1938 Century fuel pump question

[Guest Gene P]

I just installed a new AC fuel pump on my 1938 Century. When I started to connect the lines to the lower unit, vacuum, I realized that unlike the old pump, the new pump has an additional threaded port. One port labeled "in", one labeled "out", and the third with no label. My first thought was to "plug" the third port, but I decided that before I possibly damage a new pump, I might be smart to ask for some guidance.

Thanks for any info, Gene

[jenz38]

I think there on is a short open Tube for that the Diaphragm Backspace can breath. I would try to suck on it with my Mouth for where it goes throu,when there is nothing without a little moving from the Diaphragm ,then i would try it in the Car while Engine runnin'.

I woud try this Way.

Hope this helps...

Edited November 12, 2012 by jenz38 (see edit history)

[Guest Gene P]

I think there on is a short open Tube for that the Diaphragm Backspace can breath. I would try to suck on it with my Mouth for where it goes throu,when there is nothing without a little moving from the Diaphragm ,then i would try it in the Car while Engine runnin'.

I woud try this Way.

Hope this helps...

I suppose I could connect an extension tube to the port and see what happens when the engine is running. It just caused some concern on my part since the two old pumps I have don't have this port. The pump was labeled for "60, 80, and 90 series".

Thanks for your suggestion.

[Mark Shaw]

Some fuel pumps have a vacuum port to increase and even out the vacuum for wipers etc...

I am not at all sure this was done for this year and model.... but it could be a retrofit.

[idrjoe_sandiego]

Gene, I just went through this. Take a look at my thread here on this forum: http://forums.aaca.org/f165/1937-buick-90-limited-vacuum-line-338098.html The info in my last entry (dated today 11-19-2012) should help your cause. Joe