Reproduction TI Amp Issues

[Scott H.]

My car is a stock L72 with reproduction TI system.

The symptoms are hard to start (3-5 attempts) when cold and usually easy to start when warm. That was until about a month ago. Now it is nearly impossible to start (some days it starts after 3-5 tries, most days it doesn't start at all) when cold. Last week it died after driving about 2 miles, very unusual. It would not restart until I towed it home then it restarted once. Since then it will not start. It cranks fine. Plenty of gas at the carb. Except for this one instance when it started it ran great.

Specifically to the TI system there are about 4 volts at the +coil when the key is ON or START, makes no difference. There is about 9 volts from the R terminal of the starter solenoid during all the way up to the male connection of the gray wire at the TI amp connection during cranking. The amplifier module is shown on the TIamp picture.

Based on the above I have concluded that the TI amplifier has failed. Disagreement is welcomed. However, if I am on the right track the question is 'what do I replace the module with'? Should I go back with what I have? Is it common for these modules to fail at 2-1/2 years? Is the Tracy Performance module better? I drive the car most weekends so reliability is by far the most important consideration. Perhaps a rebuilt original GM board is best?

Thanks in advance for any guidance.

[Gary J.]

[Mark F.]

Re: Reproduction TI Amp Issues

Agree 100% with Gary on Dave Fiedler T/I Specialties https://www.tispecialty.com/
He re-did my amp 20+ years ago and I have not had one issue since after thousands of miles driving

[Richard M.]

Re: Reproduction TI Amp Issues

Scott, A few items....

4V at the Coil+ is within range (2.4-4.5v)

The K&B modules(green circuit board) are very reliable, but are susceptible to poor grounds via the 3 mount screws. Verify the screws are not bottoming out in the module case and use toothed lock washers for a good connection.

Also check your module external ground lead at the case and ensure it's free of any paint on the case. Also the ground lug at the core support. I always use toothed lock washers at the grounds, even though not originally installed.

Another issue with the K&B boards is the 3 internal terminals may intermittently short to the rear case cover, so verify there's clearance. You may need to bend the terminals down a bit. Also verify good clean connections at the module 3-Prong plug.

Your Cranking voltage seems low so verify your battery is fully charged. TI needs proper voltage at Crank.
During Crank, what is the voltage measured directly at the battery post?

A failing Solenoid R terminal junction during crank can be bypassed by adding a jumper directly from Bat+ to the Pink wire in the distributor connector, then try to start. If it does, remove jumper quickly or just shut down.

As far as the Ignition Coil...... What coil are you using? Repros have a terrible reputation failing hot.

Rich

[Doug M.]

Re: Reproduction TI Amp Issues

Scott,

Try disconnecting and cleaning bulkhead wiring harness connection at firewall

Doug M

[Ray K.]

[Jim D.]

Re: Reproduction TI Amp Issues

Follow Richard's steps above and you'll be fine. His posts on the TI system helped me diagnose an intermittent issue with mine. He knows these systems inside and out.

[Duke W.]

Re: Reproduction TI Amp Issues

I think most know that the TI distributor housing is the exact same part as the single point distributor housing so, especially if you're not in the judging process, it's easy to convert the unreliable TI system to a single point system.

You'll have to remove and disassemble the distributor to do the conversion, so you might as well do a "blueprint/overhaul" that I've documented and is likely here in the list of restoration documents. You'll also need a ballast resistor, and look at my breaker point article to chose the right point set for you engine, and the primary criterion is the engine redline.

Duke

[Jon H.]

Re: Reproduction TI Amp Issues

Three issues I have commonly found with TI issues:
1. The battery is not charged sufficiently. If your voltage is low you will have starting issues especially with the solid state module.
2. Ignition coil, especially the repo's
3. Pick up coil in the distributor can cause intermittent issues if you have a bad wire. The symptom here is if your car is running and it shuts off abruptly but may restart later.

[Scott H.]

Re: Reproduction TI Amp Issues

Great advice from the discussion board as always. So far I have.....

1. Contacted Dave Fiedler. Tremendous help. He recommended I address the low cranking voltage by inspecting/repairing the starter solenoid. I should also verify that the AC voltage at the distributor leads is at least 1.2Vac during cranking. This needs to be done with an analog 0-10V meter.
2. I measured the TI amp case ground and got zero resistance to the chassis. The ground wires are tight and secured with a star washer against the grounding surface.

The coil is a genuine GM 207. The battery is fully charged with a 3 amp charger.

Next I will verify the circuit board tabs are isolated from the case, reinstall the amp and hot wire 12V to the +coil. From there I will pursue the remainder of the suggestions. I got a lot to do. This may take a week or three to get through but I will report back.

Never wanting to set aside Duke's invaluable advice but for now I'm going to dig in and try to make the TI system work.

[Bill B.]

Re: Reproduction TI Amp Issues

Hi Scott,

A diagram of the TI system is shown below. I will only address the possibility of hard starting when the engine was cranking cold ... (your initial reported symptoms). If the "R" terminal of the starter's solenoid and the wire connection Yellow to pink to the distributor's white was open, or the "R" terminal was not supplying the +12V during the cranking process, it could be a root cause of difficult starting, however, once running, the engine would run symptom free. Rich M. mentioned the "R" terminal and this circuit in his second to last suggestion.

