willysmjeeps.com

I replaced the military fuel pump, the fuel pickup tube and the "in tank" filter/screen on my M38A1C. The jeeps runs good for about 8 miles and then acts "fuel starved" cutting out for 30 seconds then taking running okay for a short period getting progressively worse as it repeats.
I would appreciate any advice on what to try next.

Make sure the tank vents are open. The one in the cap and the one in the top of the tank. The easiest way to troubleshoot a plugged vent system is to test drive the jeep with the fuel tank cap removed.

Thanks Wes, Ill try that next. If I find they are plugged is there a way to clean them or is it a replacement of the cap and vent

Depends on which cap or vent you have. There were mainly three caps; fixed vent, unvented and adjustable from vented to unvented. The military unvented is not correct for the jeep. The military vented is ok to use and if plugged just clear the vent. The preferred is the adjustable which has a rotating disc on the inside to switch it from unvented to vented. This is usually the issue where someone has turned it to unvented and you are not aware of it's operation.



The tank's vent plumbing is in two forms; M38/early m38A1 which had the vent on the pick-up portion of the tank plumbed to the air cleaner. Late 53 & on M38A1 & M170 used the same style vent screwed to the top of the tank as you found on the differentials.


Early 52/53 M38A1 and M38 vent plumbing on top of tank to air cleaner


Late M38A1 / M170 non-fording type vent system.

Thank you. I'll give this a try next weekend. I appreciate your insight!