Alternate Fuel Tank

[army70deuce]

I was looking to relocate the 50gal stock M35A2 fuel tank into a jobsite box in the bed of the deuce.

My question: Is there an alternate tank that people have tried, possibly plastic vs the steel?

2nd Question: If there is a plastic version does it accept the stock fuel pump or will that need to be replaced with a civilian equivalant?

My opinion is that if I'm going through the trouble of moving and replumbing things I might as well see about upgrading them as well. A plastic tank would not rust and a civilian fuel pump would be easier to replace/fix with over the counter parts. Also I would think that a newer tank would come in more sizes/dimension options for best fit in a jobsite box.

All thoughts and opinions are welcome.

Thanks,

 

[Recovry4x4]

The sky is the limit. Put on what you think is best. What's the reasoning for moving the tank?

 

[jollyroger]

I was gonna say......

But seriously there are a ton of different aftermarket tanks you can choose from. It depends alot on the size of the job box. Why install the tank in that box? How are you gonna fill it inside the job box? You gonna run troop seats and a bed cover? If so you are gonna have to get inside the bed to fill the tank unless you run a fill hose outside the bed somewhere. Then I would worry about the fill hose being above your head.

I have seen guys relocate the stock tank to the front corner of the bed. That way it's not hanging where downed trees can catch it but you can still reach over the bed rail to fill the tank. And no need for aftermarket stuff.

http://www.jamestowndistributors.com/userportal/pdfs/Vetus Catalog/vetus_USA_catalogue_2008.pdf

This is one manufacturer I found. Looks like they are geared to boat tanks. Looks like you could incorporate your pump and sending unit into this tank and they have a few filler options. Outside of that just search Plastic fuel tanks on google.

 

[army70deuce]

The tank is being relocated along with the batteries to the bed so they are up away from any obstacles and also up out of the water when fording. The idea of the jobbox is that allows a place for them to be locked, centered at the front of the bed so that it can be filled from either side. There is no cover at this point. To fill the tank, remove lock and lift jobsite lid.

 

[jollyroger]

I edited the last post to show some search stuff I found for plastic tanks.

Seems like you would still be standing in the bed of the truck to fill it up though. I would not want to climb into the bed every time I had to fill up. Just sayin'.

I would also hesitate to put the batteries in a box that was sealed with no vents. The Job Boxes I've dealt with are sealed to the weather. When the batteries charge they give off explosive gases. With no vent this can build up and one spark bang.

Ask me how I know.

 

[rosco]

A fuel tank (and batteries), need to be vented REAL good.

 

[Kohburn]

A fuel tank (and batteries), need to be vented REAL good.

part of evaporative emissions control on modern cars involves a tight seal on the gas tank. the vent line is routed through a canister that collects the fumes that are then sucked into the engine through the intake. There is usually a solenoid valve to control when the canister is allowed to vent into the intake as well as some check valves to avoid pressurizing the fuel tank. uncork most cars now and you will hear air getting sucked into the tank.

 

[Oldfart]

The older military fording systems did take into account the need to allow air into the fuel tank to avoid tank collapse while under water. That was one of the major poor performance items that many inexperienced MV users encountered when off roading the Rockies back in the early 60's. Almost to a person, they were screwing their M37 gas caps on tightly rather than just going past the first detent. While early units were supplied with fording controls to the carb, later vehicles did not have these off the shelf. Even if the trucks had the controls most people who screwed the tank caps down tight did not think to engage the fording valves that allowed air back into the tank. At best, it was vapor lock or poor carb performance and on occasion, a tank would get collapsed. Most thought they had run over a rock and dented the tank.

It would depend on the existing fuel setup, but I would be inclined to make sure my replacement tank had what ever was used on the stock tank (fuel return line, filtered air vent line etc. even if you weren't going to used the military style tank cap. Given the replacement tank is planned for higher up, an intank pump might not be necessary. There should be enough gravity feed on the fuel to supply an inline pump. Not like an inline pump trying to get prime and suck something out of a tank and then pump it uphill.

 

[XanRa]

The older military fording systems did take into account the need to allow air into the fuel tank to avoid tank collapse while under water. That was one of the major poor performance items that many inexperienced MV users encountered when off roading the Rockies back in the early 60's. Almost to a person, they were screwing their M37 gas caps on tightly rather than just going past the first detent. While early units were supplied with fording controls to the carb, later vehicles did not have these off the shelf. Even if the trucks had the controls most people who screwed the tank caps down tight did not think to engage the fording valves that allowed air back into the tank. At best, it was vapor lock or poor carb performance and on occasion, a tank would get collapsed. Most thought they had run over a rock and dented the tank.

It would depend on the existing fuel setup, but I would be inclined to make sure my replacement tank had what ever was used on the stock tank (fuel return line, filtered air vent line etc. even if you weren't going to used the military style tank cap. Given the replacement tank is planned for higher up, an intank pump might not be necessary. There should be enough gravity feed on the fuel to supply an inline pump. Not like an inline pump trying to get prime and suck something out of a tank and then pump it uphill.

could you explain that a little better?confused:

 

[juddspaintballs]

I'd still use a fuel pump with the tank in the bed. You'd lose your gravity feed if you nose up a steep incline.

 

[Oldfart]

I should have quoted the charcoal canister post as a start. ~ Basically, most tactical vehicles of some age were set up to ford water of some depth. Whether or not fording kits were installed, the fuel tanks had caps that were designed as two position caps. If you were fording, you screwed the cap on tightly and it sealed air and water out of the fuel tank. For normal driving, the cap is only twisted a ways until you feel it pass a detent. That way, the cap vents air into the tank and fuel fumes out. All M37's/ M43's/ M56's etc. are this way, My early deuce is that way and my son's A2, 817 and 818 are this way. ~~ If you screw the cap on tightly, then you have to vent the tank by other means. When a fording kit is installed, there is plumbing that has a valve that allows filtered air from the engine air cleaner to supply air to the fuel tank. If you do not allow air back in to the fuel tank you will create negative pressure in the tank. ~~~ Newer (I think the term was modern) fuel systems have a charcoal canister to collect the fuel vapors and then recycle them back through the engine. Those fuel tank caps are non venting. They will allow air into the tank, to avoid negative pressure, but they do not allow pressure or fumes to escape. Unless one were to install a complete "Modern" system I think it makes more sense to purchase an after market plastic tank that has provisions for gas cap, and lines that perform in the same manner as the original military setup.

 

[jollyroger]

As you taught me Oldfart I put the cap on the filler, twist it till it passes the detent and then "rattle" it back and forth to know it's in the right spot. I can't tell you how many people have had vapor lock problems on their M-37's and this has reduced or fixed the problem.

Secondly I forgot that some guys that do the tank/battery relocte put the batteries under the passenger seat like they were in the M-37's. I personally would do this if I could mount them in a box and vent that to the outside of the cab. Or you can mount the whole works in a job box in the bed. I would just make sure the box is well vented.

 

[army70deuce]

Based on recommendations I've decided to go with an aftermarket tank and build a custom box. This way I'm not limited to the tank size and shape based on a jobsite box and I can vent the battery section as well. Also by going with a non metal fuel tank I can avoid any issues with rust.

You'll notice in the diagram I went with a 102gal tank used mainly in v-hull boats, I went with this version to allow for accessibility of fuel. By that I mean that the v shape will funnel the fuel to a smaller area for collection by the pump so I don't have the issue of a square tank where the pump can't access the bottom inch or so that is spread over the whole tank thus making a few gallons unusable.

Does anyone know the requirements for the pump? I know it should be 24 volt but am unsure as far as the gallons per minute and psi.

Thanks,