Help with M939 fuel tank

[jrcampbe]

Hi everyone, I just learned about this great site and have been reading lots of good stuff in the FAQs and old posts.

I just bought an MEP002a generator and scored what I think is an M939 77-gallon ful tank for $63 that I intend to use as an auxillary fuel tank for the generator. The tank looks like new old stock or possibly refurbished:

http://gsaauctions.gov/clsauctions/regn8/81QSCI12150005.JPG

I'm trying to understand what I'll need to do to make this work. It looks like the tank is missing the fuel level sensor??? I am assuming two of the small ports are for fuel and return fuel. What are the other two with little elbows on them? One must be the vent, but I really don't know what I'm looking at. Can you help me understand:

1. What are the different ports on this tank?
2. Will this work with an external fuel pump, or does it need an in-tank electric pump?
3. What size fuel line and connectors do I need?
4. Is that taped-over hole for the fuel level sending unit, and where might I be able to find that part?
5. How should this be vented for what may be fairly low consumption? Is there a check valve installed already internally? Do I need parts for venting/breathing and are they water proof?
6. Can I leave the return line connector plugged?
7. Do you know where I can find a technical document explaining these things?
8. Do you know where I can get a compatible fuel gauge and cable with the proper connectors?

Thanks in advance, guys! I'm very excited about the generator as it only has 12 hours and looks like it still has the rebuild depot manifest on it! I'll post about my progress getting it running if anyone cares (at leas I have the TMs for the generator).

Jim

 

[nf6x]

That tank does not look like the tanks on either of my M939-series trucks. All three of their tanks (1 tank on my M923, 2 tanks on my M936A1) have fillers which point straight up rather than mounted at an angle like on your tank.

Your tank will probably work for your generator once you figure out the ports on top.

 

[Derrickl112]

M939A2's have angled fillers.

 

[Danl]

Danl M915A1

as far as I know cummins dose not recirk, So I think there is no return line

 

[M35A2-AZ]

I think the two ports close to the ends are the vent ports.

 

[73m819]

as far as I know cummins dose not recirk, So I think there is no return line

It does, has to for excess fuel

 

[nf6x]

Aha! I didn't know that they changed the fuel tanks on the A2 trucks.

 

[jrcampbe]

Thanks guys! I'm going through the M939a2 TMs to figure out the ports. Can you suggest a source for parts, like the fuel-level sending unit?

Thanks again!

Jim

 

[juanprado]

Parts

If your set up is 12 volt then any commercial fuel sending unit will work. They all use the same mounting hole and gasket. Stewart Warner among others makes it. It is a universal fuel sending unit that can be adjusted for the height of the tank.
Napa has it in the Balkamp line with their gauges.

If you need 24 volt, then the military surplus sending units for deuces and 5 ton m800 or m939 series will work. Try epay or the dealers but some are awful proud of their stuff.

The other ports are standard pipe thread. They can be blocked or you can use commercial fittings or standard fuel pick up tubes with JIC fittings/flare typically.

Good luck on your project!

 

[captain]

The 90 fittings for the vents ar e1/4" compression and can be capped as such.The return line bung in the tank is 1/4 npt and the feed bung in the tank is 3/8 npt. I'm working on the same project right now. Any clue as to what style of fitting the 90's are for the feed and return? They look to be roughly 1/2" and 3/8" but they are not NPT. They do not appear to be AN or compression either unless they are some sort of female variant I dont know of.

Thanks