Starting new thread for same old problem.....

m1010plowboy · Saturday at 4:23 PM

Where did we put the fuel volume check for the G749?

I see the trouble-shooting par 133, pg. 244, where it states "Pressure should be 2 1/2 to 3 pounds". ....TM 9-8024.....but that volume test eludes me.

It's a simple test where you turn on the fuel pump, fill up a measuring jug over a period of time and should come up with a volume. It could have been on a PM magazine but if anyone finds that procedure, can we post it up please.

In this video we can hear a 'miss' but it wasn't until dark when we could see some arching from the #6 plug. It always seemed like something simple once we figured it out. Drifting in the dark is a good way to test things. You just need some snow!

Brad · Saturday at 5:12 PM

are you meaning the actual resisitor or the condenser at the points?

rustystud · Sunday at 4:51 AM

m1010plowboy said:
Where did we put the fuel volume check for the G749?

I see the trouble-shooting par 133, pg. 244, where it states "Pressure should be 2 1/2 to 3 pounds". ....TM 9-8024.....but that volume test eludes me.

It's a simple test where you turn on the fuel pump, fill up a measuring jug over a period of time and should come up with a volume. It could have been on a PM magazine but if anyone finds that procedure, can we post it up please.

In this video we can hear a 'miss' but it wasn't until dark when we could see some arching from the #6 plug. It always seemed like something simple once we figured it out. Drifting in the dark is a good way to test things. You just need some snow!

Now that "drifting" looks like a lot of fun !

msgjd · Sunday at 10:02 AM

Brad said:
are you meaning the actual resisitor or the condenser at the points?

actual resistor

msgjd · Sunday at 10:15 AM

m1010plowboy said:
Drifting in the dark is a good way to test things. You just need some snow!

sometimes after a january thaw the lower corn fields flood and then as they drain they freeze over leaving a few inches of perfect ice on the ground.. Back when my M38"A5" had very-wide tires i would take it out to do 2WD ice ballet , get a 500ft running start, crank the wheel and let 'er twirl until the ice ran out , usually another 500+ feet .. Sometimes the spinning lasted long enough you could get very dizzy .. i would have to quit when i started to feel sick but it was a blast .. the 80's were fun like that .. Had i had that jeep in the 70's, well, that've would've meant more years of fun and mayhem !

Brad · Sunday at 6:05 PM

Spent the afternoon trying different things, still no change. Truck will fire right up and idles great. Reev the engine, sounds great. Drive 2 or 300 yardsm starts cutting out and sometimes stalls. Let it set a couple minutes, can usually get it back home about the same.
Today we checked out the "primary circuit resistor". When I changed the coil Friday evening I thought the wire to the coil seemed like it was about ready to break off. But that was not the case. The wire is in good shape, only the insulation slips around a little on it and makes it seem that way. Also checked the continuity with my multi meter and it seems perfect.
Rechecked, and did reset the points. They were just slightly a little over .022, now are a bout as perfect as I can get them.
Took off the second new fuel pump after visually looking at the flow, wheich seems low? The old one seems far better. Drove it and got around 1/4 mile, before it too gave up the ghost!
So we got it home and removed the center floor pan and inspected the vac lines from carb to dist, and the flex lines at the dist. All seemed just fine and no signs of wear or deterioration?
Guys, this truck starts right up and idles and sounds just great. Even can reev it up over and over when sitting still. Then try and go down the road and usually can't get over a few hundred yards and it starts cutting out. Up a slight grade, but once it starts that it will hardly go on the level?
I do not have any idea what to do??

Mullaney · 2025-06-02T07:28:21-0400

Brad said:
Spent the afternoon trying different things, still no change. Truck will fire right up and idles great. Reev the engine, sounds great. Drive 2 or 300 yardsm starts cutting out and sometimes stalls. Let it set a couple minutes, can usually get it back home about the same.
Today we checked out the "primary circuit resistor". When I changed the coil Friday evening I thought the wire to the coil seemed like it was about ready to break off. But that was not the case. The wire is in good shape, only the insulation slips around a little on it and makes it seem that way. Also checked the continuity with my multi meter and it seems perfect.
Rechecked, and did reset the points. They were just slightly a little over .022, now are a bout as perfect as I can get them.
Took off the second new fuel pump after visually looking at the flow, wheich seems low? The old one seems far better. Drove it and got around 1/4 mile, before it too gave up the ghost!
So we got it home and removed the center floor pan and inspected the vac lines from carb to dist, and the flex lines at the dist. All seemed just fine and no signs of wear or deterioration?
Guys, this truck starts right up and idles and sounds just great. Even can reev it up over and over when sitting still. Then try and go down the road and usually can't get over a few hundred yards and it starts cutting out. Up a slight grade, but once it starts that it will hardly go on the level?
I do not have any idea what to do??

