Davy's fuel problem

Post by **wesk** » Sun Sep 06, 2015 1:36 pm

Someone named Davy sent this posting to our web site's admin email address instead of posting it here. So I will post it here for Davy.

Carburetor Issues

I am having trouble with my 1951 M38. I recently overhauled the original engine as it had been sitting many years, had low compression and I went through an entire restoration. Prior to overhaul, I had no problems with the carburetor, basic starting or idle. I did perform a basic carb rebuild including vating, a thorough cleaning, replaced original gaskets and set the float level to the correct height. I have a strong fuel pump with fuel filter. The jeep now starts fine and idles ok. Sometimes I can drive it a mile or so and then it begins to chug and will finally die (acting fuel starved). Over time, my plugs will build up carbon as if it is burning too rich (too much fuel). It does not smoke as with too rich. This coughing and sputtering seems to come and go. I have tried a fuel regulator to slow down fuel flow (because of the apparent rich plug coloration). However, it will then act fuel starved. The symptoms will go away once it cools down and then I start the process all over again. Have any of you had similar experiences or have counsel for me? Thank you.

Davy

Post by **wesk** » Sun Sep 06, 2015 1:46 pm

Davy,

I suggest starting with the fuel tank vent system and the carb bowl vent system. Plugging of either vent will result in your symptoms. Start with the quick check. Remove your gas cap and drive the jeep. If the problem goes away you either have a plugged vent line between the top of the tank and the air cleaner or you have a selectable venting cap with the closed fording position selected. Look at the inside of the cap

If it look like this make sure it is in the open position.

If your cap does not have the selectable knob then check the vent line from the top of your tank to the air cleaner (line "S" below) by blowing thru it.

If that line is clear then check the vent tube on the carb bowl ( Item "M" in the above diagram. If it is there then check by blowing though it.

4x4M38 · Post by **4x4M38** » Sun Sep 06, 2015 5:04 pm

Wes,
Could he have the carb adjustment setting done while the engine
is cold, and when it warms up it won't run right or is that
primarily an idle issue?

Brian

Post by **wesk** » Sun Sep 06, 2015 5:54 pm

No. If it was a mixture/rpm setting issue the problem would not run well for 20 minutes and quit then start right up and run again as soon as it gets cooled off. 99% of the time his symptoms point to what I posted above. Let's give him a chance to absorb the information and act on it before we load more on his plate.

Davy · Post by **Davy** » Sun Sep 06, 2015 9:30 pm

Thank you. Your advice sounds spot on. Let me chase these ideas and I will get back to you. Big thanks!

Davy · Post by **Davy** » Tue Sep 08, 2015 7:58 pm

Initially, the jeep ran great with the cap off. But then it was back to the same fuel starved performance. It does eventually getbso bad it barely idels does die immediately if pressed on the throttle. I feel confident it has a vacuum on the fuel system -just haven't figured it out yet.
An important note: much of the original fording equipment and vacuum lines were gone when I bought the jeep. However, your pointing me toward a vacuum on the fuel system is still my best guess. I'll keep chasing the problem and report back when I figure it out. Sure frustrating!
Thanks again for your help.