Locking fuel cap

[JonM934]

So my truck is parked out in a field and I worry that someone might come and help themselves to some Diesel. I also worry that some bad person might come by and throw some bad stuff in the fuel tank. So I set out on a quest to find a locking gas cap for my 7 Ton.

I found one. I have it installed on my tank and it was easy. The new cap came with a rod that is meant to go inside the tank and prevent the cap from being lost but in our trucks with the strainer in the neck, the rod could not go in like it is supposed to. The good news is that the rod does fit through the strainer's holes so I just stuck it in there.





The cap locks on by means of a cam so there are no changes required to the tank at all.

Amazon.com: Fuel Cap for 4 Inch Threaded Fuel Tanks - Locking, NPSM, Full Function Vented, 255F Thermal & Pressure Relief : Everything Else

Amazon.com: Fuel Cap for 4 Inch Threaded Fuel Tanks - Locking, NPSM, Full Function Vented, 255F Thermal & Pressure Relief : Everything Else

www.amazon.com

I get no money or anything from the above link.

You can also purchase the fuel cap directly from the seller's web site:
www.eztruckstore.com

It is item FTA-C-64.

The only downside that I could see is that it is vented. That could be bad news if you go fording with your truck and the water covers the fuel cap. Water might get into the tank. Later, I will try to figure out how to plug the vent because our fuel tanks are vented already and the vent is above the 5 foot fording depth.

I could not find a cap that did not have a vent.

 

[Smike740]

Nice addition to the truck.

I want to add a locking cap to my M1078 but couldn’t see how the cam keeps the cap secure.

How does the cap lock to the tank?

I don’t see a flange on the filler neck for the cam to catch on?

Thanks in advance for the info.

 

[JonM934]

Nice addition to the truck.

I want to add a locking cap to my M1078 but couldn’t see how the cam keeps the cap secure.

How does the cap lock to the tank?

I don’t see a flange on the filler neck for the cam to catch on?

Thanks in advance for the info.

Hi Smike740,

First, it locks on tight! I could not move it using both hands and as much power as I could muster.

Second, it locks by means of a cam that presses against the neck of the tank. You can see it in the photo above. It is the metal thing at the top of the cap. It is designed to press against the side of the filler neck and when you try to turn the cap to take it off, it actually makes the cam tighter against the neck.

Third, I found out that I had made a mistake. The fuel cap has the lock keyway exposed and the other day it snowed then got above freezing for a short time. Then the temperature dropped to about 18 degrees. So the keyway had water in it that froze. When I was trying to figure out my starting issue with the engine and I wanted to take the fuel cap off. My key would not go in even a little bit. The whole keyway had filled with water and then froze.

On a regular semi, I think the tank filler neck is protected by the cab. In the case of our trucks, the cap and filler neck are behind the cab and so are exposed to the weather. SO the moral of these story is to make a cover that fits over the locking fuel cap to prevent water and snow, etc. from entering the lock.

I made a cover of of a plastic cookie container. I strung a rubber band under the plastic cover to keep it attached to the fuel cap. So no more water will get in there.

 

[Smike740]

Happy New Year JonM934!

Thanks for the quick reply and clear explanation of how it works,

Regarding the water freezing I found some caps (Velvac) with a rubber cover over the key opening, based on your feedback this seems like a necessity.

Thanks,

Mike