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Thread: Modifying the wiring harness & assigning unused pins.

  1. Default Modifying the wiring harness & assigning unused pins.

    One of the biggest "problems" I had installing the Avenger system in my truck was the length of the wire harness. To hide the ECU in my cab the harness was too short, while installing the ECU in the engine bay left me with 3' of extra harness.

    I've relocated the battery in my '59 pickup from the passenger side firewall (stock location), to under the cab on the passenger side using a drop down box, no biggie. The ECU is mounted on a plywood sheet (for now) cut to fit the firewall and mounted with the same bolt holes the battery shelf used to hang from. The excess wire harness length was routed down along the crease of the firewall and inner fender, then across the outside of the toe board and loops back up to the firewall, and comes over the passenger side valve cover to the make the TBI and sensor connections. It ain't perfect but it got me running.

    What makes the most sense, if I keep the ECU in the same location it is now, would be to shorten the EFI harness. Again, no biggie, but a lot of work. According to Holley, the P1A and P1B connectors (at the ECU) are the better location to modify. Pushing the white tab in on one side, allows the wires with the pins to be pushed out from the bottom of the connector. If I had a supply of these pins I'd consider tackling it.

    Aside from shortening the harness length overall, some of the sensor wires that split-off near the TBI are really pretty long for my application, like the CTS and the Oil Pressure sensor wires (not using Oil or Fuel pressure sensors ATM) - I think my install would be much cleaner if I didn't have to manage a small bundle of wires right around the TBI too.

    What do you guys do to manage your wire harnesses; has anyone modified them?

    Also, I wonder how many unused pins there are in the 550-40X series that can be reassigned. Looking in the V2 software at the Pin Map, there seems to be a small number of unassigned pins - what can I do with these?
    Last edited by octanejunkie; 01-09-2015 at 04:37 PM.

    '59 Chevy 1/2 ton Pickup 3" lift (1" body all around, 2" rear suspension) & dual sway bars
    357ci SBC, Vortec heads, 214°/224° @ 0.050 cam/under .050" lift/112° LSA & roller rockers
    2.5" ram horn manifolds, dual 2.25" pipes, H-pipe behind trans, 14" Flowmaster mufflers
    Power steering, tilt column, power disc brakes up front, A/C (Vintage Air kit pending)
    700R4 transmission, 2200 stall, 3.42 limited-slip rear end & 31.5" tires

  2. #2
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    Quote Originally Posted by octanejunkie View Post
    According to Holley, the P1A and P1B connectors (at the ECU) are the better location to modify. Pushing the white tab in on one side, allows the wires with the pins to be pushed out from the bottom of the connector. If I had a supply of these pins I'd consider tackling it.
    http://forums.holley.com/showthread....als-Holley-EFI (ECU Connectors & Terminals)

    Also, I wonder how many unused pins there are in the 550-40X series that can be reassigned. Looking in the V2 software at the Pin Map, there seems to be a small number of unassigned pins - what can I do with these?
    You'll have to be more specific. What pins are you referring to?
    http://documents.holley.com/techlibr...10555rev16.pdf (Holley EFI Wiring Manual - Page 6)
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS TW 11R 205 heads, 11.8:1 comp, TFS R-Series intake, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 160A 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, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/2800 RPM converter, M4602G aluminum driveshaft, FRPP 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 tires.

  3. #3

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    I had modified my main harness due to length. Some wiring was too long and others to short.
    After this I reinstalled everything and had issues and would advise anyone to reconsider doing this.
    I consider myself very capable of tackling this, but the problem lies in that there are sensors that have only 5VDC.
    I later replaced my harness with a new one and have no issues now.

    The advise of modifying the harness at the ECU connections is similar to what I have seen some professionals do.
    Some people will refer the harness as a tree trunk and not modify the branch's.

    I think the connectors you are looking for are called metro-pack.
    SICKFOX

  4. #4
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    Quote Originally Posted by Sickfox View Post
    I think the connectors you are looking for are called metro-pack.
    The ECU connectors are Tyco/AMP sealed 1.0mm SuperSeal connectors.
    The harness connectors are Delphi Metri-Pack 150 Series connectors.
    Some of the sensor connectors are Delphi GT 150 Series (with the different colored "key index" insert).
    http://forums.holley.com/showthread....als-Holley-EFI (ECU Connectors & Terminals)
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS TW 11R 205 heads, 11.8:1 comp, TFS R-Series intake, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 160A 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, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/2800 RPM converter, M4602G aluminum driveshaft, FRPP 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 tires.

