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UPDATE! Boost referenced Regulator and pump Voltage ?
Hello,
Problem is Im not seeing 1:1 with fuel pressure and my brand new Aeromotive regulator.
QUESTION: Is 12.8 volts while in boost WOT good or no? Thats the voltage to the pump.
Cruising, voltage is 13.2 voltage then drops to 12.8 while WOT.
Last edited by 30th t/a; Apr 24, 2026 at 04:30 PM.
According to flow charts, that difference in voltage (if that is really what the pump is getting) should make very little difference. Are you sure the secondary pump is actually turning on?
According to flow charts, that difference in voltage (if that is really what the pump is getting) should make very little difference. Are you sure the secondary pump is actually turning on?
Heres what i know for sure.
At Idle, When I jumper the hobb switch wires together,
the fuel pressure goes from 50psi to 65+psi, and I can hear the 450 running. I pull the vacuum line off and reset my base pressure.
I did a WOT pull with the switch wires jumpered and fuel pressure was worse! It wouldn't even break 60psi.
With the wires jumpered together I checked power at the 450 pump at idle and it showed 13.5 volts
I have not checked power at the 450 pump during a wot pull.
Also, duty cycle using the hobb switch = 99%
fuel pressure using hobb switch = 64psi
Duty cycle with both pumps on all the time 82%
fuel pressure with both pumps on = 58-59psi
New aeromotive 13139 regulator and vacuum block LS3 fuel rails, FIC 1200cc injectors Ls3 fuel rails with two -8 fittings welded on Walbro 535/450 into a -8 Y fitting Modified fuel bucket. No socks for test run. -8 feed fitting -8 feed line and inline fuel filter OEM fuel filter removed and fuel hose and fittings in place T block with OEM return port capped off LS3 fuel rails with two -8an fittings welded on
New aeromotive 13139 regulator and vacuum block LS3 fuel rails, FIC 1200cc injectors Ls3 fuel rails with two -8 fittings welded on Walbro 535/450 into a -8 Y fitting Modified fuel bucket. No socks for test run. -8 feed fitting -8 feed line and inline fuel filter OEM fuel filter removed and fuel hose and fittings in place T block with OEM return port capped off LS3 fuel rails with two -8an fittings welded on
A couple questions, comments.
1. Have you pressure tested those hard plastic feed lines to see if they leak at elevated pressure? If not, that's where I would start.
The basis for the ?: "I did a WOT pull with the switch wires jumpered and fuel pressure was worse! It wouldn't even break 60psi."
2. Pumps of that capacity and a return line designed for a system 1/4 of that flow, is a restriction at the rail & is a "pinch point" that could cause fuel heating.
How is the tank vented?
A couple questions, comments.
1. Have you pressure tested those hard plastic feed lines to see if they leak at elevated pressure? If not, that's where I would start.
The basis for the ?: "I did a WOT pull with the switch wires jumpered and fuel pressure was worse! It wouldn't even break 60psi."
2. Pumps of that capacity and a return line designed for a system 1/4 of that flow, is a restriction at the rail & is a "pinch point" that could cause fuel heating.
How is the tank vented?
I have not pressure tested the fuel lines coming off the pumps.
I jumpered the hobb switch wires to see if maybe the switch wasnt activating the 450 to come on.
If im understanding the return line correctly, if it was too small, I would have too much pressure. I had no problem getting my base fuel pressure set to 58psi.
I went with -6 combined with using the OEM feed based off of other people's experiences and having no issues.
As far as the tank being vented, honestly never looked into it. I do believe all the evap stuff has been removed by the previous owner. The evap line is still in place but it's just an open line in the engine bay.
My goto is the pump/line pressure test. That's first.
Don't think I'd use gas as the fluid, due to a fire hazard.
I use a "Stoddard solvent" type flow fluid in the inj bench.
As for the return, it may be allowing enough flow but can cause excessive heat.
Check the vent.
My goto is the pump/line pressure test. That's first.
Don't think I'd use gas as the fluid, due to a fire hazard.
I use a "Stoddard solvent" type flow fluid in the inj bench.
As for the return, it may be allowing enough flow but can cause excessive heat.
Check the vent.
Is that 1/8" white nylon FUEL PRESSURE line going through the firewall, into the cab ?
If that IS a fuel pressure line in the cabin, I strongly recommend it's immediate removal.
Is that 1/8" white nylon FUEL PRESSURE line going through the firewall, into the cab ?
If that IS a fuel pressure line in the cabin, I strongly recommend it's immediate removal.
Look closer. That is a vacuum line off a vacuum distribution block.
Is that 1/8" white nylon FUEL PRESSURE line going through the firewall, into the cab ?
If that IS a fuel pressure line in the cabin, I strongly recommend it's immediate removal.
Tested my fuel pumps today and found out that my 535 is under performing big time. Pumping for 1 minute the 535 only pumped about 1 gallon. I then Tested the 450 and it did about 2 gallon in one minute which is right on par.
Those are free flow numbers.
What's the answer to No Juice's question?
Testing the free flow does nothing toward checking for the leaks I asked about in a previous post.
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UPDATE! Boost referenced Regulator and pump Voltage ? 
