mech. fuel pump variation

[longbedrick]

installed a fuel pump on a Big Block '69 El Camino a while back, and noticed there was (1) inlet and (1) oulet on the mechanical fuel pump. On my '73 Big Block 454 it seems there are (2) inlets and (1) outlet. Why the variation? my truck has dual tanks. there are 3 ridgid lines running from the two tanks. (2) lines to the pump, one line to the charcoal canister

Here's mine on the '73

[Prong]

The third line is the fuel return (1/4" dia hose). It'll either run to the switching valve (on a dual tank setup) or to the sender on the fuel tank itself (single tank configuration).

[gchemist]

All I see is dirt. LOL

[longbedrick]

in order to test the fuel pump, do i plug off the return line? thinking of purchasing a fuel pressure gauge to check pressure on pump. i put my finger over the line to carb inlet, and could BARELY feel anything. how much pressure should I read on a gauge?

[longbedrick]

found a Chiltons manual for 80-87 GM trucks. fuel pressure psi for 80-81 454's is 7.5-9 psi. 84-86 454's is 9.0psi. safe to say the same for a 1973 big block?

[gchemist]

Yes, if the pump is old replace it.

[longbedrick]

bought a new vacuum/pressure gauge (all non AC DELCO handtools 50% off while supplies last at Kragen). fuel pump is pushing only 1 psi.
1.)can I use a fuel pump with NO return line and block off the return?
2.)do I absolutely have to have a return line?

[gchemist]

No you don't need to have the return. However you should use a return style pump. A new fuel pump is not expensive.