Hard to start, cranking for a few seconds

[EFI]

I recently installed a fresh LS2 engine, new top end, cam etc. along with some LS3 injectors. This topend was on my previous stock engine and it worked fine, but lately it seems to have a real hard time starting.

It cranks and cranks for a few seconds before coming to life and I can't seem to figure out what's causing it. Starter is new, fuel pump is new, so now I'm starting to think it's in the tune.

I added some timing to the cranking table, I added a bunch of fuel to the VE table at 400 but not sure about the cranking VE portion. I've seen some people say to leave it at 100, while others the first thing they do on a built engine is to knock 20% off of it?

Anything else I should look at?

Here's the tune. GTOTuneAfterDynoNewVE.hpt

[rpmextreme]

Is the cam sensor syncing up?

[EFI]

Yes, I have a cam signal and it drives and idles perfectly fine otherwise. Just has a hard time cranking it seems.

[07GTS]

sometimes with a cam it might like less cranking timing at first start so it fires with more compression because u will have poor airflow from the cam it may help, think im around the 5-6 deg at cranking rpm them increase as rpm increases

[EFI]

This is the cranking spark table, which I've added 3* across the board from another suggestion. So you're saying it actually likes less timing and I should actually lower it to single digits?

[07GTS]

yep around the 150 rpm i start at cold start bout 5 deg then slowly increase as it starts to fire and rpm increases, depending on your cam u will ignite easier with more compression when cold so is worth a try it may or may not work with your setup, ive got 57 deg overlap on e85 and it helped and before i tried to add timing and it just didn't seem to improve, ill put my table up when im back on the laptop if u want a look

[EFI]

Thanks. What about for warm starts...do the same if it has trouble cranking?

[07GTS]

this is what works with mine below, also check your "idle" "airflow" "startup" those are how long it cranks before it tries to run could be worth a look but i found mine like the stock settings

[GHuggins]

If it's a rough idling lopy cam, add 10 percent to startup airflow, take the added fuel out of the VE table and dial in table correctly then change cranking VE to 85.

[EFI]

If it's a rough idling lopy cam

It's not, has 0* of overlap at 0.050 so idles pretty smoothly otherwise.

[GHuggins]

When exactly is it having issues starting - just cold, hot, both?

[EFI]

Both really.

[GHuggins]

You have a stock tune for comparison? Just finally looked at the above posted one and it all ready has WAY too high of a min air table and starting airflow / VE looks like you might be making up for some of this? If you've got an rpm signal and cam counts present then it's possibly tune related...

When it's having issues, I'm assuming you can't give it extra throttle to get it to fire? If not that's pointing straight to too much air and with that cam, unless the intake is a FAST or something there shouldn't be any need for extra airflow anywhere for running or starting.

[EFI]

GTOStockTune.hptYeah here's the stock tune for the 2006 GTO E40.

And the intake is a FAST 102 along with the cam and heads. I do think that the min airflow is a bit high as the idle RPM is about 50-100 higher than commanded...but I've never seen that cause starting problems before.

So would having too high min airflow and starting airflow cause hard cranking issues? The VE is higher because I've seen people increase that at 400rpm to help with startup...but haven't seen any changes there. And no, hitting the throttle does not help start it anymore than just leaving it on its own.

[GHuggins]

Yes, if it's getting too much air... Also make sure your fuel pressure is maintaining during start up...

[EFI]

So cut the VE airflow at 400, put the cranking VE to 80, lower cranking spark, lower min airflow and lower startup airflow?

What about the cranking FA mult stage 1 table...I have that almost doubled compared to stock but I don't remember the last time I touched this.

[GHuggins]

You most likely doubled your cranking fuel because of the high cranking airflow... Put it back to stock. Leave cranking ve with your cam stock. Lower startup air nearly to stock and min air nearly to stock. Dial in VE - don't just lower it back. See how it does then...

[EFI]

So I did all that and didn't really seem to do anything. Here's a log of what happened this morning. You can see how long it cranks for with 0rpm and then it finally catches and goes.

I see the timing is locked at 10* the whole time and then lowers when it finally starts up, does that still mean I'm too high timing there?

crank.hpl

[GHuggins]

What happens if you hook up a jump box or other power source? Control module voltage is going pretty low...

Assume you also all ready did a physical fuel pressure check?

[Codes]

Looks as though you have dropped a cell in the battery. Looks to crank for 3 seconds, in that time CMV goes from 11.8v to 8.2v and catches.