Fuel Problem

lake · Post by **lake** » Thu Jul 31, 2014 8:28 am

My 1953 M38A1 jeep will not pump the fuel out the out end of the fuel pump.I have replaced the fuel pump with 2 others ,but they will not pull the gas from the tank at all.Both pumps do work,is there anything in the gas tank that could cause a related problem .

OKCM38CDN · Post by **OKCM38CDN** » Thu Jul 31, 2014 4:01 pm

Have you made sure the line / tank outlet is clear?

Also is the tank vented? A clogged vent line will prevent the fuel from flowing...

The M-38A1 uses the 5/16" fitting in the top of the tank... the 3/16" fitting is the vent...

I know these are basic questions, but I have messed up in the past overlooking the simplest things...

Hammerun · Post by **Hammerun** » Thu Jul 31, 2014 5:21 pm

I just had my tank apart completely. I was surprised to see a filter element in there. It's about 1.5"x 4" in length. It's under the large flange that the fuel line connects to. It might be worth while to take it out and give it a look.

lake · Post by **lake** » Thu Jul 31, 2014 7:02 pm

I did blow out the lines with the air compresser and the line to the tank sounded clear.I did plow out the fent as well. Maybe my next option is to remove the seat and have a look at the fuel tank.I can,t see that the cam would be worn because it worked great a few weeks ago.I just didn,t have the time to drive my willys until now (vacation time).Would the bubbles in the fuel line leak beyond the fuel pump,thanks Lake

tomahawk715 · Post by **tomahawk715** » Thu Jul 31, 2014 9:18 pm

Not trying to be a jackwagen--- but did you hook the line back up correctly? I saw a guy who had an inline filter with not stock lines hook his pump up in reverse.

When my 38a1 wasnt pulling fuel it turned out the needle in the carb was stuck closed. But it sounds like your line is off going to the carb?? I took line off at the carb and it pumped like a firehose. Just had to tap carb to free up the needle.

Post by **wesk** » Thu Jul 31, 2014 10:57 pm

Before this post heads west or other places unknown, let's get some more info that will make for more specific and appropriate replies.

1-You say you know these pump work. How did you determine that?

2-Are these pumps stock and correct M38A1 pumps?

3-Have you checked the line from the pump inlet to the tank for leaks. If it can suck air then fuel won't move through it. That line goes into the tank to a standpipe. If the pickup tube / standpipe is corroded and has holes in it and the fuel level in the tank is below the holes then your pump will only suck air.

4-Have you been using the correct spacer between the pump and block? The correct military pump uses a thick spacer. The civvy pumps do NOT.

The vertical tube with callout "K" pointing towards it is the standpipe I referred to above.

lake · Post by **lake** » Fri Aug 01, 2014 8:12 am

Thanks for the input.After today I have checked all gas lines for air leaks and there are none .It still wants to suck alot of air,so I guess it must be in the tank itself. Now I guess the next dreadful job is to remove the seat and have a look inside the gas tank.Here,s hopeing I find the problem,