[Gmecm] Re: Big cap HEI on 7747

[Mark Romans]

Hi DarrylAndrew:

We switched the wires on the module and it seems to have killed
the module.  What's weird is that your description is so exactly what the 
symtoms are.
Keep in mind this is a big cap HEI with an internal module.

The timing varies by huge amounts and greatly by engine rpm.

It idles fine in EST bypass.

Everything has been replaced.  One more thing is that this is an EST HEI 
modified to fit
a 350 Buick running a 747 ecm.

Mark




----- Original Message ----- 
From: "Andrew Gibson" <andrewsharyn at yahoo.com>
To: <gmecm at diy-efi.org>
Sent: Saturday, June 03, 2006 5:09 PM
Subject: [Gmecm] Re: Big cap HEI on 7747


>I wasn't talking about the 4 wires from the module to the ecm. I was 
>talking about the two wires from the ignition pickup coil inside the 
>distributor to the module. If the wires are switched the timing pickup is 
>coming off the curved section of the waveform instead of the vertical slope 
>in the center. This can offset the timing by as much as 40 degress and will 
>vary greatly by engine rpm. (See the piggyback igintion module discussion I 
>started a couple of months ago.) The wires should be white and green (at 
>least off the pickup coil) I don't remember which is positive and which is 
>negative.
>
>  Also since you are obviously having problems and must have extended the 
> pickup coil wires to have a external module: If you need the module more 
> than 1.5" away (The length of  stock pickup coil wires) the spliced in 
> wires need to be twisted for noise reduction. (If you peel the insulation 
> off a piece of network cable you will get the idea)
>
>  Good luck!
>
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