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Fuel pressure keeps dropping - HELP

2019 Views 21 Replies 10 Participants Last post by  MadMonte
My fuel pressure is set at 7lbs at my gauge on the cowl. It was set at 1500 rpms as per Magnafuel. While running, whether it's racing, street driving or just idling the pressure will drop below 4lbs.
Description of the system:
Aluminum fuel cell
#12 line from cell to pump
Magnafuel 500 filter and pump unit
#10 line to Magnafuel log and regulators
#6 line going to the carb and plate.
Power comes from twin relays mounted near the battery next to the pump
so there's no volt or amp loss.
Autometer Procomp liquid filled gauge.
I've double/triplle checked everything I can think of.
Any ideas would be appreciated.

Thank you - Steve
1 - 20 of 22 Posts
does your gauge zero? what fuel? check the filter?
Vent line or no vent line?
Are you running pump gas with foam in the cell ? Dirty filter ? Old pump ?
GAUGE?
#8 vent, Filter looks clean, not a spec, Race fuel with foam in the cell, I was thinking may gauge but the car feels flat as the pressure drops.
i had the teflon plungers swell in the reg...
do you know how to purge a liquid gauge?
i had the teflon plungers swell in the reg...
do you know how to purge a liquid gauge?
I"ll Check the plungers and no I don't.
Might try the guage,just went through this.Replaced,pump,lines and other stuff to find out that 2 guages were bad.A new guage and my old one.They did fine till bout 3 min of running time and started to creep down to 4# and lower.
Its prolly bypassing too much fuel otherwise...
-8 vent is to small for -12 supply
theres usually a rubber plug on the back...drain a little glycol or air out...needle should move...
They can move from heat.. it may have been wrong when you set it...
This goes for any liquid filled gauge that sees heat...
-8 vent is to small for -12 supply
Good point.
its actually a -10 supply
-8 vent is to small for -12 supply
Does it idling. Should enough vent.
theres usually a rubber plug on the back...drain a little glycol or air out...needle should move...
They can move from heat.. it may have been wrong when you set it...
This goes for any liquid filled gauge that sees heat...
I'll try that too. Thanks
Liquid filled gauge is my bet. Change that and I bet you'll find your problem.
Liquid filled gauge is my bet. Change that and I bet you'll find your problem.
Gonna order one right now without liquid.
Dont rule out the poss. that your bypass is wrong either...
1 - 20 of 22 Posts
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