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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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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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Baer Brakes for their front and rear brakes

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American Powertrain for their ProFit Magnum T56 kit
Currie Enterprises for their 9" Third Member
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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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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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Old 04-29-2021, 01:16 PM
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This is a real thing as Jody says. When I was a mech we'd have several models that wouldn't start, but engine would turn over like a new battery. We noticed various electrical things wouldn't work right, tilt column or auto folding mirrors would stop mid travel while cranking, all while the engine was turning over just fine. We chased those for a while until deciding to try a new battery and that fixed it. It then became a quick battery diagnostic tool once we were aware.
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Old 04-29-2021, 03:39 PM
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Originally Posted by ErikLS2 View Post
This is a real thing as Jody says. When I was a mech we'd have several models that wouldn't start, but engine would turn over like a new battery. We noticed various electrical things wouldn't work right, tilt column or auto folding mirrors would stop mid travel while cranking, all while the engine was turning over just fine. We chased those for a while until deciding to try a new battery and that fixed it. It then became a quick battery diagnostic tool once we were aware.
But would they start up just fine after a combined total of, say, a minute or so of cranking? In fact, it starts instantly after such (on the third or fourth try).

I'm not trying to be a pain, but I don't know of any batteries which gain voltage whilst cranking for such a period.
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Old 04-29-2021, 03:43 PM
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Default This might be helpful for others!

Spoke with a friend/GM tech.

Apparently GM has trouble with the connection at the ECM. They call the issue "micro abrasions" and they are brought on by vibration.

The fix, according to GM, is to unplug the harness from the ECM and plug it back in, then repeat for a total of 4 or 5 times, then unplug the ECM and apply a thin smear of dielectric compound to the female terminals and plug it all back in.

According to my friend, this little issue causes all manner of odd, intermittent issues.
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  #10  
Old 04-29-2021, 06:22 PM
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Quote:
Originally Posted by ProTouring442 View Post
But would they start up just fine after a combined total of, say, a minute or so of cranking? In fact, it starts instantly after such (on the third or fourth try).

I'm not trying to be a pain, but I don't know of any batteries which gain voltage whilst cranking for such a period.
In our defense, you hadn't given us that info to start with. Hopefully the connector fixes it. Loose connectors, pins not fully locked in the connector, etc. also cause countless random issues.

Quote:
Originally Posted by ProTouring442 View Post
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?
__________________
Jody

PAST CAR PROJECTS

Like Lateral-G on Facebook!

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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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