OK I misunderstood exactly how you checked early on...
If the problem still exists with that jumper from the battery, then it cannot be caused by a flaky ignition switch.

 

Jim - no problem, do appreciate the thought and effort both

PAHonda - I've actually done the tests with my after the battery was at 100% charge (per my battery charger). My charger is also one that has a "start" function that allows you to start the car using only the charger (it'll supply cranking current for a _short_ period of time).

Your query did get me to thinking, so I checked what the voltage range should be in the shop manual. Here's what Honda's shop manual has to say (my apologies for the picture sizes - didn't realize how big they were until after I put them in the reply):

For testing the battery they give the following under 'full' load (note that my original measurements were done after extended attempts to turn the engine over trying various things):


There's also a check for the starter and conditions while cranking the engine:


Note that the 10.1V I'm reading are both well above the minimums per the shop manual.

In answer to the question after a full charge - the voltage while not in the "start" position, but with the key in the "On" position with lights and other non-starter loads is 12.9V (a tad low, but not bad - I may yet swing by Autozone and have it checked).

In regards to the video (yes, I did watch it) - the guy actually does a very good job in explaining things - I actually use water concepts when I explain electrical concepts to others as well.

For those that may be reading this thread, some more information that'll maybe help them some time and help understanding... In the video he left out (and may not know due to his acknowledged weakness on the electrical side) the reason why his testing of the example bad cable misled him and why he saw what he did (other than it being a bad cable).

The meter he was using only gave him resistance readings down to 0.1 ohms. When cranking, Honda starters will pull a continuous current between 83 amps up to around 125 amps - that's with the starter spinning under engine load. The initial current (while coming up to speed) can be more than triple that.

If the cable actually had 0.1 ohms resistance, at 125 amps it would drop 12.5V (Voltage = Current x Resistance).

In the case of my '86 Honda accord, I have the Mitsuba 1.4KW starter. That means it can pull around 117 amps of current at 12 volts while spinning (Power = Voltage x Current or in this case, Current = Power / Voltage) - and the shop manual sets a limit of 350 amps during initial spin-up (yes, three HUNDRED and FIFTY ).

Short tidbit - it would only take 0.034 ohms resistance to hit the minimum 8 Volts the shop manual calls out in the test (at 117 amps - would only be about 1/100th of an ohm at 350 Amps). On a meter that only had 0.1 ohm accuracy, it would read no more than 0.1 and might even read 0.0. This is why with most meters doing a test for voltage drop under load is a much better way to do it. They can easily measure and show differences measured in volts like he was getting, even though they won't provide good sub one ohm measurements.

A note here - smaller batteries like the standard sized ones in Hondas will show a decent voltage drop when cranking an engine over - this is expected (and why the shop manual has 8V for the minimum cranking voltage). Actually all batteries will to some degree, just the smaller spec'd ones for Honda more so. The reason - batteries have an internal resistance and as I talked about above, with the cranking current required by most cars (between the starter, ignition, etc.) it doesn't take very much resistance to get a decent voltage drop. Another informational tidbit - those CCA ratings on batteries? They are spec'd as the point where the individual cells of the battery still put out 1.2V, which would mean 7.2V across the entire battery (here's a link to an article by Optima on the subject: What does Cold Cranking Amps (CCA) mean? | OPTIMABATTERIES)



Thinking about this did also lead me to do another test - one of the simple ones that can be done to verify some starting conditions on a manual transmission. The results also eliminate one of the things that can happen to any of us when testing things to solve a problem - what I call "the law of expectations".

Earlier in this I noted I had taken the oil filler cap off the valve cover and verified that the valves were moving when attempting to start with the starter. Since I was doing it alone, it involved looking at the valves, reaching in thru the window and bumping the starter, then looking at the valves again. I was "sure" they moved and were in different positions each time (did it a few times).

But - that could have been "expectations" - I expected (and admittedly wanted) to see the valves move. So my mind could have been playing tricks on me and they weren't moving at all, but because I expected to see movement, I did.

