Fuel Pump Choice

Naugha · Post by **Naugha** » Thu Jul 15, 2021 2:41 pm

A M38A1 fuel pump (5594260) came on my M38 along with the hand lever, spacer and special mounting bolts (1 long / 1shorter). I could have it rebuilt or buy one of the M38 fuel pumps that would be proper for my late engine.

Two questions based on my reading of some old threads.

Were these M38A1 pumps sometimes used to replace M38 pumps in the field?
Do you see these pumps used by folks doing a Motorpool resto?

Yes. I have the MVPA scoring sheet.
I’m going to guess that if it’s not a M38 pump then it’s wrong for the jeep.
But.....
Did some M38A1 pumps get installed on M38s ‘at the motorpool’?

mdainsd · Post by **mdainsd** » Thu Jul 15, 2021 6:26 pm

Look into the '55 parts list (in downloads) pages 72 and 73. Four different part numbers are called out and are serial number specific. I don't see the M38A1 pump listed in there.

Did it happen? Who knows, unless we heard from someone with firsthand experience. Other than that, I imagine if the Judges don't know, they would refer to the manuals including the part list to figure out if they grade it as right or wrong...

Mark

Naugha · Post by **Naugha** » Thu Jul 15, 2021 8:05 pm

Sounds like I need to stick with the M38 pumps.

Too bad. The M38A1 pump with the priming lever looks cool and could help getting her to fire up.

RonD2 · Post by **RonD2** » Thu Jul 15, 2021 8:31 pm

Yes, stick with M38 pumps if you're all about max points for a show queen. But just because the 4260 pump isn't listed in the M38 ORD9 doesn't mean it wasn't used by the Army in the motor pool. There's plenty of old posts and opinions in this forum saying that all the M38 and M38A1 pumps are fully interchangeable. What are the odds that the Army wouldn't take advantage of that?

I'm running the late model 4260 pump on my M38, but I'm not chasing points at a show. To each his own, but I have no intention of paying money for my M38 to be judged at a jeep contest using made-up rules and if the judge is having a good day or not. Couldn't care less. I'm using that pump because there seems to be more of them available. Good luck!

Post by **wesk** » Thu Jul 15, 2021 11:03 pm

If you are working on a Factory class trailer queen then you are stuck with the pump that was shown as being introduced on your M38 by serial groups. End of that discussion.

If you are a motor pool class resto or driver builder then any will work in any serial/model. If you carefully read thru the many ORD 9 and ORD 8 issues you will see that by 1956 or so the Army showed all the pumps useable/interchangeable in the M38/M38A1/M170.

As for those special extended hex bolts the M38 used them as well. Here's fig 47 from TM 9-8012

These M38 ORD 8 SNL G-740 pages will clear up any questions about interchangeability of all of these fuel pump!

Naugha · Post by **Naugha** » Fri Jul 16, 2021 8:22 am

I recently joined the local MVPA chapter but do not plan to ‘chase points’. I just wanted a recognized standard that would bring me close to recreating the M38 with an eye to historical accuracy. This goal has proven to be, shall we say, a little complicated.

If it was easy there would be numerous M jeeps on the streets. I have yet to see one except at shows and in parades.

I like the M38A1 fuel pump so it will be going under the hood.

mdainsd · Post by **mdainsd** » Fri Jul 16, 2021 9:06 am

Your Jeep, your way! That is how it is supposed to be. Enjoy.

Post by **wesk** » Fri Jul 16, 2021 9:14 am

There are many locations where you can still see MB's GPW's, M38's and M38A1's roving the local roads but those locations are usually rural farming or wilderness locations. Since the jeeps from that period are rapidly becoming higher priced classics/antiques the urban areas drivers buy more recent 1980's to late 90's used jeeps for their hunting or snow driving adventures.

Did you notice how many M38A1 pumps there are on that M38 ORD 8 list? Of the 6 pumps listed they are split 3 & 3.

The Army's supply system is an intelligent one. As newer pumps were derived from the earlier pumps the Army supply system allow interchangeability and so they would narrow the number of part numbers they were procuring down to the newest production variants lowering the cost of maintaining large quantities of various part numbered pumps and their rebuild kits.

Naugha · Post by **Naugha** » Mon Nov 08, 2021 5:11 pm

I sent the unit out for a rebuild.
Here is the finished product.

RonD2 · Post by **RonD2** » Mon Nov 08, 2021 5:51 pm

Very pretty! If you don't mind saying, who did the work?

I'm sure you've seen these:

Fuel pump modification:
http://willysmjeeps.com/v2/modules.php? ... pump+drill

Fuel pump pre-loading the diaphragm:
http://willysmjeeps.com/v2/modules.php? ... eload+pump

Naugha · Post by **Naugha** » Mon Nov 08, 2021 8:48 pm

Hi Ron.

The work was done by one of your least favorite vendors.

It's going to be a while before we find out if 'pretty' = 'works fine'.

The carb will go to RickG's buddy.

The distributor was rebuilt by an idiot who lives in central Florida.