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Discussion Starter · #2 ·
I'm looking at wiring the primary and secondary fuel pumps on the Fore relay. The primary is straight forward.
The secondary is a little tricky, It looks like I have several choices.
1) wire both pimps with the primary pump B+ and let them both run all the time with the 1 second prime and cutout relay intact on both pumps
2) change the low pump relay (secondary pump) switched ground circuit to B+ to let the PCM control it on & off, but I lose the 1 second prime and cutout relay protection. Worst case I'm upside down at WOT and the second pump still running.
3) wire in another switch (pressure?) on the secondary pump B+ circuit before the secondary pump. That will both prime and cutoff. But that's a switch on a switch on a switch.

When the truck is tuned will the factory value for the secondary pump "ON" be changed (increased)? I will be running 18 psi ish boost.
 

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Discussion Starter · #5 ·
OK, no PCM control.
Factory key on B+ primary circuit to Fore 1, I get prime and cutoff
Factory key on B+ secondary circuit to 8PSI Hobbs switch then to Fore 2, I get cutoff
I could of use the factory secondary relay if I rewired it but as far as changing when the PCM turns it on( grounds) is questionable.
 

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10 second street truck
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OK, no PCM control.
Factory key on B+ primary circuit to Fore 1, I get prime and cutoff
Factory key on B+ secondary circuit to 8PSI Hobbs switch then to Fore 2, I get cutoff
I could of use the factory secondary relay if I rewired it but as far as changing when the PCM turns it on( grounds) is questionable.

Again. Discuss this with your tuner. They have tune through you fuel system. You're really over complicating something that doesn't need re-engineered.

And no, running both pumps isn't an issue for the regulators or we'd all have issues.
 

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Discussion Starter · #7 ·
Yes, tuner said no PCM control on secondary, he say pressure switch for 2 & 3 pump.
I ask when to bring secondary in, he say 6~10 PSI no later.
I buy adjustable or 8 PSI switch.
That will allow me to use factory primary and secondary B+ with the cutoff relay in the circuit.
Worst case I'm upside down with a beer bottle holding the accelerator pedal to WOT, It cuts off with factory inertia switch and cut off relay.
No need for 2 pumps to run when your driving on cruise, less than 8PSI boost
I'm trying to maintain factory controls but with performance it's a trade off. I get it.
I will probably work with a rewire of the factory low relay. I take no chances with that. I'll try iy with the next SVT I buy!
 

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10 second street truck
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I'm trying to maintain factory controls but with performance it's a trade off. I get it.
I will probably work with a rewire of the factory low relay. I take no chances with that. I'll try iy with the next SVT I buy!
Who's tuning your truck?

I'd be curious to hear @[email protected] thoughts on running 1 pump with second on a hobbs. I've seen two full time with a third on a hobbs. But never 1.

1000s of lightnings, mine included, running both pumps full time. Just saying.
 

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10 second street truck
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The stock fuel system runs both pumps all the time. It changes voltage through the resistor to effect flow, using the hi/lo relay.

part of the issue with the factory setup is it only applies enough voltage to the pumps to produce the required fuel flow. Most after market pumps are designed to be run at 12v constant.
 

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Discussion Starter · #10 ·
I run with the Fore relay box, so the current/amps are there for pumps 1 &2. The Fore cables size are WAY larger than factory wires but 12V 25 amp fuses each pump.
the factory wiring is only to trigger at 6.5 Volts and a 1/4 amp the Fore needs to see. Its a matter of the inertia switch and fuel cut off relay functioning with the Fore stuff.
The after market pressure switch takes the place of the factory low/secondary pump relay and PCM "ground" triggered on/off. I believe you can rewire the low pump relay to trigger the Fore relay box. but Tuner is not sure he can change/increase the PCM secondary on/off value.
I dont want both 450 LPH pumps running non stop.
 

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10 second street truck
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I run with the Fore relay box, so the current/amps are there for pumps 1 &2. The Fore cables size are WAY larger than factory wires but 12V 25 amp fuses each pump.
the factory wiring is only to trigger at 6.5 Volts and a 1/4 amp the Fore needs to see. Its a matter of the inertia switch and fuel cut off relay functioning with the Fore stuff.
The after market pressure switch takes the place of the factory low/secondary pump relay and PCM "ground" triggered on/off. I believe you can rewire the low pump relay to trigger the Fore relay box. but Tuner is not sure he can change/increase the PCM secondary on/off value.
I dont want both 450 LPH pumps running non stop.
Also I'm aware you're running the fore setup.

My wiring for the pumps is all aftermarket too. Stock wiring to trigger relays with power coming from the main fuse box under the hood.

Again, the issue with the pcm secondary is that it's not turning second pump on, but simply increasing voltage. This is why the secondary is bypassed.
 

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Discussion Starter · #14 ·
I have print,
Both pumps get 12 volts to run not more or less volts, both pumps have simple relays to turn them on and off . Secondary is a GROUND path trigger. Fore needs to see 6.5 volts to trigger it's relay.
You would have to re wire the secondary rely to not ground but send B+ to Fore, thats why its bypassed. It can be rewired to B+. But my tuner doesnt know if he can change the input value in the PCM to 8 PSI on/off
I get it just send 12 volt to both Fore inputs with key on and they run. I'm trying to keep factory control. I don't want both pumps to run on cruise
 

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You're really over complicating something that doesn't need re-engineered.
LOL! Dusten is trying to help you, but you rather give your self a Migraine.
^^^^^^^^^^^^^^^ Those^^^^^^^^^^^^^^

but Tuner is not sure he can change/increase the PCM secondary on/off value.
I take it from that reply that he has not tuned very many of these vehicles because if he has he would know there is table for that very thing.

I give you credit for thinking outside the box but as Dusten said you are over complicating things. Things that have already been well documented, tested and proven by others. Sure, mount it all in a box if you want to and put your own spin on it if you really feel you have to but stick to the basics that have proven themselves time and time again. Two properly sized pumps running full time in a return style system with the voltage controlled by the FC2/FC3, triggered by the stock power wire so the inertia switch can still do its job. If you really think you need a third pump put it on a hobbs as outlined and described by the Fore instructions.

I have put together and installed more fuel systems then I care to remember and the one very basic rule I stick to time and time again is KISS.

Good luck in whatever you decide to do,

[email protected]
 

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10 second street truck
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I have print,
Both pumps get 12 volts to run not more or less volts, both pumps have simple relays to turn them on and off . Secondary is a GROUND path trigger. Fore needs to see 6.5 volts to trigger it's relay.
You would have to re wire the secondary rely to not ground but send B+ to Fore, thats why its bypassed. It can be rewired to B+. But my tuner doesnt know if he can change the input value in the PCM to 8 PSI on/off
I get it just send 12 volt to both Fore inputs with key on and they run. I'm trying to keep factory control. I don't want both pumps to run on cruise

If you don't believe me that the pumps get varying voltage, I don't know what to tell you other than check voltage at the pumps while driving and see what happens.

You've never actually had a running driving lightning.

I have a truck I built in my own garage, that's been running for 12 years. Has a stack of time slips, runs 10s with ease, will drive cross country and will stop on a fucking dime.
 
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