Crazy fuel issue that’s got me stumped…

[72BIGBLOCK]

I had issues with the Holley pump too until I added a relay.

 

[DarthVega]

Had similar problems with blue pump also wired via relay powered directly off the trunk mounted battery going from 8 psi and slowly moving down to nothing at idle. Added a primary in tank pump and presto fixed it- best I could figure it must’ve began to cavitate when fuel was deadheaded and adding the extra 3 or 4 psi ahead of the holley stopped it from happening. Would probably have never occurred with a return line regulator system and it could also have something to do with today’s ethanol gas mix but I chased it for a while until I decided on the in tank pump. Also the fuel cell I have in the trunk has a top side fuel outlet and the holley blue is mounted underneath the floor behind the differential- lowest place I could put it so I always had concerns about it’s ability to pull fuel from the tank anyway as they’re much better at pushing it.

 

[Ratty_81]

Never had a problem with the Blue pump I put in late last year, but that said, my new motor is getting a Baker Pro-Cam mechanical pump.

 

['70 Z/28 RS]

I just went thru this recently, but my fuel pressure would only drop during hard accel, freeway on ramps. "Spirited driving" usually, but sometimes just cruising on the highway.
Pulled my hair out checking the fuel filter, changing pumps, etc. I disconnected the fuel line at the carb to drain the tank and when I turned on the pump, it barely trickled out. Turns out my Earls sintered bronze filter was full of non visible crap causing a restriction. Threw in a plastic see thru unit and it ran like a champ.

I had never floored mine until last weekend. When I did (in 3rd and 4th gear), it was like it was farting or something while trying to top out, kinda airy sounding. Like it was trying to get there, but something just ain't right. It's all stock with a more modern Holley carb on it, as my 780 carb is getting rebuilt. As far as I know the wires and plugs are good, but will check the plugs soon. It's always hard to start though, after setting for a week or two.

Runs fine at lower speeds though, but haven't floored it in 1st or 2nd gear yet. Only does the the weird stuff when I floor it in 3rd and 4th. Just doesn't want to top out fully, so I just let off the pedal. I still have the brass stone filters, but they are new, so no problem there. They can't be clogged yet.

 

[larryf3918]

I had that problem when my battery voltage would get low

 

['70 Z/28 RS]

Low battery voltage can affect your car, making it sputter, etc.? I don't really understand how that one happens. Still a lot of things I'm not aware of yet on these cars. Guess I'll check out my voltage gauge on the next drive then.