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I am rebuilding the combo fuel/vacuum pump to my "38 Eight. Any tips or tricks on changing the vacuum-side diaphragm? Instructions say I need an arbor press to separate the two disks from the stem. Looks pretty straight forward but a little confidence building is needed. It appears that I have to slightly grind some of the stem that was mushroomed over. Any ideas? I assume the fuel pump side is very similar in it's rebuild...
Thanks.

David

Dave;
I change the diaphragm all the time with out any special tools, you need to us a punch to remove the rubber seal and stake the washer over the new seal. It take some practice to hook the diaphragm back up. I don't change the shaft- if you do just grind off the end.

I decided to rebuild mine (1940) myself using BigKev's directions (available somewhere on this site) that he has posted.

It turns out that Big Kev's dual-action pump is quite different on the inside than mine, but since mine actually seemed a little simpler, the best thing I took away from his directions is that it's something you can do on your own kitchen table (I'm the king of my castle... when my wife's not at home)

My 15-year-old son helped me through the whole process.

ONE THING, though, that Kev does not show or tell about in his instructions is that the diaphragms need to be "pre-loaded" before screwing down the fuel and air bodies.
If the fuel casting screws are tightened while the diaphragm assemble is relaxed, it will tend to get stretched (when put into service) to the point of elongating the screw holes in it, and eventually the material will fail causing a leak. This is more important on the fuel side than on the vacuum side.

To "pre-load" the diaphragm, you want the assembly (rocker arm) pulled down as far as it will go before tightening the screws. On the vacuum side you only want to bring the arm far enough to see the diaphragm material flatten out between the two castings before tightening the screws.

The other important thing in rebuilding a fuel pump is making sure the casting mating surfaces are flat. With time, and pressure from the parts being screwed together, they tend to warp, causing leaks.

It's a simple procedure. We used 220-grit dry sand paper and a flat surface dragged the bodies in a circular formation until all points were touching.

Here's the page on my restoration blog where I discuss:
https://packardinfo.com/xoops/html/modules/newbb/viewtopic.php?topic_id=4307&viewmode=flat&order=ASC&type=&mode=0&start=90