g741.org

Hi folks,
I was searching for the specifications on Gas Lines and went to the trusty Service Manual.

Thought that I'd copy the data here if someone was looking for a handy reference.
( Reference Document TM 9-8030 section 141 page 212 )

"If replacement fuel lines are not available as assemblies, use 5/16-inch seamless tubing, 5/16 flexible conduit, and 5/16-inch inverted flared tube fitting nuts. Double flare the tube at each end, using a flaring tool. "

"If replacement Vent lines are not available as assemblies, use 3/16-inch seamless tubing, 3/16 flexible conduit, and 3/16-inch inverted flared tube fitting nuts. Double flare the tube at each end, using a flaring tool."

I've got a leaking rear line that needs to be replaced... Hoping to do it without turning myself into a pretzel ?

Good information, thanks.
I am planning to replace mine in the near future, using some nickel copper lines. Supposed to be very corrosion resistant and easy to form. I have two rolls of the stuff, and it certainly looks nice. I will forgo the armoured conduit as it won’t be necessary for the easy life this truck will get now.
Cheers,
Rob

A year ago, I replaced all my fuel and vent lines on my truck. I had the bed off and the engine out, which certainly made it easier to duplicate the O'EM tubing. I used tubing and fittings from Fedhill...

http://www.fedhillusa.com

Some thoughts I have from this experience. The CuNi tubing can be hand bent, but it is not easy, and hard to do with short sections. For that I used a hand tubing bender. Used a standard spinning cutting tool, which makes a small edge on the inside of the tubing which you need a small bevel tool to cut this out. As for flaring, I rented the FedHill tool, makes perfect flares. I didn't even try to use the cheap flare tools. They send to you, use it, and then box it up and send it back. I bought a tubing straightner, I think from Jegs or so, it is a hand held device with inner rollers; you pull and push your tubing thru it, and it takes the curl out of the coils. I also bought the appropriate fittings from them, and learned to be sure to put the fittings on before I flared the ends. They did caution me that the brass fittings are US made, but the hex tubing fittings to connect lengths are not the same quality, and urged me to use the ones I take off my truck, which I did. With my bed off, it was easy for access to the tank top and tubing runs to my electric fuel pump. One thought, it your leak is at or over the fuel tank, you might just use fuel injection hose with clamps for a short run to your electric fuel pump, or to where you have access to connecting to hard lines along the frame where you can more easily get the lines.

As for the armor, I reused much of mine, and found more a lot cheaper on Amazon or Bay. I have pictures of my tools (which I have since given away to another truck restore on this forum), but have a whole box of brass fittings, and would be glad to send you a assortment (free) if you will give me your address. I gave a partial coil of the CuNi tubing to a friend, who sold his old car, and might be able to get it back for you. I have some other thoughts for you, if you wish.

NAM VET

Here are pics of the top of the gas tank, maybe easier as above to run a short Fuel Injection hose to the pump, a pic of the one Charles T put in for me, a Facet 24v, pumps right at 5 psi, has an easily removable/cleanable wire filter on the bottom. He wired mine to if the motor was not running, there was no power to the pump, bypassed if the starter was turning the motor over. If you have any questions, let me know. Tank pics are with the old lines.

NV
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Thanks Nam !

I was in the middle of ordering the Gas and Vent lines when I realized I don't know what the Specs the Fittings are ?
Arghhh.
Are the all 3/8 20 or 3/8 24 or are there different sizes along the length ?

My leak is just over the rear wheel.
The whole line is brutally rusty.
Funny, I replaced the original leaking brake line ( Same area ) this past summer and though, nah, I'll get to the fuel lines when I tear her down...
Really should have replaced it all.

The good news is I have rolling chassis with it's own tank, so I can see the lines easy enough.
I can pattern a new one and hopefully "slide" it into place under the bed ??

Love your hints on Tools, especially the straightening tool, that's neat.

I don't have an electric fuel pump. My truck still has the original mechanical one.
It works fine so far and the truck runs like a champ.
However, the Fuel filter has been rerouted to a typical cartridge type.

** Say I notice the blue tank and straps, is yours ex Air Force as well ?? **

my truck is a factory M42, commo truck, with the 100 am alternator system. the Threads on the fuel line fitting are all the same thread. I am pretty sure they are 24 thread. If you can PM me with your address, I will send you some of the fittings. I won't need them. The Cu lines will never rust in your lifetime. Have fun....

NV

Mailed you a small assortment of fittings yesterday. You might consider using fuel injection hoses with the proper clamps to run from the gas tank to an easy to get to place to begin your hard line. I wasn't able to get a reply to your message to me to work. NV

Hey there Nam,
Thanks so much !
Sorry, I've been out of pocket for a week now...

I did the the chance to pull the Gas Line from my Spare Chassis so I have the right dimensions to work with.
This allowed me to measure the Flare fitting, which is a 5/16 NPT 20. Good Stuff !!
The really odd thing I discovered about my Chassis is it was actually a M152 truck and it has a T Fitting on the frame just by the rear wheel.
One line goes forward like the M37, however another one T-s off and runs over to the rear right wheel... A heater maybe in the M152 ?

Funny enough, I doubled checked the truck and sure enough, there was a rubber line already running from the tank down to the line on the rail.
On the Truck, the main line runs forward through two unions to a Flex Hose by the front wheel.
I'm thinking I'll tackle the whole line as it's all original.

The Vent is completely cut off, so I should attack that too, I already have the 3/16 line. The Flare Ends are way smaller... more investigation

I'll edit this thread when I'm done so that all the specs are listed in the very first entry.

Quick update now that I've finally had some time to work on the truck.
I picked up a 25 foot coil of 5/16 line and a bag of 5/16 flare ends.

I've since discovered that I purchased 5/16 ID line and the truck is 5/16 OD
Wow, I had no idea there were options either way.

Hopefully this post helps someone at one point.

Wow !
I am totally embarrassed.

I did some research on the manufacturer and found out that they mislabeled the Line.
They put a 5/16" label on a 3/8 inch line. ( Hence the ID is 5/16 and the OD is 3/8)

Mystery solved !
Send request for the correct product to the manufacturer ( FMSI Automotive )
I really through I was loosing my mind.