Surprise! More wiring questions

[EZ$]

What a surprise, I've got more wiring questions!

Trying to get my FAST fuel injection wired, and I had a couple of questions.

1. Can a relay be placed downstream from an initial relay. This is regarding the fuel pump and cooling fan circuits. FAST calls for a solid state relay for the fuel pump circuit, although, they show wiring for both a standard and a solid state. I guess I'll need to talk to them, because the instructions showing both are a bit confusing.

2. In FAST's wiring diagrams, the power coming into pin 30 they note as "Battery Power". Would they be referring to fused power? If they are, could I use the existing power leads running to the fuel pump and the fan, as the battery power, and use the remaining portion of that wire as the leg from the 87 pin to the pump, or fan? that would be the TAN wire for the fuel pump, and the DARK BLUE for the fan.

3. Lastly, there is a "Switched 12V" lead that is supposed to be connected to a switched ignition source (hot in on/run and crank). If this was connected to the ORANGE "Coil or RFI" wire, would that fulfill the requirements of this?

Anyhow, I'm trying to plow my way through this. Hopefully there is someone out there who's installed a FAST system that can provide some insight.

[FF33rod]

I assume you're still running the RF harness. If so, why not use the Fuel Pump relay built into fuse panel and harness? Relay is there, wire already runs back to the fuel pump area... that's what I did on the 33, works great. For the switched 12V either the Coil/EFI lead or the Electric choke lead works. Can't help you with #2.

[Papa]

The FAST EFI wiring into the RF harness using the RF fuel pump relay is pretty simple. I documented all of it a while back. Let me see if I can find the thread.

Dave

[Papa]

Check this thread ....

https://thefactoryfiveforum.com/show...light=Fast+efi

[Papa]

What a surprise, I've got more wiring questions!

Trying to get my FAST fuel injection wired, and I had a couple of questions.

1. Can a relay be placed downstream from an initial relay. This is regarding the fuel pump and cooling fan circuits. FAST calls for a solid state relay for the fuel pump circuit, although, they show wiring for both a standard and a solid state. I guess I'll need to talk to them, because the instructions showing both are a bit confusing.

2. In FAST's wiring diagrams, the power coming into pin 30 they note as "Battery Power". Would they be referring to fused power? If they are, could I use the existing power leads running to the fuel pump and the fan, as the battery power, and use the remaining portion of that wire as the leg from the 87 pin to the pump, or fan? that would be the TAN wire for the fuel pump, and the DARK BLUE for the fan.

3. Lastly, there is a "Switched 12V" lead that is supposed to be connected to a switched ignition source (hot in on/run and crank). If this was connected to the ORANGE "Coil or RFI" wire, would that fulfill the requirements of this?

Anyhow, I'm trying to plow my way through this. Hopefully there is someone out there who's installed a FAST system that can provide some insight.

1. See my previous post on how to use the RF harness fuel pump and fan relays with the FAST system. Note that the FAST recommend relay is designed to support pulse width modulation. My FAST system never worked well for me as it ran hyper rich. This may have been because I didn't use the solid state relay.

2. No! Run the battery wire connection to the batter. Don't split off of another source.

3. Yes, the orange wire in the RF harness will work in this application.

[EZ$]

FF33rod, thanks for the info. I was thinking that I could go this way, but in order to accommodate for the additional wires from the FAST harness, I was trying to determine if I could install another relay downstream from the RF relays in the fuse box.

Dave, I do have the heavy Red (+) and Black (-) wires running direct to the battery. what I was wondering is what they are calling "Battery Pos." going through a fuse to power the relay.

I also should have mentioned that I have an MSD ignition system, so the only wires they want going to the coil are from the MSD box. Also, the distributor ahs a two wire pigtail that also connects to a two wire pigtail lead coming from the MSD.

One of the issues that I'm trying to clarify in my mind are the differences between the Orange "coil or efi", Light Blue "coil/efi crank", and the Purple "coil/tach wires. At this point I'm not sure I see where the Light Blue and Purple wires, in the RF harness, are used in my application.

Did you replace the relay with the solid state, and if you did, did it help? If not, did you change systems?

[Papa]

Rick,

I ended up swapping the FAST out for the Holley Sniper. On the blue efi crank wire, it only has power when cranking. No juice when the key is in the on/run position. For the switched power on the FAST, you want power in both the crank and on/run positions.

I'm not going to be much help when it comes to the specific ignition wiring. Mine is a simple coil and HEI distributor.

Dave

[EZ$]

Thanks Dave. I hope I have better luck with the FAST than you did. I don't think I can afford to take another hit like that.

