ok long story here. I'm running an electric Edelbrock fuel pump and Holley regulator. What happens is after driving for say a 1/2 hour on the highway and I slow down to turn off I'll loose fuel pressure, drops from 6 psi to 3 or so and then starts bouncing around and will eventually go back to 6 psi for a bit and will then drop down again. I've got full voltage at the pump relay, tried another relay and no difference, tried another known good Edelbrock pump of the same type and same deal, also tried another known good regulator and same deal. Pump seems to flow ok at the outlet and after the regulator, doesn't seem to be a restriction in the tank but I did notice that it seems start doing this after I slow down from highway speed to make a hard right hand turn off the highway. Has a new pick up in the tank as well. Voltage on my gauge is 14.5 all the time. Never had it happen on short trips. What else should I be looking for? This is a 406 with Tunnel Ram and Eddy Carbs and no fuel return. Thanks for any help.
How much fuel in the tank ? The fuel will slosh around and have points of no fuel at the tank pick up and the pump gets a big gulp of air before the fuel returns.
The air won't come out until it gets to the carb and will disrupt the fuel gauge until it all passes by and is replaced with fuel.
I bet if you stand on it real hard as if you were racing it will do the same thing right after launch or just after a hard shift.
There maybe another issue, but the above scenario is very common with lower fuel amounts and no baffling in the tank.