RE: [T3] Dead Injectors Puzzler

["Fuhriman, Mark" <mfuhriman@fugro.com>]

> > Now, tonight I have confirmed the hunch of several who guessed the
> > wiring to the 3/4 injectors was switched.  It was indeed. Started
> > the car up with the injector wiring fixed and with the spare brain,
> > let it run for a while.  Drove around the block and let it idle for
> > a bit.  When at temp, the idle dropped.  Sure enough, injectors for
> > 1&3 were not firing anymore.
>
> Brain fade? I suspect that now it was 1&4 that failed. When
> properly wired, 1&4 are triggered by the same trigger point. Sounds
> like you could use that double brain swap that Greg offered. ;-)

Yes, maybe lots of different kinds of brain fade going on.  You're rght, I
meant 1&4 are failing now.  It was kind of late...
>
> Look over the injector wiring carefully again for any possible bad
> connections or potential/intermittent shorts. Wires twisted together
> wires aren't good enough; they should be crimped or soldered.

The 3/4 injector wiring harness is kind of jury-rigged, and the trigger
point harness is also a bit messy looking, although the crimped connections
all look and test (resistance-wise) OK.  But I have a couple of spare
harnesses from which I can cut pretty pieces, complete with the connector
boots.  I'll splice these in.  I know, ..be careful.!

When I'm done with that I'll look again at all those grounds and other
wiring paths with the VOM.  If, after all this, I can rule out a
wiring/ground problem I'll try another (third!) ECU and maybe a third set of
trigger points.
>
> > I remembered the dwell problems reported by Steve and Jim.  The
> > boot on my trigger connector at the dist is gone, so I was able to
> > jam my VOM probes into the top of the connectors to make contact
> > with the wires while the engine ran.  With the car still running on
> > just 2&4 (1&3 not firing) I measured voltage in turn between the
> > outer connectons and common (the middle one).  For both sides I
> > measured a pulsing signal that varied between 2 and 3 volts.  Does
> > this tell me that my dwell for both trigger contacts is similar?
> > Can I rule out trigger points?  Keith, you mentioned something
> > about resistance across a rivet in the trigger points.  Like from
> > top to bottom? Please elaborate just a little for me here..
>
> This is a pretty good test. Do it again WHILE the engine is running
> on just 2&3 (failure mode). That would show up a problem in the
> trigger points or the trigger point wiring.

That's what I did- tested this in failure mode.  However, I did *not* test
this while the car was running on all 4.  And I'm not sure I need to as long
as whatever voltage I measure here is the same for both sides.

I guess the easiest thing to do next is measure resistance across each set
of trigger points.  Measured both at the trigger connector pins and at the
corresponding ECU connector wires.

-Mark Fuhriman
 '69 Fastback

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