  5. Default

    Thanks for the replies, gentlemen!

    Quote Originally Posted by Danny Cabral View Post
    Thanks for the info and link (should be a sticky)

    Quote Originally Posted by Danny Cabral View Post
    You'll have to be more specific. What pins are you referring to?
    http://documents.holley.com/techlibr...10555rev16.pdf (Holley EFI Wiring Manual - Page 6)
    I don't have the pin-out in front of me but I recall "spare pins" - especially on the Input/Output connector.
    Could I use these to light up idiot lights under certain conditions, for example?

    Quote Originally Posted by Sickfox View Post
    I had modified my main harness due to length. Some wiring was too long and others to short.
    After this I reinstalled everything and had issues and would advise anyone to reconsider doing this.
    I consider myself very capable of tackling this, but the problem lies in that there are sensors that have only 5VDC.
    I later replaced my harness with a new one and have no issues now.

    The advise of modifying the harness at the ECU connections is similar to what I have seen some professionals do.
    Some people will refer the harness as a tree trunk and not modify the branch's.

    I think the connectors you are looking for are called metro-pack.
    Holley advised me to modify at P1A and P1B since it's easier than opening the weather pack connectors at the ends.
    My overall concern is that the harness is too long, both at the "trunk" and some of the "branches".
    Are you suggesting that trimming length will change resistance inherent in the wiring that the sensors depend on? I could see how lengthening by extending (vs. replacing a longer 1-piece wire) can increase resistance, but will shortening wires change the sensor values by decreasing expected resistance?

    FWIW, Holley Tech said, "this is done quite often" when I asked about shortening the harness...

    '59 Chevy 1/2 ton Pickup 3" lift (1" body all around, 2" rear suspension) & dual sway bars
    357ci SBC, Vortec heads, 214°/224° @ 0.050 cam/under .050" lift/112° LSA & roller rockers
    2.5" ram horn manifolds, dual 2.25" pipes, H-pipe behind trans, 14" Flowmaster mufflers
    Power steering, tilt column, power disc brakes up front, A/C (Vintage Air kit pending)
    700R4 transmission, 2200 stall, 3.42 limited-slip rear end & 31.5" tires

  6. #6
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    Quote Originally Posted by octanejunkie View Post
    ...especially on the Input/Output connector. Could I use these to light up idiot lights under certain conditions, for example?
    Of course, everything on the Inputs/Outputs connector is for custom I/O.
    The Avenger/HP ECU only has two high side Outputs (+12V switched, PWM+),
    two low side Outputs (Ground switched, PWM−), and four Multi-Inputs.
    https://www.holley.com/document/tech...useanddiff.pdf (HP & Dominator ECU Differences)

    To connect up to 4 Inputs & Outputs to the EFI Main Harness, use I/O Auxiliary Harness 558-400.
    Eight Wire I/O Auxiliary Harness Connector Pin-Out (also in the Holley EFI Wiring Manual - LINK):
    Pin A...A12...White/Blue (Input #1) F,5,2,T,H,G
    Pin B...A3....White/Red (Input #2) F,5,2,T,H,G
    Pin C...A13...White/Black (Input #3) F,5,G
    Pin D...A4....White/Green (Input #4) F,5,G
    Pin E...B12...Gray/Yellow (Output #1) H,P+
    Pin F...B11...Gray/Red (Output #2) H,P+
    Pin G...B10...Gray/Black (Output #3) G,P−
    Pin H...B3....Gray/Green (Output #4) G,P−

    The 558-400 I/O Auxiliary Harness is 20 feet long.
    It's "plug & play" into the main harness, and an easy way to connect common things like an electric cooling fan (Link).
    This I/O Auxiliary Harness isn't required for the optional oil & fuel pressure transducers, which are also "plug & play" into the main harness.
    The oil & fuel pressure transducers are used for Data Monitoring, Data Logging and setup Outputs based on oil & fuel pressure.

    Are you suggesting that trimming length will change resistance inherent in the wiring that the sensors depend on? I could see how lengthening by extending (vs. replacing a longer 1-piece wire) can increase resistance, but will shortening wires change the sensor values by decreasing expected resistance?
    There's nothing wrong with shortening the main harness.

    FWIW, Holley Tech said, "this is done quite often" when I asked about shortening the harness...
    Yes, it's a very common installation practice.
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS TW 11R 205 heads, 11.8:1 comp, TFS R-Series intake, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 160A 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, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/2800 RPM converter, M4602G aluminum driveshaft, FRPP 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 tires.

