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Re: Hot Start - I give up!! Posted by Gary Stottler [Email]  (#1463) [Profile/Gallery]
(more from Gary Stottler) on Thu, 7 May 2015 07:32:50
In Reply to: Re: Hot Start - I give up!!, Johnson  [Profile/Gallery]
, Wed, 6 May 2015 17:50:08
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Just to recap, what causes the long crank is that due to an internal leak in the fuel system, the system loses pressure when it is shut off and the gas in the 4 injector lines boils, leaving the lines full of vapor instead of liquid. It then takes forever for the vapor to clear out of the lines, hence the long crank.
You have replaced many parts and 2 out of the 3 that typically leak (injectors and fuel pump check valve), the 3rd part is the Control Pressure Regulator (aka "Warm-up regulator). You can try replacing that if you don't mind spending another $300, but still really no guarantee - pretty much every component has to be perfect to avoid this problem with the stock system.
What to do? I am a little uncertain about the previous response regarding running the fuel pump as this will not purge the vapor out of the injector lines, so I'm not sure why that helped. What I would recommend is installing a normally open push-button to supply voltage to the Cold Start injector during cranking. This is essentially what the "official service fix" (which involved a relay to automatically fire the cold start injector during a warm crank if it lasts more than 5 seconds or so)did. This gets some fuel in the engine so it starts, and then the airflow raises the airflow sensor plate which finally purges the vapor out of the injector lines.
Unfortunately I don't have any pictures of this (I sold my '77 with full disclosure of the issue and in my '78 Bosch made design changes to fix the problem). You will need to be careful with the circuit so that you don't back feed voltage to the wrong place :-)
Best,
Gary
_______________________________________ Gary Stottler
, Wed, 6 May 2015 17:50:08, Thu, 7 May 2015 07:32:50 <-- Viewing This Message, Tue, 12 May 2015 07:08:16, Tue, 12 May 2015 07:15:58, Tue, 12 May 2015 06:43:48, Wed, 13 May 2015 05:35:24, Mon, 18 May 2015 16:17:53, Wed, 17 Jun 2015 05:47:23
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