Reproduction TI Amp Issues

[Richard M.]

Re: Reproduction TI Amp Issues

Scott, Whether you need one now or not, Zip has it in stock. E-499

And whether you need it or not, I'd get one as a spare. K & B Special Products had them made here in the US.

Ken Anderson, the owner of K & B, sadly passed away a few years ago. I do not know if the business is still active or not. His original website, kandbcorvetteproducts.com is no longer there. A check on whois.sc states the registration will expire 4-29-2023.

K&B also made the reproduction instrument gauges, so I don't know if those will continue to be made either.

I had heard rumor that a family member was going to continue the business, but not verified.

Rich

[William F.]

Re: Reproduction TI Amp Issues

Right Duke. That's the optional system i had on mu '67 442-red distributor cap and all. Never had trouble taking standard engine GTO's. Never ran a Hi output one.

[Scott H.]

Re: Reproduction TI Amp Issues

Sorry to go AWOL. I am back now. The carb shoots two solid streams of fuel into the engine when accelerator pedal is pushed. Additionally, the fuel level in both the primary and secondary fuel bowls is at the bottom of the level holes (no fuel spills out when screws are removed but fuel will spill out if the fender is bumped).

The resistance across the distributor pickup is 686 ohms. Dave Fiedler said check the voltage at the distributor feed (see photograph). It is 1.2 volts during cranking. A picture of the spark is attached.

[Richard M.]

Re: Reproduction TI Amp Issues

Hello Scott, several years ago I had similar starting problems with my 1966 427/425 with TI ignition. It had a replacement solid state board installed in the amplifier. I found out that some of the solid-state boards will not pick up a signal from the original pick-up coils in the distributor. I checked all connections and voltage readings and found no issues. I spoke with Dave Fiedler and he recommended replacing the amplifier with a stock unit and confirmed that he has also seen issues with the solid-state boards not processing the signal. I installed an original unit, the engine immediately started and has been running flawlessly for years. I run the stock amplifiers in both my 1966's and 1967 with no problems. John

John, Yes I've heard that from Dave too, but he may have been talking specifically about the early M&H(potted) boards. There was a hardware bug in those and they had to revise it.

I verified the bulkhead connection was solid. It's a Lectric Limited harness that I put on about 3 years ago. No reason to think the connections are dirty. I changed out the solenoid. It appears to have added a volt to the coil during cranking. With the new solenoid I get:

- 12.6V at battery terminal, not cranking
- 3.5V at +coil ON
- 4.3V at +coil cranking

I tried the jumper to the pink/white connector too. Still doesn't start. I didn't pull a spark plug but did get a signal from an inductive timing light. I'll keep doing that since the start/no start appears to be so random. I'll verify the resistance across the distributor, looking for 500-700 ohms.

Scott, I'm thinking it's time to get back to basics.... Fuel? or Ignition? I'm not convinced which is at fault now.

Have you re-verified adequate fuel flow at the carb since your first reported issue? If so, then back to Ignition diagnosis.

Since it appears to show activity of a spark condition with the timing light, it would be wise to actually check spark at a sparkplug, to see how healthy the spark is. When you checked it with the timing light, was it at a sparkplug or the coil wire? If at the coil wire, there's still a path through the distributor rotor to get to the plugs. May be time to check things inside the distributor at this point as well.

As a reminder, with a TI system, do NOT remove the coil wire and check spark there at the distributor cap. Always only at 1 spark plug.

Rich

Sorry to go AWOL. I am back now. The carb shoots two solid streams of fuel into the engine when accelerator pedal is pushed. Additionally, the fuel level in both the primary and secondary fuel bowls is at the bottom of the level holes (no fuel spills out when screws are removed but fuel will spill out if the fender is bumped).

The resistance across the distributor pickup is 686 ohms. Dave Fiedler said check the voltage at the distributor feed (see photograph). It is 1.2 volts during cranking. A picture of the spark is attached.

