Alright, ive read the stillen V1/V2 instructions and the writeup.

The more and more i read it the more i get confused.

I have the FMU and pump infront of me. There are 3 wires on the pressure switch.

So basically, is this just a pressure switch, or does it have a built in relay, i was under the assumption it did both, but i dont think it does.

Correct me if im wrong, but the 3 wires on here are, black (Ground), Red (12V), and the Yellow, which goes to the Fuel pump relay.

So the pressure switch is activated by the fuel pump relay, i guess thats what its using for power. the 12V is sent to the FMU Relay when boost pressure is above 1PSI, that 12V is used as a trigger, for the FMU Relay, so it can draw power directly from the battery to power the pump.

So something like this:


Ill Explain it.



Pressure Switch:

The pressure switch gets its power from the fuel pump relay, once this switch sees positive manifold pressure, it sends the 12V to the FMU Pump Relay, Ground, obviously is ground.

FMU Pump Relay:

This FMU Pump relay, i dont know if i numbered them correctly, its not overly important i just threw numbers on them. Typical 5 pronged relay. 30, is directly from the battery. Ground is grounded to the body. Now, 86 Goes to the positive of the pump, while 85 goes to the negative of the pump. 87 is the trigger 12V from the pressure switch.

Correct me if im wrong, i would like to make sure this is right before i do any sort of wiring. To sum it up, the pressure switch, is triggered by positive manifold pressure, it sends its triggered 12V to the relay, which sends direct 12V from the battery to the fuel pump.

Now, heres where im kinda confused. The auxillary fuel pump is not active, untill there is positive manifold pressure. If you have the main fuel line from the fuel filter going into the auxillary fuel pump, would that not restrict the flow?

If you guys could let me know. perhaps im over thinking this or im tired, but looking at it, i was getting confused lol.

 

You are definitely over thinking this.

Just follow the schematic provided in Stillen's instructions/Ptatohed's writeup and you're good to go.

The hob switch is just that, a switch. It doesn't have a relay built in. That's why there's a separate relay needed; and was made part of the original Stillen kit. Do you have one?

The aux pump does not impede flow when it's not being utilized.

 

Thanks. I figured you or ptateohead would know.

Would the diagram i made work?

I think i would just wire this up as a normal switch to relay setup right? I was thinking about it at work, and i think i really put too much thought into it.

But just to get this final.

For the Hobb switch, does it receive its power from the yellow wire that goes to the fuel pump relay inside the car, or is that the wire that goes to the fmu fuel pump relay?

 

It may work, but I don't see any benefit to it. In fact, I see a disadvantage. The relay acts as protection, or a circuit breaker so to speak. Following the diagram in Stillen's instructions gives added protection to the Hobb switch and Aux fuel pump since the relay is first in the chain of wiring. I'd just follow what is given in Stillen's instructions.

 

Why not just upgrade to a Walbro 255 since you are going turbo? I understand if you are doing the auxillary thing if you happened to have the parts already, but you could have just done a Walbro and afpr.

 

What does going turbo (or Supercharged) have to do with using a Walbro?? T-rex pump can be utilized in either situation.

FWIW, the T-rex pump flows the same or higher than the Walbro IIRC. Walbro isn't exactly what I'd call an upgrade over the T-rex aux pump.

 

T-rex pump is perfect for FI. My boy has been running 11 to 14 PSI with the stock injectors and T-rex for 6 years now...

 

Okay just to put an end to this for future noobs trying to figure out how.

Your Hobb Switch(Pressure Switch), has 3 wires, you'll only be using the red and black. The black gets grounded to the battery, now before you run that to the battery and crimp anything, run the ground from the auxillary fuel pump onto that ground going to the battery. just crimp the two wires together in the O style connector.

The Red on the Hobb Switch, is used to activate/deactivate the relay. this pin, you will need to put a female spade connector on there. It will connect to pin 86 on your 5 pin relay.

