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willysmjeeps.com :: View topic - M38a1 carb leaking fuel from top screws
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M38a1 carb leaking fuel from top screws

 
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RichJohnson
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Joined: Apr 15, 2005
Posts: 146
Location: San Diego CA

PostPosted: Sat Oct 23, 2021 5:59 pm    Post subject: M38a1 carb leaking fuel from top screws Reply with quote

I rebuilt the stock M38a1 carb with a kit from midwest and fuel keeps coming out the top from the throttle cable bracket screws and the 1 screw forward of them on the forward side of the fuel inlet line.

I have verified my float setting per the manual and I just cant figure why this is happening.

Is it a faulty gasket?

Is there too much fuel pressure, it has a new autozone CJ fuel pump but it ran ok before I rebuit it....

Opinions on what to do next.

I had it running good for a bit today then it just clogged up and doesnt want to idle, or start or even drive. the high speed circuit just dropped off entirely. It must have clogged up for all this to happen, Ive rebuilt several of these carbs over the years so Im pretty good at it and yet this one has me stumped.
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1954 M38A1 (first civilain owner)
1965 M37B1 Commo shelter truck
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wesk
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Joined: Apr 04, 2005
Posts: 15626
Location: Wisconsin

PostPosted: Sat Oct 23, 2021 11:28 pm    Post subject: Reply with quote

Two quick checks come to mind.

1 - Remove the top section (air Horn) after you are sure the bowl has filled up and confirm the inlet needle is firmly seated and not allowing any more fuel in.

2 - With a pressure gage T'd into the line from the fuel pump to the carb check the actual output pressure of the pump.

Looking at my illustration below which # screws are leaking?


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45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100

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RichJohnson
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Joined: Apr 15, 2005
Posts: 146
Location: San Diego CA

PostPosted: Sun Oct 24, 2021 12:11 pm    Post subject: Reply with quote

Screws # 1,2 and 6 are leaking. I dry them, then you can see a film slowly develop and then a puddle.

The only needle I am aware of is the one above the float right?
Once I lift the air horn off the bowl the float will droop and the needle will open all the way simulating an empty bowl.

I know that when I set the float level, and then reset it again per the manual, the float was sitting on the spring of the needle, which I read is how it should be gauged if I was correct. The float could have been pushed down on the air horn further compressing the spring (while air horn is inverted of course)

Im not aware of how to perform the needle test you suggest.

I will look into how to test the fuel pressure. have no idea currently. Google and youtube academy should help.
_________________
"Those who enjoy freedom must endeavor to preserve it"

KI6EZA
1954 M38A1 (first civilain owner)
1965 M37B1 Commo shelter truck
MBT
GRC-122 TTY rig
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wesk
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Joined: Apr 04, 2005
Posts: 15626
Location: Wisconsin

PostPosted: Tue Oct 26, 2021 1:56 am    Post subject: Reply with quote

To leak from the screws the carb bowl has to be overfilling.
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Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100

Mjeeps photo album: http://www.willysmjeeps.com/v2/modules.php?set_albumName=Wes-Knettle&op=modload&name=gallery&file=index&include=view_album.php
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Yarder
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Joined: Feb 18, 2009
Posts: 43
Location: Seattle, WA USA

PostPosted: Fri Oct 29, 2021 8:44 pm    Post subject: Reply with quote

I had an issue just like that. I had set my float, etc. Turns out that my float wasn't correctly floating. It had, over the years, gotten fuel inside it. I followed the book to put the float in a pan of hot water, watch at the bubbles came out, and noted the location. Then removed the float and sanded the area, and soldered the leaking spot.
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RichJohnson
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Joined: Apr 15, 2005
Posts: 146
Location: San Diego CA

PostPosted: Sat Oct 30, 2021 10:33 am    Post subject: Reply with quote

Ok, I will look for a leak in the float.

I guess other problem could be the pump is too much pressure and pushing past the float needle since the float is set properly.
I still need to get a fuel pressure test done.
_________________
"Those who enjoy freedom must endeavor to preserve it"

KI6EZA
1954 M38A1 (first civilain owner)
1965 M37B1 Commo shelter truck
MBT
GRC-122 TTY rig
Back to top
View user's profile Send private message Visit poster's website MSN Messenger
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