M38 fuel/vacuum pump

JahRafa · Post by **JahRafa** » Wed Jun 24, 2020 12:42 pm

Hello. I am having problems with the fuel system on my 1952 M38. I need some wisdom as I am not too familiar with the Fuel and Vacuum pump. I just took off the fuel pump and there is oil inside the vacuum part when I took the bottom cover out. Is that ok?

RonD2 · Post by **RonD2** » Wed Jun 24, 2020 2:12 pm

Hi RJ,
Have you seen this post?

http://www.willysmjeeps.com/v2/modules. ... +fuel+pump

Good luck!

JahRafa · Post by **JahRafa** » Wed Jun 24, 2020 2:24 pm

Thank you for the info. I read it but what I have is not oil on the top part of the pump (fuel pump). what i have is oil inside the vacuum part of the pump, the bottom where it looks like a cone. I am not sure if this is normal.

Post by **wesk** » Wed Jun 24, 2020 10:24 pm

Do you have the complete M38 fording system underhood plumbing?

JahRafa · Post by **JahRafa** » Thu Jun 25, 2020 4:55 am

Wes, 90% of the lines are connected. Only two are missing and are the two lines that connect to the distributor, since the system was converted to 12v. Also, the vent line that connects to the center of the fuel pump, the one coming from the transmission/transfer case, is plugged, as I saw on a post here, since I could not find the ball check valve.

P.S. I'll be installing the original distributor as I found a 12v ignition coil that fits inside like the original 24v.

Post by **wesk** » Thu Jun 25, 2020 10:19 am

There, you hit the nail on it's head! The center vent on the fuel pump if plugged will cause the suction half of the pump to suck on the oil sump of the engine. You must vent that port to the atmosphere.

The vent fitting will alleviate the oil in the vacuum side of the pump problem.

The military distributor is designed as a sealed unit to allow fording operations. The two vent lines are critical to the well being of your military distributor.

Their real purpose is to vent out ionic gases from the distributor to prevent an explosion inside the distributor. In very hot climates they extend the life of your coil by keeping it cool and the venting keeps moisture from collecting in the distributor.

4x4M38 · Post by **4x4M38** » Thu Jun 25, 2020 5:41 pm

And there is a simple fitting used to vent if the fording system is not used.

Post by **wesk** » Thu Jun 25, 2020 8:49 pm

Brian,

JahRafa already posted above:

the vent line that connects to the center of the fuel pump, the one coming from the transmission/transfer case, is plugged, as I saw on a post here, since I could not find the ball check valve.

So if you know where he can get his hands on one you should add that to your post.

4x4M38 · Post by **4x4M38** » Fri Jun 26, 2020 5:37 am

Hmmm. 1/4” vs 3/16, wonder what the angle of the flare is?

https://fitandcp.com/product/1066-14-ma ... -use-only/

Post by **wesk** » Fri Jun 26, 2020 7:50 am

JahRafa,

Ignore Brian's attempt at confusing you. This issue has been addressed dozens of times right here on this site. We have a Canadian member whom has been selling replacements for at least 5 years.

I have a photo album that addresses this system as well:
http://www.willysmjeeps.com/v2/modules. ... _album.php

Other Discussions:
http://willysmjeeps.com/v2/modules.php? ... pic&t=9850

http://www.willysmjeeps.com/v2/modules. ... ic&t=12472

http://willysmjeeps.com/v2/modules.php? ... pic&t=7132

http://www.willysmjeeps.com/v2/modules. ... pic&t=7674