This part is wired in line on the negative ground wire to my fuel pump. What is its purpose? My newly installed fuel pump works fine without it. Any ideas?

 

It might be a capacitor, Dubilier makes these, and used for noise suppression????

 

Valerie got it right. It's for noise suppression and common on cars of that era to avoid static on AM radio.

 

. . . and your somewhat fuzzy final pic shows that it is of 1uF capacity, rated to a max of 150V DC working voltage.

Cheers and best wishes,

 

Most electrical parts past the easy, common things are past my pay grade so I’ll try the new fuel pump and radio at the same time and see how it goes. If I get any radio static I’ll install the capacitor but wonder if it will be necessary since my distributor no longer has points installed.

 

But your fuel pump has points, and produces RFI
.

 

Just did some looking closer so all this may be a mute point.

Based on the product specifications, this pumps is a "Gerotor" style pump design, which is an internal rotor system - not traditional points.

Gerotor pumps use a pair of rotating gears (an inner rotor with external teeth meshing with an outer rotor with internal teeth) to create the pumping action. This is different from older mechanical fuel pumps that used contact points and diaphragms.

 

I sure wouldn't use this old capacitor... god knows what condition it's in a this point in its life!

 

I temporarily wired and plumbed both a fuel pump with points and the one mentioned above with no points and neither one caused static on my AM radio so all is good.

 

Valerie's point is entirely correct.
Caps this old should be scrapped as a routine.
All of them . . . I hate 'em. Chuck 'em out!
If they fail "open" then they contribute no benefit.
But, if they fail "dead short", they can send you down a rabbit hole of frustrating fault finding.

The only essential cap straddles the points in cars still using OEM "old technology". These and the RF suppression caps fitted in AM radio days have all outlived their lives. They are now enjoying that stage best known as death! Best advice for ignition points caps; replace them. For RF caps; chuck them. I defy you to tell the difference in today's radio broadcasts. Have we not switched to FM . . . or digital?

During ground up overhaul of my very first 50s Jag (avatar), the highly modded XK engine refused to fire. Day after day went by and my Jag went nowhere. Close to giving up, my throw-away, last ditch, Hail Mary, saw me replace the OEM capacitor in otherwise fully re built dizzy. You guessed it . . . new capacitor had that bored and stroked XK engine roaring at first attempt. Subsequent test showed OEM cap had failed, partially dead shorting the points. "Partially" is critical . . . enough for a spark on the plug by rocking the dizzy near TDC but, as I later learned, that first spark forced a breakthrough in the cap's dielectric and shorted further sparks. Result? One nice spark to fool me into thinking I had HT, but thereafter, effectively dead points, coil and plugs.

Cheers and best wishes,