  7. #7

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    I do not see any reason adjusting the wire length would change the resistance. I think my issue was tying in multiple commons into one butt connector.
    Using a large crimper and shrink tubing, I still had issues reading some sensors correctly. However I did have success on my injector harness.

    I run a Dominator and I felt the harness did not have a great finished look from Holley. The electrical tape wrapped around the wire braid and very large stickers with numbers on each injector. I removed all the tape and finished it with shrink tubing. The large numbered stickers were replaced with small round numbers similar to whats found on spark plug wiring, designating which plug it is assigned to. The wiring length was left the same.

    I did speak with some wiring professional on what they charge to modify a ECU harness like a Holley. Your looking north of $500.
    SICKFOX

  8. #8

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    I know it's too late, but this is the reason I buy an Unterminated Harness on anything Holley I install now. Much nicer in the end.
    Tom

  9. #9
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    Quote Originally Posted by FuelieNova View Post
    I know it's too late, but this is the reason I buy an Unterminated Harness on anything Holley I install now.
    The Holley 550-605 Unterminated Universal Harness Kit isn't always worth the trouble. If your harness only needs to be shortened, I think it's much easier to modify a fully terminated harness. It already has all the plastic connectors & wire seals, you just need the appropriate terminals (cut & crimp). Unfortunately, a lot of people who purchase the Unterminated Universal Harness Kit, really aren't that experienced with wiring and/or reading electrical schematics, and just get themselves into trouble.
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS TW 11R 205 heads, 11.8:1 comp, TFS R-Series intake, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 160A 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, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/2800 RPM converter, M4602G aluminum driveshaft, FRPP 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 tires.

  10. Default

    Quote Originally Posted by Sickfox View Post
    I do not see any reason adjusting the wire length would change the resistance. I think my issue was tying in multiple commons into one butt connector.
    Using a large crimper and shrink tubing, I still had issues reading some sensors correctly. However I did have success on my injector harness.

    I run a Dominator and I felt the harness did not have a great finished look from Holley. The electrical tape wrapped around the wire braid and very large stickers with numbers on each injector. I removed all the tape and finished it with shrink tubing. The large numbered stickers were replaced with small round numbers similar to whats found on spark plug wiring, designating which plug it is assigned to. The wiring length was left the same.

    I did speak with some wiring professional on what they charge to modify a ECU harness like a Holley. Your looking north of $500.
    I'm very comfortable with modifying the harness. Plus, I will be shortening, not lengthening. If I were, and I was concerned about changes in resistance I would not multi-splice nor would I use butt connectors - those are for down and dirty, not permanent install in my experience. I'm a solder-heat shrink-multimeter kind of guy.

    Quote Originally Posted by Danny Cabral View Post
    The Holley 550-605 Unterminated Universal Harness Kit isn't always worth the trouble. If your harness only needs to be shortened, I think it's much easier to modify a fully terminated harness. It already has all the plastic connectors & wire seals, you just need the appropriate terminals (cut & crimp). Unfortunately, a lot of people who purchase the Unterminated Universal Harness Kit, really aren't that experienced with wiring and/or reading electrical schematics, and just get themselves into trouble.
    I have the I/O sub harness ready to go. I will unsleeve my entire harness to set proper length on all sensor connector wiring to suit my tastes, then mock it up & shorten from the ECU connector ends. I'm ordering not just the pins, but new P1A and P1B connectors, so I can keep a physical sample of the pin-out when I cut my harness down.
    It's time consuming and detail-oriented, but I love that sort of work...kind of like like electronic knitting (if I were to knit, which I don't).

    Thanks for all the info & support!

    P.S. I've done a few Painless harness installs that are fusebox to bare wire - one of my favorite things to do! I just hate working under the dash for long periods of time. Body and engine harness, no problem, but I don't think I'd tackle a bare ECU harness first time out.

    '59 Chevy 1/2 ton Pickup 3" lift (1" body all around, 2" rear suspension) & dual sway bars
    357ci SBC, Vortec heads, 214°/224° @ 0.050 cam/under .050" lift/112° LSA & roller rockers
    2.5" ram horn manifolds, dual 2.25" pipes, H-pipe behind trans, 14" Flowmaster mufflers
    Power steering, tilt column, power disc brakes up front, A/C (Vintage Air kit pending)
    700R4 transmission, 2200 stall, 3.42 limited-slip rear end & 31.5" tires

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