Fuel air mixture screw

[1SGCAV77]

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I have a question about what the two washers on the fuel air mixture screw in attached page from TM. #9 is a medal washer. #10 is what type material? My question is, what is their purpose ? Carburetor on my Jeep does not have them. It starts and runs fine.

[Mr. Recovery]

#10 should be a O-ring seal for the needle, #9 should be a thin metal washer to protect the O-ring from the #8 spring.

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[rickf]

#10 is actually a flat rubber washer but an o-ring would work. The reason you do not have any of that is because you have a 13660 carb which was an emissions carb and you will have a plug (originally) over the internal screw. So, you still have an adjustable mixture screw, it is just hidden. When I rebuild them I replace that internal screw with an external setup like you show.

[raymond]

Before Rick rebuilt my carburetor, I had the "hidden" adjustment screw.
It is recessed into the carburetor slightly so it might not be noticeable.
Often, you will find it is sealed with a bit of silicone to keep people from messing with it.
So you may have to pop that bit of silicone out of the recess to adjust it.
No real need to reseal it when finished with adjustment.

[rickf]

If you happen too have a carb that was never tampered with and it is a 13660 carb then it will have a metal plug over that screw so it cannot be adjusted. That was how they did emissions controls back then. You have to very carefully drill a small hole in that plug without going through far enough to hit the adjuster. Then thread in a sheetrock screw point and pop out the plug.

[1SGCAV77]

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Carburetor on my Jeep is 13660. It has the screw. Just doesn’t have the two washer. That will be corrected in couple of days.

[rickf]

The rubber one is just to keep crap out of the hole so an o-ring will work, or you could pack the hole with grease. The threads start down a bit from the top and anything in that tiny area will stop dirt from getting in. Actually once you put the small metal washer on there nothing is going to get past it anyway. I do notice that you have the filter screwed directly into the carb. This is a no-no since the original threads are NOT pipe thread and the filters are pipe thread. If you tighten that filter too much it will split the carb body. If that happens the carb is junk.

[glcaines]

I do notice that you have the filter screwed directly into the carb. This is a no-no since the original threads are NOT pipe thread and the filters are pipe thread. If you tighten that filter too much it will split the carb body. If that happens the carb is junk.

My M151A2 has the filter screwed directly into the carb. I don't see any damage to the carb body but, based on your advice, I would like to install the 90 deg. part. The locking nut (8764823) is readily available. However, I haven't been able to find the 90 deg. elbow (11668003).

[rickf]

The A2 uses the 30 degree angle fitting since the gas line comes in from the passenger side over the front. The A1 uses the 90 degree fitting with the gas line coming out of the cowl on the same side as the carb and the line running along the fender and looping up at a 90 degree angle to the inlet. I think Army Jeep parts has the 30 degree fitting. Depending on how far in the filter was threaded into the carb over the years the correct fitting may or may not work because the tapered pipe thread of the filter has enlarged the outer part of the threads in the hole. I say to try it, if it does not work go back to the filter but just do not force it to tight.

[glcaines]

Thanks Rick!

[Horst]

Many years ago not knowing enough about these little trucks, I actually managed to split the carb by installing the filter directly and tighten it a little bit too much. I fixed it with JB Weld and fortunately it is still working after 10+ years...

[rickf]

Your one of the lucky ones!

[1SGCAV77]

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Well I did finish with carburetor on my Jeep. Wasn’t able to find the angle fitting but did get the 90 degree. Also needed a Dorman fitting from O’Reilly. Installed a Wix 33046 fuel filter. The 90 degree fitting installed easily. Old filter didn’t damage carb. Also got washer and o-ring on the fuel air mixture screw. I’m happy with results. Jeep runs great. Thank for all advice.

[rickf]

You have an extra line coming into the air filter. It is the rubber one on the 90 coming in from the same side as the fuel pump vent. What is that line?