'69 L68 with TI Getting No Spark

[Jack O.]

Hi everyone,

I have some questions about the TI diagnosis from the '64 Service News and a TI issue in general.

Background: I had disconnected plug wires and distributor/coil connections when doing some other engine work (rebuilt carbs). When I hooked everything back up I had the plug wires off by one on the distributor but once I straightened that out engine fired right up and ran fine for about 30 minutes. Next day I routed the plug wires correctly and installed the the distributor shielding which meant I had to disconnect/connect the coil and distributor wires. Car started up and ran for about 20 seconds and cut off and I couldn't get it to start again. Figured I flooded it so left it a day and next morning it initially started for about 5 seconds and hasn't started again.

I've checked and I am not getting any spark. I checked my coil (which is a correct TI coil) and I get 1.5 to 1.7 ohms across the terminals and 13.1k ohms across the secondary. Does this indicate a bad coil? The coil is also getting 11.4 volts on both the pos and neg sides which according to the diagnosis procedure indicates bad ground resistor wire or wiring harness. But do my first resistance readings invalidate these voltage readings?

I also tried to do the deflection test but wasn't sure how to make the connections. I used an extra plug wire and connected it to the coil positive terminal (should the positive coil wire be connected?) and the distributor connector that contains two pink wires. I used tester's RPM connector to attempt to pickup off of the plug wire and I got nothing but I'm not sure if I had all this connected correctly.

In any case, anyone have any thoughts in general given my wordy description above?

Thanks,

Jack

[Jack O.]

Re: '69 L68 with TI Getting No Spark

I think my last post was too wordy - perhaps someone can simply tell me if the readings I took from my TI coil indicate it is bad and could be causing no spark. Both primary and secondary are reading high:

primaries: should be in .35 to .55 ohm range and mine read 1.5 to 1.7
secondary to primary: should be 8000 to 12,500 and mine read 13,100

Thanks,

Jack

[Duke W.]

Re: '69 L68 with TI Getting No Spark

Do the static resistance check on the pickup coil, and wiggle the wires while reading the meter. Also do a dynamic test. The voltmeter should show repeated deflections during cranking. Broken pickup coil leads is what I'm thinking. - not uncommon on TI and HEI.

Does the engine quit as if you turned off the ignition, or does it stumble and miss briefly before it stalls.

Duke

[Jack O.]

Re: '69 L68 with TI Getting No Spark

Hi Duke,

Thanks for the help. The engine ran perfectly about 30 minutes. Next morning I started it after re-routing spark plug, dist and coil wires and putting the dist shielding back on and it started right up, ran about 30 seconds and cut off. Wouldn't restart so I hoped I had just flooded it. Let it sit and the next morning it started and ran for only about 5 seconds and has never fired again. That's when I started the TI diagnosis and determined I'm getting no spark.

I wasn't sure how to wire things up to do the deflection test. The diagnosis procedure says to "connect a tach between coil pos terminal and the black/pink wire at the 3--wire connector...". I have a '69 so I assume it would be the two pink wires at the three wire connector? Do I disconnect the 3-wire connector when I do this or leave all wires, including the coil pos wire, connected? Some help on how to wire up this test would be much appreciated!

Thanks,

Jack

[Duke W.]

Re: '69 L68 with TI Getting No Spark

I don't have the TI troubleshooting/flowchart in any of my documentation, but it's pretty much the same as the HEI, which I do have.

When the engine turns the pickup coil sends a timing voltage pulse to the amp every 90 degrees. It occurs when the projections on the stationary and rotating pole pieces pass each other.

Disconnect the two-wire distributor pigtail from the TI harness and first check static pickup coil resistance at the pigtail I think the spec is 500-700 ohms. Wiggle the pigtail with the meter attached and look for resistance fluctuation, which could indicate broken wires. If you have a Mity Vac or equivalent, pump down the VAC a few times, which rotates the pickup coil and watch for resistance fluctuations.

