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Thread: LS wonít fire on startup sometimes

  1. #1
    Registered User lukevl's Avatar
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    LS wonít fire on startup sometimes

    So itís an L98 thatís been used in a conversion with the stock E38 ECU. Basically every now and again (once every 4 times or so maybe) it cranks but wonít fire. Havenít checked if injectors or coils are both not going or just one but it just doesnít even try. Then you key off and go again and itís like a factory car.

    Iím confident wiring is sound and I know someone else with the same issue so could be common. Any one seen this and rectified it? VATS related? Dodgey cam angle sensor?

  2. #2
    Registered User lukevl's Avatar
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    No one else heard of this issue? I hate being the only one..

  3. #3
    no mods, leave it stock Jack Nicholson's Avatar
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    You're special dude
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    People must assume you are some sort of drug dealer with all these nice cars turning up to a fibro home

  4. #4
    Unregistered User Permit Roadsailing's Avatar
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    is this in the RX7? might just be adapting to the environment and starting first time every second time.

    Fuel pump priming like it should? any DTCs?

  5. #5
    Registered User lukevl's Avatar
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    Yeah in the FD. No DTCs. Fuel supply is fine. It can happen after it's been running or stone cold. It is definitely missing 100% of something because it doesn't even give a snicker of combustion then it's just key off and on and starts like a dream. A know a guy with an LS3 in a patrol with the stock ECU and does the same thing.

  6. #6
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    Had a issue like this in a trophy truck. Changed starter motor and its never been back.

  7. #7
    Registered User darwinschops's Avatar
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    Quote Originally Posted by lukevl View Post
    No one else heard of this issue? I hate being the only one..
    When you go to to start it does it just click (when you say doesn't even try)? I have had multiple infuriating issues (cranking, slow cranking and click noise) of this sort and some resolutions included...

    - loose wire on starter motor
    - above at terminal
    - when just cranking (and slow cranking) wound up replacing battery and alternator and it was good

    When it has happened, I've never investigated CAS or leads but nor were they issues as fixes in place above it was usually good for another year or so before some random (usually commodore electronics) fucked me about again.

  8. #8
    Registered User darwinschops's Avatar
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    Quote Originally Posted by marshy View Post
    Had a issue like this in a trophy truck. Changed starter motor and its never been back.
    Before my motor cacked, I was looking at this as next on the agenda as the problem had started recurring and I'd sorted most of the bits above. They're in a prick of a spot on my car though, made worse by piping.

  9. #9
    Registered User lukevl's Avatar
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    No it cranks absolutely fine. It cranks at the same speed as when it fires up. Just wonít go bang

  10. #10
    are hairy Dogsballs's Avatar
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    Wonder if they used the wrong cam gear
    Quote Originally Posted by 50RTD View Post
    Dave, have you uploaded the data from the carby?

  11. #11
    Registered User lukevl's Avatar
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    Good point. I converted it from a single bolt to a 3 bolt cam but used the 58X reluctor I needed on the adjustable cam gear. Comp part number 7106

  12. #12
    are hairy Dogsballs's Avatar
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    Confusing me. Did you change the cam sensor as well?!

    You need this one if L98 or 58x tooth. Irony I had this at home for 2 years, until mate with same issue needed it


    Sent from my Nexus 6 using Tapatalk
    Quote Originally Posted by 50RTD View Post
    Dave, have you uploaded the data from the carby?

  13. #13
    Registered User lukevl's Avatar
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    Yeah I bought a 3 bolt cam, 3 bolt timing gear with the 58X reluctor

  14. #14
    are hairy Dogsballs's Avatar
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    Crank angle sensor or reluctor has seperated then is my guess
    Quote Originally Posted by 50RTD View Post
    Dave, have you uploaded the data from the carby?

  15. #15
    Registered User lukevl's Avatar
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    Low risk of that I think- Crank angle sensor (and crank) hasnít been removed from the motor. You think the cam sensor could be dodgey?

  16. #16
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    Without a cam signal the ls starts only 50% of the time doesn't it since it cant tell if its 180 out?

  17. #17
    Registered User lukevl's Avatar
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    Interesting point. I have to DTCs for the cam sensor but Iíll try and find one and do a swap

  18. #18
    are hairy Dogsballs's Avatar
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    Quote Originally Posted by lukevl View Post
    Low risk of that I think- Crank angle sensor (and crank) hasnít been removed from the motor. You think the cam sensor could be dodgey?
    Good point. Sensor or maybe harness. Do you have 2 big earth's to the engine as well?!

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    Quote Originally Posted by 50RTD View Post
    Dave, have you uploaded the data from the carby?

  19. #19
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    My SS ute does this. Can crank it for a minute straight and nothing will happen, let the key off for a sec and the next sniff of starter and she'll fire. Fuck knows why it happens, but I'll be following this closely.

  20. #20
    Registered User lukevl's Avatar
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    Interesting. All stock wiring and motor and ecu?

  21. #21
    Registered User Tardinator's Avatar
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    Faulty ignition module?
    Quote Originally Posted by 1uz-zte View Post
    You're not exactly Mensa material yourself there champ.

  22. #22
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    Quote Originally Posted by lukevl View Post
    Interesting. All stock wiring and motor and ecu?
    Nah heads and cam. Stock ECU and wiring though. Maybe it is cam sensor related?

  23. #23
    Registered User Tardinator's Avatar
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    I donít have much knowledge of LS engines but should it start in limp home mode even with a faulty crank angle or cam sensor?
    Quote Originally Posted by 1uz-zte View Post
    You're not exactly Mensa material yourself there champ.

  24. #24
    Registered User lukevl's Avatar
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    Would really expect a code to be thrown if it was the cam angle sensor though wouldn't we?

    Thanks for the info this rules out a lot of stuff for me.

  25. #25
    are hairy Dogsballs's Avatar
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    Quote Originally Posted by Tardinator View Post
    I donít have much knowledge of LS engines but should it start in limp home mode even with a faulty crank angle or cam sensor?
    No. If they arent in sync it may make a mess
    Quote Originally Posted by 50RTD View Post
    Dave, have you uploaded the data from the carby?

  26. #26
    Registered User Tardinator's Avatar
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    Any progress on this?
    Quote Originally Posted by 1uz-zte View Post
    You're not exactly Mensa material yourself there champ.

  27. #27
    Registered User lukevl's Avatar
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    No. Cranked it on the weekend and it didnít start. Key off and on and happy days.

  28. #28
    Registered User [TUFFVQ]'s Avatar
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    Mine started to do this (Stock VY2 Adventra) as of last week, but it's also down on power.
    Had a check engine fault come up when it first did it, now no dash fault, just the starting issue and down on power.

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