fuel pump question

so my BG400 went bad and i replaced it with the magnafuel prostar 500 , on every pass that i made when i decelerated my carb fuel pressure spiked to 12psi and stalled the car . do i need a different regulator ? or is there something else going on

Dirt? Degraded hoses?

The Magnafuel I put on my Tbird is a 300 series and I had to turn the bypass regulator way back on it. It had so much pressure it was bouncing the hand on my pressure gauge so much I couldn't read it. I'd bet I turned at least 3 or 4 full turns back. And it still has alot of pressure.

bruno wrote:so my BG400 went bad and i replaced it with the magnafuel prostar 500 , on every pass that i made when i decelerated my carb fuel pressure spiked to 12psi and stalled the car . do i need a different regulator ? or is there something else going on

My gas carb used to do that, and Lem fixed it with the air bleeds on top.

Air bleeds won't fix 12 lbs. of fuel pressure blowing by a gas needle valve and seat

56Tbird wrote:Air bleeds won't fix 12 lbs. of fuel pressure blowing by a gas needle valve and seat

I'm sorry, Fix my car

What reg are you using for the carb and is it a deadhead style?

richter69 wrote:What reg are you using for the carb and is it a deadhead style?

Was about to ask the same question. I'd assume a large pump like that would require a return style. What size supply and return lines Nick?

Negative G's forcing MORE fuel to the front of the car?

Is the return line from the pump hooked up?

jbozzelle wrote:Is the return line from the pump hooked up?

yes that is hooked up

D. Sea wrote:

richter69 wrote:What reg are you using for the carb and is it a deadhead style?

Was about to ask the same question. I'd assume a large pump like that would require a return style. What size supply and return lines Nick?

Negative G's forcing MORE fuel to the front of the car?

and then as soon as the fuel pump picks up the fuel it bangs the shit out of the regulator ....thats my thought also

richter69 wrote:What reg are you using for the carb and is it a deadhead style?

yes the reg to the carb is a dead head style ........ the first reg for the plate i made a return line with a .016 jet

Clean everything out and look at the hoses real close if they are more than 5 years old thing about replacing them.

Are you sure the pump is not cavitating from loss of fuel on deceleration?

Mine was bouncing the gauge so bad I couldn't read it.I called Holley and the tech told me the reg. was not big enough to handle all the pressure and it was bouncing the spring, or the spring in the reg was weak. I changed reg.and it stopped.

if your still on 16 volt call MF and tell them whats up, they will prolly send you a lighter spring and or have you enlarge the hole in the poppet on the pump return. Even when I had the bigport MF regulator I had it hang up once coming out of the waterbox and flood the motor..............this was on gas.

richter69 wrote:if your still on 16 volt call MF and tell them whats up, they will prolly send you a lighter spring and or have you enlarge the hole in the poppet on the pump return. Even when I had the bigport MF regulator I had it hang up once coming out of the waterbox and flood the motor..............this was on gas.

the funny thing you say that the next day i ran a 12 volt deal and didnt have that issue , thxs Jon

I had mine on 16 as well when it had the issues, the pump bypass struggles with the added gph of the bigger voltage. Again call MF and get their opinion on how to resolve it.

I just installed a voltage reducer to the pump. with 16 volts I couldn't get the fuel pressure under 9 psi with 12 volts all was ok

if your regulator is too small it means you're not making enough PAH!!!

Hi Bruno! I have the same Prostar 500 pump in my Fairlane. I bought a like new 500, Magnafuel regulator, and a bunch of stainless lines and fittings for a song and a dance. It's total overkill for my car, but the price was right! I have my pressure set at 7psi, and when I ran a temporary outside gauge to check it to 6500rpms, it never moved, even with my foot off the gas. I'm thinking it's your regulator too.

Here's a couple pics of what the pump/regulator look like in my Fairlane. I have -12 out of the fuel cell into a filter and into the pump. The top line is the -08 bypass to the fuel cell, and the bottom line is -10 to another filter, then the regulator under the hood. I have two -08 lines to the carb. All I need now is another 200HP to use all of this.

patfromjersey wrote:Hi Bruno! I have the same Prostar 500 pump in my Fairlane. I bought a like new 500, Magnafuel regulator, and a bunch of stainless lines and fittings for a song and a dance. It's total overkill for my car, but the price was right! I have my pressure set at 7psi, and when I ran a temporary outside gauge to check it to 6500rpms, it never moved, even with my foot off the gas. I'm thinking it's your regulator too.

Here's a couple pics of what the pump/regulator look like in my Fairlane. I have -12 out of the fuel cell into a filter and into the pump. The top line is the -08 bypass to the fuel cell, and the bottom line is -10 to another filter, then the regulator under the hood. I have two -08 lines to the carb. All I need now is another 200HP to use all of this.

Real nice setup!
Gary