Fluctuating fuel pressure

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Fluctuating fuel pressure

Post  Tore on July 4th 2010, 4:43 pm

I have a Holley Black pump and I can set the regulator at 7 pds come back tomorrow and it can be at 9 or 11 pds or it might be down to 5pds. What gives? Its a new regulator and I am dead heading the pump. I dont have a volt regualtor on the pump. When I hook a big battery charger up to the car you can hear the pump pick up but the pressure doesnt increase.

Thanks Tore

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Re: Fluctuating fuel pressure

Post  richter69 on July 4th 2010, 7:28 pm

what regulator?
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Re: Fluctuating fuel pressure

Post  Lem Evans on July 4th 2010, 7:47 pm

You thinking reg. creep?

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Re: Fluctuating fuel pressure

Post  DFI429 on July 4th 2010, 8:37 pm

Two questions...

Are these pressure readings taken after just turning the pump on & not flowing anything?

What kind of fuel pressure gauge are you using (liquid-filled under the hood, in-car, non-liquid..)?

The liq-fil stuff is really affected by heat - especially under the hood. I've seen 'em influence the reading 4psi Shocked
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Re: Fluctuating fuel pressure

Post  Tore on July 4th 2010, 8:58 pm

richter69 wrote:what regulator?

Its an aeromotive SS regulator.
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Re: Fluctuating fuel pressure

Post  Tore on July 4th 2010, 8:59 pm

Lem Evans wrote:You thinking reg. creep?

Thats a good question never have had this problem before.
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Re: Fluctuating fuel pressure

Post  Tore on July 4th 2010, 9:03 pm

DFI429 wrote:Two questions...

Are these pressure readings taken after just turning the pump on & not flowing anything?

What kind of fuel pressure gauge are you using (liquid-filled under the hood, in-car, non-liquid..)?

The liq-fil stuff is really affected by heat - especially under the hood. I've seen 'em influence the reading 4psi Shocked

Up until yesterday the only gauge was in the engine compartment and that is liquid filled, But I installed a gauge on the hood so I can see it driving.
It makes no difference if I am flowing fuel or not. Right now its set at 8 pds, I guarantee I can let the car sit and it will be off 2/4 pounds either way if I fire it Tuesday. If its not one thing its another.

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Re: Fluctuating fuel pressure

Post  richter69 on July 4th 2010, 9:11 pm

In detail describe the whole fuel system.
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Re: Fluctuating fuel pressure

Post  Tore on July 4th 2010, 9:16 pm

Fuel cell, single 5/8 line going into canister filter, new element, 5/8 line going to pump, 5/8 line going to to cool can, then 1/2 line out of can to regulator and 2 lines going into dominator.

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Re: Fluctuating fuel pressure

Post  richter69 on July 4th 2010, 9:19 pm

if the gauge is right either the reg is wacked or the return in the pump might have some stuff in it..........reg could have trash in it too, or one or both are junk.

How much motor you trying to feed with that pump?
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Re: Fluctuating fuel pressure

Post  Tore on July 4th 2010, 9:26 pm

514 ci, I had a Holley volumax on it 160 thats what I ran in my torino and it didnt run any difference.
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Re: Fluctuating fuel pressure

Post  Tore on July 4th 2010, 9:27 pm

richter69 wrote:if the gauge is right either the reg is wacked or the return in the pump might have some stuff in it..........reg could have trash in it too, or one or both are junk.

How much motor you trying to feed with that pump?

What do you mean by the return in the pump?
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Re: Fluctuating fuel pressure

Post  richter69 on July 4th 2010, 9:44 pm

I've had better luck running too much pump as opposed to not enough, but thats doe another thread. That pump has a bypass regulator in it, I think they are sprung at 14 psi if I remember. If its got trash in it it will not allow the deadhead regulator to work properly.
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Re: Fluctuating fuel pressure

Post  Tore on July 4th 2010, 10:01 pm

Well thanks for the info on that, Looks like one day this week its coming apart.

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Re: Fluctuating fuel pressure

Post  69F100 on July 5th 2010, 10:32 pm

I have a black pump on the ranger I got from Rick aka 557 mazda had the same thing happen take the screw out of the pump and spring and clean it if it get alittle trash in it it will act up like that mine was going way up until he cleaned it and it started working right
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Re: Fluctuating fuel pressure

Post  Tore on July 6th 2010, 8:34 am

I am going to try that later today,

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Re: Fluctuating fuel pressure

Post  69F100 on July 8th 2010, 7:53 pm

Tore you get it fixed
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Re: Fluctuating fuel pressure

Post  Tore on July 8th 2010, 10:14 pm

Right now I will say yes. I took the pump apart Wednesday and found some dirt in the filter screen not alot but who knows. I reset the pump and will go out tomorrow and turn it on and see what happens. I am going to try the car Sat if I can find the time and see how it works.

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