Relay questions

[Jespinosa]

I am in the process of researching and planning the electrical systems in the car. To be honest this is the most daunting part of the process so far, but I felt that way when I started bending the brake lines and flaring them, and started running the fuel system, etc. In my research I noticed that I needed a 30amp relay for the fuel pump I chose.

https://aeromotiveinc.com/products/83-97-efi-mustang-stealth-340-hanger?_pos=8&_fid=c8ea1c123&_ss=c

I had read a recent post showing that the Aeromotive 340 LPH pump draws only 13 amps at 60 psi but when I called aeromotive tech they recommended a 30 amp relay for the fuel pump. So, I found that aeromotive sells a kit with the 30 amp relay, and the wiring needed for their pumps but it is $164.95 which I found quite expensive for just some wiring and a relay. As I kept researching, I notice that Painless performance sells a similar kit for $35:

https://www.amazon.com/Painless-50102-Fuel-Pump-Relay/dp/B00062Z5G6?ref_=ast_sto_dp

Then it got me thinking, since I am already buying a 30 amp relay for the pump, should I buy a a bank of 3 relays since I am going to need a 30 amp relay for the Flexlite fan and probably something else in the future.

https://painlessperformance.com/product/3-pack-relay-bank-part-no-30107/

So, should I just purchase the wiring for the 30amp relay for the pump or should I buy the system with the 3 relays? I know the fan will need a 30amp relay but is there something else that might need and additional relay that I am not thinking of?

[michael everson]

all of that is already in the fuse box.
Mike

[Rebostar]

If your using the RF supplied wire harness and fuse box, as Mike E said above the fan and horn relay's are already there. If your not using the RF fuse box or you plan to have seat heaters or a defroster or fan blowers to vent the footboxes you may want to get multiple relays. Summit has lots!

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[Jespinosa]

I am using the RF harness, but it includes a 15 Amp fuse for the fuel pump. Additionally, the Terminator X computer instructions mention that the optional 12v fuel pump wire can be used to power a fuel pump but in bold it states, "Do not use this to power fuel pumps that require over 15 amps".

Trust me if I can just change the fuse to a 30 Amp fuse on the RF fuse box that would make my life much easier. Is the RF harness fuel pump wiring 12 gauge? The pump manufacture recommend a 10 gauge wire to the fuel pump. As usual, I am probably over thinking this, but I want to make sure I am doing things correctly and there is so many knowledgeable people on this forum that I figured I would ask.

On another note, I did notice that the fan has a 30 Amp fuse on the RF harness so I should be ok for the flexlite fan. I don't think I will need to wire anything additional for the new fan.

[Kbl7td]

10g overkill.

[CraigS]

Not a good idea to take a circuit that is designed for 15 amps and install a 30amp fuse. You don't want the wires to become the fuse. 10g wire might be overkill, but if the people who make the pump say that is what it needs, I wouldn't argue to point. I don't know the details of the pump/efi system but often there is a steady running amp draw rating and also a startup amp draw rating which can be significantly higher. I would use the existing harness to run the relay in a complete ad-in pump circuit.

[Jespinosa]

Not a good idea to take a circuit that is designed for 15 amps and install a 30amp fuse. You don't want the wires to become the fuse. 10g wire might be overkill, but if the people who make the pump say that is what it needs, I wouldn't argue to point. I don't know the details of the pump/efi system but often there is a steady running amp draw rating and also a startup amp draw rating which can be significantly higher. I would use the existing harness to run the relay in a complete ad-in pump circuit.

I am using the automotive 340lph pump. Here is the link:

https://aeromotiveinc.com/products/83-97-efi-mustang-stealth-340-hanger?_pos=8&_fid=c8ea1c123&_ss=c

I think it is a pump that is commonly used and at first glance I believed I could use the existing wiring but as I read up a little more I started doubting since the instructions recommend using:

https://aeromotiveinc.com/products/premium-hd-30-amp-fuel-pump-wiring-kit

[Its Bruce]

I suppose this is anecdotal, but I use the same fuel pump at 58psi and have no issues with the RF wiring in the Texas heat and Houston traffic. I will, however, note that I have bypassed the RF relay to make use of a GM ECU-controlled 30A relay for the fuel pump.

Where are you mounting your battery? If in/under the trunk, it would be easy to run 10g wiring to the FP with the relay triggered by the RF wiring. This would have been my plan B, but the pump draws no more than 12A, from what I've measured. This is me assuming, but I imagine the 90" wheelbase of these cars makes up for a few sins on wire gauge requirements.

Edit: Protip - whatever relay type you go with, know the interchangeable PN's of it and/or keep a few spares in the trunk.

[michael everson]

I have used that pump with the RF wiring with no issues.
Mike

[Jespinosa]

I have used that pump with the RF wiring with no issues.
Mike

Well that is great news, so you used the Rf wiring and relay to run the same pump?? Well, that makes my life much easier as the wiring should be similar to what is used when installing the Coyote's. I can use the Terminator X to turn the fuel pump relay on or off.

[michael everson]

Yes. with no issues. BTW look at the gauge of wires they are using on the hanger. Cant understand why they want a 10 gauge wire.
Mike

[BEAR-AvHistory]

Can you just cut out the RF section & wire the fuel pump with a stand alone kit?

https://thefactoryfiveforum.com/attachment.php?attachmentid=204445&d=1727136594

[rich grsc]

WHY are you installing a 340 LPH pump? You have 600HP or more? Is this a track car, not a street car?

[Jespinosa]

WHY are you installing a 340 LPH pump? You have 600HP or more? Is this a track car, not a street car?

Great question. To be honest I wanted to make sure that the I had enough pump for my current and future setup. The current motor dynoed at 537 hp and 624 tq on the engine dyno. Here is a video of the engine on the dyno: https://www.youtube.com/watch?v=0HCJWKMQz7E&list=WL&index=13

This is more than enough power honestly, but I wanted to make sure that the fuel system would be able to keep up with any future upgrades. A simple cam change will take these motors north of 600hp. I don't really think I will need the extra power, but I am more interested in the additional cam lope at idle that would come from a cam change. According to the engine builder the current setup will have a slight chop. I also would like to add an eight stack to the motor but that would require some more changes to the current setup, and I will most likely leave those changes to the future. So, after my long-winded answer, I just want to make sure I have enough pump for the future which this pump should hopefully provide.

[BEAR-AvHistory]

Does the Fuel Pump relay become hot to the touch in normal street driving?

[Jespinosa]

Does the Fuel Pump relay become hot to the touch in normal street driving?

I am currently working on the wiring of the car and am not yet at the point where I am street driving the car. I just wanted to make sure I wouldn't have to rewire the fuel pump wires in the future but from Mike's post above it seems that it should not be a problem.