Then disconnect the harness from the TI amp. Put the two voltmeter probes between the two wires on the distributor pigtail and crank the engine. You should see voltage spikes every 90 degrees of crank rotation. An old analog meter is best for this test set at the lowest voltage setting as you can just look for multiple needle deflections. If the first test is negative, reverse the voltmeter leads on the pigtail and run the test again.

I'm not sure of the test you describe with the three wire connector, but I believe that connector is 12V power plus the coil wire and maybe a ground. The two wire connector on the TI harness connects to the distributor pigtail. It sounds like it's basically the same dynamic pickup coil test that I outlined above, but uses a tach instead of a voltmeter. If the pickup coil is okay cranking the engine will cause the tach to read cranking RPM.

Since the pickup coil wires are constantly being strained by VAC action, they eventually fatigue and break, and with no pickup coil voltage signal, there is no spark even if everything else is okay. The pickup coil performs the same function as mechanical breaker points. I had a pickup coil failure on the HEI system on my Cosworth Vega.

If there is no spark the pickup coil is a prime suspect, and should be the first thing to check.

Duke

[Jack O.]

Re: '69 L68 with TI Getting No Spark

I'll give it a go tonight and report back. Thanks again Duke!

[Jack O.]

Re: '69 L68 with TI Getting No Spark

Ok Duke, here's what I did, to be sure I did it correctly, and results:

1) Disconnected the distributor pigtail and connected each of my two probes, one to each pigtail wire, and measured resistance and came up with about 610 ohms so that seemed to check out. I also moved them around and bit and applied vacuum to the pot and saw no change.

2) With everything connected EXCEPT
- distributor pigtail disconnected
- harness lead from the TI amp disconnected from engine compartment harness

I used an analog meter, set to read voltage, and again connected each of the two probes to one of the two wires coming from the distributor pigtail. I cranked the engine and I'm saw no movement - deflection. I then reversed the probe connections and still got no movement.

Does that mean the distributor pickup coil is bad?

Thanks,

Jack

[Richard M.]

Re: '69 L68 with TI Getting No Spark

Jack, the voltage out of the pickup coil is so small you cannot read it with a analog meter. 610 ohms with wiggling it around is fine. Your PU coil is probably not the problem.

Is your TI Module the original Delco type? If so, did the engine backfire on restart with the plug wires improperly configured?

Rich

[Jack O.]

Re: '69 L68 with TI Getting No Spark

Rich,

It is an original and as far as I know it has not been redone or updated and does not look like it has been gone into. Yes, I believe at least once it did backfire. It did run fine for about 30 minutes subsequent to that.

Are you saying that because my resistance readings were okay the voltage check was not necessary?

Jack

[Richard M.]

Re: '69 L68 with TI Getting No Spark

Jack, You can try reading pulsing voltage at crank with a analog meter on a very low scale. I've not been able to get a valid reading using a analog meter on a TI system. Maybe on HEI as Duke mentioned. Digital meters, never. A oscilloscope is the best way.

For reference you can see how low the DC levels are in the waveforms shown Here. The yellow trace is on a 500MV scale and the PU coil output reads about 1 volt at varying frequencies. The PU coil is basically a motor, ie a pulse generator. If you read 500-700 ohms static, chances are it's okay. As Duke mentioned, the wires coming out of the PU coil are usually the culprit. Every time the pole piece moves as driven from the VAC, it strains the 2 wires inside.

Getting back to your 1st post....Your Ign coil reading of 1.5 ohms on the primary is a bit high, but probably because your meter leads are about .5 to 1 ohms, thus adding up to the 1.5 ohms. Touch the 2 meter leads together. Whatever you get, subtract it from the primary reading. BTW, TI will work with a Non-TI coil just fine. It just won't supply the high voltage(30Kv) that a TI coil will. The TI coil uses heavier gauge wire on the primary, and less of it, so the resistance is lower. Therefore the current in the coil is higher, to supply the higher voltage to the plugs.

