M38 Carburetor Issues

redrad · Post by **redrad** » Thu Oct 08, 2020 8:32 pm

New M38 owner trying to figure out why Jeep dies after about two miles and want restart. Jeep starts good cold but will not stay running without being partially choked.
12 volt conversion with prestolite distributer and Solex carb. Any ideas what may be happening?

Jeep was parked for 10 years before I purchased it.

Mike_B · Post by **Mike_B** » Fri Oct 09, 2020 9:46 am

It sound like you're running out of gas as soon as the carb bowl is empty. Is there gas in the tank? Is the filter clogged? Have you confirmed you have a working fuel pump (pressure and flow)?

Mike B

redrad · Post by **redrad** » Fri Oct 09, 2020 10:17 am

Fixing to pull gas tank and check the tank filter. this morning would not start except for spraying starter fluid then dies right away I could not see gas in the in-line filter by the fender wall.

If this doesn’t work on to the fuel pump

redrad · Post by **redrad** » Sat Oct 10, 2020 10:35 am

Well pulled fuel line off tank and hooked up portable gas tank with primer bulb and got Jeep to run. I noticed that bubbles going through the inline fuel filter by the fender well this has been happening since I purchased the Jeep still not running right then I noticed leak around the top of the fuel pump I tried to tighten the screws but no luck. Should there be any bubbles in fuel filter?

Also while looking down in the carburetor the bottom choke does not open it appears the bi metallic does not work.

Not sure what fuel pump I have no glass bowl on bottom and can only see made in Canada on top. Debating whether to send fuel pump for repair or repair myself

Any suggestions?

Post by **wesk** » Sat Oct 10, 2020 8:38 pm

Also while looking down in the carburetor the bottom choke does not open it appears the bi metallic does not work.

The only choke in this system is the plate at the top of the carb. The plate at the bottom of the carb itself is the throttle plate. Are you referring to the heat riser plate inside the intake manifold?

redrad · Post by **redrad** » Sun Oct 11, 2020 9:12 am

Your right it is the throttle plate it opened when I moved the throttle. I am still learning.

I see a leak on the fuel pump that could be keeping it from running it is a double action fuel pump with vacuum going to windshield wipers and to the manifold.

That either needs to be repaired with a kit or replaced. Several companies offer rebuild services and I found a replacement omix from one vendor.

Would the omix-ada be a good choice?

Post by **wesk** » Sun Oct 11, 2020 9:24 am

The easiest way to let us know which fuel pump you have is to post a photo of it. Also if it is an AC fuel pump the last four of it's part number are on the mounting flange.

4x4M38 · Post by **4x4M38** » Sun Oct 11, 2020 12:59 pm

The AC fuel pump is not too difficult to rebuild. Kits are available from several vendors including Then and Now.

I do not believe it is as difficult as the carburetor.

Just my two cents.

redrad · Post by **redrad** » Sun Oct 11, 2020 1:40 pm

Thanks I am gonna contact them tomorrow.

On another note anyone knows how to post pictures from an IPad, I tried from my desktop using instruction from the sticky note with no success.
Using Windows 10 tried both google chrome and Microsoft edge.

Eades · Post by **Eades** » Mon Oct 12, 2020 7:18 am

I suggest calling Midwest Military for rebuild kit. I put the Then and Now kit in mine and had some issues with the valves being a bit too high and then not allowing the diaphragm to flex to maximum extent which reduced fuel pressure. Midwest's kit has proper valves.

Post by **wesk** » Mon Oct 12, 2020 9:55 am

On another note anyone knows how to post pictures from an IPad, I tried from my desktop using instruction from the sticky note with no success.
Using Windows 10 tried both google chrome and Microsoft edge.

Our web site is a "Powered by phpBB © 2001 phpBB Group" and as you can see is date 2001. It is not very compatible with portable devices. The easiest way to load a photo to a post in this system is by using a photo album in our "Member's Albums" page.

You cannot load a photo direct from your home computer files. That is an expensive later program thing that Facebook can afford but we cannot. If you follow the directions I have posted in the Photo's Board then you will see that I said the photo you intend to load must already be loaded to a photo storage site. There are dozens of pay sites and a few limited use free sites but it is hard to beat just using one of our "Member's Albums" which are free.

CapnDan · Post by **CapnDan** » Sun Oct 18, 2020 4:42 pm

I have been trying to diagnose a fuel supply problem as well. Spring of last year I had replaced a functioning after market pump with a Precision Fuel Pump from O'Reilly because I thought the after market pump was not flowing enough fuel. The after market pump is one of those with the glass bowl on top, the bowl never gets full regardless of how high you rev the engine. On a recent test drive after doing some differential repair work the engine stalled and restarted after choking, but re-stalled and would not restart. I disconnected fuel line at carb and engaged the starter to verify no fuel flow. I took the fuel pump off and returned to O'Reilly, got a replacement Precision Fuel Pump under their Limited Lifetime Warranty. The new Precision Pump did not pump when I installed it on engine. I purchased a Pittsburgh fuel pressure and vacuum gauge from Harbor freight because it was the only one I could find that reads 0-10 psi. Verified with gage that Precision Pump is not making any pressure on engine. I then took if off and pressure tested it on bench, pumps up to about 4.5 psi and holds pressure. The problem seems to be that the pump has too much free play in the pump arm mechanism compared to the after market pump, so the cam lobe is not able to lift the arm far enough for it to work. Any recommendations on where to purchase a better quality, correctly function fuel pump? I do not have the vacuum wipers, so only need a single action pump. I am looking at Kaiser Willys catalog and Midwest Military's web page. My jeep when we got it had an AC pump with a metal bowl and a primer lever, I am going to call John at Midwest military and see if he has a kit for that pump, number on flange is 3476.

Post by **wesk** » Sun Oct 18, 2020 11:30 pm

What pump to block spacer size are you using with this assortment of pumps you have gone thru?

CapnDan · Post by **CapnDan** » Mon Oct 19, 2020 7:24 am

No spacer, there was not one on block when I replaced the pump that was on the jeep when I got it.

Post by **wesk** » Mon Oct 19, 2020 10:43 am

If you read the parts manual carefully you will see a specific thickness steel spacer that goes between the Military dual action pumps and the block to regulate output of the pump. It is on page 73 of the 55 ORD 9 SNL G-740. Your last four digits of your fuel pump 3476 is not shown because that pump was a design introduced later on the M38A1. But as you said it has the priming handle that makes it a M38A1 pump. Still compatible with the M38 and both the M38 & M38A1 used the same thickness spacers.

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