The Relay, is your standard 5 pin relay, pins labeled 85, 86, 87, 87a, and 30. Pin 85 will go to the fuel pump relay inside the car, in the drivers side kick panel, tap into the yellow/black relay wire. Pin 87, will go to the positive on the fuel pump. Use thick wire for this, as this current will come directly from the battery. I used 10-12 gauge wire. Pin 30, will come from the battery positive. Use 10-12 gauge on this. For the rest of the wires 14-16 gauge is fine, they are basically used for signal only, so low current runs through them.

To test it do the following, get yourself a battery or battery pack

Positive Connection: The wires coming from the relay go to the positive: Pin 85 and Pin 30

Negative Connection: The Main ground. This main ground consists of the Fuel pump ground and Hobb Switch ground.

Pin 87 goes to the positive on the fuel pump.

Now the pump should be active, dont run it to long, as there is no lubrication. I initially thought i had done something wrong, but then i realized, this switch is activated by manifold pressure, it will only be active when manifold pressure is not negative (Vacuum). The vacuum hose coming from the Hobb switch, goes to the manifold, to test to make sure everything is working, just suck on that hose. The Aux. Pump should turn off. If it does, everything is okay.

I just thought id clarify this, to put an end to this thread, for future reference. It can never hurt to have several sources to verify your doing it correctly.

 

There is so much wrong info here (based on my understanding of how the relay works with the input/output of wires), I don't know where to begin. Also, I fail to see why you are so determined to wire it differently than the schematic provided in Stillen's instructions. Their method is tried and true. I even provided a disadvantage of doing it your way. The discussion of not using the yellow wire from the Hobb switch is also discussed in Ptatohed's writeup.

So please tell me, what's the advantage of wiring it up your way?

 

That is the way it is wired up from stillen. The switch is used only as a "trigger" for the relay.

The relay allows the Fuel pump to get power straight from the battery. It is the same deal when wiring up HID's to the stock harness. The stock harness is used as a "trigger" once the relay sees input from the "trigger" source it opens the relay allowing the current directly from the battery to go to its intended source.

I read the stillen schematic, the only thing different about the way i did it, is the way they had there relay labeled.

The relay is not used to protect the switch, the relay is used so the direct battery voltage can be sent to the fuel pump. Same when you hook up any switch with a large current.

The switch sees manifold pressure. When positive manifold pressure is seen, or manifold vacuum is succeded, the switch sends the signal down to the relay to activate the relay, allowing it to open, sending 12 volts directly from the battery to the fuel pump.

I am like 99% sure this is how it works. The stillen instructions are vague at best, but, it probably was not a hot topic for discussion.

 

You still have yet to explain an advantage of your way vs Stillen's way. It seems to me that you understand your method where Stillen's is "vague at best". Is that all it boils down to?

Your diagram shows the yellow wire from the Hobb switch being utilized. Stillen doesn't use the yellow wire from the hobb switch, hence why it's cut to a short nub. I fail to see how Stillen's instructions are vague. They make sense to me.

 

Sorry, disregard the diagram i drew. The way i ended up doing it, is pretty much exactly what stillen had instructed to do so, except the wires on the relay i labelled a little differantly.

I think the diagram is what you thought i was going by. The Diagram i drew the night i was trying to figure out how to wire this thing up, after i thought about it more with some sleep i realized how simple it was to hook this up.

Its not really my own way, i just elaborated a bit on stillens instructions, i know for people like me, i like an explination why you would do something, rather then just being told thats the way

 

The Wizard and others--I am having an issue that I think is related to the aux fuel pump and was hoping you could help. (also sent this by PM when the .org wasn't loading threads)

A few weeks after installing 370ccs, z32 mafs, and jwt ecu (which included removal of the Vortech FMU), I began getting a rich condition at start-up that eventually prevented the car from starting. When plugs are pulled after an attempted start-up, all are wet and smell of fuel. (The fact that all are wet has me convinced that the issue is not due to a leaky injector/o-ring.)

