XFI, fuel pump, fan connection

[jjump59]

Just trying to get this thing wired up and am confused! I have an aeromotive pump controller and a DC fan/water pump controller. I see that my ECU has wires for the fuel pump and the fan, how does this come into play? Do I use the ECU wires to the switch terminal of the controllers, do they just tell the fans/water pump and fuel pump it's ok to run? Another concern is the tach signal, I understand I need one for the ECU and one for the fuel pump controller, can I splice one wire into two from the MSD box tach signal or will that screw up the signal? Thanks for any help you can provide.

[musclepro]

I haven't seen an aeromotive pump controller. is it a fuel pump relay for the aeromotive fuel Pump? if so you would send a 12v to the relay and the ecu will trigger a ground to activate the relay. At least it works this way on most systems.

same basic deal with the fans. the ecu typically monitors the water temp and grounds the relay to activate the fans.

tach signal? the ecu usually shouldn't need a tach signal it sends your tach a signal. the ecu if it controls the ignition gets its info from the distributor or the crank trigger. depends on what type of motor you have. No idea why the fuel pump controller needs a tach signal unless it increases pressure as rpm increases.

I am just guessing on most of this. maybe you could be more specific on what type of units you have.

DB

[parsonsj]

I have an aeromotive pump controller and a DC fan/water pump controller. I see that my ECU has wires for the fuel pump and the fan, how does this come into play?

Those wires are to ground a relay that powers the pump and fan.

Another concern is the tach signal, I understand I need one for the ECU and one for the fuel pump controller, can I splice one wire into two from the MSD box tach signal or will that screw up the signal?

No, that will work fine.

I spent a couple weeks wiring up my XFI/eDIST/DC Fan/Pump controller last summer. I can probably help if you have other questions.

jp

[EFI69Cam]

most aftermarket ecus follow the gm convention to switch +12 for the fuel pump relay. All other triggers switch to ground. Sharing the tach signal should be fine.

[parsonsj]

most aftermarket ecus follow the gm convention to switch +12 for the fuel pump relay

Not the XFI. The fuel pump (pin B5) signal goes to ground, and is intended to ground a relay.

jp

[jjump59]

Thanks for the replies. Jp since you've been down this road before I would like to pick your brain some. I probably have the same understanding of this type of stuff that a 12 year old would. I don't know or understand what a relay does. Do I even need one with the DC control? I'm pretty sure the fuel pump does. I have wires in the painless harness for the fuel pump and the fan do I use them or just tuck them away somewhere? If i need to use them where and how? When we're talking about the ECU wires for the fuel pump and fans, do they go to the relay, do they just tell them when it's good to turn on or do they provide power somehow? Feel really stupid right now but I have never put much effort into learing about the wiring part of building a car. I could barely get it running and working when we put the painless kit in!

[parsonsj]

I don't know or understand what a relay does.

You're right: you need to understand this concept. Go here. Read, return, and report.

Do I even need one with the DC control?

No. The DC control has a relay built in.

I'm pretty sure the fuel pump does.

Yes, it does require a relay.

I have wires in the painless harness for the fuel pump and the fan do I use them or just tuck them away somewhere? If i need to use them where and how?

You'll need to check what amperage those wires are designed for. You will probably find that they are intended to switch the relays, not provide the power directly to those devices. When you understand relays, this will make more sense.

When we're talking about the ECU wires for the fuel pump and fans, do they go to the relay, do they just tell them when it's good to turn on or do they provide power somehow?

See above. You've got the right idea. Just go and understand relays, then we can get you sorted out.

Feel really stupid right now but I have never put much effort into learing about the wiring part of building a car.

No time like the present.

jp

[jjump59]

Lesson #1 is complete, is there a test? LOL! That was a very good link. I understand what a relay does and why you need it. After reading that I would agree that the wires from my painless harness are the trigger wires, I would also guess that the wires from my ECU are also trigger wires. My guess at this point is to use the wires from the ECU to trigger the relay and tie up the harness wires. I'm not sure about this but that's what i'm thinking. anyway gotta get some sleep, work tomorrow, i'll post more then. thanks again for the help.

[DeltaT]

The aeromotive pump controller wants a tach signal because the controller has an rpm-adjustable point under which it cuts the pump duty cycle to 50%, essentially running it at half speed. The MSD tach signal works fine.

I use the same box and have it set around 2000rpm. It has helped my fuel heating problem some.

Jim

[jjump59]

With JP's help I'm on track to get this done tomorrow. Still waiting on a backordered crank trigger bracket for my pontiac but the wiring will be done. Called the F.A.S.T tech line today with some quick questions and talked to some jerk, real difficult to get any help from him. He finally admitted that another guy there understood the wiring better then him and he put that guy (David) on. David was very helpful and was able to answer every question I put to him. I can't wait to hear this thing run! Thanks for the help and advice guys.