[T3] 69 FI trouble shooting

[R. David]

Steve Crispino has been working on getting his 69 Automatic Fastback put
back to FI from a carb conversion. He has received some help from the list
here and has made great progress getting it running....however it still has
a running issue, so I tried to help him out with it tonight.

This car has early FI system on it with the "B" FI parts, a 2 plug TPS and
it has the pressure switch setup. The car started right up, seemed to run a
normal slightly rich condition until a few minutes of warming up - then
smoothed right out nicely. Dwell @ 46, timing right on zero, idle speed
easily adjustable for timing. Brought idle speed back up to 950, idling real
nice. It didn't want to quickly respond to accelerate (under a no load
condition), and it almost seemed to respond as poorly if I unplugged the
pressure switch or not. (The pressure switch is confirmed to electrically
trip once suction is applied, and Steve ran new wires back to the brain for
it to make sure it's connected to the brain.) I sat in the drivers seat to
put it in gear and power brake it to see how responsive the motor was under
a load.... and it was not! Once I did this the motor started a slow death
spiral that could not be saved. I went back to the motor to feather the
throttle by hand to keep it going but it kept slowly loosing power and speed
until it stalled. It would crank after that, but no fire. This only took
about a minute to die once it started to loose power.

After this; just by cranking it we still had a dwell reading, and the timing
light confirmed each plug was getting a spark. Spraying a flammable spray
into the IAD got it to fire up for a few seconds, but once the spray was
used up there was no more fire.....so it appears to not be getting fuel at
this point. Steve says that once this motor cools back down again; it will
fire back up and run until it gets warm again......then the same thing
happens. He has a constant 29 psi of fuel pressure. We did a ohm reading on
both temp. sensors when cold and when hot and they both are reading correct.
He did a ohm test reading on the pressure sensor and it is showing correct.
Trigger points look good and clean, although he cleaned them off with a
business card to be sure. TPS is adjusted properly and I could hear it
function correctly when I operated the throttle by hand. AAR seemed to be
working good when it was running. Steve says the valves are adjusted
correctly, and the compression runs around 140 or so except for #3, which is
down to about 110-120. Steve just put in new jugs, and he said the heads
looked great so he re-used them as-is for now.

At this point Steve has no other brain or pressure sensor to swap out and
see if it matters.
I think it has a bad brain in the car, but without spare to swap out; we
can't try it.

Thoughts or suggestions?

Dave Pallo
'72 Square ~ "Elwood"
Fairport, NY