Why is the FPSS connection to ground on the NO and C sides both????
09-16-2007, 04:57 PM
#1
Why is the FPSS connection to ground on the NO and C sides both???? I am having problems understanding the concept of connecting the NO side of FPSS to the 60 amp relay white wire (85), then, connecting the C side of the FPSS directly to ground. Can somebody shed some light for me on the operational principal of how the FPSS works?
09-16-2007, 07:55 PM
#2
although some schematics show the fpss on the high current side of the setup, I really don't recommend it. It's not made for high current. An fpss switch is a "connect/disconnect" switch. Like taking a wire, cutting it open, then reconnecting it. Put it on the low current side. Easiest is on the low current ground line. Post your schematic. Pin 85 is the low current side. 87/30 are the high current terminals.
09-16-2007, 08:00 PM
#3
On both of my 60 amp relays, I have the white wires (85 side) running directly to a grounding point on the body of the car. I'm wiring my kit up by the diagram directly from the Nitrous Express website. The diagram shows the NO side of the FPSS going to that white wire. On the C side of the FPSS, it shows it going to another direct ground point. Am I doing something wrong? Below is the installation manual in .pdf format from the Nitrous Express website. When it opens, go about halfway down and you'll see the diagram.
http://www.nitrousexpress.com/Instructions/stage1.pdf
http://www.nitrousexpress.com/Instructions/stage1.pdf
Last edited by JEB99TA; 09-16-2007 at 08:12 PM.
09-16-2007, 08:18 PM
#7
both sides don't go to ground. In the first schem only one side is going to ground. the other side is going to the coil on the relay. Go to the sticky "nitrous basics" and look at my post on pg 2 on electrical. I show how a relay/solenoid work. Read "blowing fuses" part. It may help you understand the principle.
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09-16-2007, 08:23 PM
#8
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Originally Posted by JEB99TA
I have that one and it's very helpful, but, I just don't understand why both sides of the FPSS go to ground. It'st the concept I'm trying to figure out.
When the FPSS pressure is too low its contacts opens, now the relay can not find ground so it will not close the contacts.
So the FPSS is in series on the ground circuit.
Ricky
09-16-2007, 08:54 PM
#9
The NX installation instruction manual diagram shows the NO side going to ground on the relay (white wire 85 on the relay). The Nitrous Outlet shows the same NO side of the FPSS going to a hot lead on the relay (red wire 86 on the relay). While the latter seems correct and makes sense to me, no way can both configurations be correct. Thanks to you both for helping, but, which one is correct? Going to read the sticky now.
09-16-2007, 09:12 PM
#10
OK gotcha' ... so it really doesn't matter which side of the relay (85 or 86) the NO side of the FPSS gets wired to because both 85 and 86 are low current coils (not hot or ground sides ... all the FPSS does really is just break the circuit when the fuel pressure is not up to the correct level. Nice write-up Todd. Ricky, thanks for weighing in, as well. Thanks to both of you for helping guys like me setting up our nitrous systems.
09-16-2007, 11:56 PM
#11
Yea it doesn't matter where in the low amp wire you put the FPSS inline. Think of it this way, the wire is still carring current through wire, until ya actually ground it out it's an open circuit. meaning, you could read the current right at the end of the wire where it goes to ground. The FPSS is a mechanical switch, it needs fuel pressure to activate not current, so if ya have the pressure then the contacts are closed. Then the relay uses the current (milla amps on low side) to activate high amp side having a now complete circuit.
robert
robert
09-17-2007, 06:44 AM
#12
... so that's why the manual says to use a jumper on the FPSS to test the solenoids to see if they're firing before connecting lines ot the bottle or fuel rail. Since there would be no fuel pressure, the circuit is open and dead, thus, you'd have to use a jumper wire to complete the circuit. Now I think I fully understand. I was looking at it as more an electrical device instead of a manual device activated by fuel pressure. Thanks again!!!!
Now, I think I'm gonna' have to order a T and extra lines to tap into the fuel line going to the fuel solenoid from the driver's side fuel rail, right? Anybody got a picture handy that shows the easiest way?
Now, I think I'm gonna' have to order a T and extra lines to tap into the fuel line going to the fuel solenoid from the driver's side fuel rail, right? Anybody got a picture handy that shows the easiest way?
09-17-2007, 08:22 AM
#13
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To install a FPSS just purchase a -4 dual port manifold. The female end will attach to your fuel rail, then your hose will attach to the male end. Now you have 2 npt holes left to attach the FPSS and a Gauge if you like.
NX pn ??? maybe 15513 its been a little while.
NX pn ??? maybe 15513 its been a little while.
09-17-2007, 12:17 PM
#14
I already have a NX GM/Chrysler fuel tap #16185, which has two ports where I could put the FPSS and a guage, as well. If I use this, could I still tap straight into the end of the fuel rail with the line from the fule solenoid? It doesn't really matter which place I put the FPSS, does it?
