[Sven59]

Originally Posted by Ryephile

Ok cool.

The only reason from a calibration side I would allow for long crank is to prime the oiling system.

If someone can datalog rail pressure and injector pulsewidth during cranking, that would put a lid on the situation really quick. I'm away right now so it'll be a bit before I can get back to my car and datalog it myself.

Or you could just say its normal because they all do it.

[Ryephile]

Originally Posted by Sven59

Or you could just say its normal because they all do it.

Except it's not normal in terms of industry-wide, just in terms of LT1/LT4.

[travislambert]

Originally Posted by Ryephile

Ok cool.

The only reason from a calibration side I would allow for long crank is to prime the oiling system.

If someone can datalog rail pressure and injector pulsewidth during cranking, that would put a lid on the situation really quick. I'm away right now so it'll be a bit before I can get back to my car and datalog it myself.

I have an HP tuner's scanner log somewhere of this long startup (more than one actually). I can tell you it is absolutely the high-pressure fuel pump that's the hold-up. The injectors don't pulse until the fuel pressure reaches a certain threshold. (It's completely normal and there's not much that can/should be done to improve it from a tune perspective as far as I know.)

I discovered in my case that the perceived elapsed time is much longer than the actual elapsed time. My car on occasion sounded like it would crank forever before starting, but when I actually logged it the time never exceeded the GM specs (previously posted).

(If I remember I'll post the log when I get home this evening.)

[Blown67]

Guys, guys.....i think we can all agree that whatever the cause, the first start of the day is always the best and the loudest. It's music to my ears, and everyone else's at my complex.

[Ryephile]

Originally Posted by travislambert

I have an HP tuner's scanner log somewhere of this long startup (more than one actually). I can tell you it is absolutely the high-pressure fuel pump that's the hold-up. The injectors don't pulse until the fuel pressure reaches a certain threshold. (It's completely normal and there's not much that can/should be done to improve it from a tune perspective as far as I know.)

I discovered in my case that the perceived elapsed time is much longer than the actual elapsed time. My car on occasion sounded like it would crank forever before starting, but when I actually logged it the time never exceeded the GM specs (previously posted).

(If I remember I'll post the log when I get home this evening.)

I would appreciate seeing the log. Thanks.

[Sunsnare98]

Originally Posted by snackbar64

Has anyone else experienced the starter spinning for several seconds before the car will start? Is this common? Rarely does the car ever fire right up. Almost thought it was out of gas and then VROOM!!!

This is a LT1 issue. It's normal. As others said it's direct injection and it gets worse when it's cold out. In my corvette manual it talks about this. Not sure if it's in the camaros manual or not.

[Infern0]

Great thread! I came to post the exact same thing but paused to consider which section it belonged in hahah!

I have an M6 and mine takes maybe a second to second and a half longer than the video as well. Very comforting to know I'm not alone, as well as the cause that's been posted already. Nice!

[WhyUMad1LE]

Read on this forum to hold the power button with foot off the clutch until the accessories turn on and i hear a priming noise. Then push in the clutch, press start again and it cranks right up. I do this every time I cold start the car.

[Shorty45]

After a few times seeing mine cranking about 1-1.5 sec and reading the OM it states you don't have to hold the Engine start button the entire startup. Just press and let off it takes over. Thought I would mention this as I'm new to these type starting systems. Oil pressure is a big part of it I believe.

[Infern0]

Originally Posted by WhyUMad1LE

Read on this forum to hold the power button with foot off the clutch until the accessories turn on and i hear a priming noise. Then push in the clutch, press start again and it cranks right up. I do this every time I cold start the car.

If it's mechanical through something like the cam as posted above, this could not possibly have a benefit. It isn't electrically primed if I understood the above correctly.

[travislambert]

Here's a HP Tuners VCM scanner file with a little over a second crank time.
(It's from an LT4.)

https://drive.google.com/open?id=0B0...DF2b2ZHVEdCMkk

@ 14.9 seconds, rail pressure ~15 PSI, cranking starts
@ 15.2 seconds, rail pressure ~33 PSI.
@ 15.4 seconds, rail pressure ~61 PSI.
@ 15.6 seconds, rail pressure ~103 PSI.
@ 15.8 seconds, rail pressure ~323 PSI.
@ 15.9 seconds, rail pressure ~538 PSI, first injector pulse
@ ~16.0 seconds, the car starts

I've logged this several times and it's the same sequence every time. The rail needs AT LEAST 500 PSI before the injectors will pulse. Once the injectors pulse the car starts pretty much immediately.

[travislambert]

Here's a nice little crank time chart.



This of course if the crank time... not the time from the press of the start button. Sometimes there's nearly a second (usually much less) that goes by while the low pressure pump pressurizes before the cranking starts.

[travislambert]

(I have too many channels being logged to get a great refresh rate on this file as well as the previously posted file, so keep that in mind.)

Here's another log with a ~1.4 second crank time.

https://drive.google.com/open?id=0B0...lUzNFFwWC1mdDg

Trust me, 1.4 seconds seems like forever when you're listening to an engine crank. Many would call this 2-3 seconds by a subjective measurement. I'm guilty too. I was thinking it was taking 2-3 seconds before I starting logging it with a laptop.

[Ryephile]

Originally Posted by travislambert

Here's a HP Tuners VCM scanner file with a little over a second crank time.
(It's from an LT4.)

https://drive.google.com/open?id=0B0...DF2b2ZHVEdCMkk

@ 14.9 seconds, rail pressure ~15 PSI, cranking starts
@ 15.2 seconds, rail pressure ~33 PSI.
@ 15.4 seconds, rail pressure ~61 PSI.
@ 15.6 seconds, rail pressure ~103 PSI.
@ 15.8 seconds, rail pressure ~323 PSI.
@ 15.9 seconds, rail pressure ~538 PSI, first injector pulse
@ ~16.0 seconds, the car starts

I've logged this several times and it's the same sequence every time. The rail needs AT LEAST 500 PSI before the injectors will pulse. Once the injectors pulse the car starts pretty much immediately.

Thank you for posting that. I wonder why the LT1/LT4 HPFP takes so long to get pressure? Very interesting, and very different from other GDI engines in my experience. The fact that it's roughly a half a second at less than the feed pressure from the in-tank low pressure pump is fascinating. It's almost as if the in-tank pump isn't priming. Hmmm.