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Old 04-26-2021, 06:36 PM
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Default Help! Weird Issue L99/6L80E

We have a 2010 Camaro L99 (ECM and harness by Speartech) in my father's '59 Impala.

The issue usually happens when the car has been driven, then allowed to cool off. We get a no start condition where I have spark, but no injector pulse.

Although everything tested good, I replaced the crank and cam sensors and ignition switch "just because."

I don't see anything on datastream that looks out of place.

Thoughts?
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Old 04-27-2021, 10:58 AM
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Not a clue?
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Old 04-27-2021, 02:52 PM
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I would think it's an issue with the ecm not getting an rpm signal. Not sure why it only does it after a cool down. Have you looked at the battery voltage when cranking in this condition? If it has any kind of heat soak issue or similar and the volts are dropping to 10 volts or so it will cause what you're seeing. Had this on a friends car and a new battery with more cranking amps fixed it. Thing is the engine seemed to spin over fine, but looking at the voltage when cranking told us what was going on.
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Old 04-27-2021, 05:49 PM
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Quote:
Originally Posted by camcojb View Post
I would think it's an issue with the ecm not getting an rpm signal. Not sure why it only does it after a cool down. Have you looked at the battery voltage when cranking in this condition? If it has any kind of heat soak issue or similar and the volts are dropping to 10 volts or so it will cause what you're seeing. Had this on a friends car and a new battery with more cranking amps fixed it. Thing is the engine seemed to spin over fine, but looking at the voltage when cranking told us what was going on.
But wouldn't I lose spark, too?
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Old 04-27-2021, 06:02 PM
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If the battery voltage drops under 11 volts or so during cranking all sorts of weird things happen. I'm pretty sure that's what my buddies car was doing, spark but no fuel, but I'm going off memory. It's a simple thing to check though. As a test next time it happens plug in a battery charger and see if it starts. Like I said before his seemed to turn over normally, not slow at all, but it wouldn't fire.
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SPECIAL THANKS TO:
Jacob Ehlers and Amsoil for the lubricants and degreasers for my 70 Chevelle project
Shannon at Modo Innovations for the cool billet DBW bracket
Roadster Shop for their Chevelle SPEC Chassis
Dakota Digital for their Chevelle HDX Gauge Package
Painless Performance for their wiring harness

Ron Davis Radiators for their radiator and fan assembly.
Baer Brakes for their front and rear brakes

Texas Speed and Performance for their 427 LS Stroker
American Powertrain for their ProFit Magnum T56 kit
Currie Enterprises for their 9" Third Member
Forgeline for their GF3 Wheels
McLeod Racing for their RXT street twin clutch
Ididit for their steering column
Holley for their EFI and engine parts
Lokar and Clayton Machine for their pedals and door and window handles
Morris Classic Concepts for their 3 point belts and side mirrors
Thermotec for their heat sleeve and sound deadening products
Restomod Air for their Tru Mod A/C kit
Mightymouse Solutions for their catch can
Magnaflow for their 3" exhaust system
Aeromotive for their dual Phantom fuel system
Vintage Air for their new Mid Mount LS front drive
Hydratech Braking for their hydroboost system
Borgeson for their stainless steering shaft and u joints
Eddie Motorsports for their hood and trunk hinges and misc parts
TMI Products for their seats, door panels, and dash pad
Rock Valley Antique Auto Parts for their stainless fuel tank
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Old 04-27-2021, 07:43 PM
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Quote:
Originally Posted by camcojb View Post
If the battery voltage drops under 11 volts or so during cranking all sorts of weird things happen. I'm pretty sure that's what my buddies car was doing, spark but no fuel, but I'm going off memory. It's a simple thing to check though. As a test next time it happens plug in a battery charger and see if it starts. Like I said before his seemed to turn over normally, not slow at all, but it wouldn't fire.
It's something to think about... though the fact that it will then start on the third or fourth try (and start immediately, regardless of how long you had been cranking it previously), seems to demonstrate the battery has more than enough juice.

I do really appreciate the thoughts, though! Like I said, it's a weird one!
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