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-----Original Message----- From: Ken W Stephenson [mailto:kss37215@xxxxxxxx] Sent: Sunday, July 24, 2005 11:42 AM To: dickb@xxxxxxxxx Subject: Question, of course!
The lead from pin 6 of the Power Module to the CCC and ASDM. Obviously controls shutdown. For what reason? The ignition pulse train does the same thing. Can I disconnect it at the PM and ground the side to the CCC and ASDM without losing anything? Just trying to simplify this design. Did anyone ever do a theory of operation on the Power Module?
It will no doubt astonish you to learn that I do not have the whole power module schematic stored in my fuzzy, gray little headbone!
I will dig out my notes on it (which are now approaching 9 years old!) and refresh my so called mind on the subject, and then get back to you.
Before I do that, though, I will advise that I don’t think it wise to attempt any modification to these circuits without a very complete study of the operation under all modes. The rule of unintended consequences is lurking at all times!
We did do an exhaustive attempt at a theory of operation for this and the other circuit boards in the system (except the CCC) in 1996. The thinking was done primarily by Jeff Gaurino, with some comments and subsequent changes by me and by Bob Harris - resulting in a pretty clear version of what and why.
You can try an archive search for those names on the IML site to see if you can turn up any of those discussions. I archived them also, but that was 4 computers ago, and was probably written in word perfect, so I'm not sure I can resurrect them at this late date.
It may be sufficient to say that the power module consists of a DC coupled power amplifier to process the fuel demand signal from the CCC in order to produce a 0-12 volt drive signal for the Control Fuel Pump.
There are some ancillary functions on the board, notably; The 23 volt regulated power supply The Fuel flow meter signal processor The start-up vapor purge cycle circuit The fuel temperature signal processor
This much I do remember, but as to what signal is on pin 6, I haven't a clue at the moment!
But I still would caution that this was all on a theoretical basis, and no one has had the guts to try "improving" anything on the design. A healthy original part seems to work just fine, so there has been no likely pay-off for trying experiments.
I've taken the liberty to post this discussion to the whole IML, in hopes that one of the other guys who have studied this critter can chime in with some factual analysis or experimental observations, while I start digging in my "Stack of Stuff".
Dick Benjamin
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