Fuel Tank very slow leak and Fuel gauge not registering full

[Indyharleyguy]

Hi All,
I've read some of the forums about this but wanted to ask the community these questions.
My 1986 M1009 didn't do this when I bought it a year ago but now after playing around 4 wheeling it has started. Wanted some opinions.

1. After my truck sits a day or 2 I get a very small wet spot of fuel on the ground. It seems to spread a out little then the leak seems to stop? Even now with over 200 miles after a fill up it happens. I'm guessing about 1/2 tank left of diesel? Wanted to see some suggestions about what to check. It seems weird to me that it doesn't happen when I first park it but seems to take a day or two?

2. My fuel gauge used to work great. Now most of the time it registers a little over half a tank when full. Right now I've driven over 200 miles and it's showing just under half a tank. Sometimes though it will change to full for a minute or two then drop back to just over half.

Since both items deal with the fuel tank my thought was to drop the tank and see what I can see. Sound reasonable?
Thanks for any suggestions.

 

[porkysplace]

The fuel leak could be a line leaking since only leaves a small spot . The fuel gauge is either a bad ground or bad sender . But your on the right track to drop the tank . While you do that replace the rubber fuel lines at the tank and the sock in the tank . Good luck .

 

[M1008BOV]

Is the spot of fuel from under the tank or up under the bellhousing area? There is a drain tube up there and it's common to get that wet spot after you shut it off and it sets.

 

[cucvrus]

Common to have a fuel leak. Maybe if you have a fuel leak somewhere. But I would not call that common. I would call that get out there and fix that Exxon Valdez. There is no such thing as a normal fuel leak. A common area they leak from but it still needs fixed. Have a great day.
. Have tool box and will fix anything, anywhere, for any price as long as it's reasonable.

 

[Drock]

Agree with porkysplace. It sounds like one of the short rubber lines on top of or around the tank leaking.

 

[Indyharleyguy]

The leak is at the back of the truck. With the metal plate on it's hard to tell exactly. My first thought is to get the metal plate off and see what I can see.
Thanks for all the replies too.

 

[porkysplace]

The leak is at the back of the truck. With the metal plate on it's hard to tell exactly. My first thought is to get the metal plate off and see what I can see.
Thanks for all the replies too.

The tank is still going to have to come out to fix the fuel gauge , it's a 30+ years old truck it's time for some maintenance .

 

[cucvrus]

It could be as simple as a rusted out fuel tank. And as complicated as a missing fuel tank vent hose. Still all and all a needed fix and update. Time to clean ,replace , sand and paint everything that you remove and expose. Good luck. use a little heat on the fuel tank strap nuts to get them off. Save you a lot of money if you clean and salvage the old straps. Also I have been using seat belt material as an isolator for the tank straps.

 

[C15TA]

Great tip on the seat belt material Rick. I have the tank out of my Allis Chalmers and have been looking around the shop for something to fit between the straps and the tank. I never thought to go out in the yard and get a seat belt. Thanks for that.
Cheers,
Barry

 

[Drock]

Bicycle inner tube would work as well, and much easier to obtain.

 

[4x4 Forever]

Strap coverings need to breath, if the materiel does not breath and allow the moisture to dry, you will have rust forming under the straps. Seatbelt materiel is good for this.

 

[Drock]

Okay, exhaust heat wrap then. It's just easier to obtain then seat belts.

 

[cucvrus]

Bicycle inner tube lasts about 2 years and is cracked and rotted. Seatbelts have been on a few of my trucks for 20 years. Every vehicle has at least 10 feet of seat belt material. And the nylon is less absorbent then the old tar paper. But do as you wish. I guess cardboard and old socks would work also.