[Gmecm] Hard cold starting

Sun Jan 15 07:05:41 UTC 2012

I would like to see some logged data. Do you log with winaldl?Start the data logger prior to engine start and make sure all boxes are checked except the raw box.Then after you shut it off hit stop. Then save the tables separately. BLM, int, spark counts. The TPS can be adjusted by simply using a small rat tail file on the holes so you can rotate it.TPS should be below 2.1% but I try to keep mine between 0 and .7%. From: jryan at caminofx.org
Date: Sat, 14 Jan 2012 22:56:40 -0600
To: gmecm at diy-efi.org
Subject: Re: [Gmecm] Hard cold starting

More than once, yes.  I verified the minimum air setting just the other day.  The TPS is not separately adjustable on this throttle body.
It starts VERY easily and runs very smoothly.  But something changes within the first minute of running, and wham, it quits.  (In summer, it may sag and hit the stall saver, but stay running, instead of dying totally.)  It runs beautifully in closed loop.  It has been a long time since I tried logging data, but as I remember, the BLMs hovered near 128 in the cells that showed anything in WinALDL.  Something is changing after it "catches" before it is warmed up, and that is what has me stumped.
What is the function of the "choke air fuel ratio multiplier vs. coolant temperature" table?  I have been Googling it and not finding a clear explanation.  In the $61 ANLU .bin, it goes from about 75 at warm coolant temperatures to about 96 at warm temperatures.
I do not see any table in TunerCat for a spark or choke delay or decay.

On Jan 14, 2012, at 9:56 PM, Bill Hamilton wrote:And
Have you performed the initial setup procedures(min idle speed/TPS) to include verifying the IAC is functioning properly?
There is a keep alive mode anytime the rpm drops below the preset limit.
If the IAC is not flaring open right before it dies then it may not be working at all.
Your rpm decay may be just from the cold timing increase.

Date: Sat, 14 Jan 2012 19:31:57 -0800
From: dunvegan at sbcglobal.net
To: gmecm at diy-efi.org
Subject: Re: [Gmecm] Hard cold starting

have you verified that the fuel pressure is maintained, before you start modifying tables? rule out the obvious first
 -rick

From: Jared Ryan <jryan at caminofx.org>
To: A list for discussing General Motors EFI <gmecm at diy-efi.org>
Sent: Sat, January 14, 2012 9:17:07 PM
Subject: Re: [Gmecm] Hard cold starting

I have ruled out the oil-pressure switch as the cause.

I did in fact have a bad oil pressure switch.  It was as old as the car (it was used for the choke relay originally, and I used it for the TBI system when I converted it over).  I changed it out, and it started fine - once.  However, I let it sit for several hours, and just tried it a few minutes ago, and it was back to the same behavior.  It's about 45 F outside right now, much colder than the mid-60s when I changed the oil-pressure switch this afternoon.

It catches quickly and runs STRONG, but I can hear the idle slow down gradually, and that is when it dies.  It goes from a gradual idle slow-down 15-30 seconds or so after it catches, to dying.

What is the name of the table in TunerCat that I can modify to increase the delay for taking out the crank enrichment?

On Jan 13, 2012, at 8:58 AM, David Allen wrote:

