Barry's70LT1

Regarding 12V from the horn terminal................. FWIW

I carry an HEI module as backup to my TI amp. The "pink" ignition wire will barely run the HEI module, not enough current.

I permanently installed a relay to power the TI (White Wire) from the horn terminal. I use the "Pink" ignition wire to energize (pick) the relay.

This gives me the ability to run the HEI module or the TI amp.

3X2

Are the 3 wires inside the TI module connected correctly? And is the 3 wire plug that connects the TI harness to the TI module clean and tight?

Forgive me for not giving credit to whomever originally posted this.

For better visual reference you may want to attach your Timing light pickup directly on the HT coil wire.

A few things to try.....

Using your voltmeter, attach meter lead + to coil+ and meter lead - to coil-. Turn ignition switch to ON, no crank...

What is the voltage? It should be 2.5 to 4 volts. Use the troubleshooting flowchart at tispecialty.com for more detailed info if not correct. If correct, there are TWO other possibilities that come to my mind that may be causing your intermittent/weak spark condition....

Background.....The PU coil generates a very small pulsed DC voltage to trigger the TI Amp module at each rotation of the 8 distributor poles/plug wire positions. The voltage is around 2 volts. It is VERY important that the polarity of the 2 distributor PU coil lead wires to the harness is correct. Since you've had to replace some wires, it is possible someone else before you had the connectors apart, and reversed them, or maybe you did accidentally.

Additionally, certain TI module circuit board designs may be more sensitive to these low input voltages. It has not been determined which of the 3 types of boards are in your system, original Delco, M&H reproduction, or K&B reproduction. You would have to open the AMP Module case to verify. Internal module grounds to the circuit board of course are important as well. You may have to open it up to verify at some point.

I would check the following:

The PU coil WHITE wire connects to the harness PINK wire. This is the source power to both the PU coil AND the TI Module.
The PU coil WHITE/GREEN (or if PU was OTC replaced, the GREEN wire) connects to the harness GRAY wire. This is the PU coil output wire which is the trigger wire to the TI Amp.

If these 2 wires are reversed, it can cause intermittent/weak trigger pulses to the Amp. You may have to remove the dist cap and carefully trace the wire colors inside at the PU coil wire pair down to your repaired external connector.

If those appear correct......

At crank, the PU coil pulses are of short duration, therefore a higher voltage is required at crank as the battery supply is being reduced by the starter motor current draw. This much like a Ballast resistor bypass in a points ignition system at crank. The harness includes a small gauge PINK wire which directs full battery voltage to power the AMP AND PU coil input. This higher voltage is needed to ensure proper supply voltage at crank.

The PINK wire source is the Starter Solenoid "R" terminal. In the engine/forward harness, there is a single plastic plug wire terminal from the solenoid R which connect to the associated TI Harness plug, likely running along the upper hood ledge area. Visually check that is there and verify proper voltage at crank, below.

Connect your - meter lead to ground, + meter lead to the distributor PU coil WHITE/ TI Harness PINK wire. Turn IGN ON, no crank. You will see a reduced battery voltage on the meter as there is a resistor wire in the harness to drop voltage to the AMP. Record voltage reading.

Then while observing the meter, crank the engine and record voltage. It should be higher than previous reading, at or near full battery voltage during crank. As a reference, you can record the battery voltage at the +cable during crank also.

There of course are other possibilities causing your weak spark. These are just a few to try, but should be verified to help diagnose the fault.

1969monzared

3X2,

What a great wealth of info, I've got some homework to do. I'll work on it this Friday and let you know what I find. Thank you again for the help.

1969monzared

3x2,

ok, so I got a new to wiring harness from m&h and installed, no spark. New r43 plugs, no spark. I have always been concerned that the red wire from my ignition switch reads 9 V. I unplugged the pigtail plug from the TI harness to the amplifier and re-tested voltage at the ignition switch wire and it now reads 12 V. Tested the pink wire at the terminal end pigtail plug just prior to it plugging into the amplifier with the key on and it reads 12 V. I am losing 3 V when the TI harness is plugged into the amplifier. Do I have a short in the amplifier board? Again this is in the key on position but not cranking.

TimAT

If you look close at the GM TI wiring diagram, you can see the resistor built into the harness.

1969monzared

timAT

so when I test the voltage at the ignition switch with the amplifier plugged into the harness the voltage will be less than when it is unplugged? If so, I am at a dead end again. I have a amplifier with a m&h module and one with a k&b and neither allow spark. New coil that checks out ohm test, new distributor that checks out via ohm test, new wiring harness from starter to coil/ti harness and two new modules one k&b and one m&h. Should I flush another $200 buy another module and assume that both modules were faulty? Or buy a points distributor? Really frustrated.

1969monzared

TimAT

in reviewing my measurements, shouldn’t I have 12v from the starter solenoid R terminal and from the ignition switch at crank? Both at 2V low. I assume that’s enough to prevent spark.

