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M38 was easy to start, now hard?

Posted: Thu Apr 21, 2022 3:42 pm
by ramapoarmyjeep
Our family has had 2 M38's, a 1951 and a 1952, continuously since 1965. We have had the '52 since 1975 when the '51 rusted out. all authentic running gear, 24v system.

For all their other foibles, neither was ever a hard start, even after sitting an extended period. Two pedal pumps, 1/2 to full choke and it would catch after 1-3 seconds of cranking. Last year, the '52 became hard to start: endless cranking, ether, even with pumps, full choke etc. Also became hard to restart even warm. once running it runs fine and strong.

I suspected a bad fuel pump and took to my 30+ year mechanic (for other vehicles, this was his first shot at this one) . No, he says, the pump is fine. He rebuilds points, carb (i got him the kit from Kaiser), adjusts timing, replaces the PCV, and it runs ok, but is still a devil to start and restart. "They are like that" he says, yet i have 55 years experience going the other way. "Leave the PCV valve off" he says, well it ran great before with it on and with it off, that opening is a "road draft" oil exit....

all constructive suggestions welcome. Many thanks

Posted: Thu Apr 21, 2022 4:55 pm
by 4x4M38
Yes it is

Posted: Thu Apr 21, 2022 5:07 pm
by RonD2
Hi Ramapo (? name ?),
Need to know what carburetor is on it.
The original M38 carb is a YS-637S and it's vacuum operated.
"Pumping the gas pedal" to start the motor does nothing with these carbs (doesn't inject gas to the intake). Closing the choke uses vacuum to pull gas to the bowl and on from there.

There's many possibles with what you describe.
Do you have copies of the M38 manuals that can aid a lot in troubleshooting?
They're free for download in this forum.
They help tremendously to avoid communication confusion when troubleshooting and provide logical steps to follow.
They also give specs (for things like fuel pump pressure) so you can test what you have is working properly or not.

There's a tremendous amount of knowledge in this forum, but likely need more details to help.
I'm not the expert. They should chime in shortly.....

Good luck!

Posted: Fri Apr 22, 2022 7:27 am
by ramapoarmyjeep
thanks, Ron

yes i have TM9-804 manual

Carb is stamped Carter W-O on the top

i have good pictures but cannot dope out how to load pictures to this site, yet[/list]

Posted: Fri Apr 22, 2022 8:13 am
by ramapoarmyjeep

Posted: Fri Apr 22, 2022 9:59 am
by wesk
Ramapo, I took the liberty of viewing your three drop box links and copied the correct URL for each of the three photos and reposted that URL inside the Image brackets so folks don't have to search the internet for your photos. One of the boards on this web site is for Photo questions. If you use that board you will find detailed instructions for how to use photos here.

Now back to your topic: That is a WWII Willys MA/MB and Ford GPW jeep carb. It does not have vacuum operated accelerator pump or metering rod. It is listed in the TM 9-1826A which is a free PDF download right here on our web site's downloads page so you can determine how to troubleshoot and repair your WO carb. Proper operating pressures and adjustment data will be there and also in the old WWII jeep TM 9-803. I will assume you already changed that carb fuel inlet filter just to be sure it wasn't starting to plug up?

Posted: Fri Apr 22, 2022 10:30 am
by ramapoarmyjeep
Detective Wes:

Aha, thanks very much for the key fact - somewhere before 2019, somebody swapped out the M38 carb for another!

would that WO struggle to adapt to the pvc and or M38 waterproofing? sounds like not....

yes, I bet the mechanic checked that inlet filter but i will confirm, and i will run down adjustments via TM 9-1826A.

Many thanks again!

Posted: Fri Apr 22, 2022 11:27 am
by wesk
I would also check the carb fuel bowl vent to insure it is not plugged up.

Posted: Sun Mar 26, 2023 5:14 pm
by ramapoarmyjeep
Wes and all:

The saga of this M38 and not starting is long but comes out well. Apologies for the delay, but it did not come back from the mechanic (John Santos, Milllis MA - did great job) until November 2022 and I have been waiting for good weather to run test it.

Recall that the problems were endless cranking to start, whether hot or cold, then very poor running, huge backfires (literally exploded the muffler). Would never idle down below about 1100 w/o stall. Rebuilding Carter WO = NG, replacing fuel pump 2x = NG. New coil, points etc all NG. Towed back to my house twice in 2022 and went to Santos on a flatbed for tow #3.

New Carter WO from Kaiser Willy's = only partial fix. New points, plugs wires and coil again = only partial fix.

Then he found "It". "It" was an aftermarket jury rigged fuel filter/ sock on the end of the pickup line inside the fuel tank, created by some mechanic in the last 70 years. The sock clogged over time, the line cracked over time, again inside the tank. Result: some fuel got through when the engine was merely cranking but the the car would immediately suck air once the engine was actually running. the heavy choke countered that, some.

so a long battle and some $ sacrificed but i found a determined and capable fellow who fixed it.

on we go.

now I have a spare "recently rebuilt" (by the prior mechnic) W/O if someone is looking

best wishes for safe and happy jeeping to you all

Posted: Sun Mar 26, 2023 10:16 pm
by wesk
Hi ramapo,

Glad you resolved the issue. Enjoy the jeep again! Just for the heck of it what is your actual first name or nick name?