Help! Weird Issue L99/6L80E

[camcojb]

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.

[ProTouring442]

Originally Posted by camcojb

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!

[ErikLS2]

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.

[ProTouring442]

Originally Posted by ErikLS2

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.

[ProTouring442]

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.

[camcojb]

Originally Posted by ProTouring442

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.

Originally Posted by ProTouring442

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?

[ProTouring442]

Originally Posted by camcojb

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.

You know, I didn't, did I. Oops. I meant to also include that you can crank it until your blue in the face, shut it off, then crank it again, and on the third or fourth try, it will fire right up.

Unfortunately, the fix didn't fix it.

Did I mention this is driving me crazy?

[Ketzer]

Unfortunately with all the billion successful LS swap stories about how simple and wonderful and glorious it is...there are also plenty of stories just like yours...swaps are simple when they work, and absolutely maddening when they don't.

Please follow up when you figure it out!!!


Jeff-