LS1 starting issues - 1 in 4 or so

[volospian]

Hi guys,

I've pretty much sorted my cam signal issues. After a few red herrings, it turned out that an earth strap was a bit duff, and a replacement seems to have done the trick.

However, I now have an issue with getting the car to start. It does seem to start after a few attempts, but often seems to sync incorrectly for the first few attempts at starting. Often it seems to give a few backfires, and then if you try cranking again it starts easily. When you shut it down, it then has the same issues again, starting on the 4th or 5th cranking attempt, usually preceded by a cranking session with a backfire...

I've seen a similar thread from 2012/2013 or so, but it seems this thread was when the LS trigger settings were in early stages and the issues were pretty much sorted with new firmware, but I think I'm using the latest version.

I've attached a comp log of the signal (although it didn't start on that attempt). I've also attached my current base tune.

Any ideas?

Rich.

[gui67]

I had the same issue when I did not have the cam sensor on my LS1.
1 chance out of 2 to start on the wrong sync: firing the spark 360° off. As soon as I wired the cam sensor the issue was solved.

[volospian]

I have the cam sensor connected and I'm getting a signal from both cam and crank.

[jsmcortina]

Does it start ok if you select "Wasted COP" instead of "Coil on plug" ?

Please also post a datalog of some attempted starts.

James

[ashford]

what opamp is in your vr circuit?

[volospian]

Sometimes it just takes a push in the right direction

I just tried it on wasted COP and it started pretty much on the nose each time, so I had a closer look at the cam sensor and, where I'd been fiddling with it before, it still had a slight gap (when I was having issues with the cam signal before it seemed more stable if I moved the sensor out by a smidge, although this did indeed turn out to be a red herring ).

Anyway, it was a few weeks ago when I last fiddled with it and I had forgotten all about it, so I reseated the cam sensor and tightened it all up again...

And now it seems to start every time

The only thing I can say now is that it's not exactly an immediate start. It takes, say, on average maybe 3 seconds or so of cranking to fire up, sometimes a little quicker, sometimes a little slower. I didn't really do any comparison, but it may have been slightly quicker to start on wasted COP, but that may have just been me being surprised at it starting at all

What do we think? Does this sound about right on this engine (L33 5.3 HO 9.9:1 compression, with a basic aftermarket starter off eBay, cranking speed is maybe 170rpm)?

Rich.

[gui67]

Hi Rich,
You should work on the priming pulse and cranking pulse.
I also had the same "problem" that the engine needed 2 to 3 seconds to start. I added a lot of fuel to the priming pulse (cold weather and E85) after that the enine started after less then half a second. That was OK with cold temperature.
I have to tune it with warm temperatures now as it was starting quicker at 0°C then with 30°C...

How I realized I needed More fuel : while making changes in TS, I removed and put ignition several times in a row without starting the engine, which lead to 3 priming pulse instead of just one. And the car starteed much better like that. I increase the time (3x) and it was perfect.
Guillaume

[gui67]

make also sure the pump has enough time to build pressure during the priming time. you can increase it on Cranking/Startup Settings: Prinming Pulse delay.

[volospian]

That makes a lot of sense. I've noticed that I get the initial priming pulse when I switch the ms on, but that initial pressure dies off quite quick, so if I delay cranking for even a couple of seconds the pressure dies back and needs a second or so to build again (engine starts from a seperate starter button rather than the ignition key, so the ms often finishes its initial pump before I press the button).

I'll try the priming pulse delay and increasing the fuelling as suggested

Cheers,
Rich.