Grimace5.0

Ok, so as I drive down the road loading the engine I have 6-7 PSI of fuel pressure. At idle or coasting it's all over the place, sometimes as low as 3 PSI. When the engine is under load, like when I drive down the road the pump sound is smooth and one pitch. At idle it sounds different. My thought it that it either is not getting enough power at idle or I need a return line to the tank. Plus tonight I put a clear fuel filter near the carb to observe fuel delivery and the darn canister for the filter barely has any gas in it. The reason I mention the low power possability is because I have a electric fan and water pump. Your thoughts?

306
BG 650 carb
New Holley red electric pump
3/8" hose from the tank to a filter, then to the pump.
3/8" hose from the pump to the stock fuel line right in front of the tank.
From the stock fuel line in the engine bay I have 3/8" hose to another filter to the carb.

marx91

what amp alt. are you running?

HACKGT350

i was going to say the same thing what amp alt are you running

Grimace5.0

I don't recall. I was just telling my G/F we should run over to the garage and get my other one. I know it's atleast a 100.

HACKGT350

your alt is def not big enough. they say to upgrade your alt to a 130 when you do an electric fan and you have an electric water pump on top of that you should def get a 130 or higher alt.

meiguoren33

Get a volt meter and measure batt voltage as well as voltage at the pump at idle, they should be nearly the same. Did you use big thick heavy gauge wires on the pump to eliminate voltage drops? Is the ground to the pump a really, really, good ground? Is the fuel pump relay a good quality relay? Voltage drops in the FP wiring are probably the culprit.

Grimace5.0

I used 12 ga wire, soldered all connections and sanded ground points. I was trying to eliminate as much drop as possible.

meiguoren33

As a diagnostic tool, I'd take the tank out, duct tape it to the roof, run garden hose to the carb, and gravity feed it. Otherwise, is wiring to the relay good and solid? if the voltage into the relay is too low, it'll open, and quit providing power to the pump. Best to measure voltage at the pump with a volt meter.

Grimace5.0

Heres is what I did tonight. I put the 100A alt on. I used a volt meter and checked where I have the power to the pump ( ign solenoid ), 13.xx volts. So on a experimental basis I checked the charging post? on the alt, it read 14.xx volts so I rerouted my power for the pump to it. By the time I was done it was dark so I said F it for the night. We'll see what happens tomorrow. I think it might be that the pump is located too high. Or I need a return line. I don't know....

HACKGT350

where did you mount yours?