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Thread: Extended Crank Times on stock 5.3L

  1. #1

    Default Extended Crank Times on stock 5.3L

    Hi guys,

    I'm running an Atomic LS on a bone stock 04 5.3L LM7 (1x cam 24x crank wheel). Everything about the system is great except about 1 in 10 starts takes a solid 6-7 seconds of cranking to get the motor fired up. During these extended crank times I have measured fuel pressure (58-62 psi), I am getting spark according to my spark tester, I even put a lab scope on the cam and crank sensor outputs and am getting a textbook waveform. After these extended crank events I am getting no error codes, current or in history. Has anyone ever experienced this issue before? Thanks for the help!

  2. #2

    Default Extended Crank Times on stock 5.3L

    While experiencing this long crank,does it back fire?

    Watch the cam and crank in the menu while cranking every time you crank on a startup to try and "catch" a cam error. It may not show after the issue.

    Lemme know.

  3. #3

    Default Extended Crank Times on stock 5.3L

    Sometimes it does backfire, maybe 1 in 10 mess up events. I have received a history error once, but for the vast majority of the times there is no history code or backfire. It seems like I'm getting everything but injector pulse.

  4. #4

    Default Extended Crank Times on stock 5.3L

    A history error on the cam? The random backfire and occasional hist code is from a missing cam signal during cranking. I actually had the exact same problem as you. Our engines will start and run with no cam signal (you can even unplug it) it'll just be rough at first.

    I belive my cam sensor was is bad. To solve this (for me) and to not have to remove my Intake (not that big a deal,i know) i went so far as to convert to a timing cover mounted cam sensor. For 3 reasons.

    1) i wanted an easily replaceable cam sensor

    2) not to remove my intake

    3) degree and varify my cam timing with a comp timing set i had.

    After replacing the cover and cam sensor,i still had a random cam code.(pissed off) I discovered while diagnosing that the "front cam" harness is pinned with a 5V power source. After looking at the OE schematics, you can see its supposed to be 12V. I moved the 12V wire in the main harness to where the 5V was and bam! Its perfect! No more cam error code and starts instantly every time.

    TThat's my long winded experience, lol.

  5. #5

    Default Extended Crank Times on stock 5.3L

    Thanks for the info, which front conversion kit did you go with? Was it still a 24x?

  6. #6


    I had similar cranking issues. Typically needed to cycle twice to start the engine. Using the front cover cam location. I believe the parts are all stock 2004 LS1. Swapped the 5v reference over to 12v and immediately noticed a difference. Though when the car sits a few days it still takes two cycles to start.

    Other than color, are 24x and 58x cam sensors the same? Will they function proper regardless of location or reference voltage?

  7. #7


    Fox12303, your extended cranking may be due to fuel pump prime. Most will loose pressure after sitting. Will your system hold pressure or it bleeds off? After sitting for longer periods, try to prime it key on/off a couple times first to see if that helps.
    From what ive looked at in schematics, the cars and trucks all were 12v front cam sensors. After switching mine to the 12v source the startup has been like an OE application. I turn the key, let it prime for 1 sec and it lights right off, even on e85 !

  8. #8


    Its bleed off and I do exactly that, cycling the key twice if needed. Its not really an issue anymore. Pressure drops after awhile and I've swapped pumps with the same results. Injectors are not dripping either.

    lspwrd if you have a chance would you read my thread, "need some help please." I have a slight stumble cold and power still seems off. Any suggestions would be really be appreciated.

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