86 SVO won't start.

[SVOJames]

I finally got the Grey car back together, and it started on the first try! Warmed it up, then turned it off to hookup the wire to the temperature gauge. Car would not start. Called it a night, and the next day it started right up. Couple of more situations like this (would not restart when warm), so I replaced the TFI & Pip with new Motorcraft parts. Started right up, but after being warmed and turned off, the starter failed. New starter, and the car failed to cold start. My neighbor wanted to replace the PE computer, I wanted to do some more reading what to check, so I got him a spare PE, he swamped it out, and the car started. Warmed the car up, put the original PE back in, and the car started while warm. Since then it has failed to start.
Where I am now:
Oil level plug is "missing", so is not connected. My white car leaks oil, I have started it many times after seeing the light (the EGO/overboost light), so I'm guessing this is not an issue.
KOEO codes:
23 TPS out of range
51 ECT input too high
Went to check the TPS voltage, some confusion resulted in me checking the voltage between the Orange wire and green wire, instead of the green & black wire, we saw .3 volts. Could I have messed something up by doing this?
Checking the voltage between black & green, I see 0.00 volts.
Checking the resistance between those two wire with an analog gauge shows no "flat spots", but noticed the resistance was lower at idle than at WOT. That seems backwards to me. Is this correct?
I'm suspecting a wiring problem, but I don't know where to go from here.
I've got a breakout box, a nice Fluke DMM, a cheap VOM, OEM repair manuals, a Chilton manual, a greasy, inked up and page-marked "2.3L EFI Turbocharged Engine" that was printed in Tucson, AZ, USA during August, 2006, and 2 other working 86's I can get known good parts off of (but I'd rather not).
Where do I start?

[MikeFleming]

Just to be clear: it CRANKS but does not start when it's acting out?

On the TPS voltage/resistance measurements: As long as none of the wires were shorted together when Ken On, then there would be no damage. If the 5V REF line was shorted to EEC ground, then there may wel be issues in the EEC.

[SVOJames]

Yes, it cranks but does not start. Noid light connected to wiring harness at the #1 injector does not flash. 40'ish PSI on fuel pressure while cranking, good spark from coil and at #1 plug. Timing good at 10 degrees BTDC with spout out. All that was checked after it started the first time.

[MikeFleming]

Noid light connected to wiring harness at the #1 injector does not flash. That's a bad sign.

How about when connected to 2, 3, 4? Sometimes it's a good idea to have multiple noids around.

Does the tach needle bounce around (200-400 RPM) during cranking?

[SVOJames]

Dang 30 year-old wiring harness (and possibly booze). I was pretty sure the tachometer did jump to the 200-400 RPM range while trying to start, but I got my wrench guy to help me. With a known working TPS off another SVO, breakout box, and spare PE, it started and ran decently. Started/stopped it couple of times, then decided to try to pull KOER codes without checking the instructions. (remember booze was a factor)
KOER codes:
21. ECT out of range
23. TPS out of range (expected, saw this on koeoi test, and is a different tps)
25. I have no clue to what this code means.
26. VAF out of range
34. Possibly this an EGR code, Grey car doesn't have EGR.
41. System always lean. The car has not been started in 15 plus months, how did the ECC decide this?
76. Possibly caused by me not doing the throttle stomp-test
Car is back at my place, cranks but will not start,
How(where) do I start troubleshooting this issue?

[SVOJames]

Still chasing this non-start problem. Engine turns over but does not start. It does start about 1 in 8 trys. Still getting code 21 (etc temp out of range), and 23 (TPS out of range). It does seem to start more often when it is cooler outside (Texas temp in the summer, so around 80F for cooler outside).
I have noticed that the tachometer stays at 0 when it is hot outside, but jumps around 250 to 500 RPM before the time that it starts. New Motorcraft TFI, etc. I know new doesn't mean working, but does the tachometer showing 0 while attempting to start indicate anything

[Raven855]

Have you checked the ignition switch James?

[Mike S]

I believe the TPS and ECT are in the same wire loom. Double check the connector that is on the firewall above the turbo.

[MikeFleming]

I have noticed that the tachometer stays at 0 when it is hot outside, but jumps around 250 to 500 RPM before the time that it starts. The tach staying at zero during points to primary ignition: TFI, PIP, wiring between TFI and coil, ignition power to TFI and coil, coil, wiring, and or power (ignition switch). Did I mention wiring?

The EEC is out of the loop for cranking speeds on the primary ignition side.

[SVOJames]

Still chasing this issue, and it's cooler now. Also new ignition parts (and I know new doesn't mean good). It's most probably a wiring issue on a 30 year old car, but I appreciate the feedback.

[brsvo]

If you haven't done it yet you might try a new ignition switch. They are cheep and easy.

[SVOJames]

Newish ignition switch. I'm more working on when it's hot outside and the tachometer doesn't move at all while attempting to crank, yet does bounce around while trying to start when it's cooler.
I do have have a few NOS ignition switches, so ill put one in. I'm gonna be pissed if that ends up being the problem. And happy too!

[SVOJames]

Does finding something else wrong count as "progress" in figuring out this problem? Tach bounces, and car starts/runs/drives after 4 or so attempts, however the battery is not being charged. 3G serpentine system, alternator is about 2 years old, got a nearly 3 yo PAT_in_LA wiring harness. While the car is running, I'm seeing under 12 volts across the battery posts, or from the big wire off the alternator and battery neg.
Wiring from the alternator looks correct (not worn). Does this point more towards a bad ignition switch, or do I need to look deeper?
Yes, my 2 year old alternator could be bad, anyway to check it at my shop? (No scope. Have dmm, vom, etc.)

[MikeFleming]

The "...4 or so attempts" makes me think of a fuel pump and/or check valve issue so it takes some time to build fuel pressure. I suspect a low battery *could* give that symptom also, but then it's not have enough power to crank very fast. Is it cranking really slow?

Full-fielding the internal-regulated 3G series is a bit different than the external-reg types but there are lots of descriptions/examples on the web on how to do this. Depending on how it was sired in, that infamous dash ALT light could be the issue if it was wired into the field circuit.

Don't recall if the Pat_in_LA harnesses came with other than the large power wire (and fuse). In any case, check the fuse.

Field power comes (normally) from the ignition RUN circuit. If it does start and the radio works, then I'd not suspect the ign switch.

Then again - they're cheap and easy to replace.

[SVOJames]

Newish fuel pump, New fuel filter. Seeing 40 plus fuel in all situations. Battery is strong, cranks fast. Radio has a removable front plate, it's been removed for months now. I will replace the ignition switch next.

[SVOJames]

Problem "could be caused" by year plus old fuel, injectors plus another set are set to be sent off for testing/cleaning soon. Still haven't found my NOS/OEM ignition switches. Why do I like these 30 year old mustang so much? :)
Just out of recent testing, I cycle the turn on/attempt to start 4 times, fuel pressure is around 40 psi the first time. Is there a check-valve in the 86 fuel system?
As always, thanks for feedback and ideas.

[MikeFleming]

If you have ~40PSIG after the first key-on, the fuel system is doing fine.

The check valve is in the in-tank pump outlet tube. Not a separately replaceable item on the in-tank pumps.

No need to use OEM ignition switches. Newer, aftermarket ones are more better (and cheaper too).

Why do you like these 30-year old cars? Cause you're sick (in the head), old, crabby and set in your ways. It's what usually happens when we pass 39. Welcome to the club.