Okay, I'm looking at the factory wiring diagram for my car and I have no idea where the tach signal comes from.

The tach signal is the purple and black line on the diagram below:


http://forums.pelicanparts.com/uploa...1332906046.jpg

According to the factory manual, "1" indicates "on coil, to primary distributor lead." However, it also connects to "terminal C" on the CDI unit (N15). The coil is "N". "T2" is "Cable Connector, Double".

I have no clue where that purple and black wire goes. Is the switch supposed to be the points?

Also - I picked up a pair of terminal clamps and a DC momentary switch today so that I can put together a simple remote starter switch (so that I can pull all the plugs and check the spark while cranking the engine).

Theory part:
I'll assume the tach signal from your coil goes to both the tach and the CDI box. Mine is wired differently as I have the 6 pin CDI where your's appears to be the 3 pin type.
Switch is most likely the points. As they close they connect and pulse a signal.
Signal is picked up by tach and CDI.

Possible problems:
My Wild A$$ Guesses would be as follows:
Coil is faulting intermitently shorting to ground and blocking the pulse to the tach and CDI stopping plugs from firing.(rare, usually coils fail completely)
CDI unit faulting not processing signal, failing to fire coil? Bad ground at CDI?
Points are weak and do not operate consistently.
Is there a condensor in there somewhere? could be a bad cap failing causing same problem.
Wear on distributor shaft causing points to not operate consistently.

This is where advice from Loren or other CDI experts would be very valuable.
As an electrical technician I can troubleshoot the components and from the schematic take a stab at how they operate, but I currently have not taken the time to learn how the CDI box works(yet)...;)

"The car is firing on starting fluid now... I think I may be getting somewhere."

That's great! Carb/Brake cleaner would have been a better choice, but that's O.K.

Now if the tach is connected to the coil directly and the tach only works when the engine runs,
i.e. It doesn't work or move when the engine won't fire or run, then the CDI or coil is intermittent,
or the points aren't opening properly.

Once the ignition issues are resolved, then focus on potential fuel issues. Only focus on solving
one problem at a time, so you don't get 'overloaded'.

Thanks for adding your comments Loren. It's nice to know I wasn't steering Damion down the wrong path with my theories.
I agree totally with getting one system functioning before moving to the next one. Analytical troubleshooting requires it.

Any chance you have a spare coil and CDI box available to you to swap out if it's not the points Damion?

"Any chance you have a spare coil"

Any old coil will work with a CDI, even an old VW coil for testing.

"I agree totally with getting one system functioning before moving to the next one."

It's good that at least some believe in not using the 'shotgun' approach to troubleshooting!

Thanks for the info, guys.

Unfortunately, I do not have an extra coil. However, I do not mind picking one up. Would either of these coils work:

MSD/Ignition Coil - Performance (8202) | AutoZone.com

Accel/Ignition Coil - Performance (8140C) | AutoZone.com

Those are the "in stock" coils at autozone.

There is also this "duralast" coil for a '77 VW beetle:

Duralast/Ignition Coil (LU800) | 1977 Volkswagen Beetle 4 Cylinders 1.6L FI OHV | AutoZone.com

It's only $26.

Would any of these coils work?

As Loren said, any old coil for testing...
Check your points that you converted from pertronix before you spend money...

Okay, here's the latest update.

I'm ordering a new coil for the car because I don't want to spend the money on a coil just for "testing" purposes. I'll update once I get the new coil.

I have cleaned every electrical contact I can find. I cleaned the main ground connections, all of the wiring harness connections, all of the fuse box contacts (under hood and engine compartment) and the ignition switch connections.

Here's something that I have noticed:

When the battery is fully charged, or when I'm jumping the car off of my truck (and my truck is running) the car doesn't fire. It turns over really fast but it doesn't fire. Also, the tach does not register any revs.

However, when the battery gets low, the car will start to fire. Also the tachometer will show the engine revving between 800 and1000 rpm.

Once the tach starts to show revs, the car fires. I can't get it to stay running yet, but if I keep the charger on 10 amps, the car will nearly start. It even made a few revolutions on its own tonight. If I switch the charger over to the 200 amp "engine start" it goes back to no tach and no firing.

This seems very significant hint to the problem, but I have no idea what it means.

In summary, if the tach is not registering any revs, the car won't fire. However, once the tach starts to show revs, the car will fire.

A fully charged battery almost certainly means that tach won't show revs and that the engine won't fire.

A nearly discharged battery means that the tach will show revs and the engine will fire.

Also - the car is now firing on its own, without starting fluid, carb cleaner, or brake cleaner.

Does this mean anything to anyone?

Okay, another update.

I pulled the CDI box out of the car today and rigged up a bench test.

The results were interesting - at first the plug would fire fine (although it looked a bit weak).

However, after 10 or 20 seconds, the box would make a loud humming sound and the plug would fire continuously. I would then have to shut off the power to the unit. At this point, the permatune unit also gets very hot, very quickly.

At first I thought it might be caused by the fact that I was not using points to trigger the spark, I was just grounding the terminal on the CDI unit. So I then included the distributor in the bench test. Same result. The unit would start to whine very loudly and the plug would fire continuously.

If I leave the unit unpowered for about 10 mins. it will work again (for a short time as before).

