1953 M37 Carb Flooding. Assistance needed.

Backfire can be ignition, I thought this was a flooding issue.
Any progress?

We had a lot of the same issues as I've read here with the 1958 M37. After taking it to an engine machine shop, I think we have it fixed!

The main problem that we had was that the truck would not idle well at all. You could smell the fuel in the exhaust, and the carb was flooding. We adjusted the valves, checked the compression, checked the vacuum, all of the normal things. The vacuum was reading low at idle and would jump to normal just above idle, and the truck would drive fine. Also, the idle would speed up just a tick, and smooth right out, if you pulled the choke out about 1/2 inch. This was the giveaway to the machine shop. They advised that the idle circuit on the carb was too small. This causes the carb to pull fuel from the main jet because it's starving to stay at idle. The result is a flooding situation. They opened up the idle circuit a fraction and the all of the issues are gone. The truck starts, ideas, and drives like new.

I a familiar with this issue, however it is not the main circuit being puled over it it the idle circuit siphoning, not mixing.
But the OP has indicated that this same problem exist with 2 totally different carbs.

This is our second carb with the same problem too. Both "new", from the same place as the OP. I wanted to post the info as another avenue to investigate.

Any updates, given the above possibilities?

I read through this entire thread and I have to tell you, this is a great group of people.

I am having a very similar issue with my 54 M37. Cool days (in Florida) I could drive my M early in the mornings with little issue but as soon as the engine heated up, it would sputter to the side of the road. I just had to let it cool down and she started again until I limped home. I just took off the electric pump and installed a new mechanical pump from John at MWM. The flooding problem in the OP is almost identical including backing up gas into the crank case. I employed the help of a long time retired mechanic in town who has a love for military vehicles. We've rebuilt the carb (which seemed to be working previously except for the stalling / flooding) and now we're looking at the float etc.. There's gotta be an easy fix here and I believe it's something to do with the sealed vacuum system this truck has. The gas pressure is just to high and it's flooding the system.

I want to hear about a happy ending to the original OP's issue.

Check your float. They will get gas in side the float. Put next to ear and shake the float , you can hear or feel the gas in side the float.

Chances of two bad floats on separate carbs is remote.

Sorry guys I haven't updated this in a while, unfortunately I have given up on the old girl. I sold her to a great guy in Florida that was planning a full restoration so I sent him both of mine. I have a couple of willys I have to get running right now and some day will get back on an M37. Last I heard from him he was still unable to get it running and was pulling the engine to take to another friend. thanks for all the help troubleshooting though, I really appreciate it.

Hope the person who bought it is a SS member so we can follow what he is doing.

I am having the same problems my my m37. Sitting 10 years, rebuilt carb, flooding out of the pcv port. Here is my thread on g741.org

http://www.g741.org/PHPBB/viewtopic.php?f=3&t=7853

Sure would have been good to have an answer.
New owner?

I am having the same problem with my m37 right now! Here is my thread on g741.org
http://www.g741.org/PHPBB/viewtopic.php?f=3&t=7853

I had this same problem wit my m37. My friend had a 230 in a 53 dodge car with the same problem as well. It was ignition related on both. I put on new plug wires to fix my m37 and he converted to electronic ignition on his 53 car.