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Thread: Questions on sensors & harness need to complete an HP Kit.

  1. #1

    Default Questions on sensors & harness need to complete an HP Kit.

    Hi everyone, I have a Holley 550-606 HP EFI ECU & Harness Kit. This is going in a 1991 Mustang and wanting to get the rest of the parts/pieces needed to try and install it. I'm going to use the stock TFI for now. This is what I've figured out that I still needed to buy, and I want to stick with sensors that require no repinning, etc. TFI Harness 558-305, IAC Motor 543-105, I/O Auxiliary Harness 558-400 & Accufab Adapter. Am I correct on this?
    It does look like I'll have to make a connector for the TPS. Anyone know of a connector that will plug into the TPS plug on the harness? Thanks in advance!

  2. #2
    Join Date
    Dec 2009


    Quote Originally Posted by mondo View Post
    TFI Harness 558-305, IAC Motor 543-105, I/O Auxiliary Harness 558-400 & Accufab Adapter. Am I correct on this?
    Yes, those are compatible parts.

    It does look like I'll have to make a connector for the TPS. Anyone know of a connector that will plug into the TPS plug on the harness? (Related Forum Post)
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS T/W 11R 205 heads, 232°-244° duration/.623" lift/114° LSA camshaft, 12:1 C/R, TFS R-Series FTI ported intake, BBK 80mm T/B, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 200A 3G alternator, Optima Red battery, A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, -6AN fuel system plumbing, Walbro 255 LPH pump, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/3000 RPM converter, B&M Hammer shifter, FPP aluminum driveshaft, FPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 M/T Street Comp tires.

  3. #3


    Just one minor FYI (LINK): In order to mount the Holley 543-105 IAC motor to the Accufab IAC adapter, you have to make a very minor enlargement of the bottom screw hole on the IAC, as they are just a TAD out of alignment. The Accufab piece is designed for the GM later style IAC and the Holley piece is the Chrysler variant, which flows more air than the GM. The two parts are not 100% identical, they appear to be to the naked eye. But once you push the Chrysler style IAC into that Accufab adapter, you will see that the bottom screw won't go in, you will cross-thread it quickly if you try to force the issue. Don't round out the entire hole; just a small area on the bottom left needs to be trimmed away and then you're good to go. Dremel is your friend. Good luck with your project.

  4. #4


    I'm new here, but have similar kit, Holley 550-604, and sourcing extras now also. If I understand your question correctly, try Delphi 150 connectors, that's what I've just ordered to terminate my own TPS (not supplied in kit) to make my own loom to TPS. EDIT: Try

    My current issue, is I have an Australian built 304 ci Holden V8, using a GM dual sync distributor, and I want to utilize a Bosch part #0 227 100 124 module, to ignite a regular Bosch coil (and save expense of an MSD). There are no clear instructions for this setup anywhere on the net. I'm unsure to run the white "Points Output" wire (pin A6) to the Bosch igniter, or EST/SPOUT (pin A28) to igniter. Someone here would have done this already. I would order the Holley parts, but takes 14 days to get to OZ, and need to be on the dyno in three days.

    Try LS1 to LS3 at an auto salvage. Most LS use Delphi connectors. You can open the pins sometimes, but I recommend just ordering a full new connector Delphi 150 type, which comes with new male & female pins.

  5. #5


    I have a 1991 Mustang 5.0L as well, and I'm wondering how you're wiring the electric fuel pump? Are you going straight from the harness to the pump via a very long extension on the harness wire, or are you taking it to the relay under the drivers seat and wiring it there? If doing it that way, which wire would I need to tap into to make it work? Thanks for the information on the TPS & IAC. That helps a lot, and I'm sure I would have cross threaded the IAC right out of the gate.

  6. #6


    The way I did mine: I used a new 30 amp relay, wired the green fuel pump trigger wire from the Holley HP to the relay coil and grounded the other side of the coil, and then used the existing fuel pump wiring in the car including the inertia switch on the contact side of the new relay. I have a '92 Mustang and my fuel pump relay is under the hood on passenger side near the original mass-air plug was. Whatever the location, you should be able to make it so that you still have the safety of the inertia switch in case of a crash, so the fuel pump will shut down if that switch is triggered. I don't suggest that you try to use the green trigger wire to directly power the fuel pump, always use a relay. You could simply just change the wiring on your existing fuel pump relay to use the green trigger wire on one side of the relay coil, and ground the other side. The diagram attached shows the wiring, hope this helps.
    Attachment 3172

  7. #7
    Join Date
    Jul 2014
    Aptos, CA


    I'm in the finishing stages of a HP install, and used the supplied Holley Fuel Pump relay (86) trigger wire (red) to go through the Inertia Switch, and activate the green (fuel pump) wire and go directly to the pump. I don't like Ford's idea of running the pump load through their Inertia Switch. By doing it this way, you not only shut down the fuel pump, but also shut off the injector harness as it feeds from the same (30) terminal on the Holley relay. I've done this on several Ford systems without issues.

    Attachment 3173

  8. #8


    Depending on what pump you use, they can draw more than the 30 amps the stock wire can handle. I put a high current relay next to my HP and then ran fresh wires to the pump.

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