WTF.. Please help me with Warm Starts
10-23-2011, 05:15 PM
#1
WTF.. Please help me with Warm Starts My truck fires first piston up when its cold. But if the coolant temp is anywhere over 120 degrees, the thing will crank and crank. I have to crank it for three seconds, stop, crank it for another three seconds, stop, and then it will fire on the third crank every time. ??? Any ideas why this would happen?
10-23-2011, 09:04 PM
#4
9 Second Club
iTrader: (7)
Join Date: May 2005
Location: Cabot, AR
Posts: 3,126
Likes: 0
Received 0 Likes
on
0 Posts
COuld be an issue with open loop commanded fuel. Could be a base idle or startup airflow issue. Really could be a lot of things. Can you post a log? I use efilive but there are several hp guys that should be able to help too.
10-24-2011, 04:05 PM
#7
Moderator
iTrader: (11)
Join Date: Mar 2002
Location: East Central Florida
Posts: 12,605
Likes: 0
Received 6 Likes
on
6 Posts
Look at your IAT, and if it's crazy high then think about
relocating the sensor.
Look at your cranking VE table and see whether it makes
any sense at all, relative to what you've done to the
main VE. You can only guess, but that cam has got to
be making a lot less VE at very low cranking RPMs. Which
will make the cranking mixture piggy piggy rich if you left
the cranking table stock.
relocating the sensor.
Look at your cranking VE table and see whether it makes
any sense at all, relative to what you've done to the
main VE. You can only guess, but that cam has got to
be making a lot less VE at very low cranking RPMs. Which
will make the cranking mixture piggy piggy rich if you left
the cranking table stock.
Trending Topics
10-25-2011, 12:07 PM
#9
TTT
My IAT is in the MAF which is pretty far from the motor in my application. 2003 Silverado. I don't think it could be as heat soaked as it's acting... Plus how does GM tune stock applications to start perfect if we have the same IAT location. I'm frustrated
My IAT is in the MAF which is pretty far from the motor in my application. 2003 Silverado. I don't think it could be as heat soaked as it's acting... Plus how does GM tune stock applications to start perfect if we have the same IAT location. I'm frustrated
10-25-2011, 01:00 PM
#11
After I drove the truck around for a while, I let it sit for about 45 minutes. Scanned it and the IAT was showing 81 degrees. Once I started the truck, on the third crank again, The IAT lowered to 78 degrees. So what tables can I start playing with to fix this. Its obviously not the IAT
10-26-2011, 07:33 PM
#14
Moderator
iTrader: (11)
Join Date: Mar 2002
Location: East Central Florida
Posts: 12,605
Likes: 0
Received 6 Likes
on
6 Posts
I think I'd move on to the cranking VE then.
But also have a look at your commanded EQ at cranking. High MAP and
high ECT might be telling it to dump fuel, some tunes raise enrichment
at hot and high MAP. Which would only be worse if you also have a
cranking VE error that says more air's coming, than really is. Any
cranking enrichment adds to the EQ vs ECT vs MAP table. I recall
taking out all hot enrichment and still having to shave cranking fuel
after my cam swap, which is way milder.
But also have a look at your commanded EQ at cranking. High MAP and
high ECT might be telling it to dump fuel, some tunes raise enrichment
at hot and high MAP. Which would only be worse if you also have a
cranking VE error that says more air's coming, than really is. Any
cranking enrichment adds to the EQ vs ECT vs MAP table. I recall
taking out all hot enrichment and still having to shave cranking fuel
after my cam swap, which is way milder.
10-26-2011, 07:54 PM
#15
I think I'd move on to the cranking VE then.
But also have a look at your commanded EQ at cranking. High MAP and
high ECT might be telling it to dump fuel, some tunes raise enrichment
at hot and high MAP. Which would only be worse if you also have a
cranking VE error that says more air's coming, than really is. Any
cranking enrichment adds to the EQ vs ECT vs MAP table. I recall
taking out all hot enrichment and still having to shave cranking fuel
after my cam swap, which is way milder.
