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Got a 1980 vette with built SB 350 , 10.6 compression I just removed Holley fuel pump that we deadheaded the return .... was never happy seeing 7 psi sitting at the carb for weeks or months ... Last weekend I installed factory style pump (Delphi) with return . after bending a new 3/8 stainless fuel line and testing return line after 10 yrs its clear able to blow air thru to the tank . Is it normal for the pressure gauge to read 4 psi when the car is not running ? is there a check valve in the fuel pump return ? and my gauge is very erratic when running 4-7 psi . any Ideas ? would think the gauge would be at zero.
The erratic gauge is probably caused by the fuel pulsating because of the pump. I put a liquid-filled gauge next to the carb. The liquid/oil stabilizes the needle.
At work we have those liquid filled gages but the heat from the surrounding area causes the liquid to go from clear to brown over time. It may be the type of liquid they use but I would think that the engine compartment would be the same or worse from a heat perspective. We also have some applications where they use snubbers in the fitting to the gage to dampen pulsation.
Last edited by ddsmith60; Sep 24, 2021 at 10:16 PM.
2020 Corvette of the Year Finalist (performance mods)
2019 C3 of Year Winner (performance mods)
2016 C3 of Year Finalist
theres nothing wrong with the fuel pressure staying at 4 pi and in fact you want it to. Without the back flow prevention you have the possibility of your float bowls being siphoned back through the fuel line depending on the carb and the problem of hard starts. THere are tons of threads on people whining about that. Be happy that you dont have a fuel issue. And I always had a liquid filled gauge after my regulator and it didnt bounce but the gauge needed an atmospheric purge valve to release pressure internally from the heat build up prior to start to equalize it to get and accurate reading before the engine compartment heated up again.
2020 Corvette of the Year Finalist (performance mods)
2019 C3 of Year Winner (performance mods)
2016 C3 of Year Finalist
you only want 4 to 6 psi on those old style carbs and the pumps they sell now a days are all over the map in pressure. I run one to see what the pressure is and to tell when the pump is starting to **** the bed so I can change it...its a Carter pump thing. And a regulator is never a bad idea
I had a regulator and a gauge on my car for a while. Once you check your pump for correct pressure,,,, none of it's necessary. Just extra stuff to go wrong.
Thanks Guys , Im going to order a liquid fill gauge . I didn't know if it had a check valve or not . I do feel better not seeing 7 psi at the carb when its not running . I cant even see were I could put a regulator . I have seen were it can help to reduce the gauge bounce . buy turn ing it down to 6 or 6.5 psi
Last edited by scottred80; Sep 25, 2021 at 11:17 AM.
FUEL PUMP and Return Question
