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Thread: Possible cam/crank sensor issue with no start.

  1. #1

    Default Possible cam/crank sensor issue with no start.

    Here's the details.
    427" twin turbo LSx, methanol
    Billet crank no reluctor
    MSD Flying Magnet crank trigger with Holley Hall-Effect 554-118 pickup, air gap set at .040".
    RCD cam gear drive with 4x reluctor using a factory LSx 4x sensor, air gap checked at .030".
    Waterman cam driven fuel pump.
    Billet Atomizer 700s
    Crank sensor parameters are Custom, 1 Pulse/Fire, 50° Reference Angle. Digital Falling.
    Crank sensor parameter is 4x sensor.

    Problem: Tried cranking to see RPM signal from ECU and the indicator said syncing then flashed error. So I did a System Log to see the sensor square wave pattern. (This is where I'm in unfamiliar territory don't know what it should look like) I took a screenshot of the pattern and it makes no sense.

    So I changed cam sensor to Single Pulse Digital Rising and then I had an RPM signal. So I added fuel and began attempting to see if it would start or at least had spark and it'd backfire. Although hard to tell whether it was in the intake or exhaust side. It'd pop sometimes and other times It'd almost give signs of life, but not really. So it has spark & fuel, but spark seems to be wrong.

    I tried a myriad of combinations of Digital Falling vs Digital Rising on the cam & crank sensors and even went as far as removing the cam sensor to see if Batch Fire strategy would allow it to run. It was unsuccessful although battery was dying at this point so it could be inconclusive.

    I also supplemented it with fuel to be certain it's not lacking fuel delivery because of the mechanical pump situation. Also manipulated throttle position while cranking to see if it wanted more air with the fuel I supplemented.

    I've gone through the typical no start check lists in a old thread I saw Danny steer people to in the past and I think I have all the bases covered. Wiring has been verified 5V and sensor grounds are all correct for cam/crank. The typical sensors all display normal values, air temp, coolant temp, MAP pressure, etc.

    Looking for a little assistance as to what to check next. I'm at work this morning and plan to take another look this evening. I plan to roll the engine over to 50° BTDC and verify the crank sensor is hitting a magnet. I used a piston stop and a 18" degree wheel to install the timing pointer and then I fabricated the crank sensor bracket to get the sensor at a magnet while at 50° BTDC.

    Problem I have seems to stem in the cam sensor setup. I'm uncertain is to why when the cam sensor is configured properly (4x) that I have no RPM signal and it flashes error (maybe flashes per revolution). But I could have more than one issue considering it won't light off when the cam sensor is taken out of the picture (batch fire mode).

    Click image for larger version. 

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  2. #2

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    Here's a scaled version of the System Log to make it easier to see:
    Click image for larger version. 

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  3. #3
    Join Date
    Dec 2009
    Location
    Connecticut
    Posts
    26,002

    Default

    Quote Originally Posted by Steve Marsa View Post
    RCD cam gear drive with 4x reluctor using a factory LSx 4x sensor, air gap checked at .030".
    Is that RCD cam gear drive an actual GM LSx 4x cam sync pattern? Although, since RPM is derived from the crank sensor, I'd investigate that first. Maybe it's happening at the wrong time (LINK) or the engine isn't cranking fast enough (LINK). Charge the battery.
    Read posts #7 & #13: https://forums.holley.com/showthread...3910#post73910 (Belt Driven Mechanical Fuel Pumps)
    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.

  4. #4

    Default

    The RCD cam sync pattern is described in there exploded view as a 4 lumps. http://rcdengineering.com/Portals/0/...PORT%20BOM.PDF The exploded view doesnt show the part, but I plan to remove the fuel pump and examine the construction of the cam sync.

    I was able to get a crank RPM after changing the cam sensor to Single Pulse, instead of 4x. Although I know it's incorrect, for whatever reason it gave me a RPM signal. I also attempted No Cam Sensor at all and tried to get it to run in batch fire and it didn't still was backfiring through the exhaust which leads me to believe I may have incorrectly setup the crank trigger.