Ok I had to go back and see where we left off... I added the quoted posts sequentially, because if a reader is in Hybrid Display mode, your previous post gets buried in the thread as you replied to my last post. If in Linear Display Mode, it keeps everything sequential from bottom-to-top.

So 686 ohms at the Dist PU coil connector is a good reading. DId you wiggle the wires with it connected to the meter?

Your 1.2VAC at the connector, is with it connected to the Dist, during Crank using a AC meter, correct? I don't want to assume so I have to ask.

You have good fuel flow, and spark. That's a pretty cool timed shot of the spark. But.... if that's the max intensity of the spark it seems a bit weak to me.
Scott_SparkMag.jpg

Here's what I get on a benchtest with a Delco board.... Go directly to Time 8:00 to see it.

Screenshot at 8:18...
1967 Corvette Transistor Ignition Bench Test 8-18 screenshot.png


Did you try adding another Hard Ground wire directly to Coil-? May want to do that as a quick failsafe. If it's no change, I'm now wondering if your 207 coil is marginal.

Since you have the K&B TI board in there, you can definitely run a Standard points coil(e.g. Napa IC12) as a verify tool. I ran one for a year on a K&B equipped '67 L71 until we found a 207. Years ago Dave confirmed it'll work fine too. It just won't have the High RPM capability as the TI spec coil.

Rich

[Scott H.]

Re: Reproduction TI Amp Issues

Hi Rich,

I did wiggle the wires during the pickup coil resistance test. However, the voltage test was done just like my picture showed. The connector was not connected. Additionally, I got no voltage on the AC setting, only the DC setting gave me a reading.

The spark in my picture was as good as it gets. I thought it was very weak too. I wasn’t clear on what you meant by “another hard ground”.

In any case the amp is on its way to TI Specialty for testing. I will report the outcome. As for the coil I never could get a Napa IC12 to work when I was fighting my reproduction coil failure. Since then I replaced the Lectric Limited plug wires with Parker’s 440’s.

[William F.]

Re: Reproduction TI Amp Issues

Richard,
Thanks for clarification about voltage with TI and info on my442's CD ignition.

[Richard M.]

Re: Reproduction TI Amp Issues

Hi Rich,

I did wiggle the wires during the pickup coil resistance test. However, the voltage test was done just like my picture showed. The connector was not connected. Additionally, I got no voltage on the AC setting, only the DC setting gave me a reading.

The spark in my picture was as good as it gets. I thought it was very weak too. I wasn’t clear on what you meant by “another hard ground”.

In any case the amp is on its way to TI Specialty for testing. I will report the outcome. As for the coil I never could get a Napa IC12 to work when I was fighting my reproduction coil failure. Since then I replaced the Lectric Limited plug wires with Parker’s 440’s.

Scott,

The voltage test you did was not valid. You had the leads connected at Bat+(Pink) and the TI AMP input(Gray), which is normally from the PU Coil output. What you measured was the trigger transistor quiescent state(open) input with respect to plus voltage. Not a valid reading.

I believe Dave wanted you to test the output of the PU Coil during Crank, to verify the coil and magnet were functional, operating as a pulse generator to the AMP input. You'd need the distributor plug connected for that. The AC voltage test should be at the Gray wire with respect to ground. But it's tough to get a reading on a AC voltmeter. It may deflect but tough to get it measured accurately. Here is a example of the Gray wire PU Coil output on a oscilloscope.

The yellow waveform is the PU coil output during simulated Crank(I used a TI distributor run by a drill).
Scale is 500MV per vertical square unit. The reading is apx 1.25V AC.

DS0004.BMP

But since you are getting "some" level of spark, it appears your PU Coil/magnet is working. It's the HV condition that I'm suspicious of.

I'm surprised you couldn't get the IC12 to work in the past. I've used them several times for troubleshooting, and as mentioned, for a year on one TI car.

Do you still have the Repro TI Coil. They work fine when cold. Just don't drive more than 20 minutes or you'll need a flatbed. Not bad for judging(minor deduct), and Operations test. NO WAY for PV.

