m211 fuel problem?

[makeshiftrod]

Hi everyone, hoping you all might be able to help. so my m211 idels great and can do it all day long, but when i put it in drive and tell her to go i get about 300 ft and she feels like she is starving for fuel. but she will start right back up and idle great after it happens. would that be a fuel pump/ carb issue or something else i may not be thinking of ?

 

[M215]

Check the in-tank fuel filter screens, bad in-tank fuel pump? Clogged fuel lines, modern gasoline gum up your carb? Read the TMs, very helpful, good luck.

 

[MWMULES]

Those tanks need 5 gal in them just to be empty. You can pull the pump and check the screens on the pump.

 

[m1010plowboy]

Idles without VROOOOM

I always start with a good picture of my truck before I try fixing anything.
Do you have a good picture?.....of your truck?

The M211 and M135 are similar trucks and the same manuals apply. ( A year ago I didn't know that)

These guys MilitaryTrucks.ca - Welcome! have links to TM's.

If you click on the M135 on the main page it'll take you here

MilitaryTrucks.ca - M135 Deuce Truck

TM9 8025-1 is about the motor/ fuel system and might be a place to start.

It's a little challenging when there's 1100 pages of data but if you check index's you can get to the trouble shooting sections easy.

Once you've got good fuel, good spark and good air then you can start trouble shooting. It's real challenging just guessing what could be wrong because there are trani/throttle linkages, governers , fuel pump pressures, fuel lines, choke settings, and pieces inside the carb that can fail to allow it to idle but not "REV".

Without putting it in gear.......can you get a good range of RPM?

I pulled a mouse nest, seeds, grain out of my "air cleaner, oil bath" and needed the TM tech manuals just to learn how to take the air breather apart.

The spark plugs were destroyed so they got replaced. I blew out the fuel lines and replaced or cleaned everything in the fuel system to get mine running better.
Dirt/rust in the fuel system can plug the carb just enough to

I'll be back here to see what you fixed because I'm sure to have the same problem some day.

 

[Gunner0311]

Fuel Line?

Also check for a kinked fuel line. It can allow enough fuel to flow for the engine to
idle just fine, but flow is inadequate to run at "power"....

 

[topo]

When I first bought my m211 1986 I installed a safety switch on the fuel to turn off the fuel when the oil presser dropped to low so if the engine died it would not keep pumping fuel . and I had this kind of problem because the oil presser on the 302 is not very high when idling and it would shut off the fuel pump and then when I would get going it would die because of no fuel due to the pump being off when idling .

 

[JGBallew]

One I've run into with M211's using external pumps, is the standpipe that ran from the top of the pump housing to where the pump used to be , coming loose or cracking.

Another thing to check is the air hose/SCAT hose from filter to carb, as I've seen these collapse internally and choke out the engine at much above idle.

 

[hippiedude]

Were the fuel line goes into the bottom of the carb there is a little screen that catches lots of crap ..........

 

[nattieleather]

Also check the diaphram on the governor on the carb. M211 had that almost same problem and I found that the diaphram was bad and it was kicking the governor in when I would try to give it gas. It's either the fuel delivery system or the carb or a combo of both.

 

[makeshiftrod]

thanks for everyones help. it turned out to be the fuel filter. she runs great now. thanks agin

 

[Gunner0311]

Thumbs Up!

Way to go! Problem solving is a required trait in MV driving.

 

[135gmc]

Check that the carb's needle valve doesn't have some grit in it. Even with those large in-tank filters, you can get grit from someplace. Install an in-line fuel filter just in front of the carb as well. One other sneaky problem you can run into is the accelerator pump - whent he carb is used in an armored vehicle, it is set for maximum stroke, but for the GMC trucks, it needs to be in the center position. My truck would fall flat on its face after I replaced the carb with a new one - then I found out about the accelerator pump, reset it, and it ran perfectly.

 

[m1010plowboy]

Plugged fuel "Filters"

Ironic Bump on this post.

After hours of -Break In- the M135 'limped' back to the shop.

She had similar symptoms and would catch full RPM range parked but under load would hesitate as the RPM's reached peak.

The fuel tank was filled to 3/4 for the previous trip and obviously dislodged gunk from somewhere in the recently cleaned fuel system.

Had the 'normal' removal of the fuel pump from the tank..... breaking the 90 fitting on the top of the tank.... too fast strong, too slow smart. The cut away on the cab and the box location give the pump assembly just enough room for removal.

The fuel tank was nearly spotless and we removed the outer "screens" from the pump assembly to blow them out. These pieces look more like 'covers' then screens and maybe someone can tell me what they're made of and how they work. Appears to be a magnesium type metal 3/16 thick......yet porous.

The inner Pump Screens were still spotless.

Taking advice from this thread our next removal was the filter that hangs off the bottom of the carb fuel line in-let. This pencil size filter picked up the last of the junk left over from R+R and was slightly contaminated.

I am going to add another inline clear filter tomorrow to monitor better but it looks like the 3 existing level of screens did their job well. Love that G749.