Battery: 12.93 v
Pink ignition switch wire with key on: 8.86 v
Yellow wire with key on: 5.45 v
R terminal on solenoid with key on: 5.57 v
Coil + to ground with key on 2.22 v
Coil + to - with key on 1.92 v
Pink ignition switch wire on crank: 10.37
R terminal of solenoid on crank: 10.78
Yellow wire on crank: 10.55
Coil + to ground on crank: 4.30 v
Coil + to - on crank: 3.84 v
Checked the resistance of the distributor and was 640 ohms

3X2

Let me digest the volt readings you posted. I'm not ruling out a blown TI module yet. I went through 2 of them in June with the wrong coil. My car would has a second or two ignition, then nothing when the wrong coil blew out the modules.

Now, let's get back to basics so I'm clear headed in my thinking. Car ran with the points distributor, converted back to TI and car does not start. Did you ohm the pickup coil and keep reading the ohms when applying vacuum to the advance and wiggle the wires to see if the ohms go to open? You say you have a 263 coil. Did you ohm it? Primary Resistance… .41 to .51 ohms Secondary Resistance… 3,000 to 20,000 ohms. You should check the resistance wire in the harness too…. .43 to .68 ohms. TI module has good ground and wired correctly to harness. I have to ask: distributor is rotating when cranking and has a rotor? Coil to dist wire ok?

I've attached another diagnostic flow chart. Not sure if I sent this before or not.

1969monzared

3x2,

Thanks for the info. The amplifier is connected properly and grounded. The distributor has a rotor and is rotating with crank. Ground for the amplifier is good, even ran another to the alternator ground to see if it was the problem. Distributor unplugged from ti harness reads 650 ohms and cycles between 650 and 1100 ohms when cranking. Coil ohms check out, both primary and secondary. I just ordered another module from David crane but don’t want to plug it in and blow another due to not diagnosing the problem. There were multiple problems initially and I think I have eliminated a few. Voltage of the ignition switch wire is 12.4 v when disconnected from the ti harness and about 10v when connected.

69427

Is that 10v reading at the ignition switch (not good!), or at the pink wire going into the module (normal)?

You can do a simple brute force check of the module internals. Looking at the diagram that TimAT supplied, it should be the white/green wire coming off the distributor pickup wiring (or the Gray wire going into the module) that does the timing/firing signal that causes the module to shut off the coil primary current (causing the ignition coil to fire the plug). You could take a jumper wire and hook one end to the white/green wire, and with the key ON, tap (don't hold) the other end of the jumper wire to ground. Every time you tap/ground the white/green wire the coil should fire.

PAmotorman

if the corvette originally had a points distributor the original wire to the coil must be replaced as it is most likely a resistor wire cutting the volts to less than 12 volts

1969monzared

I replaced the the wiring harness from the starter solenoid to the TI harness as well as the TI harness. The pink wire from the ignition switch unplugged from the TI harness measures 12.4v with the key on. When I plug the pink wire into the TI harness and measure the pink terminal at the pigtail plug with the TI harness unplugged from the amplifier it reads 12.4v. When the TI harness is plugged into the amplifier I can take a reading at the plug (pink ignition wire to TI harness) and it reads 8.4v. I assume it is due to a draw on the system due to resistance wires heading back to the coil and distributor. I am going to try another amplifier module on Friday and see what happens. If no spark it’s back to the points.

TimAT

Someone should have an AIM with the K66 option pages. IT shows exactly how the factory cut the coil wire for points and bypassed it for TI, then connected the TI into the ignition switch. I have an AIM on my computer, but it's locked so I can't print or extract pages.

69427

It's normal for the voltage reading at the pink wire (when plugged into the module) to be lower than the battery/ignition voltage. The TI system is designed/wired so that there is always current going through the coil (exact opposite of an HEI), and it's the rotation of the distributor pickup coil system that tells the module to interrupt that current briefly so that the coil/plug fires (it's like your engine always stopping with the points closed. The distributor has to rotate to interrupt that coil current.)

1969monzared

If anybody can get me a copy of the AIM on k 66 option I would appreciate it. Maybe I need to modify the harness. Can you send me a screen shot from your computer?

7T1vette

I don't think the AIM drawing will do it for you. You need a good electrical schematic for the K66 installation (not just the TI system). You might also need one for the points ignition system install, so that you can see where the differences are.

Barry's70LT1

Here is the AIM on K66 for a '70. As 7T1vette says, there is not much detail. I do know that on a NON TI wiring, there is an "ignition" power wire going to the + side of the coil, contains two wires on the clip. One to the "ign" (resistance wire) and one to the starter.

On mine (TI), the ignition wire (non resistance) is a single wire running thru the firewall to the "ignition" on the fuse panel under the dash.

Also here is a wiring diagram on connecting an HEI module in place of the TI amp. I know this works as this is my backup setup I carry which I hope I never have to use.
You could use this setup to get yours running, then work backwards to get the TI working. Barry

TimAT

Look a the 2 NOTES in the upper right corner of Barry's AIM page- That's where the resistance wire is disconnected and the TI is plugged in. At the coil, the wire from the bulkhead is cut and taped back into the harness, (that eliminates the resistance wire from the switch.) The wire from the starter "R" terminal AND the white wire from the TI harness go to the coil +. The black wire from the TI harness goes to the coil - .

1969monzared

Thank you guys, I’ll work on it this weekend and let you know what I find out.

69427

Unless I'm misunderstanding your description here, I believe you mean the module +/ignition terminal.