[phileas_fogg]

As Dave says, the RF orange "Coil or EFI" wire provides +12V when the key is in RUN and START, and the RF light blue "Coil/EFI Crank" provides +12V ONLY when the key is in START.

The RF purple "Coil/Tach" wire is intended to provide an RPM signal to your tachometer. You'll have to check with the MSD documentation (or someone who's using it) to figure out how to wire in your tach.


John

[rich grsc]

The solid state relay is only used if you are using a pulse modulated fuel pump for a returnless fuel system

[EZ$]

John, Thanks for that info. I'll check into the use of the purple coil wire.

Rich, Thanks so much for that. The wiring diagrams that FAST provides are confusing to me with the multiple options. They don't make it clear on the diagram or the written instructions.

Thanks again guys.

[EZ$]

I decided to do some more searching on these wiring issues. OK, so when did Ron Francis update their Chassis Wiring Harness instruction book? The copy I received when I ordered my kit in 2012 is 35 pages long, with virtually no detail regarding wiring connections, or much of anything else. Low and behold, I check their website to see if they may have any information I could use, decided to look at the instruction book online, and find out it's now 68 pages long with unbelievable detail that my instruction book only dreams about! Turns out that they now address the questions that I was asking.
Only thing I need to check with them now is what to do with the Purple "Coil/Tack" wire.

[OnlyAndy]

I am watching this thread with great interest..... I am THERE Now also and I am having a hard time getting past just looking and thinking about it. I have done 3 old hot rods in past from A to Z and now I have gone brain dead on this one. F5 told me this am to use the RF harness wires to power the Speedhut Legend gauge unit for Oil Pressure and Water Temp and the Supplied "gauge cables" for rest of hook ups. Then the Sniper for Fan and Fuel Pump. My wire harness book from RF is geared to the cobra not 33' and the 33' Bible is not clear enough for me to follow.... ( very well ). I have the new RF manual with my kit but still have questions. Like CUT the jumper at panel as shown or NOT as one member has said.... I know, one wire at a time gets it done. Thx for sharing all this knowledge.

[EZ$]

Andy, obviously the wiring has been my biggest challenge. I wish I could say that anything that I post amounts to something along the lines of knowledge. Mostly it's me stumbling around in the dark, and finding something by accident, That is, unless someone shines a light on the answer for me. I hope you're able to solve your issue. I know I want to solve mine. It's really the only thing between me and an attempted first start. (I almost typed just "first start", but I have to be realistic!) I must have missed the thread where someone said not to cut the jumper. I thought I had finally found the answer.

[OnlyAndy]

Earlier in the thread "Papa" shared a link that shows a detail on each wire and color... Also in Red letters is a line that says Do NOT cut any jumper at the fuse box... But not,,, WHY,,, not to cut it. Thx, I'll get through it but my confidence level is not where I would like it.

[Papa]

Earlier in the thread "Papa" shared a link that shows a detail on each wire and color... Also in Red letters is a line that says Do NOT cut any jumper at the fuse box... But not,,, WHY,,, not to cut it. Thx, I'll get through it but my confidence level is not where I would like it.

If you want to use the RF relay for the fan and fuel pump with the FAST EFI, don't cut the jumpers. The FAST EFI uses a ground signal on the fuel pump control wire. Wiring it through the inertia switch will let you use the RF wiring as-is. For the fan, the relay in the RF harness is already configured to allow a ground signal provided by the fan control wire to operate the fan through the RF relay as-is.

Dave

[EZ$]

Dave, I'm not totally clear on what you're explaining, but that's just my minimal understanding of the electrical system. My confusion has been that Ron Francis instructions talk about cutting those jumpers to use the efi leads for those items to trigger the relay. In the FAST instructions, it says not to control any high amp items directly through the ECU, but only through relays. Will connecting on the ground side, which I think is what you're saying, trigger these items through the relay? I'm going to contact Ron Francis tomorrow to get their feedback. I'll probably be more confused than I am now, even though that may not be possible.

[Papa]

Dave, I'm not totally clear on what you're explaining, but that's just my minimal understanding of the electrical system. My confusion has been that Ron Francis instructions talk about cutting those jumpers to use the efi leads for those items to trigger the relay. In the FAST instructions, it says not to control any high amp items directly through the ECU, but only through relays. Will connecting on the ground side, which I think is what you're saying, trigger these items through the relay? I'm going to contact Ron Francis tomorrow to get their feedback. I'll probably be more confused than I am now, even though that may not be possible.