> Jared, IIRC there is a table in the ECM that determines how long it takes for the
> cranking-enrichment to be decayed out of the fuel delivery.
> 
> I've been working on a Buick engine with a "mild" cam, and it too requires
> richer mixture to stay running when cold. I don't have the tuning program in
> front of me to look at - but I beleive I doubled the time it takes to remove
> the enrichment.
> 
> Also the ignition timing curve was VERY sensitive compared to the stock cam.
> To idle correctly there is about a 2 degree window between stall out and and
> going "zoot-zoot-zoot-zoot" when it idles.
> 
> Hope this helps!
> David
> 
> ----- Original Message ----- From: "Jared Ryan" <jryan at caminofx.org>
> To: "A list for discussing General Motors EFI" <gmecm at diy-efi.org>
> Sent: Friday, January 13, 2012 7:40 AM
> Subject: [Gmecm] Hard cold starting
> 
> 
>> I have tried working on this before but never had any success, nothing that
>> made a real difference.
>> 
>> Here is what I have:
>> 
>> 1984 Chevrolet El Camino
>> '87-later-style 350 GM long block, NEW in 2005
>> Crane 2032 roller camshaft
>> Edelbrock Performer TBI intake manifold
>> GM throttle body with 55 lb. injectors (IIRC; I have a spec sheet for them
>> at home)
>> Stock 305 exhaust manifolds
>> Painless Wiring TBI wiring harness
>> 
>> It is a relatively tame engine, meant for street reliability in a small
>> pickup.  My problem is cold starting.  Here is what happens:
>> 
>> When it is cold outside, and the engine has not yet been run that day, I
>> turn the key, crank it, and the engine catches after four or five seconds,
>> and goes to a smooth, moderately high idle (1300-1400 IIRC).  Then, after
>> a short period of time - yesterday it was about ten seconds - it will
>> suddenly stop running.  There is little warning; sometimes it will run
>> rough for a second or two, but it is very abrupt.
>> 
>> When I turn the key, it starts back up in a second or two, but it usually
>> does it again.  Yesterday I went through three cycles of this before it
>> started and stayed running.
>> 
>> What I do not understand is that the car previously had a 305 in it, with
>> the exact same setup with the exception of the roller camshaft and
>> Edelbrock manifold (used a modified GM TBI manifold), and I never, ever
>> had this problem with the 305.  Ever.  It just started up and stayed
>> running, smoothly, like a fuel injected engine should.  Same wiring
>> harness, same fuel pump, same fuel lines.
>> 
>> This behavior usually does not happen in the late spring and summer
>> months.  Whether it happens, and how long it takes before the engine
>> quits, seems to be highly dependent on the ambient air temperature.
>> 
>> What I have seen from the ALDL seems sane, especially regarding coolant
>> and intake air temperature.
>> 
>> I have tried both a 1228746 ECM with a '90 Caprice 350 chip, and a 1227747
>> ECM with a '91 1500 Suburban 350 chip.  I reset the minimum air when
>> changing ECMs, but the behavior is the same.
>> 
>> I may have a possible clue.  I tried enriching the open-loop mixture in a
>> chip for the 1228746, and I got it so that it would - most of the time -
>> stay running when it is cold outside.  However, this was at the expense of
>> the exhaust smelling VERY STINKING RICH.  Like, stinging the eyes.  But
>> that at least gives me the idea that it is somehow going lean, and that is
>> what makes it die.
>> 
>> I looked at the EGR valve yesterday and it looked like it was stuck open,
>> so I put a new one in, but there was no change.
>> 
>> Is there something really stupid obvious that I may have overlooked?
>> Something, anything, that might make it go lean and stumble and die when
>> it is cold?  It seems like, once the combustion chambers warm up a little,
>> it is fine, but getting it to that point can take starting it three or
>> four times.
>> 
>> What I am wondering is if there is something beyond the ECM programming
>> that would allow it to start easily when dead-cold, but then somehow make
>> it go lean after a few seconds.
>> 
>> I am very, very frustrated with this.  I love the vehicle but I can't
>> trust it to drive it on cold days.  It is not normal behavior for GM TBI,
>> and I don't know where to turn.
>> 
>> Once it is warm it runs GREAT.  Smooth idle, even acceleration, 22 mpg gas
>> mileage - just a joy to drive.  But that hardly makes up for not being
>> able to just start it and GO first thing in the morning!
>> 
>> Jared
>> _______________________________________________
>> Gmecm mailing list
>> Gmecm at diy-efi.org
>> http://lists.diy-efi.org/mailman/listinfo/gmecm
>> 
> 

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