[Gmecm] Re: Warm start problem

[DOZIERHC at aol.com]

Mike...
 
It could be the fuel system leaking down.
 
Try putting a fuel pressure gauge on the Schrader fitting and watching the  
fuel pressure decay.
A good system will hold pressure within about 10psi for 24 hours.
If your decays off to near zero in a few hours, I would then try and  isolate 
if it is leaky injectors, or a leaking check valve in the fuel pump, or  bad 
pressure regulator.
 
As for cranking fuel PW, the system experiences hottest fuel at about 20-30  
minutes into a hot soak, after that, the temperature decays back towards  
ambient.  So Hot starting vapor lock would be at that time, if it is going  to 
happen (fuel flash to vapor in the nozzle of the injectors, therefore  effectivly 
blocking injection PW).
 
IF that is the case, you might have to bump your cranking fuel PW for  higher 
MAT temperatures, NOT ECT, to try and alleviate the fuel  starvation.
 
BTW, do you have a Wideband in your system to see what the post crank  
fueling Lambda profile looks like?
 
Hank
 
Date: Wed, 11 Jul 2007 18:28:14 -0600 (GMT-06:00)
From: Mike Frels  <mfrels at ix.netcom.com>
Subject: [Gmecm] Warm start problem...
To:  diy_efi at diy-efi.org, gmecm at diy-efi.org
Message-ID:
<29180054.1184200095220.JavaMail.root at elwamui-milano.atl.sa.earthlink.net>

Content-Type: text/plain; charset=UTF-8

I am trying to  diagnose a hot or warm start problem. I've got a gm TPI 350 
running $8D for a  305 that has been modded to work with my setup. Morning 
starts she fires right  up. Hot starts if she's only been sitting for less than 
10-15 minutes also fine.  A restart between 15 minutes to 5 hours sitting takes 
some cranking. Looking  through my tables I've got various Start Up Enrichment 
and Crank Fuel Pulse  Width settings that I am thinking I need to adjust. Can 
someone enlighten me on  what the differences between Start Up Enrichment and 
Crank Fuel Pulse Width? BTW  I have acquired this summer time problem since I 
switched to LS1 injectors last  year.

Mike


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