Cranking no start with cold weather

[RiggsStubbs]

2004 GMC Sierra 2500 HD swapped in a ATK HP109. Stock manifold, stock injectors. got it to initially start and run with this tune when it was about 80 degrees outside. Now its about 40 degrees outside went out to continue idle tuning it and wouldn't start. pedal to the floor flood mode can hear engine firing out of exhaust. I've tried adjusting so much and nothing has helped start it. will upload the tune it initially ran off of and a scan of the current crank no start as well as the one log I took when it did run. Any help is appreciated.

[edcmat-l1]

I'd start by diagnosing it as a no start. Everybody always thinks "It's the tune!" and it's rarely "the tune".

Your voltage while cranking goes as low as 9.6 volts. Maybe start there.

[RiggsStubbs]

Battery voltage is so low because this was recorded after many cranking attempts with charger on battery. I have done all the basics I can think of. I'm getting fuel to cylinders, I have good spark. I haven't checked for any intake leaks, maybe ill do that next. Ill double check everything again.

[edcmat-l1]

Battery voltage is so low because this was recorded after many cranking attempts with charger on battery. I have done all the basics I can think of. I'm getting fuel to cylinders, I have good spark. I haven't checked for any intake leaks, maybe ill do that next. Ill double check everything again.

Why didn't you have a battery charger on it? It's not going to start with a battery that dead. It's cranking at less than 120 rpm. No way that's gonna start.

[blindsquirrel]

Does it run if you shoot it with brake cleaner? If so, despite your certainty of "getting fuel to cylinders", it's not enough fuel.

If it doesn't run if you shoot it, does it run if you disable the fuel pump or injectors and THEN shoot it? If so, then it's getting too much fuel.

A can of brake cleaner is an incredible cranks-no-start diagnostic tool. An engine will run surprisingly well with no fuel source other than squirts of brake cleaner, enough to not only just make it run but even move a car around under its own power.

[TheMechanic]

Does it run if you shoot it with brake cleaner? If so, despite your certainty of "getting fuel to cylinders", it's not enough fuel.

If it doesn't run if you shoot it, does it run if you disable the fuel pump or injectors and THEN shoot it? If so, then it's getting too much fuel.

A can of brake cleaner is an incredible cranks-no-start diagnostic tool. An engine will run surprisingly well with no fuel source other than squirts of brake cleaner, enough to not only just make it run but even move a car around under its own power.

What is funny to me is here in Kalifornia the Brake Cleaner is so bad it will barely fire on a running vehicle. Gotta' use Carb Cleaner.

[RiggsStubbs]

Does it run if you shoot it with brake cleaner? If so, despite your certainty of "getting fuel to cylinders", it's not enough fuel.

If it doesn't run if you shoot it, does it run if you disable the fuel pump or injectors and THEN shoot it? If so, then it's getting too much fuel.

A can of brake cleaner is an incredible cranks-no-start diagnostic tool. An engine will run surprisingly well with no fuel source other than squirts of brake cleaner, enough to not only just make it run but even move a car around under its own power.

With fuel injectors plugged in and squirting found that same condition. With injectors unplugged it began backfiring through the intake a little. What should i do next?

[edcmat-l1]

With fuel injectors plugged in and squirting found that same condition. With injectors unplugged it began backfiring through the intake a little. What should i do next?

First thing you need to do is check the battery with a good electronic battery tester. Normally when a battery dips well below 10 volts it's bad.

Then diagnose it like any other no start. First thing is try using spray. Put fuel pressure gauge on it. Check the spark with a real spark tester.

[RiggsStubbs]

First thing you need to do is check the battery with a good electronic battery tester. Normally when a battery dips well below 10 volts it's bad.

Then diagnose it like any other no start. First thing is try using spray. Put fuel pressure gauge on it. Check the spark with a real spark tester.

planning on getting new battery today but jumping it with another truck fuel pressure reads 60 psi. Pulled fuel pump relay and cranked again and engine would start to try and fire. maybe i have too much fuel while cranking? with spark plug removed and grounded on header can see very good spark.

[blindsquirrel]

What is an "ATK HP109"?

It may have run on that tune before, but the only changes from a stock LQ4 is a bunch of fuel pulled out of the VE up to 1600 RPM, and some spark changes around the same range, and some idle airflow changes.

[RiggsStubbs]

What is an "ATK HP109"?

It may have run on that tune before, but the only changes from a stock LQ4 is a bunch of fuel pulled out of the VE up to 1600 RPM, and some spark changes around the same range, and some idle airflow changes.

its a crate engine from the company ATK part number is HP109. Just thought it was a good reference in case it would help. is there other changes I should have made from the stock tune?

[gtstorey]

As an example of how easy this can be, ATK HP109 is a supposed to be a 500hp 6.0l. I didn?t pick out cam specs from the link but I didn?t look that hard.

How can people not see that not giving information that things are a lot different than a stock engine is important. Probably not the immediate problem, but still important. It?s enough of a change from stock that the listing said that it must be tuned.
https://www.jegs.com/i/ATK-Engines/059/HP109/10002/-1

[horsepowerguru427]

According to the link it not only needs a tune but also 36lb injectors minimum. I dont see any cam specs in the link though.

[SiriusC1024]

Update .040 bore at General>Cylinder Volume to .76086 L

Lower values at Fuel>General>Cranking Fuel

[RiggsStubbs]

Thanks will make those changes when I get a chance and see what happens. Also horsepowerguru427 contacted ATK for cam specs they sent me this 228/234@50 .604/.609 112LSA

[kevin87turbot]

Thanks will make those changes when I get a chance and see what happens. Also horsepowerguru427 contacted ATK for cam specs they sent me this 228/234@50 .604/.609 112LSA

That's a pretty healthy cam, but it should start and idle when cold.

You mentioned that it's backfiring out of the exhaust. That indicates that the coils aren't firing in the correct sequence. That's typically caused by one or both of the coil harnesses being flipped end over end.

[RiggsStubbs]

That's a pretty healthy cam, but it should start and idle when cold.

You mentioned that it's backfiring out of the exhaust. That indicates that the coils aren't firing in the correct sequence. That's typically caused by one or both of the coil harnesses being flipped end over end.

It was backfiring out of the intake but I think that's because I had the fuel injectors unplugged creating a lean condition. Matched up both the fuel injector and ignition coils wiring harnesses with diagrams and they are lined up with the correct cylinders. Also updated cylinder volume and lowering cranking fuel to what SiriusC1024 said and lowering the cranking fuel made it sputter a bit but no start.

[SiriusC1024]

You said it started in warm weather. It ran and idled ok? Then it's adjustments.

Give this a shot. Do a little flood clear first to make sure there's no residual fuel puddled up on the pistons.

[horsepowerguru427]

You might try reducing cranking VE some as well. Im sure that cam is not near as efficient with the higher duration and overlap.

[SiriusC1024]

Yep did that in the attached. Wanted to also mention make sure the battery is fully charged.