    Crank RPM is not fast, but I think it's fast enough to start in my opnion. It's around 125-140 RPM during cranking. The fuel situation isnt a real concern at the moment I gave it supplemental fuel and opened the throttle more and did a TPS Autoset. The result was more backfires through the exhaust.

    I'm going to confirm the crank sensor position and make sure I didn't set it up on exhaust stroke mistakenly. Then I'm going to see what the timing light indicates for cranking timing. I also purchased a GM OE cam sensor to replace the existing one I have which was made by BWD to eliminate that as any potential concern.

    I'll update the post later this evening after I do these checks. Thanks Danny.

  5. #5
    Join Date
    Dec 2009
    Location
    Connecticut
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    Quote Originally Posted by Steve Marsa View Post
    Crank RPM is not fast, but I think it's fast enough to start in my opnion. It's around 125-140 RPM during cranking.
    Yes, that's enough cranking RPM.

  6. #6

    Default

    So I rolled the engine over to TDC compression and confirmed the sensor is pointed at the magnet, it's just about off the sensor as I was anticipating running Digital Falling. This all looked correct, I swapped out the cam sensor and did a System Log same results as I expected it was OK to begin with. I didn't end up taking the fuel pump off yet. I decided to leave it in Batch Fire mode and try to get it running. I got it to a point where it would fire and run, but only for a few seconds then it would die. I'm struggling to determine whether it needs more or less fuel and I've been messing around with Cranking Timing because it seems to influence whether it will fire or not. So at the moment I'm bouncing around with the amount of fuel it has and how much timing it has. I wasn't able to put a light on it during cranking because there was no helper around this evening. So my next step is going to be put the light on it to see what the timing light is indicating the crank timing is to see whether I should adjust the pickup position or if I'm just way out to lunch to begin with. It seems and sounds like the timing is way off and then there's the fuel which could be way off as well.

  7. #7
    Join Date
    Dec 2009
    Location
    Connecticut
    Posts
    26,002

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    Quote Originally Posted by Steve Marsa View Post
    I wasn't able to put a light on it during cranking because there was no helper around this evening.
    If you're working alone, use a remote starter switch (LINK) to jump the starter and crank the engine (key-on).
    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.

  8. #8

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    Danny, take a look at this short clip of the car cranking over. This was my first attempt overall, so it was configured 1 Pulse/Fire, 50° Reference Angle, Digital Falling, 4x cam. It says syncing then error and never produced a RPM signal. What are your thoughts on that, what direction would you think to look?

  9. #9

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    Here's a picture of the cam sync plate. I don't currently have the information to determine where & how it should be in relation to the cam sensor.
    Click image for larger version. 

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  10. #10

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    So I found in a old thread and in the instructions a description of the function of the 4x cam signal and it stated that the unique tooth pattern event the ECU is looking for was around 210° BTDC so I rolled the engine over to 210° BTDC and examined the position of the cam sensor in relation the unique tooth on the reluctor and it seems to line up exactly as intended. So I'm confident the 4x pattern isnt timed incorrectly or anything like that. In the notes it mentioned not using less than 40° Ignition Reference Angle and I was at 50° so I added 10 more degrees and made it 60°, repositioned the crank pickup, and put it all back together to test crank it and I now have a valid RPM signal while it's configured in 1 Pulse/Fire crank and 4x cam. It mentioned that these signals could cross and cause issues so I'm going to assume that's possibly what happened. So now that that's resolved I'll continue to attempt to fire it, which I've been unsuccessful. I suspect a older/weak +16V battery is holding me back (it doesn't allow me to crank for long before the RPM slow and battery voltage drops to 10-9V which it loses RPM signal) in addition to the slow cranking RPM from the starter. I'm going to call Powermaster tomorrow and see if I can get one of there "ultra high speed" starters for this engine. I'm calling it quits for today, I'll update my progress when I have more information.

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