[Gmecm] Hard Starting

[Rick McLeod]

My understanding on hot-start mashed pedal the ECM is in 'clear-flood' mode where it disables injection in an attempt to clear a flooded engine, therefore your assumption that it is adding fuel by opening the throttle (if mashed) would be incorrect, it is actually cutting fuel drastically. It may still be 'flooded' as evidenced by the black poof, the routine is doing it's job. I would think reducing hot-start fuel @ crank would be the first attempt, but the rest of the board may chime in and challenge


----- Original Message ----
From: Jared Ryan <jryan at caminofx.org>
To: gmecm at diy-efi.org
Sent: Tuesday, August 15, 2006 3:48:58 PM
Subject: [Gmecm] Hard Starting


I just need a starting point for this.  I need a good guess at which 
way to go to correct this problem.

This engine "catches" *fast* on a cold start.  I just turn the key, and 
after a few revolutions it's running.  It smoothes out, and the ECM 
gradually reduces the idle speed.  No problem.

On a hot start, it usually won't catch.  It cranks very fast, but just 
doesn't catch.  However, if I hold my foot down all the way on the 
accelerator pedal, it will always catch after several seconds of 
cranking.  It's just like if I was trying to clear a flooded engine and 
I open the throttle all the way on a carburetor.  When it does catch 
after doing this, there is a puff of black smoke from the tailpipes.  
Once it catches, it idles smoothly and there is no problem keeping it 
running.

So... I have the programmer and TunerCat and WinALDL... what should I 
alter to make the hot starts easier?  Is there anything I can analyze 
with WinALDL that would tell us?  I call this a hot start problem, not 
an idle problem (again, once running, it's very stable and relatively 
smooth).

My impression - based on having to open the throttle and that black 
smoke comes out when it catches - is that it's too rich on hot starts, 
but maybe it is too lean and I am adding fuel by opening the throttle.  
I don't really know how the ECM "thinks" at start-up.

Any thoughts are appreciated!

Engine: New GM long block 350, 9.2:1 compression, Crane 2032 camshaft, 
.214? int., .220? exh. @ .050" lift.

Injection system: Rochester TBI, unmodified throttle body, 65 lb./hr. 
injectors, Edelbrock 3704 intake manifold, 14 psi fuel pressure 
measured before the filter.

ECM: 1228746, ANLU .bin (1989 Chevrolet Caprice 9C1 Police calibration)

  ---> Jared Ryan <---
jryan at caminofx.org | http://www.caminofx.org
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