OT: update on fuel starvation question.

[Slowpoke]

The '76 Chevy van 350 engine has has the fuel pump replaced, tank cleaned, and several new hoses. The fuel pressure gauge needle vibrates rapidly between 3 & 9 psi at idle. Higher rpm improves it only slightly. I can bend the guage hose back on itself to change the reading. Completely bent over and the reading is a steady 10psi. Less bend and the reading can be made to sit rock steady down to about 6psi. After that, the rapid pulses increase.
(I once had a 12 volt air compressor with a 300 psi gauge, and I changed it to a 100 psi gauge. It vibrated like crazy until I experimented with plugging the nipple with epoxy and drilling the tiniest hole thru the epoxy.)

I've used this fuel pressure gauge before on other vehicles and had steady pressure.
Is the problem with the new fuel pump? Or could it be a worn cam and/or pump rod?
The vehicle seems to run OK.

 

[ASEguy]

If you're certain you have clear lines, you may have a short fuel pump rod. I have replaced several years ago, though I can't remember the correct length. If you find they are tricky to install put grease on the rod to keep it in place during assembly. I can't remember a cam with a worn out fuel pump lobe.

 

[Slowpoke]

The instructions with the pump say to use a hacksaw blade to hold the rod in, but it didn't work for me, so I did use grease and it stayed in. The rod is original and doesn't seem to have wear.
Maybe I'll put the old pump back and see if the pressure remains steady.
Slowpoke

 

[ASEguy]

It doesn't take much wear to cause a problem when you have a high demand for fuel. If it's worn 1/4 inch I would replace it. I'm not saying the cam can't be worn, just that I haven't seen it. The fuel pump lobe doesn't have the same load on it that regular cam lobes do so I have never seen one bad. If the old rod was shorter drive it with the new one in and see if there is some improvement in driveability.

 

[ASEguy]

Basically with a cold engine(we don't want a fire) and ignition disabled you should be able to fill a quart jar in about 10 seconds of cranking. Cranking any longer can ruin a starter. If you get 3/4 of a quart that should be good.

 

[ASEguy]

Sorry I didn't see the part about it runs ok...problem solved

 

[Bob]

"it runs ok...problem solved"

Da DING!

We have a WINNER!