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  • Crank Signal at end of datalogs.

    I have a GM 8.1L, aka 496 in a marine application. I have HP ECU and Holly EFI V5.0. This has ran before, but every once and a while after the boat would sit for a period of time, the boat would not start or run really bad when started almost like it lost it's tune. I identified a ground short on my crank sensor connection. I was able to correct that, but I'm unable to get the boat running again. I have setup a System Log to start immediate for 20 seconds. I datalogged while cranking for 10 seconds and then let the datalog complete without turning the key off. What I'm seeing is a good CAM signal while cranking. The Crank signal seems to only come at the very end of the cranking, almost as though when I release the key the cam signal start, but only for about .4 seconds. The same for the RPM which goes from Stall to Sync at the last .4 seconds of the datalog. The Cam and Crank both are wired to the same B20 pin for +12V reference and A14 pin for ground. I've tested the wiring using a multimeter with key on and get +12V to both cam & crank as well as ground. Crank signal is pin A30, and CAM signal is pin A22. Attached is the datalog as well as the Global File. Any help would be appreciated as this is driving me crazy. I have replaced the Crank sensor a with a new one a couple of times and I only get a signal with the original sensor. For some reason not able to get a signal with the new Crank sensors. Any diagnostics help would be greatly appreciated.

    30ft Kuchina
    Mercruiser 496 (GM 8.1)
    Modifided intake, heads, cam & throttle body.
    Attached Files

  • #2
    Originally posted by dynoman8618 View Post
    The Crank signal seems to only come at the very end of the cranking, almost as though when I release the key the cam signal start, but only for about .4 seconds. The same for the RPM which goes from Stall to Sync at the last .4 seconds of the datalog.
    Ensure the Switched +12V red/white wire is powered in the "Run" and "Crank" key positions.​​
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385"/6.3L SBF, Dart SHP 8.2 block, forged steel crankshaft & H-beam rods, forged pistons, Trick Flow Twisted Wedge 11R 205 CNC Comp Ported heads, 12:1 compression ratio, 232-244 duration/.623" lift/114 LSA camshaft, TFS R-Series FTI Comp Ported intake, BBK 80mm throttle body, Holley Dominator MPFI & DIS, Holley 36-1 crank trigger, MSD 1x cam sync, PA PMGR starter, PA 200A 3G alternator, Optima 34/78 Red battery, 100HP progressive dry direct-port NOS, R134a A/C, Spal Dual 12" HP 3168 CFM fans, Frostbite 3-core aluminum radiator, Pypes dual 2.5" exhaust, off-road X-pipe, shorty headers, Earl's -6AN fuel system plumbing, Walbro 255 LPH in-tank pump & Pro-M -6AN hanger, S&W subframe connectors, BMR upper & lower torque box reinforcements, LenTech Strip Terminator wide-ratio AOD, 3000 RPM C6 converter, B&M Hammer shifter, Stifflers transmission crossmember & driveshaft safety loop, 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.

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    • #3
      Pull the power to the coils and injectors. Switch the cam and crank sense wires (A30, A22) at the ECU plug (J1A). Then do a System Log. See if the problem follows the wiring or stays with the ECU.

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      • #4
        Originally Posted by Danny Cabral
        Crank & Cam Sensor Wiring Tips:
        The 10-pin Ignition Connector has one "Chassis Ground" (loose black wire ground) and two "IPU Grounds" (clean ECU ground).
        Don't use "Chassis Ground" to ground an ignition module (or crank & cam sensors). It's quick & easy to move the ignition
        module ground wire from (cavity) pin D "Chassis Ground" to pin C or G "IPU Ground", where it should be.

        If you don't have the actual Metri-Pack terminal release tool, a "safety pin" will work.
        It just needs to be a stiff wire between .030"-.035" in diameter to release the terminal tab.
        Then reopen (bend) the terminal tab before reinsertion, so it will clip (lock) into the cavity.
        http://www.whiteproducts.com/removal_tools.shtml (T-6 Micro Terminal Release Pick Tool)

        Also, don't use (cavity) pin E "Switched +12V" from the 10-pin Ignition Connector, to power an ignition module
        (or crank & cam sensors), unless you've modified the wiring source to connect from pin B20 - EST 12V Output
        (P1B ECU Connector). This LINK explains why & how to do it.
        http://documents.holley.com/techlibr...10555rev17.pdf (Holley EFI Wiring Manual, Sections 2.1 "Pin-Outs" & 13.0 "Wiring Appendix")
        May God's grace bless you in the Lord Jesus Christ.
        '92 Ford Mustang GT: 385"/6.3L SBF, Dart SHP 8.2 block, forged steel crankshaft & H-beam rods, forged pistons, Trick Flow Twisted Wedge 11R 205 CNC Comp Ported heads, 12:1 compression ratio, 232-244 duration/.623" lift/114 LSA camshaft, TFS R-Series FTI Comp Ported intake, BBK 80mm throttle body, Holley Dominator MPFI & DIS, Holley 36-1 crank trigger, MSD 1x cam sync, PA PMGR starter, PA 200A 3G alternator, Optima 34/78 Red battery, 100HP progressive dry direct-port NOS, R134a A/C, Spal Dual 12" HP 3168 CFM fans, Frostbite 3-core aluminum radiator, Pypes dual 2.5" exhaust, off-road X-pipe, shorty headers, Earl's -6AN fuel system plumbing, Walbro 255 LPH in-tank pump & Pro-M -6AN hanger, S&W subframe connectors, BMR upper & lower torque box reinforcements, LenTech Strip Terminator wide-ratio AOD, 3000 RPM C6 converter, B&M Hammer shifter, Stifflers transmission crossmember & driveshaft safety loop, 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.

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