New to the 151

[Fallujahveteran]

Hello

After I bought my M1165 my dad mentioned how he always wanted a M151 like he had in the USMC. I came across one that is decent enough for being a 1966 model, bought it and gave it to my dad for his 71st birthday. Someone did a basic restoration some time in the past and both my dad and I are happy with it. I know these thing aren't meant for speed and it runs great around the neighborhood just goofing off. Recently I decided to use it to take the dog to the vet about 5 minutes down the road. I got it up to speed (about 40-45mph) and after a little bit it was almost unresponsive and felt like it was backfiring a little. A couple down shifts and slower speeds and it ran fine again. I'm a novice mechanic and this truck was converted from a 24v to a 12v system so the TMs aren't helpful for every system but I'm thinking it might be a timing issue. Just curious what opinions/advice I might get from here. Thanks

 

[G744]

It may be cheaper to put it back to 24V than sourcing civvy ersatz parts. Lots of them around.

A good running Mutt will pin the speedo any day.

G744

 

[NDT]

Sound like fuel starvation. Plugged filter?

Be aware of the handling characteristics of the A1, yank the steering wheel at high speed and you will roll.

 

[G744]

All Mutts, -0, A1, A2 will roll just like an original VW bug. The A2 is least likely to, but I have looked down on a hard leftt turn in an A2, and saw light under under the rear tire.

G744

 

[Fallujahveteran]

Life got in the way and it's been a few months and getting back around to diagnosing the problem. Started simple (fuel) before taking things apart to check timing and discovered rust in the fuel tank. Now I'm thinking the problem isn't timing at all but fuel starvation due to all the rust debris in the lines. Not seeing much for replacement tanks online so now I'm reaching out to see if anyone more mechanically inclined than me knows of a way to effectively restore the inside of the gas tank.

 

[NDT]

Probably won't find the tank online. Reach out to vendors such as RAPCO, TJ Murray, Red River Parts for a new one or good take out.

 

[joshs1ofakindxj]

Your problem is pretty common. Fuel system issues plague a lot of M151 owners. I drained my tank, cleaned the inside the best I could, changed the pick up filter, and keep it full as best I can. I installed a clear universal fuel filter in the rubber line before the carb so I can quickly look at it to confirm fuel or debris.

Most guys find that cleaning the carb is best done with an ultrasonic cleaner. I rebuilt 3 carbs before I got one that performed steller.

There is a specific way to set the choke cable, easily found in the TM. Most people, myself included, find that their jeep will run better with the choke cable slightly pulled out, for whatever reason.

The accelerator pump diaphragm can be installed in the wrong orientation, and one TM out there does show it backwards, so do your homework on that.

If you have a carb that doesn't have an adjustable mixture screw, the plug can be drilled out and replaced with a thumb screw.

99% of M151s seem to have the Zenith same carb, with a variation being if it is an earlier model or later model with non-adjustable mixture screw, but very early M151s had a Holly carb that is supposed to be way better than the Zenith carbs. So if you have a Holly lucky you.

Checking timing and valve clearance isn't hard. The little timing mark on the crank pully can be hard to find but it is there. When I got my jeep it ran rough. My timing was off and my valve clearance was comically random. I corrected those issues and that helped, but my main issue was a dirty fuel system and dirty carb. I also had a couple of vacuum leaks and that wasn't helping. Check out your vacuum lines that run around the engine.

You will need to rig up a civilian plug wire for setting timing. Your timing light won't pick up the spark through the factory wire.

Also, don't do too many things at once. I made that mistake when I was fixing up my jeep. I changed many parts and made numerous adjustments, then I had an issue where the jeep would idle fine, but as soon as it revved up it was breaking up and back firing. The problem ended up being a NEW condenser from a reputable vendor of miliary jeep parts. Not really their fault, since NOS don't exist anymore, and they just got a bad one from China. It is what it is. I swapped back in my original condenser and problem solved. Luckily I didn't have to swap out too many new parts to figure that out.

Oh, and one way you can clean a fuel tank is to put some ball bearings in it and solvent/cleaner, seal the openings, and strap it to a tractor/lawn mower tire. Jack that tire off the ground, fire up the tractor, and let it slowly turn awhile. The ball bearings and solvent will tumble around in there and clean the surface.

 

[glcaines]

I did the same thing basically, cleaning the fuel tank of an MEP003A generator. Only, I used gravel, water and Dawn dish soap. Oh, also I didn't jack up the tractor, I drove it around for a very long time! I'm still using that tank somewhere around 10 years later.

 

[rickf]

Does this A1 still have the original electric pump in the tank or has it been changed to an engine driven pump?

 

[Fallujahveteran]

Does this A1 still have the original electric pump in the tank or has it been changed to an engine driven pump?

It's been a month or so since I've messed with it (only working on it when my dad comes over) and I've worked on several other engines since then but if my memory is correct it's an engine driven fuel pump. I'll have to double check this weekend.

 

[rickf]

I would suggest you pull the tank and take the top off of it. This will be a test of patience because all those bolts will be rusty, you really want to try to avoid breaking them. Once the top is off you will probably find the original electric pump still in there. You can stay with the mechanical pump on the engine but they are getting very hard to find also. The electric pumps are 600.00 plus if you can even find one. I have a used one I cleaned and tested but it will not be cheap. The list of things to check in the fuel system are the in tank filter, if the original pump is in there it will ba a large filter around the pump. If someone has put in an early A2 pickup it will be a curved pipe with a small sock filter. Next will be to check the steel lines inside the tank, if the tank is rusty there is a very good chance this line rusted through. If all of this is good then check the line from the tank to the pump on the engine. If there is any leak at all it will suck air. After that you need to check the fuel pump to see if it is pumping and holding pressure. If not the main reason is usually a cracked diaphragm. but it could also be a piece of rust stuck in one of the two valves in the pump. Then and Now in Maine was rebuilding those pumps for about the same price as a new pump. The problem with a new pump if you can even find one is that the diaphragm is going to be 500 years old and probably dried out.

The tank itself can be cleaned and coated with tank coating kits.