Dash mounted fuel primer

Deadguy · Post by **Deadguy** » Thu Nov 10, 2011 8:43 pm

My M38A1 has a hole for this, but no primer. How easy is it to mount one to my existing set up? And how common of a feature was it? My technical manual mentions it, as does my 1954 in cab heater I'm now installing.

Post by **wesk** » Thu Nov 10, 2011 11:01 pm

The heater kit instructions usually contain the detailed installation instructions for the primer. If you can't find it they are the same as the M38's installation instructions here. Less than 2% of the tasks we must at one time or the other perform on these old jeeps are not shown to us in the available publications. The only additional task we have is to read them.

http://www.willysmjeeps.com/v2/modules. ... _album.php

"How hard is something" is a very relative question. Asking :How hard something is for someone to do" will give you their answer for themselves which is not a lot of help for you because you do not know their level of competence, their level of experience or their available tooling and facilities. For this reason it is usually much better to simply locate the instructions, read them and apply them to your own level of competence, your own level of experience and your available tooling and facilities.

Deadguy · Post by **Deadguy** » Thu Nov 10, 2011 11:36 pm

The heater kit instruction manual just mentions the fuel primer on the dashboard, it doesn't say anything else about it. I found what you provided the link to, but it looks like part of installation instructions for something else as well, and I wasn't sure. It sounds like it's a fairly easy install, and people like Pete Debella have a $125 kit for sale online. I'm mainly wondering how common it was, and if I really need more than the kit provides.

Post by **wesk** » Fri Nov 11, 2011 12:24 am

You are correct on the A1 instructions. They were integral to the gas heater heater kit manual. But they are a complete set of installation instructions and illustrations and if followed to the letter will work as advertised.

How common were they? Well today they are like machine guns. ??? Well during the life span of these jeeps less tan 10% had machine guns mounted. More had radios mounted yet nearly 30 to 40% of restored M jeeps have machine guns.

The factory stopped installing dash primers early in M38 production. No A1's left Willys with dash primers. How common were they? Well the military only installed them in jeeps that were fitted with arctic tops, arctic heater kits both gas personel and power plant and were assigned to ares prone to regular drops below 20 below zero.

How about early M38's that came from Willys with then? Well the Army has an MWO to disable them.

So the answer is in service not very common. As a resto toy/gadget they are right up there with WWII canvas water buckets and machine guns.

If you are wondering why the Army came out with an MWO to disable them it was because they could easily ruin an engine in several ways depending on just how ignorant the operator was.

1-Cosmolined units often had stuck (in cosmoline) check balls in them causing them to leak/bypass internally.So they were defective from day one of field installation.
2-Over priming in 20 to 40 below weather leads to loads of raw gas in the oil pan which leads to bearing destruction from the thinned oil and often to large explosions when the gas exploded from the ignition flames slipping down the sides of worn pistons/rings.
3-If they leak enough to allow air to be sucked into the intake from the dash barrel they can cause an extremely lean running condition that can burn exhaust valves.

skyjeep50 · Post by **skyjeep50** » Fri Nov 11, 2011 9:20 am

My M1951 M38 had one installed when I bought it, may have been original equipment since it is a "early" M38 but I can't document that. Thought I would get it working but I found that the seals for the piston are not available (at least I couldn't find any as a seperate kit). The seals are leather and the ones in my primer were shriveled, brittle and literally turned to dust when handled. You can buy an entire NOS primer installation kit but if the seals start leaking or wear...then what? Replace all the hardware again? You could also try to make the seals out of leather or rubber and maybe someone has had some luck doing that. But the primer isn't really needed for most situations and I felt fooling around with something that could drip gas on my left leg (while sitting on top of the gas tank which is mounted above the hot exhaust pipe) was probably a no-go.

In the end, I just cleaned up the primer, unhooked it from the fuel feed and left it there for demonstration purposes.

Deadguy · Post by **Deadguy** » Fri Nov 11, 2011 9:26 am

Thanks again Wes! I think I'll skip it, that info was the real help I needed.

4x4M38 · Post by **4x4M38** » Thu Nov 13, 2014 8:41 pm

Hello Wes,
When the MWO was issued did the Army fill the hole where the primer pump handle stuck out of the dash and with what?

Tks,
Brian

Post by **wesk** » Thu Nov 13, 2014 10:23 pm

The same button type plug listed in the ORD 9 SNL G-740 page 153, 5th item from the top of the page.

4x4M38 · Post by **4x4M38** » Fri Nov 14, 2014 1:09 pm

Thank you Sir. At the moment I have a rubber covered push button in that hole for the starter............................

PaulB · Post by **PaulB** » Fri Jun 12, 2015 9:50 am

Looking for a copy of MWO that talks about disabling the pump, really the how? What hardware do I need?

MWO ORD G740-W2 13 NOV 52

I think my jeep is doing #3...
3-If they leak enough to allow air to be sucked into the intake from the dash barrel they can cause an extremely lean running condition that can burn exhaust valves.

Thanks...

Post by **wesk** » Fri Jun 12, 2015 5:27 pm

Look here ;
http://www.willysmjeeps.com/v2/modules. ... _album.php

Keep in mind this only disables the use of the pump by blocking off it's fuel supply. If you are having lean issues from a leaking plunger or sticky popit balls they will still leak and give you grief. To prevent that you must remove the two injectors in the intake and put 1/8" P plugs in the intake.