Too bad you sent the AMP out already. I really think you have a either a weak coil, or some other high voltage related issue. Did you open up the distributor and check the cap and rotor as I mentioned before? I hope it's not a extended tip rounded tip rotor. Those can cause spark scatter on a TI ignition system. You want a standard sharp edged rotor tip with TI.

I see you said you replaced the plug wires. Are they SOLID CORE? According to Dave, those won't work with TI.

Rich

[Richard M.]

Re: Reproduction TI Amp Issues

Richard,
Thanks for clarification about voltage with TI and info on my442's CD ignition.

William, Yes your post sparked my interest(lol), and I went researching. Funny thing is Duke was writing too when I was, but he hit the "go" button before me.

[Duke W.]

Re: Reproduction TI Amp Issues

I was faster because I didn't do any research... just wrote my post with what I was able to recall from memory.

I have a 1967 vintage SAE paper on the CD system, and that's the source for the spark dwell times I quoted.

I mentioned that data in an article I wrote back in the nineties for the Cosworth Vega Owners' Assc. on the HEI system , which is pretty much the same circuit as the TI system... just implemented with a different technology - thick film hybrid rather than discrete components on a circuit board, so both systems have very similar performance characteristics.

Duke

[Richard M.]

Re: Reproduction TI Amp Issues

I was faster because I didn't do any research... just wrote my post with what I was able to recall from memory.
.
.
Duke

I kinda' figured that.

[Scott H.]

Re: Reproduction TI Amp Issues

Thanks to everyone for all the suggestions. Dave Fiedler says the amp is fine. The wire is stranded, same wires I've used for at least 1000 miles. The rotor and distributor cap appear fine to me (pictures attached). I tried testing a spark plug and a reproduction coil. The coil didn't help. The spark plug was intermittently much stronger using the 207 coil. The problem does seem to be intermittent on the HV side as Rich suggested.

I'm trying to find a loose wire somewhere.

[Richard M.]

Re: Reproduction TI Amp Issues

Ok, AMP is good, as suspected.

My next steps would be....

1- The rotor tip could use a cleaning. Couldn't hurt. Remove it to clean it with a fine file or sandpaper.

2- With the rotor off, observe to rotating pole piece with the 8 tips(image below). Check that the magnet/stator hold down screws are not loose.
The pole piece will rotate a bit when the centrifugal cam springs stretch. (Tick the starter a bit if needed). Take a piece of a business card and make sure it fits between all of the rotating tips and the stationary tips of the stator, held by the magnet hold-down screws. The tips should never touch. If any touch, slightly loosen the magnet screws to ensure they're free. Tighten screws and recheck. Don't over tighten, it could crack the magnet.

3 - Reassemble everything, test. If it still won't start....

4 - Add a #14 gauge jumper wire from a solid engine ground to Coil-. The Coil gets it's ground far away at the AMP module, via the core support, the chassis, and the horn relay mount bolt. Not the best method.

Rich
P6240125.jpg

[Scott H.]

[Richard M.]

Re: Reproduction TI Amp Issues

Scott, Good effort.

Since it started and ran well after your checks, you had fuel and spark. This confirms cap and rotor were working.

When it did not start the second day, did you verify first step? no fuel.... or no spark?

It has to be one or the other. Without knowing which, you should maintain the methodical approach to diagnose the root cause of the no-start. Swapping parts is one way of trying to fix it, but not ideal. Yes sometimes that's the only way when it comes to intermittent faults, the most difficult type to nail down, but best to stick with basics again. Sometimes parts-swaps can mask the problem, as well as introduce new faults, making it even more difficult.

Previously your spark appeared weak. After you verify fuel(again), I think you need to again concentrate on the weak spark syndrome as that appears to be the culprit from the last diagnosis.

Coil- : To recap, yes you read 0 ohms at engine to coil-, but.... it's possible that the connection is marginal when the coil is under load. All of the coil current passes through the negative terminal to ground when operating. For now, while diagnosing, add that extra solid ground from clean engine ground to coil- to rule that out as a issue. Leave it there until root cause is isolated.

Rich

[Doug M.]