Tech Tip:FPSS (how to adjust & "Y" Have).

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Jan 31, 2005 | 03:39 PM

NXRICKY

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From: Wichita Falls, TX

Tech Tip:FPSS (how to adjust & "Y" Have).

The fuel pressure safety switch or FPSS is a normally open switch; that closes at a preset pressure. It is used to prevent engine damage in the event of fuel pressure loss, or the lack of fuel pressure. It is installed in the fuel line between the fuel rail (or pressure source) and the fuel solenoid. The FPSS monitors the fuel pressure that the system feeds to the solenoid. It has two terminals that are wired in series with your groundside of the relay.
http://www.nitrousexpress.com/Instructions/fpss.pdf here is the standard wiring for the FPSS.
For an older MSD window switch the yellow wire that normally went to ground would connect to one terminal on the FPSS and the other terminal on the FPSS would go to ground.
There are many ways to use this switch to help prevent engine damage. The one thing that all the diagrams will have in common is the FPSS is put into series with what ever wire is controlling the system.
The FPSS is adjustable. On the topside of the switch there is a rubber plug. Removing this plug and you will expose a hex type screw. Tuning the screw clockwise will raise the set point. Counterclockwise will lower the set point. Normally there is no need to adjust these switches they come from the factory preset. WARNING: setting the FPSS to close to the operating fuel pressure of your system will cause the nitrous system to bounce, chatter or go on off really fast. And setting to far away will not do you much good.

Ricky

Jan 31, 2005 | 04:09 PM

Wile_E

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From: Miami ,Fl

Let me ask this in here. This is the schematic I drew up prior to wiring everything. The only change I was told to make is in the red. This is how I have it wired now and have yet to test it out.

http://www.ls1camaro.net/freehosting...wiring%202.JPG

Is this correct?

Jan 31, 2005 | 04:30 PM

NXRICKY

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From: Wichita Falls, TX

Yep looks good to me. here is another link for a window switch
http://www.nitrousexpress.com/Pages/FPSS_diagram.htm
http://www.nitrousexpress.com/Instru...ndowswitch.pdf

Ricky

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Originally Posted by Wile_E

Last edited by NXRICKY; Jan 31, 2005 at 04:49 PM.

Jan 31, 2005 | 05:07 PM

97LT1

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From: Clear lake TX (From LaPorte)

Ok let me ask this. I really am not goint to go over 150 shot at the moment on my dual stage. I have 2 FPSS switches i havent messed with the settings. You say the factory settings are good and not to mess with them. My question is what are the factory settings? Also IF i was going to adjust these, how on earth do you do it?