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Thread: Digital Dash Startup Question

  1. #11
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    It won't be +12V while cranking. A battery will drop about two volts when cranking to start.
    https://forums.holley.com/showthread...9369#post79369 (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 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.

  2. #12

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    OK, so it’s fine for me to be sitting at 10.2 while cranking? I knew it would drop some, but I thought that was too much.

  3. #13

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    In regards to battery voltage drop, is ECU datalogging more accurate then the Data Monitor? Before cranking, the Data Monitor shows 12.3 volts, the datalogger shows 11.8 volts.

  4. #14
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    I haven't noticed that. The Data Monitor & Datalogger are reading from the ECU.
    https://forums.holley.com/showthread...anyone-explain (Somewhat related forum thread.)
    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. #15

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    Basically my car has been a hard start from the beginning, so I'm going back looking at everything from battery voltage to grounds, etc. If I check my voltage with a multimeter at the battery and look at my Digital Dash, they match @ 12.3 volts. However, when I run a datalog, it will show 11.8 as the highest volts. I've run a few datalogs and my voltage has gone as low as 10.2, but will stay constantly 10.2-10.6 through the datalog. I know there's going to be voltage drop. I'm not sure if this is too much of a drop, as I have read the ECU does not like to be below 11 volts. My weakest link at this point might be having #2 wire as a ground from the engine to the battery instead of 1 gauge wire. (This could be the issue, but I'm not totally convinced). The datalogs have showed the cam & crank signals are good, and I immediately get sync. RPM gets to 120-130. I've also checked the cam & crank trigger wiring, should I be seeing 12 volts on the signal return wires? Thanks.

  6. #16
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    Quote Originally Posted by robertc68 View Post
    I've also checked the cam & crank trigger wiring, should I be seeing 12 volts on the signal return wires?
    https://forums.holley.com/showthread...0957#post90957 (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 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. #17

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    Thanks for the info, it’s really helping. Do you think I'm having voltage transfer issues?

  8. #18
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    Quote Originally Posted by robertc68 View Post
    I know there's going to be voltage drop. I'm not sure if this is too much of a drop, as I have read the ECU does not like to be below 11 volts.
    I don't think 11 volts is too low.

    My weakest link at this point might be having #2 wire as a ground from the engine to the battery instead of 1 gauge wire. (This could be the issue, but I'm not totally convinced).
    Maybe if the battery is in the rear of the vehicle, but I doubt it too.

    The datalogs have showed the cam & crank signals are good, and I immediately get sync. RPM gets to 120-130.
    This sounds good. It seems you don't have a cranking voltage drop issue. Check/charge the battery.
    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.

  9. #19

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    Thanks. I was able to check my crank signal return, and cranking the voltage is dropping from 11.8 to 5 volts. Isn't it suppose to drop to 0 volts?

  10. #20
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    Quote Originally Posted by robertc68 View Post
    Isn't it suppose to drop to 0 volts?
    Read 3rd column of page 2: http://www.wellsve.com/sft503/Counterpoint3_1.pdf (Understanding/Troubleshooting Hall-Effect Sensors - "Troubleshooting", Page 2)

    "If the sensor has power & ground, the next thing to check would be sensor output. The voltage output signal should switch back & forth from maximum to near zero as the engine is cranked. No change would indicate a faulty sensor. Watching the sensor’s voltage output on an oscilloscope is a good way to spot problems that might escape normal diagnosis. You should see a nice, sharp square wave pattern that goes from maximum to near zero (or vice versa) every time the sensor switches on & off."
    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.

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