Rick,

I completely understand how you feel. I was in exactly the same boat when I was trying to figure the EFI connection out. Brien (BB767) talked me through it after he made the mistake of cutting the jumper wire per the RF harness instructions. Believe me, this is not that difficult when you realize what is happening. The RF harness relays for the fan and fuel pump are already wired on the positive input side. For the fan circuit, there are two green wires in the engine harness labeled something like fan thermo switch. They are green wires, one at the top of the engine and one down near the bottom of the radiator. These two wires are on the ground side of the relay, so completing the ground will trigger the relay. You can prove it to yourself by simply turning your key on and touching one of those two green wires to a good chassis ground. The fan will come on or if you haven't wired up the fan yet, you will hear the relay click as you complete the ground. The fuel pump relay, wired as is, will trigger the fuel pump when the key is turned on. If you haven't connected your fuel pump yet, turn the key on and you will hear the relay click. The ground wire for the fuel pump relay goes through the inertia switch. When the switch is triggered by impact or a roll over, it breaks the ground and turns off the fuel pump. The FAST EFI green fuel pump control wire is a (-) wire controlled by the ECU. When the ECU wants to turn on the fuel pump, it completes a ground on that wire. By connecting that wire to the ground side of the inertia switch, when the ECU sends that ground signal, you are completing the fuel pump relay circuit and powering the fuel pump. I hope this clears up some of the fog.

Dave

[edwardb]

I decided to do some more searching on these wiring issues. OK, so when did Ron Francis update their Chassis Wiring Harness instruction book? The copy I received when I ordered my kit in 2012 is 35 pages long, with virtually no detail regarding wiring connections, or much of anything else. Low and behold, I check their website to see if they may have any information I could use, decided to look at the instruction book online, and find out it's now 68 pages long with unbelievable detail that my instruction book only dreams about! Turns out that they now address the questions that I was asking.
Only thing I need to check with them now is what to do with the Purple "Coil/Tack" wire.

Quick caution. There has been a least one update to the harness since your 2012 version. My Coupe kit, delivered in late 2017, had the a version and a 2017 revision S instruction book. I see the instructions your referencing on RF's website, now revision U. Granted there's more detail in the newer manuals. But also be aware there are actual changes to the harness compared to what you received. May/may not make a difference for your build. But just so you know. One of the major things was they made the dash harness more compatible with the Speedhut gauges. But there are also other differences.

[EZ$]

Dave, I think I actually understood that! I'm going to do some tests as soon as I get the chance. Our business has been really dead lately, a good thing for my build, but today the phone rang off the hook, so I'll be tied up for a bit.
Paul, that was my concern when I was reading through the website. I'm going to check in with them tomorrow, if I can steal some time out of the day. This is killing me to be as close as this feels, and still fighting with this wiring. I'll either be better at this, or we'll see the magic smoke soon!

[Papa]

For everyone else reading this that wants to use the RF fuel pump relay with their particular EFI system, be sure to verify your EFI's specific outputs! FAST fuel pump control is (-). My Sniper fuel control wire with the Holley relay is (+), but (-) if you eliminate that supplied relay. Both systems use (-) on their fan control wires.

[EZ$]

Dave, Spent almost an hour on a tech call with Ron Francis. The techs name is Dave. He was awesome in trying to explain some questions that I had for him. As you had mentioned, he recommended not to cut the loops at the fuse box relays. He felt that installing two new relays would be the better choice, would be easier to troubleshoot down the road, and if the car was ever taken back to a carb, the wiring that will be added could be removed, and everything that you need is still there in the original harness. Now in wiring up the relays, he said to run power to the #30 terminal on the relay through a 30amp fuse for the fan, and 20amp for the fuel pump. Power would need to come from an ignition, not accessory circuit for the fuel pump, because it has to be hot in start. The FAST wire leads for the fuel pump and the fan would connect to the #85 terminal, and the #87 terminal taken to the fan or fuel pump. Now #86 terminal would be connected to switched 12v. We were talking about so many things that I didn't get clarity, or I don't remember his explanation of the 12v switched source. I'm using the orange "coil/efi" lead to provide switched 12v to the ECU, so could this same lead be tapped off to provide the switched 12v to the two relays that I would be adding, or should it be drawn from a different source? This layout matches the wiring diagrams in the FAST instructions (I'd attach the diagrams, but I don't know how to attach anything other than pictures). Also, would I need to disconnect the wiring to these devices that is in the RF harness, or just leave it as it is?
I just hope I'm getting close in my understanding of this. I'm getting frustrated trying to sort it out. I hate wiring, but I'm sure the wiring hates me right back!

[Papa]

Rick,

It's completely up to you, but I don't see any value in running new relays. If you want to give me a call, just PM me.

Dave