[RichardJ]

The pump arm on a L6 pump runs directly on the cam lobe. No push rod.
As with any leaking fuel pump, sniff the oil on the dip stick. The gas can run into the engine and you need to change the oil and filter. NOW.

The old pumps i have pulled off had a tab riveted to the pump arm. I believe it to be a sacrificial metal to prevent wear on the cam pump lobe. The new Carter pumps don't have the tab. I spent time finding out that Airtex pumps still have the tab. i spent more time and gas getting an Airtex from the Truck Shop. I tested it before installation and found that the pressure dropped between successive pump strokes.

I then bought a Carter from NAPA. It pumped to 4 psi on the first stroke and stayed there on every successive pump cycle.