Anyway, so I did another test. This afternoon when leaving work I left the tranny in 1st gear and turned the key briefly to the start position. The starter obediently tried to start the car and the car lurched forward a foot.

Verification that the solenoid is engaging the starter with the flywheel and that the starter is generated enough power (and the battery is supplying enough voltage for the starter to do its job). Also verifies I hadn't fallen prey to my "law of expectations"

Unfortunately, I still don't have the actual cause identified and problem solved The discussion has led me to think of other things to test and eliminate - and led me to find out that it's spark I'm missing when trying to start it with the starter. Just don't know why it's missing :/ I do know I'm missing something (besides a key piece of info on the Honda ignition system that would explain the results, maybe some good ole fashion sense ... and will likely smack my forehead once it's figured out.

Anywho - hope you guys don't mind the super long post. Thought some of it might help others in the future. Figure since I'm here asking for help, I should share some info too that might help others.

In the meantime, if you or anyone else has any ideas or possibilities, throw 'em on out there. I'm still stumped....

 

If you look a few pages past the diagram you show, I think the green wire is for the pickup coil (signal for the ignitor to switch off ground).

I can think of two easy tests to try, because I'm out of reasonable electrical tests. What happens if you unplug the radio condenser and try to start the car? What happens if you unplug the alternator and try to start the car?

 

The condenser unplugged I've already done several times, once early on (didn't remember to list it - was checking for an internal shorting condition of the condenser), and then again when I monitored the voltage to the coil via the condenser lead while attempting to crank it (had unplugged the condenser and plugged my meter probe into the wiring harness connector in its place).

I'll try it with the alternator unplugged tomorrow night.

An additional test I did tonight that I'll do a follow-up test for tomorrow - my meter has a clamp-on for current. Put it on the battery and did several readings.

With the key off, verified their isn't any current flow.

With the key in the "On" position and the engine not running - 4.3 Amps of current.

Can't measure cranking current - outside the range of my meter.

I also tried clamping on the bl/yel wire to the coil both with the key on and while attempting to crank the engine with the starter - never saw more than 100 milliamps (meter has a peak hold function). This is the one I'll do again tomorrow night when I first get to the house, and see how much current goes to the coil with the engine running.

Regarding the green wire - you're likely correct, as it isn't present in the external wiring harness after closer examination. Tomorrow night (or near future anyway) I'll partially disassemble the old distributor and verify.

On a semi-unrelated note: my ancient timing light gave up the ghost last year. I've been looking into getting a new one, but have read a lot of negative things about the less expensive ones I've been able to find (mostly things along the lines of 'quit working after second use'). Can anyone give brand/model recommendations on current gen decent simple timing lights that aren't too expensive which they've personally owned?

As always - sincere thanks.

 

Update (still no luck in solving the problem)...

With the alternator disconnected, it still does not start with the key/starter. I didn't try a push start in this state due to concerns of accidental shorting of the dangling connections.

To check off another piece for comprehensiveness and to provide reference values for others, this time on the fuel side of things, I checked the throttle position sensor. It read 4900 ohms between the outside 2 contacts. Shop manual says 4000 to 8000 ohms is good. Also checked from one side to the center terminal. Reads 512 ohms with the throttle at idle, increases in resistance as the throttle is opened up, with full throttle reading 4900 ohms.

I was looking over the ignition system wiring diagram again and started making some other checks.

Disconnected the negative plug to the condenser (black wire) and measured to ground. Read 0 ohms as expected, so getting a good ground there.

I forgot to take the current measurement of the battery supply to the coil while the engine is running... next time.

Still no joy in resolving the puzzle....

 

My gut feeling is that the voltage is too low when you are cranking to have the igniter work properly.

I didn't see if you tested the voltage on the battery posts when cranking or just at tp1.

The other thing you can try is to verify that blue2 wire is getting a switching ground signal. Does the tachometer move when cranking the engine?