Fuel pumps interchangeable ?

[mellie]

Just wondering if these are interchangeable - both came off  218's but the radical difference in pump arms has me wondering - just hit the lobe differently?

[Sam Buchanan]

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Edited December 17, 2022 by Sam Buchanan

[Bingster]

I've just been through the project of rebuilding the fuel pump off my '47 DeSoto Custom. I did a lot of research on these type of pumps and in my travels I came across a series of great videos by the owner of Then & Now, who sells rebuild kits for the pumps. They are first rate. Anyway, he shows how to rebuild various models of these pumps. In fact, I believe your pump with the glass bowl on the bottom is the same type as mine.  Maybe a 588? Anyway, it's a good chance you might see your pump arm in one of the videos. I'd go on the YouTube site and enter Then & Now or Rebuild Fuel Pumps or both. Good hunting.

[mellie]

Thanks. I’ll have to check out videos. The top one is tagged 587 which came off engine now in car. I would like to use the bottom one (no tag) as it matches up with fuel lines etc from removed engine. From what I can gather the top one is from earlier vehicles but researching if they can be swapped without issue. 

[Los_Control]

I do not know the real answer to your question ....

Looking at the photo, seems they are made from different manufacturer's .... Trying to picture the cam lobe turning in the engine operating the pump.

Seems the top one the lever pushes up.

The bottom one pushes down.

Is one design better then another?

 

I can only think about installing a pump holding it with your left hand with no bolts installed, while rotating the engine by hand with your right hand.

I would slowly rotate the engine looking for the spot with the least resistance on the lever. Where the high point of cam lobe is away from pump lever.

Probably still be some resistance on the lever holding the pump away from block.

 

Then I would do the same with the other pump & compare the least resistance between the two pumps.

The cam lobe does not change so they both will get pushed just as far .... so long as they are both starting at the same low point.

 

I only see a problem if you find the low point on 1 pump, & the pump is held 1" away from the block .... the other pump is 1/4" away ...

I would think that the 1rst pump would never release enough to get full stroke.

 

In real life, I would just grab the pump I wanted .... bench test it just to make sure I hear sucking sounds .... & install it.

Chances are if they have not been rebuilt with modern rubber for modern fuels, you will be visiting this area again soon.

With a new pump with a different design.

[DonaldSmith]

It looks like one pump has the arm riding on top of the cam, the other on the bottom. 

Look at the pivot points, and the angled ends of the arms.

[mellie]

Yes looking at the rub spots the top lever pushes back towards pump where as the other (588?) goes under the lobe. They both feel/sound good and various posts seem to indicate a transition between the two in about ‘39 or ‘40. I think I’ll do what Los control suggested and bolt in the one I want and take it from there. 
What could possibly go wrong…. 
Thanks for the info!

[andyd]

The cam lobe doesn't care where the pump arm hits it so long as it does........I'd use whichever one fits the fuel lines......andyd