Fuel gauge

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

Moderators: rickf, raymond, Mr. Recovery

Post Reply
User avatar
Bucolic
Sergeant First Class
Sergeant First Class
Posts: 219
Joined: August 28th, 2014, 12:22 am
Location: North Hills, CA

Fuel gauge

Unread post by Bucolic » May 14th, 2017, 2:43 pm

Would inaccurate fuel level readings most likely be caused by a bad sender unit or a faulty gauge? Yes, I ran out of gas with the gauge showing 1/2 full. :( :( Luckily I was only a block from home. :D :D
1964 M151 A1

User avatar
rickf
General
General
Posts: 19740
Joined: November 26th, 2007, 1:28 pm
Location: Pemberton, NJ.

Re: Fuel gauge

Unread post by rickf » May 14th, 2017, 4:53 pm

Most likely the sending unit, is it a replacement unit? Have you checked the ground between the tank and the body? A lot of people will add a ground wire from the sending unit to a good ground spot on the body. The aftermarket sending units are known for being less than reliable. Mine said half a tank at the beginning of the season when I turned on the electric pump to drain the tank. (A1's are nice that way, disconnect the hose from the carb and extend it to a can and bypass the safety switch, pull the distributor wire off and turn it on.) Mine pumped out exactly 5 gallons. Now that is out of a 17 gallon tank! There was still a pretty fair amount left on the bottom it could not grab but that just goes to show, the best gauge is to take the cap off and look in that big damn hole. :lol:
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone

User avatar
Bucolic
Sergeant First Class
Sergeant First Class
Posts: 219
Joined: August 28th, 2014, 12:22 am
Location: North Hills, CA

Re: Fuel gauge

Unread post by Bucolic » May 14th, 2017, 7:17 pm

rickf wrote:Most likely the sending unit, is it a replacement unit? Have you checked the ground between the tank and the body? A lot of people will add a ground wire from the sending unit to a good ground spot on the body. The aftermarket sending units are known for being less than reliable. Mine said half a tank at the beginning of the season when I turned on the electric pump to drain the tank. (A1's are nice that way, disconnect the hose from the carb and extend it to a can and bypass the safety switch, pull the distributor wire off and turn it on.) Mine pumped out exactly 5 gallons. Now that is out of a 17 gallon tank! There was still a pretty fair amount left on the bottom it could not grab but that just goes to show, the best gauge is to take the cap off and look in that big damn hole. :lol:
Yes, it is a replacement unit. I refilled the tank from gas cans I had in the garage. The tank overflowed before I emptied the third one, each one a five gallon can. The fuel gauge now reads slightly above full. I replaced the in-online fuel filter and cleaned the points, rotor and inside of the distributor cap. Now it won't start at all.
1964 M151 A1

User avatar
rickf
General
General
Posts: 19740
Joined: November 26th, 2007, 1:28 pm
Location: Pemberton, NJ.

Re: Fuel gauge

Unread post by rickf » May 14th, 2017, 7:59 pm

You will need to check and see if you have spark and narrow it down to whether it is a spark issue or a fuel issue. Just pull the line off the carb and put it in a can and crank it to see if you get gas. Is this an A1 or A2? Electric pump or mechanical? If it is electric jump the 77 and 77A terminals in the oil pressure safety switch connector, take it off to do this. Then when you turn on the switch the pump will run all the time. You should get gas out of the line pretty quickly. If not and the pump is running then there is an issue in the tank. If you have a mechanical pump and no gas then the either the pump is shot or there is an issue in the tank. Since this ran good right up till it quit then I suspect it is electrical in nature. Coil is suspect since you did mention points, no electronic module to go bad.
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone

User avatar
Bucolic
Sergeant First Class
Sergeant First Class
Posts: 219
Joined: August 28th, 2014, 12:22 am
Location: North Hills, CA

Re: Fuel gauge

Unread post by Bucolic » May 15th, 2017, 6:59 pm

Ok, the jeep is running again. I did not run out of gas. I replaced the spark plugs and put a different coil in. Fired right up. What I didn't notice yesterday was a small burnt spot inside the distributor cap real close to the positive terminal of the coil. Apparently the coil was loose enough to let the terminal short out and kill the coil. Anyhow, seems to be fixed.
1964 M151 A1

User avatar
rickf
General
General
Posts: 19740
Joined: November 26th, 2007, 1:28 pm
Location: Pemberton, NJ.

Re: Fuel gauge

Unread post by rickf » May 15th, 2017, 7:38 pm

Didn't you have the hold down screws in the coil?
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone

User avatar
raymond
Major General
Major General
Posts: 3425
Joined: November 26th, 2007, 8:29 pm
Location: God's country, Clarksville Mo.

Re: Fuel gauge

Unread post by raymond » May 15th, 2017, 8:15 pm

The only sure fire way to properly gauge the amount of fuel in the tank on a M151 is to remove the cap and look :idea:

Otherwise, I advise AAA, a cellphone, and comfortable shoes.
Raymond


"On the day when crime puts on the apparel of innocence, through a curious reversal peculiar to our age, it is innocence that is called on to justify itself." Albert Camus

User avatar
Bucolic
Sergeant First Class
Sergeant First Class
Posts: 219
Joined: August 28th, 2014, 12:22 am
Location: North Hills, CA

Re: Fuel gauge

Unread post by Bucolic » May 15th, 2017, 8:28 pm

rickf wrote:Didn't you have the hold down screws in the coil?
Yeah, they're there, but they apparently came loose. What can I say. 8)
1964 M151 A1

ErEyal
Sergeant
Sergeant
Posts: 69
Joined: March 1st, 2014, 4:05 am

Re: Fuel gauge

Unread post by ErEyal » May 16th, 2017, 3:30 am

raymond wrote:The only sure fire way to properly gauge the amount of fuel in the tank on a M151 is to remove the cap and look :idea:

Otherwise, I advise AAA, a cellphone, and comfortable shoes.

+1 for that!

csmith
Brigadier General
Brigadier General
Posts: 2083
Joined: July 20th, 2009, 11:49 pm
Location: Va. Beach & NC Outer Banks

Re: Fuel gauge

Unread post by csmith » May 18th, 2017, 12:08 am

I always keep a paint stir in my rig so if any doubt and when it starts reading around a QT i can give it a check.
1976 M151A2 4 Color Cammo Mutt, aquired August 09
1976 or 7? M151A2 "Miss Sandy" Driver, aquired May 2010
Former owner M151A2 "Miss Saigon" Vietnam Rescue Sold Sept 09
Fond appreciation for the M151 Breed!!

Post Reply