165 ECM question, "single fire" vs "double fire"

[Kevin Crain]

I'm looking at the Helms manual to my '88 GTA harness, it shows circuit 467
coming off one injector bank and terminating at ECM pin D15...also shows
circuit 468 coming off the other injector bank and terminating at ECM pin
D16.  This makes it look like two separate ground paths.

However, the ECM diagram on the same page only shows one 'Injector Control'
with both circuits wired into it in parallel.

If I'm interpreting this correctly, there are two ground paths but only one
driver pulsing both banks simultaneously.  It was my understanding that the
ECM fires the injectors twice per revolution, however.  Can't find anything
in the manual on this, tho.

-Kevin Crain

At 05:02 PM 5/4/00 -0700, you wrote:
>>From looking at the wiring harness on my 87 Vet,  (86-89 F&Y bodies all use
>the 165 ecm) there is only one wire providing ground to the injectors
>through the ecm, so only the single fire, batch mode is used.  All injectors
>fire once every engine revolution.  No it may have to do with synchronous
>versus asynchronous pw.
>Mark.
>----- Original Message -----
>From: "Rick Lindstedt" <rick at mafb.org>
>To: "GM-ECM" <gmecm at diy-efi.org>
>Sent: Thursday, May 04, 2000 1:36 PM
>Subject: 165 ECM question, "single fire" vs "double fire"
>
>
>> Can some please tell me the difference between double fire and single fire
>> on the injectors and why/how/when the ECM uses these variables??
>>
>> Thanks so much.....
>>
>> Rick
>>
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