But also have a look at your commanded EQ at cranking. High MAP and
high ECT might be telling it to dump fuel, some tunes raise enrichment
at hot and high MAP. Which would only be worse if you also have a
cranking VE error that says more air's coming, than really is. Any
cranking enrichment adds to the EQ vs ECT vs MAP table. I recall
taking out all hot enrichment and still having to shave cranking fuel
after my cam swap, which is way milder.
10-28-2011, 04:17 PM
#16
Moderator
iTrader: (11)
Join Date: Mar 2002
Location: East Central Florida
Posts: 12,605
Likes: 0
Received 6 Likes
on
6 Posts
Commanded EQ comes from the scan tool (straight, or
14.7/commanded_AFR, but all the tables work on EQ).
All these other things roll up to make it. The fuel air
multiplier sweeps fuel trying to "find what works" and
hope to catch. But if it's multiplying something that's
already too fat, it may never get on the right side of it.
I just kind of cut-and-tried my way to "no more problem"
but have you gone and looked at repository tunes for
big-cam cars where the owner / tuner was proud of the
drivability / startability result, and compared them to
stock looking for ones where that stuff has been touched,
and then those against yours for hints about what works?
My advice is only what I recall but there's plenty out
there to learn from (problem is, how to know which ones
are actually worth learning from...).
14.7/commanded_AFR, but all the tables work on EQ).
All these other things roll up to make it. The fuel air
multiplier sweeps fuel trying to "find what works" and
hope to catch. But if it's multiplying something that's
already too fat, it may never get on the right side of it.
I just kind of cut-and-tried my way to "no more problem"
but have you gone and looked at repository tunes for
big-cam cars where the owner / tuner was proud of the
drivability / startability result, and compared them to
stock looking for ones where that stuff has been touched,
and then those against yours for hints about what works?
My advice is only what I recall but there's plenty out
there to learn from (problem is, how to know which ones
are actually worth learning from...).
10-30-2011, 07:43 AM
#18
Can you post your tune and a couple data logs? One of a cold start and one of a warm start? There as a few fuel tables for cranking fuel, after start enrichment, prime pulse mass, etc. But most of the time these don't need to be modified unless you're running real big injectors.
I'd like to see what the IPW is, the throttle blade position, the timing during cranking, etc. Make sure to start your scanner before you crank the key.
If you want help figuring it out, we/I need to see logs and the tune.
I'd like to see what the IPW is, the throttle blade position, the timing during cranking, etc. Make sure to start your scanner before you crank the key.
If you want help figuring it out, we/I need to see logs and the tune.
10-30-2011, 05:22 PM
#19
Okay so here is my current tune and three start ups. The first is cold, been sitting all night. I don't know why it didn't start first crank like usual but maybe you can see something weird.
The second shows me shutting it off after the cold start up and idle until it gets to 140 degrees or so. Then cranking it.
The third was me cranking it after it had sat for about 45 minutes after it was fully warmed up. It will crank and crank the first time, then starts up after i let off and try again. Also I took a little drive just for fun. If you see anything weird in the drive, sharing would be appriciated. Thanks for the help guys
The second shows me shutting it off after the cold start up and idle until it gets to 140 degrees or so. Then cranking it.
The third was me cranking it after it had sat for about 45 minutes after it was fully warmed up. It will crank and crank the first time, then starts up after i let off and try again. Also I took a little drive just for fun. If you see anything weird in the drive, sharing would be appriciated. Thanks for the help guys
10-31-2011, 03:19 PM
#20
Can you post your tune and a couple data logs? One of a cold start and one of a warm start? There as a few fuel tables for cranking fuel, after start enrichment, prime pulse mass, etc. But most of the time these don't need to be modified unless you're running real big injectors.
I'd like to see what the IPW is, the throttle blade position, the timing during cranking, etc. Make sure to start your scanner before you crank the key.
If you want help figuring it out, we/I need to see logs and the tune.
I'd like to see what the IPW is, the throttle blade position, the timing during cranking, etc. Make sure to start your scanner before you crank the key.
If you want help figuring it out, we/I need to see logs and the tune.