Based on the fact that you moved the distributor wires off by one and had them on and off a few times, I'd say it's something simple. It's a pain, but I'd get back to a baseline. Set your balancer to the timing mark. Doesn't matter, either for #1 or #6, pull the dist cap and ensure your rotor tip is at the right position, either 1 or 6. Double check your plug wiring routing to each cylinder to make sure it's configured properly. Since you had a few backfires, it may be just a miswire on the plug wires or a loose wire at the cap or plugs.

If your TI module is the original Delco, it's possible it got damaged due to the miswires, but my gut feel is it's probably okay. More than one plug open circuit can cause them to blow, but I've seen some more rugged than others.

Seems several folks are having issues with TI lately. Maybe the moon phase or something. Don Harris had some questions and last night I posted some info too on his thread. See this post for more info.

Rich

[Duke W.]

Re: '69 L68 with TI Getting No Spark

Ok Duke, here's what I did, to be sure I did it correctly, and results:



I used an analog meter, set to read voltage, and again connected each of the two probes to one of the two wires coming from the distributor pigtail. I cranked the engine and I'm saw no movement - deflection. I then reversed the probe connections and still got no movement.

Does that mean the distributor pickup coil is bad?

Thanks,

Jack

...depends on the meter, and it may take a high end type because of the low voltage and short duration of the spike. The static test wiggling the wires and exercising the breaker plate probably means the pickup coil is okay. Look at the pole pieces and check for any physical damage. Also check all connectors, and run a resistance check on all the wires in the TI harness.

Richard said you moved the wire positions on the cap, which I didn't pick up, but if you did, reindex them IAW the CSM. l If you removed the dist. at any point maybe it's not installed properly

Rotate the engine to the initial timing point (not TDC) on #1. I suggest removing the plug and feeling for compression to make sure #1 is on the compression stroke. The rotor should be pointing to #1 on the cap.

Rotate the dist. base until pole pieces line up. This should result in timing within a couple of degrees of the target. If the base won't rotate enough to line up the pole pieces without interfering with something, the distributor is probably not installed at the correct indexing.

Duke

[Jack O.]

Re: '69 L68 with TI Getting No Spark

No, I haven't disturbed anything since it had ran. Once for ~ 20 seconds and just cut off and again for about 5 seconds and then cut off. I'm definitely not getting any spark either. Have I narrowed it down to either the amp or harness from the amp?

[Edward J.]

Re: '69 L68 with TI Getting No Spark

Jack the early model TI module were suspect to water intrusion as the connector points up and corrosion was common to the connections Try and unplug and take a peak for corrosion at terminals.

[Jack H.]

Re: '69 L68 with TI Getting No Spark

I'm not big on what's in print for troubleshooting TI systems. As a retired EE, the advice given is a bit 'See Dick, See Jane' to be specific enough to troubleshoot properly. Here's my take.

All grounds in the system have to be right and of low resistance. One that's frequently overlooked is the TI amp module where it's mounted to the radiator. But, regardless of where the fault(s) might be, I take my oscilloscope out and monitor the primary side of the coil. With a helper keying the ignition, you ought to see a nice uniform square wave pulse train of voltage feeding the coil when the engine is cranking. If you don't, go back up stream from the coil and find out where you're losing the signal...

[Jack O.]

Re: '69 L68 with TI Getting No Spark

Okay, what is the most likely culprit when the spark comes and goes within minutes!

I decided to fall back and double check that I was not getting any spark by using my timing light. I had to reconnect the distributor pigtail and the TI harnes to the amp pigtail. Damn thing fired right up. Cut it off after only a few seconds and tried again and I'm getting no spark - as shown by my timing light. Wait a couple of minutes, it fires up once again but now hasn't the next few attempts before I decided to come in the house to fire off this update (and my battery is getting weak).

So is there a component more likely than another to exhibit this type of "come and go" behaviour?

Thanks,

Jack