the distributor, three wires? I haven't opened the fuel tank to check the pump. Figured if it was working why mess with it? I read other posts stating the fuel pump comes on with the "safety switch" so I assume there is no fuel pump operation unless there's oil pressure. I'm guessing with the PO installed switch, on before cranking, the engine will start a little faster since it's not waiting for oil pressure to activate the pump?

Hambone
Brigadier General
Brigadier General
Posts: 2486
Joined: October 1st, 2010, 12:19 am
Location: El Dorado, Arkansas

Re: Electric fuel pump question

Unread post by Hambone » November 27th, 2023, 12:52 pm

Yes, 3 wire switch down by distributor, you can jump it out if you want to test the original wiring. I wouldn't want to run a direct wire to the fuel pump, you delete the safety factor and if accidently left on, that pump runs about $300 now.

User avatar
rickf
General
General
Posts: 19707
Joined: November 26th, 2007, 1:28 pm
Location: Pemberton, NJ.

Re: Electric fuel pump question

Unread post by rickf » November 27th, 2023, 3:09 pm

The fuel pump is wired so it starts pumping when the starter is engaged, plus you also have gas in the carb bowl to work off of until the fuel pump catches up. If you had that pump going tap-tap, taptaptaptap. Once the carb is full and fuel pressure builds up the pump will stop. Then it is the factory pump and it is working fine. You just need to see if the original wiring is still there. I believe in your pics I did not see the wires but it was a small pic if I remember correctly. I am working with you and one other with electric pump/ fuel related issues and I tend to get people mixed up unless I am looking at the pics. If you have an A1 then the wiring should be there is some shape or form. The safety switch is available, the plug for it might be tough to find. I have a few old harnesses that I may be able to scavenge one from.
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone

Sundawg3
Corporal
Corporal
Posts: 49
Joined: November 18th, 2023, 11:26 am

Re: Electric fuel pump question

Unread post by Sundawg3 » November 27th, 2023, 7:55 pm

I assume one wire in the safety is for the fuel pump. What would the other two wires be used for?

User avatar
rickf
General
General
Posts: 19707
Joined: November 26th, 2007, 1:28 pm
Location: Pemberton, NJ.

Re: Electric fuel pump question

Unread post by rickf » November 28th, 2023, 10:35 am

Fuel pump, power for fuel pump and a power wire from starter to run pump while cranking. There are only two pins on the safety switch.
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone

Sundawg3
Corporal
Corporal
Posts: 49
Joined: November 18th, 2023, 11:26 am

Re: Electric fuel pump question

Unread post by Sundawg3 » December 25th, 2023, 4:46 pm

I sure as hell can't find where the 77 wire was cut behind the instrument panel. Thinking about running a new one from the switch to the fuel pump. Looks like M13466/1-5 14 gauge wire. Anyone know who sells it by the foot?

User avatar
rickf
General
General
Posts: 19707
Joined: November 26th, 2007, 1:28 pm
Location: Pemberton, NJ.

Re: Electric fuel pump question

Unread post by rickf » December 25th, 2023, 8:01 pm

The 77 wire does not come from behind the dash, it goes from the safety switch to the fuel pump through the dash but not connected to anything in there but the rear connector. The 77A wire comes off of the circuit breaker and goes to the safety switch and the 77B wire connects the safety switch to the starter. Connecting the pump directly to the switch can be done, it will make the pump run anytime the switch is on. I do not recommend it but it is your vehicle. Be aware that the pump will only run if there is a need for gas, If the carb is full and the line is pressurized then the pump will stop running. So if you do not hear it running and it has power that may be why. The wire will be available from any of the regular surplus dealers like red River, Rapco, Frontline, TJ Murray, Army Jeep Parts.
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone

Sundawg3
Corporal
Corporal
Posts: 49
Joined: November 18th, 2023, 11:26 am

Re: Electric fuel pump question

Unread post by Sundawg3 » December 25th, 2023, 9:49 pm

Rickf,

Someone prior to me cut the wire under the dash. They then ran a wire from the battery to a switch. I want to hook it up the factory way. I can’t find the wire that was cut from the switch to the fuel pump. I plan on splicing into the factory wire, at the switch, and running to the fuel pump just as the factory did. It’ll run off the safety switch just as it did when it was new. I’d like to use factory wiring so it doesn’t stand out so badly.

User avatar
rickf
General
General
Posts: 19707
Joined: November 26th, 2007, 1:28 pm
Location: Pemberton, NJ.

Re: Electric fuel pump question

Unread post by rickf » December 25th, 2023, 11:09 pm

Do you have the wiring diagram? The factory wire comes from the circuit breaker behind the dash left of the gauge panel. It never goes to any switch.
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone

User avatar
muttguru
Colonel
Colonel
Posts: 1992
Joined: November 26th, 2007, 12:18 pm
Location: Li'l ol' England.....

Re: Electric fuel pump question

Unread post by muttguru » December 26th, 2023, 10:23 am

Here's the wiring diagram from April 1963 which should cover the safety-switch wires 77, 77A and 77B.

Image

If you need a larger diagram, go to:-
http://www.surfacezero.com/g503/data/50 ... _63-A1.jpg

Ken
Kind regards....
Ken

Always wanted - Details and pictures of M416 Trailer data plates & M151 data plates & body-tags for my research. Thanks!

Contact address - - muttguru@aol.com

Note for 2023..... Ken..."Less Stress - More Exercise!"

User avatar
rickf
General
General
Posts: 19707
Joined: November 26th, 2007, 1:28 pm
Location: Pemberton, NJ.

Re: Electric fuel pump question

Unread post by rickf » December 26th, 2023, 10:38 am

Click on pic for MUCH bigger diagram. Click on it again to get even bigger.
M151A1_wire.jpg
You do not have the required permissions to view the files attached to this post.
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone

Post Reply