m725 fuel system trouble shooting

[GreencountyM715]

Working on getting the 725 going so I can get it home and actually start working on it. carb wasn't getting any gas so I rebuilt the fuel pump, carb is still dry so I'm looking for a second opinion.maybe a hole in the gas line somewhere, or the sock filter in the tank is clogged, any thoughts?

thanks for the help

[Barrman]

There are two flexible hoses in the fuel line between the tank and the pump. either or both could be cracked/plugged. I would suggest pulling the input line at the pump and putting about 10 psi air in the lines back to the tank. Have someone listen for bubbles from the filler tube. No bubbles mean no flow or not enough fuel.

A tank in good condition needs about 1" of fuel on the bottom to actually get fuel to the carb.

[Don Cavey]

For what it is worth, when I started my truck for the first time, with a new fuel tank and lines, I had a terrible time getting fuel to the carburetor. I filled the bowl and got it to start and run for a while. I did not touch the fuel pump.

Just trying to say that it may take time to get it "primed".

[GreencountyM715]

I think it maybe in need of new lines, its still at the PO's shop he said he blew out the lines while he had the fuel pump off. really makes me think their is a hole in the line

lol guess i got a new project for the weekend

[moose3d]

Check the in line fuel filter might have filled up with trash from the tank.

[MJCougler]

Advance Auto Parts has the see-through plastic fuel filters. I put one on the hose coming out of the tank. The original is at the Carb inlet line. Both are see through so you can monitor the crud level. When I'm ready to "clean it out", I just shake the one at the tank, disconnect the inlet hose and let the crud drain into a pan, and put it back on. You'll have to do this a few times, but eventually you will have to change-out the filters.

Keep in mind, the ethanol is "cleaning" the crud out of the inside of your tank and it is then pumped into the first filter. You should add Stabil for ethanol to the gas too as you add only 10 gal at a time. Keep the gas "fresh".

[GreencountyM715]

Finally got the 725 goin, the fuel pump was not working properly so we installed an electric fuel pump and it fired right up, going to try and drive it home this weekend. then ill see if i cant get some pics posted

thanks for all the replies

[Don Cavey]

Glad you got it going! What are long range plans, rebuild the fuel pump, replace the fuel pump with the civilian version or just use an electric fuel pump?

Just curious...

[randyscycle]

Good to hear you got going.

When you start work on it, you may as well drop the tank and clean it out well, then have a look at all the lines, hoses, etc. Every truck I've seen has rotten rubber hoses and often pitted or perforated steel fuel lines. The pickup line into the tank also likes to get holes in it both inside and outside the tank.

If its something you plan on driving much it will be time and money well spent to get the fuel system in top order.

Here is what I found when I did my tank:

Fuel tank pickup mod/rebuild

[GreencountyM715]

The long term plan is to make it my DD
*frame off resto on the body
*axle swap/ probably from the m1008 truck
*new engine/ depending on how I like the 230, but most likely drop in an amc 360 or a 6bt as well as and OD transmission

But for now I just plan on getting it road worthy for winter. As far as the fuel pump goes ill see if I cant find out whats wrong with the original, repair it if I can. If not, then ill just run the electric one until I get to work on the list above
eventually it will be a new truck inside and out, should be a good project cant wait to get started on it!