I understand that the hob switch activates the aux fuel pump when it sees positive manifold pressure. Does that mean the pump should be off at start-up? My aux pump comes on at start-up. If it should be off, could its activation be causing my rich condition? Or should the fuel pressure regulator (mine is OEM) prevent the start-up fuel pressure from getting too high even if the aux pump is on?

Right now its unclear to me whether the hob switch, fpr, or some other component is causing my issue.

I'd greatly appreciate any insight you can offer.

 

Wel the pump should be off at idle, but when you start, the pump will be on because there is no manifold vacuum. That shouldnt really affect anything though, it cant cause it to flood if the injctors arent open.

The FPR should prevent the fuel pressure from getting too high to prevent a start. If it gets too high, the excess fuel is "releaved" thru the return.

Id be more lilkely to say its your FPR that might have gone bad.

But hey start with the easy things first. Disconnect the ground on the pump, see if it fixes your problem, if it doesnt, id maybe consider trouble shooting the FPR.

Good luck man!!

 

Thanks for your help. Disconnecting ground from the aux pump does eliminate the rich condition and it starts right up. (should have mentioned this earlier)

 

Well, the problem i could see, is the pump activating while your cranking, just too much fuel pressure and its flooding it. I cant think right now, but is there is manifold vacuum while cranking right? So the Hobb switch shouldnt be triggering the relay. Perhaps its a issue with your Hobb switch? The way i tested to see if i had hooked mine up right, is sucking on it, but maybe if you use a vacuum pump and hook it up to properly test it.

I cant offer any solid advice, but maybe someone with more experience with the Hobb switch can chime in!

Good luck man!

 

Yep--I hope someone will chime in. I suspect that either the hob switch or relay is broken, but i don't understand why the auxiliary pump--if on while starting--causes a rich condition.

Shouldn't the fuel pressure regulator keep the fuel rail from getting too much fuel?

 

The first question I have is: Is the JWT ECU programmed specifically for the mods you have??

 

Yes

 

Ok. Second question.

How do you know the injectors are good and not leaking?
Is it possible the injectors were installed poorly, thus causing the leaking?

 

I am reasonably certain the injectors aren't leaking because when the aux pump is disconnected, there is no rich condition (no trouble starting, no black smoke, no fuel on plugs, no misfiring.) When the aux pump is connected, all of the plugs get wet--and it is very unlikely that all 6 injectors were installed poorly and thus leaking. This suggests that the problem is tied to the aux pump arrangement (whether it be the switch, relay, or pump itself).

 

ok. I wasn't implying all 6 were leaking/installed wrong. All it takes is 1. Now I see that you mentioned all 6.

Well, I'd check your wiring first as there are plenty of wires between the hob switch, relay, and fuel pump. Follow the Stillen schematic to a 'T'??

Then, I'd replace the relay, as it's only a $5 part, then the hobb switch. I doubt the pump is bad. If it was bad, it would be just the opposite and you wouldn't know you had a problem unless your were boosting and went lean.

 

Well, everything was running right for months while I was at 6psi and then 3 weeks while at 14psi (w/ jwt, z32 maf & injectors, etc.) so I assume the wiring is fine. I should check it again though. I should also check the vacuum line to the switch to make sure it isn't cracked.

I agree with your analysis w/r/t the symptoms of a bad aux pump.

Do you know where I can buy a replacement switch or relay? I called Stillen and was told they're no longer sold.

(Thanks for your help!)

 

Good point on checking for a cracked/bad vacuum line. The hobb switch seems very fragile to me, maybe the nipple broke/cracked there as a possibility too.

Well, a quick search yielded many Hobb switches, but not the exact one we have.

I did find these though.....I think this will work for you, but not entirely sure. I'll keep looking for our style.

http://cgi.ebay.com/ebaymotors/_Car-...4506.m20.l1116


http://cgi.ebay.com/ebaymotors/_Car-...4506.m20.l1116