Incidentally, the CDI unit is the blue permatune (and is likely original to the car). It's actually dated on the back - Jan. '77.

I'm now starting to believe that the problem is the permatune. I am now planning on buying an MSD-6al locally to swap into the car... unless someone sees a problem with my test setup...

http://forums.pelicanparts.com/uploa...1333473912.jpg

Basically I've wired the permatune to a fully charged 12V battery. I have a 12V switch that I'm using as an "ignition switch" (power switch). The fuse block was something I had lying around and is actually being used as a grounding block. I have the distributor grounded and I'm using the points to trigger the CDI. The coil is wired directly to a spark plug lead. I have the plug grounded directly to the battery. I turn the "ignition" on and spin the distributor, activating the points, and thereby trigger the CDI.

Ground the case of the permatune as well. It is normally grounded to chassis. See if it acts the same.

Tried this tonight. No change. Basically the box heats up and then it "sticks" and constantly sends the spark signal to the coil.

I gambled and picked up an MSD Digital 6AL and MSD coil today. I know that I should have put the MSD coil in my test setup to see if that made any difference, but I was afraid of damaging the new coil. Of course, now I found out that the MSD blaster coil can't be mounted in the stock manner... so I will probably end up buying the "better" MSD coil so it can be mounted upside-down.

I'll update once I have the MSD installed.

SUCCESS!!!

Hooked up the MSD.

The car started INSTANTLY. Revs strongly, the tachometer works without an adapter, and the new digital MSD has a built in adjustable rev limiter.

Apparently the intermittent/weird failure of the Permatune CDI made this insanely difficult to solve.

A BIG THANK YOU TO EVERYONE WHO FOLLOWED ALONG AND OFFERED ADVICE.

This forum is absolutely wonderful. I wish I would have had the patience to order the MSD from Pelican, but I was on a roll.

Fortunately, Pelican will be getting a good chunk of money from me as I move on to the next stage of my project - putting my car back together post a full repaint.

THANKS AGAIN!!!

Here's a shot of the temporary install of the MSD:

http://forums.pelicanparts.com/uploa...1333514414.jpg

Obviously I have a lot of finishing work to do, but I did manage to fit the MSD unit into the engine compartment in place of the original Permatune. I drilled two new holes into the mounting plate and used the rubber mounts that come with the MSD. It is only secured with three of the four bolts, but it does seem very secure.

I have power to the unit coming from the starter solenoid and it is grounded directly to the engine. Tomorrow night I hope to shorten and properly route the wiring and maybe take the car for a run around the house (no windshield = short ride).

I also have to figure out where to relocate the rear window defrost relay.

One silver lining to all of this is that I have tuned up the CIS system and freshened every electrical connection I could find. Hopefully the car will be back to its old reliable self.

"The car started INSTANTLY. Revs strongly,"

It's great that the problem is solved! This is the result when one focuses on NOT doing
the 'shotgun' troubleshooting approach that many previously suggested, e.g. checking
for fuel pressures, air leaks, fuel pump, sensor plate, etc., and quickly eliminating
what NOT to focus on. Too bad the thread was initially lead in multiple directions.

Awesome, glad you were able to solve the problem.
For an alternate coil mounting location you could mount it to the left of the distributor on the 2 studs of the camchain cover where the air pump bracket mounts on my engine. It will reach the distributor, won't stress the wiring harness and probably neaten things up a little for you. Mine fits there using the factory bracket with no modification needed.

The problem was pin pointed in post #30.......
 

Damion,

You did not test and verify the presence of consistent and reproducible ignition in your system. And you have mislead many into different direction by ignoring the early recommendations. Now that you have found the culprit, you'll know who was guessing. You could spray tons of starting fluid and that would do nothing to make your engine start. You needed good ignition and that should have been determined in first place before doing further investigation.

Congratulation for all the hard work.

Tony

Actually, I did verify the presence of "consistent and reproducible ignition" - the problem is that the permatune functioned for the first 10-30 seconds, and then it sent out a constant signal to the coil. That's why the car would fire but never actually run.

The stronger the battery was, the faster the permatune would fail. Then it would cool down and function again in a minute or two.

I never cranked the car for 30 straight seconds when I was checking spark, so I wasn't able to identify the problem.

In fact, the coil was still sending out a spark after the permatune went into its "failure mode"- it was just constant power. When the permatune failed it stopped waiting for the signal from the points. It would just fire steadily, with the spark at the plug getting much, much brighter (if that would even still be considered a spark - it was arcing like a welder).

That's what happened when I connected the plug directly to the coil. However, when connected to the distributor, the plug would still "spark" - on and off as the rotor rotated inside the distributor. When the unit failed it would make a sort of popping sound and then start to whine really loudly. With the unit on the bench I could very easily hear that happening. When it was in the car that was not the case.

Granted, if I had an extra CDI laying around I could have identified the problem component more quickly, but that wasn't an option for me. One thing I could have done was bypass the distributor on the car and ran a plug directly off of the coil. However, I still probably would not have cranked the car long enough to find the problem.

Why do you think I was so frustrated? I had fuel and I had spark! What else did I need?

Reviving this old thread as i maybe going down the rabbit hole.

Some seem to forget the wealth of info that's been posted on Pelican Parts over the last 9+ years.