Ok so I got the injector part of the equation figured out at least.....
Upon closer inspection, it appears that the injectors I pulled are specific to a 4.3.....
At the time I pulled them, I had no idea there were any differences but I did at least look at the numbers and thought they were the same.... so today I cleaned a little better and lo and behold that 6 was actually a 3 ....
5235206 is for v8
5235203 is not
So I guess I'll be testing, possibly reverse flowing, and HOPEFULLY reusing what I had on there to begin with....I really can't afford a new set so it'll be back to the treasure yard with new knowledge if these don't do it....
Just thought I would put my experience wth these to maybe save somebody else the same trouble....
Hey RJ,
Your persistent TBI injector woes made me realize that I had a big hole in my knowledge base about these
things. (Then again, I haven't actually seen one in person since the previous century?) And back then,
they seemed to work well enough that I never really got a chance to troubleshoot them in anger.
Since I might someday find the same thing under the hood of a rust-free southern belle, why not see
what we can still dig up in 2023? So I've pulled together the following info. Hopefully it will
help you take your fix across the finish line. (And if nothing else, it can be a little repository for
this TBI info, for as the years pass this stuff is starting to fall off the edge of the internet table.)
First off, here's a nice chart covering the different TBI injectors that were made, arranged by
application / flow rate / color code / GM part #. This might be helpful the next you're at
the treasure yard:
NOTE: Both of the part numbers you referenced above are included in this chart.
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(Credit: Craig, one of those detail-oriented dudes over at the International Harvester parts
website?)
OK, now that we can identify which TBI is before us, I wanted to get a view of the business end
in order to better understand the drooling? Here's a screen snap from a YouTube video:
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Alright, now if we can find a nice cutaway diagram to get a better idea of how the internal parts interact?
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Now it's starting to come into sharper focus. The design is supposed to be all (open) or
nothing. (closed) And with the miracle of PWM (Pulse Width Modulation) this is how we control
the quantity of fuel delivered over time.
With full fuel pressure, the nozzle gives us a nice atomized spray pattern. And with the ball seated,
nada. But IF the interface between the ball & seat is dirty, a small, relatively low pressure stream
will dribble off the ball & right through the nozzle opening. (And the nozzle designer would tell you
that a non-sealing ball valve in this 'all on/all off' design is an
*illegal* condition.)
NOTE: This is also why
@Schurkey correctly said that the 'repair kit' (for
the external supporting structure) I referenced earlier wasn't going to fix the drooling issue. (!)
And in order to pull this all together, here's a 14-year-old YouTube video by a guy that
was testing/cleaning these old TBI injectors. (No nonsense 5 min vid showing bad vs good,
must-watch!)
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Notice that he's using an ultrasonic parts cleaner to take care of business. Reading around,
some crafty guys were taking a low-tech approach & energizing the TBI solenoid & then
pumping carb cleaner (or equivalent) through the injector, some guys in both directions, and
were reporting success. To recap, at some point you need to regain positive control of the
fuel so that you aren't driving the computer nuts while it's trying to tune around the gross
error you showed us
previously.
****
OK, now for the sudden 'no-idle' on it's own. Here's another cut-a-way diagram to help
us understand what the engineers put in place for a steady idle:
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So it looks like when the throttle is closed, *all* the air is supplied by the IACV. (Idle Air Control
Valve.) The computer is going to be controlling this, but in addition to a good, clean IACV we
also need good wiring between it and the computer. Any possibility during all the recent surgery
that the wiring to this got bumped/disconnected/or the wire pulled apart inside the connector?
Given your symptoms, I'd put a lot of focus in this area until I could prove to myself that it's working
properly under computer control. And don't forget the document that
@pressureangle shared
previously. (
good stuff)
BIG PICTURE TIME
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I think that you've mentioned that you have performed DC resistance and/or voltage checks on
these sensors, and while that is OK for a 1st-level 'Go/No-Go' troubleshooting pass, when you
connect up a scan tool & see the actual data streams that the computer is being fed is when it
all falls neatly into place. At the same time, you said that you weren't in a position to use a scan
tool, which I understand.
If that's the case, then our only strategy is to troubleshoot this like we would troubleshoot an old
Quadrajet. And when someone asked me to look at a similar rough-running 'drooling fuel' situation out of the
carb's primary venturis at idle, I knew immediately that the float was saturated with fuel & that we
needed to replace it/reset the float level. In your case, we gotta get your injector's ball valves all cleaned up.
To summarize, you need to do the following:
* Identify the TBI injectors that are now in circuit. And are they the flow rate that your computer
is expecting/calibrated for?
* Clean those injectors up until the dribbling fuel issue is resolved.
* Figure out why your Idle Air Control Valve circuit stopped working & fix that.
And then (assuming that the fuel is now completely under computer control & the engine will idle)
get it all dialed in so that you go get some of that gold!
Happy hunting! And I really like your attitude about seeing this through until it's fixed!
