M38A-1 stuttering on hills

[sportpilot]

I have a 53 M38A-1. I just put in a new rebuilt long block that I purchased from KaiserWillys.com. It runs fine on flat roads, but on even the slightest hill, it stutters and coughs until I pull out the choke about 1/3 of the way. Then it goes up the hill fine. I have a Carter carburetor in it, and no adjustments seem to make a difference. It has a new mechanical fuel pump and an electric one for back up. The fuel filter is new, the lines are clean, and the tank has no sediment in it. This carb is not new, and has been tinkered with by a prior mechanic that is no longer in the picture. I am thinking about replacing the carb with a new rebuilt Carter. Anybody have any suggestions as to why it coughs and spits going up the hill unless the choke is put in, but runs fine on flat roads without any choke? Thanks.

[wesk]

Check the float level.

Check delivered fuel pressure between the mechanical fuel pump and the carb.

Is the carb a Carter YS950S?

Why the electric fuel pump? These engines have done very well on properly overhauled and maintained mechanical fuel pumps for over 70 years. An electric pump is usually a band aid applied by someone who didn't know how or didn't want to correct the jeep's original fuel feed problem. It's part of the old Bigger Hammer theory in that the owner assumes more pressure will guarantee performance. An improperly installed / plumbed electric pump can actually hinder a mechanical pump's ability to draw fuel from the tank. Most electric pumps require a pressure regulator to reduce their output pressure to within the carb's float valve's capabilities.

[sportpilot]

The carb is a Carter YK, The electric fuel pump is there because about 6 years ago the manual gave out and we were out in the middle of the Mojave Desert. A number of Jeep club members had suggested I put one in just in case. Without it we would not have made it back. I put it on just in case I might need it, and I am happy I did. I only turn it on if I need it, and to test it here and there to be sure it is working. The installation was checked by several mechanics to be sure it was put in right, and it is installed properly.according to those that have checked it.
Your fuel pressure check and float level check are good ideas. This carb was rebuilt about 2 years ago, and it has never run right since in my opinion. I changed from a Solex to the Carter, and it was a rebuilt one that a local Jeep mechanic had in the shop. New different size jets were put in according to a friend of mine that remembers the conversation with the AZ mechanic. He also adjusted the float. Today I noticed that when the vehicle is idling, I could not see any fuel in the clear housing of the fuel filter. When I turned on the electric, fuel pump for a moment, fuel appeared in the filter, and when I turned it off, it slowly disappeared. I would certainly like to avoid the purchase of a new carb if I can.

How do I determine if the float level is correct and how do I determine if the fuel pressure is correct? Thanks.
Darryl

[wesk]

Download the free manuals on our downloads page and follow them step by step.

[sportpilot]

Thanks for the information and tips. I checked and the float was set very low indeed. Took the Willys out after adjusting it and it performed much better going uphill. I also made sure all the lines were clear and checked the fuel pressure. It measured at 2.5 psi.