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[GMCnet] Broken 1227747 ECM [message #61206] Thu, 22 October 2009 18:38 Go to previous message
GMCWiperMan is currently offline  GMCWiperMan   United States
Messages: 1248
Registered: December 2007
Karma:
Senior Member
Has anyone found a schematic for the 1227747 ECM? Not for connecting it
to the outside world -- its guts.

Some may recall that I had a Holley fuel injector apparently fail
recently. When I replaced it, the new one would not shut off until I
changed the ECM for the one I'd just modified for the EBL Flash board.

Not knowing whether the failed injector damaged the ECM or the failed
ECM damaged the injector is not a comfortable position to be in. Don't
know what to expect next.

Today I checked the resistance of the "failed" injector -- about 2 Ohms
which is in spec. But I couldn't hear it click when I applied 5 VDC or
12 VDC. I suspect it's been sticking for a long time. I've read
reports that Holley's preservative for them sometimes causes them to
stick when new.

Then I opened the '7747. Right away I realized that I have a hard
failure there: CR25, a 1-6 amp diode, PN as yet unknown, is cooked. To
the extent that it's almost melted its solder joints into the PC board.
I don't see any board damage beyond that. But, it's a single diode, not
one of a set of 4 as it would probably be if it was a part of the quad
drivers for the injectors, so I can't even speculate how it was
subjected to such excessive current. Spontaneous failure is extremely
unlikely.

I sure don't want to have to reverse engineer the board in order to
figure out what caused the failure. It may have been something I
inadvertently did while troubleshooting. Even worse, it may NOT have
been something I did. I can prevent repeating my own errors, but I
can't fix something else if I don't know what to fix -- so a repeat
could be imminent. Replacing the ECM is not a good option with my
current lack of understanding of the failure.

Surely someone, somewhere, has reverse engineered or otherwise acquired
a schematic for the board. Any ideas out there?

Ken Hating Hardware w/o Schematics H.

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