Fuel pressure question

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Fuel pressure question

Post  blu69MachI on Sat Jun 25, 2016 1:25 pm

I don't know if this is something to worry about or not. But I have a fuel pressure gauge coming off of my Holley regulator with vacuum port. It reads 7psi at idle if I rev it up it drops to around 3. The regulator vacuum port is going to the base of my E85 SV1. I have one side of the regulator going to the carb and the other going to the the fogger system. Overall the car is running great but I want to spray it soon so I was just going over things and found this. I have a Magna Fuel 500 pump. Will it make a difference between the car being in Park vs. WOT with a load? Or maybe I just need to try a new pressure gauge? I thinking I need to get a new gauge for in the car. Thanks in advance, for any insight.

-Jeff
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Re: Fuel pressure question

Post  69F100 on Sat Jun 25, 2016 2:13 pm

blu69MachI wrote:I don't know if this is something to worry about or not.  But I have a fuel pressure gauge coming off of my Holley regulator with vacuum port. It reads 7psi at idle if I rev it up it drops to around 3.  The regulator vacuum port is going to the base of my E85 SV1.  I have one side of the regulator going to the carb and the other going to the the fogger system. Overall the car is running great but I want to spray it soon so I was just going over things and found this.  I have a Magna Fuel 500 pump. Will it make a difference between the car being in Park vs. WOT with a load? Or maybe I just need to try a new pressure gauge?  I thinking I need to get a new gauge for in the car. Thanks in advance, for any insight.

-Jeff

The mallary I had with the vacuum port was not vacuum activated it was boost activated. Mine would do just like what you are saying yours is doing. Pull the vacuum line off the carb with the engine running try blowing in the vacuum line and see if the pressure goes up, if it does then it is a pressure activated. I just left the vacuum line unhooked and set it at 7.5psi I was running a1050 alky carb on my 552 without any problems.
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Thanks!

Post  blu69MachI on Sat Jun 25, 2016 7:19 pm

I started the car and gave it a quick rev and it dropped again. I blew into the hose and it pretty much stayed the same. After blowing into the hose, I reconnected it and revved the engine and it went up. I notice the gauge ticking up and down so I tapped the glass and it dropped, tapped it again and it went back up. I think I need to get another gauge for sure. I appreciate you dropping your knowledge on me, thanks!
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Re: Fuel pressure question

Post  Gregaust on Sun Jun 26, 2016 1:29 am

Never heard of vacuum to the fuel reg ? As mentioned only connected and used if running boost. Product engineering use a little sintered bronze breather to block the hole if not using boost

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Re: Fuel pressure question

Post  blu69MachI on Mon Jun 27, 2016 2:16 pm

The vacuum port causes the regulator to increase fuel pressure for WOT.
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Re: Fuel pressure question

Post  Gregaust on Tue Jun 28, 2016 5:02 am

blu69MachI wrote:The vacuum port causes the regulator to increase fuel pressure for WOT.

Ok Thanks . Never come cross that before

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Re: Fuel pressure question

Post  jbozzelle on Tue Jun 28, 2016 8:42 am

What regulator do you have?

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Re: Fuel pressure question

Post  blu69MachI on Tue Jun 28, 2016 1:06 pm

It's a Holley I got it from Pro-systems with the Carb.
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Re: Fuel pressure question

Post  jbozzelle on Tue Jun 28, 2016 2:27 pm

You should call Pro Systems with your problem. Doesn't sound correct to me

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Re: Fuel pressure question

Post  blu69MachI on Tue Jun 28, 2016 2:43 pm

My fuel pressure gauge turned out being bad, everything is working the way it should.
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Re: Fuel pressure question

Post  jbozzelle on Wed Jun 29, 2016 8:07 am

Good. Do you have anymore pictures of the car posted somewhere? Looks nice.

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