.
Since we are shooting in the dark - what about getting yourself a can of Either (Starting Fluid)? Crank the truck, then spray the left side of the motor. Then around back and down the right side. If you find a vacuum leak, the motor will speed up... Cheap way to hunt a really odd problem.

Brad · 2025-06-02T09:56:08-0400

Thanks for the suggestion, already tried that, twice?

Brad · 2025-06-02T10:15:45-0400

I just noticed something that may or may not matter? The fuel pump on this truck originally had two wires going to it. So did the after market pump that had been on it for many years and it ran fine. So I installed the new ones using those same wires.
BUT, as I was looking at the wiring diagrams in the manual for this truck, it shows ONE wire to the fuel pump and the pump being grounded to the frame?
I have tried this both ways with no difference, but could there be a problem here??
I know, I am grasping at straws, but I am just whipped with this?

USMC 00-08 · 2025-06-02T11:29:07-0400

You might try to find a copy of TM 9-8647 and go through that carburetor. Did any jets or tubes get switched around when you opened it up?

Brad · 2025-06-02T12:59:55-0400

My manual is TM9-8024, I will look for that.
When I took the carb apart I used air to blow thru some of the holes / jets. Two press fit brass things, jets? came out. In looking over a TM I think they are called "MAIN WELL TUBES"? Hard to tell?
They looked identical but could have been different? I put them back where they came from. I was concerned that they didn't seem to fit as tight as before?
But since I was having the running problem before I took off the carb, and there was no change, I dismissed that as a cause?

m1010plowboy · 2025-06-02T16:30:42-0400

It would be hilarious if after all this effort it was just an exhaust / muffler restriction or a loose ground wire. We'll get this figured out,.......ain't no deuce gonna just sit there or fail to show up at a parade when the veterans need it.

Page 188 para 111 on the 9-8024 has the compression and vacuum test. Vacuum should be between 18 and 21 at idle. The test is fairly simple but there are a few steps. A bouncing gauge means valves or head gasket, ........and I see gauge is spelled GAGE in the book so that will save me some typing.

After the compression test, pull that plug on the intake manifold T, as per the manual, hook up the vacuum gage and run through those steps to check vacuum. Posting up those numbers will help the mechanic brains with more clues.

The trouble-shooting section and the symptoms keep bouncing back to page 154. It's a little nuts with #9 stating, "If governor prevents engine from attaining specified governed speed.........Replace carburetor. "

If you've got something wanky and feisty going on with the carb, the vacuum test will tell you within just a few minutes.

USMC 00-08 · 2025-06-02T17:26:43-0400

m1010plowboy said:
It would be hilarious if after all this effort it was just an exhaust / muffler restriction or a loose ground wire.

That's a good idea too. Take off that crossover pipe that goes to the muffler and see what happens. Ground wire check would be a good thing.

Brad sent me a video of the fuel pump output and it seems to be inadequate compared to the stock fuel pump output that I have seen.

biscuitwhistler37 · 2025-06-02T18:16:17-0400

I went back and found where you listed the part number for the pump, 32gph, 4.5-9 psi, 1/8"x27 npt fittings. Is that correct?

This one? https://www.napaonline.com/en/p/BK_6101034

If it is I think your guess is correct and it's not supplying nearly enough fuel to keep that thirsty girl fed, that's HALF of the quarter inch they scoffed about in the first place. Not seeing where they're getting 5/16" fittings on the pump from.

m1010plowboy · 2025-06-02T22:12:53-0400

USMC 00-08 said:
That's a good idea too. Take off that crossover pipe that goes to the muffler and see what happens. Ground wire check would be a good thing.

Brad sent me a video of the fuel pump output and it seems to be inadequate compared to the stock fuel pump output that I have seen.

That reminded me of a post from Stan Leschart from 13 years ago. It doesn't make sense for Brad's case unless something changed/bounced/broke or fell back in place with the way they did fuel pick up in the tank.

Maybe someone that puts an external fuel pump on in the future and has similar symptoms and can benefit from Stan's experience. Gotta start by checking the check thingy that stopped someone else from success when they put on an external fuel pump.

I guess it could be Brad's problem too if the fuel flow isn't great but Stan basically mentioned a check valve where the fuel would suck from. Seems like it allows fuel to push out of the tank but when you try to suck it out, it stops ya.

Sounds like Brad's deuce ran with an external pump before the issues started.

From Stan

""""""""""Side note:

If your in tank fuel pump on the M135 ever goes out, buy the rebuild kit .... if you can find it!

Otherwise, you CAN plumb an inline pump, but you MUST replace the fuel pick up foot.

It has got a built-in pressure release passage, which will not allow an external unit to function for more than 200 Meters! Don't ask how I know.

If our wrench basher was not in the crew, this would have cost $1,200 just to figure out!
The hard to get pump kit was selling for $75 on E-Pay."""""""""""""""

Starting new thread for same old problem.....

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