When cranking, the solenoid's "R" terminal and associated wiring bypasses the voltage drop of the white resistance wire of the TI harness and temporarily supplies full available voltage to the TI system in order to compensate for the vehicle (battery and wiring) voltage drop as the starter motor draws a significant amount of current. The starter motor current increases during cranking when the engine is cold, as the oil viscosity is thicker at that time, compared to that of a comparatively warm engine.

I consider Dave Fiedler the TI King! He knows his stuff!

66-71_Diagram.jpg

[Richard M.]

Re: Reproduction TI Amp Issues

Great advice from the discussion board as always. So far I have.....

1. Contacted Dave Fiedler. Tremendous help. He recommended I address the low cranking voltage by inspecting/repairing the starter solenoid. I should also verify that the AC voltage at the distributor leads is at least 1.2Vac during cranking. This needs to be done with an analog 0-10V meter.
2. I measured the TI amp case ground and got zero resistance to the chassis. The ground wires are tight and secured with a star washer against the grounding surface.

The coil is a genuine GM 207. The battery is fully charged with a 3 amp charger.

Next I will verify the circuit board tabs are isolated from the case, reinstall the amp and

hot wire 12V to the +coil. (SEE BELOW)
From there I will pursue the remainder of the suggestions. I got a lot to do. This may take a week or three to get through but I will report back.

Never wanting to set aside Duke's invaluable advice but for now I'm going to dig in and try to make the TI system work.

Scott, No, do NOT run 12V directly to coil+. It could damage the TI board. That's only done to bypass the ballast on a Points ignition system. The TI Coil+ input is sourced directly from the TI module power transistor output circuit.

You want to run 12V to the PINK wire at the Distributor connector. This will bypass the Solenoid R terminal.
TI_DistConn.jpg

Also, when you check the internal module terminals, also remember to check the 3 screws holding the circuit board to the case. Make sure they're tight, not bottomed out, and have toothed lockwashers. Original screws for the old Delco boards are too long for the K&B boards.

One last item. The GM TI Wiring Diagram can be a bit misleading. Corrected below for 66-67. Note the Solenoid R wire is Yellow only on 1968-1971. Pink for 66-67.
66-67_DiagramCorrected.jpg

Rich

[Scott H.]

[Richard M.]

Re: Reproduction TI Amp Issues

Scott, Not sure if the K&B boards could handle that. Hopefully the output circuit is rugged enough. A telltale of a open in the primary of the Ignition coil or open wire on Coil-(hard grounded), would cause a similar reading of 12V, but that's because the transistor would be in a no-load condition.

But..... You're not alone. Some folks on the web tell owners to put Bat+ on Coil+ to bypass the Solenoid "R" Crank wire. They don't understand TI as it's totally different from points when it comes to troubleshooting.

I know the original Delco boards are not ruggedized for that. I hit +12v on the Coil+ of a Delco testbench setup I had several years ago, using my makeshift home-grown TI wiring harness. Inadvertently, my 12V power wire fell and hit my coil+ wiring while disconnecting the setup. I forgot to pull Bat+ first, silly me. It blew the output transistor. Fortunately I had NOS spare transistors so I was able to fix it.

Not sure if you have a copy of the GM Diagnosis Chart. Here's a jpeg version. PDF also attached.

Note the Ignition Distributor Test, lower left of the Chart. Double check that you have 500-700 ohms on the Dist Pickup Coil plug. Disconnect from TI harness to test it. Also check both leads to ground. This is a static test of the internal windings of the PU coil. While you're meter is connected, wiggle the 2 wires(green/green-white) as they go into the distributor. Sometimes they fail there as they're in constant motion internally during advance cycles, and also vibrate continuously while driving. If you get unusual readings, pull the distributor cap and check the wires inside too. I've only had 1 PU coil ever fail, and it was a bear to diagnose as it was intermittent. It was a cold solder joint from the lead wire to the coil internal windings. Surprisingly, it was a NOS distributor.

Rich
66-71_TI_Diagnosis_Chart.jpg

[Scott H.]

Re: Reproduction TI Amp Issues

To my amazement the car started (no R terminal jumper) so I think the TI amp isn't fried. Rich, your initial instructions were perfectly clear. I was just being stupid.

However, it still isn't anywhere near right. I've cleaned the connection from the ignition switch and the pink wires at the distributor like Doug said. They appeared clean and well connected.

So I took some additional voltage measurements:

- Battery voltage before cranking: 12.94V, during cranking and 10.97V measured at the battery terminals
- +coil with jumper from battery+ to the two pink wire/white wire to distributor during cranking: 4.9V and 6V with ign switch ON
- +coil no jumper: 4.5V cranking and 3.5V with ign switch ON
- at the two pink wire/white wire to distributor during cranking: 9.5V and 7V with ign switch ON

The attachment should be an illustration of the same measurements.TI wiring.pdf

I'm thinking the 9.5V at the pink wires versus 10.97V at the battery during cranking suggest a new solenoid? This is the same voltage I initially measured at the R terminal. To add to this I tried starting with an R terminal jumper and based on one attempt it started easier than without a jumper.

The circuit board screws are the same ones that came with the K&B amp. They do have the K&B washers.

Thoughts? I've got a solenoid ready for pickup in the morning.