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Spacer plate under fuel pump?

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Vintage Don View Drop Down
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    Posted: 04 Apr. 2021 at 12:53pm
OK, I have never figured out the right answer on this one....

Is there supposed to be a spacer installed under the fuel pump - or not?

The fact that they EXIST would certainly imply they need to be used. Yet when I pulled it off of my (running, and hadn't been messed with for a long time) little Go-Devil to rebuilt the fuel pump - there was NOT one there. In my '48 pickup (same engine), it was there.

What's the official ruling?  Find one and put it under there - or it doesn't matter?


Edited by Vintage Don - 04 Apr. 2021 at 12:55pm
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Vintage Don View Drop Down
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Vintage Don Quote  Post ReplyReply Direct Link To This Post Posted: 04 Apr. 2021 at 1:18pm
I think I found my own answer - it's about if it's a dual action (vacuum also) pump, or not.

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Post Options Post Options   Thanks (1) Thanks(1)   Quote Bruce W Quote  Post ReplyReply Direct Link To This Post Posted: 04 Apr. 2021 at 4:16pm
  Clap  You got it.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Oldpappy Quote  Post ReplyReply Direct Link To This Post Posted: 07 Apr. 2021 at 11:13am
I have encountered that spacer on M38 and M38A1 Jeeps, but not on CJ3s or CJ5s with a dual action pump. I think the military application originally used a slightly different pump than the civilian as part of the fording kit, but not sure about that. 

There were also at least two different engine plates used after they started with the dual action pumps, so the spacer may have something to do with which plate. It is something that has puzzled me.
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Bob W View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Bob W Quote  Post ReplyReply Direct Link To This Post Posted: 07 Apr. 2021 at 1:21pm
Most dual action fuel pumps require a spacer. There are different thickness spacers. Check the Parts List to be sure for your application.
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Ron D View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Ron D Quote  Post ReplyReply Direct Link To This Post Posted: 07 Apr. 2021 at 8:34pm
Without checking the tech manuals, am fairly sure that CJ dual-action fuel-vacuum pumps on the L134 take the thinner spacer (1/8-inch?) while the M38 L134 fuel-vacuum pump uses the thick spacer (5/8-inch?). Very easy to tell them apart. I've never seen any other size spacers but those two thickness spacers. Not sure if they only go with dual action pumps or if a straight plain-jane fuel pump needs a spacer too. Pretty sure the tech manual would say one way or the other?

Another clue is in your parts manual if it says you need 2 gaskets to mount that kind of pump then you need the spacer. Also fairly certain that the tech manuals for both jeeps describe how to check fuel pump output (volume) and pressure (with a gauge) to see if everything is working properly --- before lighting it off.

Farting around without tech manuals and measuring tools can be frustrating?

Good luck!


Edited by Ron D - 07 Apr. 2021 at 9:05pm
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muley View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote muley Quote  Post ReplyReply Direct Link To This Post Posted: 07 Apr. 2021 at 8:43pm
Ron, you know the spacer for the M38 is 1/2inch thick. Wes would have you drop and give him ten the hard way!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Ron D Quote  Post ReplyReply Direct Link To This Post Posted: 07 Apr. 2021 at 8:45pm
LOL! That'll teach me to speak before cracking the book!

Already doing them........

Thanks!




Edited by Ron D - 07 Apr. 2021 at 8:48pm
1951 M38
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Ron D Quote  Post ReplyReply Direct Link To This Post Posted: 07 Apr. 2021 at 9:36pm
Ok, paid my dues. Big smile

It also helps when mounting the pump if you rotate the engine by hand a few degrees to find the low spot on the cam lobe for the fuel pump arm so you don't have to fight the pump arm spring pressure while you bolt it up to the block. A tiny dab of assembly grease on the pump arm where it rides on the cam is also a good thing.

Good luck!




Edited by Ron D - 07 Apr. 2021 at 9:41pm
1951 M38
1951 M100
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