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Thread: Startup issues on 03 LM7 with a small cam?

  1. #1
    Senior Member
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    Default Startup issues on 03 LM7 with a small cam?

    Been fighting this for a while now. I'm doing a tune for a friend. Its an 03 Silverado rcsb 5.3, it has headers, ss3600 stall and an Isky 212/212 cam 112 lsa. Now I've tuned MULTIPLE cammed LS engines but never had this issue before. Basically when you try to start it up it just cranks and cranks but doesn't fire, then just let off and try again and most of the time it'll fire, it doesn't do it every time though. Once it fires up it runs fine. We've tried cycling the key before starting thinking mabe it was bleeding fuel pressure off but its not. I sure wouldn't think with a cam that small I'd need to do any crank/start adjustments in the tune... I'm not around my pc right now so I cant upload my tune, but I will as soon as I get home tonight. Any ideas?
    -John

    1991 RCSB 2WD Sierra LQ4 swap, 220/224 112 cam, Twin VSR 6766 turbos
    4L80e w/shift kit, PY 3600, and 3.73 gears.
    22 PSI and E85, 4300# with driver. 9.7@138, 1.47 sixty
    :drivin:

  2. #2
    Joe (Moderator) joecar's Avatar
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    Can you determine if it is getting too much fuel or not enough fuel during the first crank...?

  3. #3
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    Quote Originally Posted by joecar View Post
    Can you determine if it is getting too much fuel or not enough fuel during the first crank...?
    Is there a good way to? I've tried messing with the Commanded Fuel While Cranking table, it didnt seem to do much, but it might have seemed as though it'd like more fuel if anything...
    -John

    1991 RCSB 2WD Sierra LQ4 swap, 220/224 112 cam, Twin VSR 6766 turbos
    4L80e w/shift kit, PY 3600, and 3.73 gears.
    22 PSI and E85, 4300# with driver. 9.7@138, 1.47 sixty
    :drivin:

  4. #4
    Joe (Moderator) joecar's Avatar
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    Compare injector pulsewidths between 1st crank vs 2nd crank.

    Also compare CYLAIR or DYNCYLAIR [g/cyl] between 1st and 2nd cranks.

    And also rail pressure.

    Are all the various cranking tables stock...?

  5. #5
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    Found out it had some kind of Bosch platinum plugs, swapped them out for some TR5s and starts up perfect now
    -John

    1991 RCSB 2WD Sierra LQ4 swap, 220/224 112 cam, Twin VSR 6766 turbos
    4L80e w/shift kit, PY 3600, and 3.73 gears.
    22 PSI and E85, 4300# with driver. 9.7@138, 1.47 sixty
    :drivin:

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