Ti ignition has weak spark
Thread Starter
Instructor
Joined: Jan 2006
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From: brea california
Ti ignition has weak spark
New engine and new rebuilt TI distributor from Crane. I also replaced the Amplifier from ti specialty. I called for help but havent got a return call.
If I put a jumper from the plug wire to almost 1/8" ground. It will spark but not from 1/4" I went over the ground on radiator. Is there more grounds I"m missing?
Any ideas?
The engine ran a month ago but was hard to start then. Now it wont start at all.
If I put a jumper from the plug wire to almost 1/8" ground. It will spark but not from 1/4" I went over the ground on radiator. Is there more grounds I"m missing?
Any ideas?
The engine ran a month ago but was hard to start then. Now it wont start at all.
Team Owner
Joined: Jan 2006
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From: Crossville TN
The wiring powering the TI system is different (different resistance levels, etc.) than the points system uses. If you just stuck a TI amp and coil in the points system wiring, I'm not sure what would happen. Maybe it would do what yours is doing.... 
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Instructor
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From: brea california
The car came originally with the ti and thats why I'm putting it back together stock.
Thread Starter
Instructor
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From: brea california
I did clean up another ground on the amplifier itself still spark is so weak it wont even light the timing light
Does the stock system just have one wire each to the coil? A big white wire to the plus terminal and a smaller black wire to the neg?
Plus the coil is pretty warm just from me troubleshooting and turning the engine over..normal?
Last edited by georgeculolias; Dec 21, 2011 at 06:28 PM.
Team Owner
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From: Crossville TN
I am no 'expert' on the TI system. I only can pass on things that I've read [and tried to learn] from the Chevrolet Chassis Service Manual (Section 6Y, Engine Electrical). There really isn't a 'functional' electrical schematic for with the TI system in place; only the one with the points type system. The section 6Y details some of the components and has a very basic electrical layout of the parts in the TI system (Fig. 19i), and that shows three electrical connections to the coil: "ground", an input line which receives the pulse signal from the TI unit, and an output line which I assume is going to the distributor. However, those 3 connections are likely only 2 wiring hookups and a chassis ground via the outer shell of the coil can. I also noted that two of the resistors in this system {R7 & R8} are apparently built into the wiring as resistance wire (also being different resistances than found in the points system wiring), and another resistor {R6} might be built into the TI circuit board OR it might be built into the vehicle wiring. So, it would seem that all TI units are not interchangeable from vehicle to vehicle.
Looks like the proverbial "can 'o worms" to me. Hope you can get to a more knowledgeable source that can fill in the gaps and get you up and running.
Looks like the proverbial "can 'o worms" to me. Hope you can get to a more knowledgeable source that can fill in the gaps and get you up and running.
Last edited by 7T1vette; Dec 21, 2011 at 08:41 PM.
Le Mans Master
Joined: Dec 2003
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From: Fremont CA
You don't ever test a K66 by doing spark gap testing. You ground the coil output. I learned this from an oldtime Vette mechanic. He would insert paper clips into distributor plug terminals then ground them with a jumper wire. If you pull a plug lead trying to do a cylinder balance test you will kill the amplifier. Weak spark will be coil or amp, that's it.
Le Mans Master
Joined: Dec 2003
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From: Fremont CA
I just thought of something, you do have the amplifier case grounded to the radiator support don't you? I'm sure you already checked all the wiring and connections. You have full 12VDC at the pink wire to the harness. Get a GM manual and start doing the voltage and resistance checks.
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Tech Contributor
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From: I tend to be leery of any guy who doesn't own a chainsaw or a handgun.
You don't ever test a K66 by doing spark gap testing. You ground the coil output. I learned this from an oldtime Vette mechanic. He would insert paper clips into distributor plug terminals then ground them with a jumper wire. If you pull a plug lead trying to do a cylinder balance test you will kill the amplifier. Weak spark will be coil or amp, that's it.
You mentioned that the amplifier has been replaced/(updated?). I don't know if the circuitry has been modified or if parts have been updated to newer/better parts. Newer style parts are more durable, but it's best during testing to assume the module is still a delicate piece of electronics.
Le Mans Master
Joined: Dec 2003
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From: Fremont CA
Poster is talking about Crane's Corvettes in So-Cal. Cranes is a wrecking yard that specializes in Vette parts. I have known people who have had problems with the Crane K66 repro distributor coils but, didn't have time to help them out, and I suspect they had terminals in wrong position in connector. You might want to try swapping the wires in the distributor pick-up coil connector, if they are reversed you would see a weak spark. When your done fighting it, swap a Pertronix Ignitor3 and black coil in Yor Vette. Leave the K66 box on the fender, and put the TI coil label on your coil (heh! heh!)
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From: brea california
I just thought of something, you do have the amplifier case grounded to the radiator support don't you? I'm sure you already checked all the wiring and connections. You have full 12VDC at the pink wire to the harness. Get a GM manual and start doing the voltage and resistance checks.
Is there only 1 wire on the neg terminal and one on the pos?
Thanks everyone for trying to help I need it!
What about the coil being pretty warm while I'm trying to get the system to work. Is that normal?
Tech Contributor
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From: I tend to be leery of any guy who doesn't own a chainsaw or a handgun.
I'm still lost on this. What about a jumper from the neg terminal straight to ground? Can I do that without screwing something up?
Is there only 1 wire on the neg terminal and one on the pos?
Thanks everyone for trying to help I need it!
What about the coil being pretty warm while I'm trying to get the system to work. Is that normal?
Is there only 1 wire on the neg terminal and one on the pos?
Thanks everyone for trying to help I need it!
What about the coil being pretty warm while I'm trying to get the system to work. Is that normal?
Pro
Joined: May 2011
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From: Karlsruhe (Germany)
Please measure the voltage you have at the coil,
it should be around 7 Volts.
If you have this or higher voltage, the coil is the reason for weak sparks.
The TI-Amp has only 3 transistors inside (i mean the original unit from back then. Dont know newer circuits.).
The spark is generated by cutting off the voltage from the coil.
Well as your only problem is the a weak spark, i guess the distributor and the amp are working good. Cant imagine the amp pulls the coil only 3 volts down, what could also cause a weak spark.
But what is very important is, that you have the right polarization at the coil! If you twist it wrong, you will have less spark power.
Maybe you try this first, its no big deal to change the connections
If you have no spark afterwards, it was already right. If its stronger, you got the root cause.
Le Mans Master
Joined: Dec 2003
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From: Fremont CA
The TI wiring harness going to amplifier (3 terminal plug) should also have a black wire with 2 ring terminals on it. One terminal goes on bottom amp bolt (make sure the case has no paint on it) the second ring terminal bolts to the radiator support. Make sure these connections are clean and tight, poor amp grounding will cause low spark output.
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Instructor
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From: brea california
This is quite normal.
Please measure the voltage you have at the coil,
it should be around 7 Volts.
If you have this or higher voltage, the coil is the reason for weak sparks.
The TI-Amp has only 3 transistors inside (i mean the original unit from back then. Dont know newer circuits.).
The spark is generated by cutting off the voltage from the coil.
Well as your only problem is the a weak spark, i guess the distributor and the amp are working good. Cant imagine the amp pulls the coil only 3 volts down, what could also cause a weak spark.
But what is very important is, that you have the right polarization at the coil! If you twist it wrong, you will have less spark power.
Maybe you try this first, its no big deal to change the connections
If you have no spark afterwards, it was already right. If its stronger, you got the root cause.
Please measure the voltage you have at the coil,
it should be around 7 Volts.
If you have this or higher voltage, the coil is the reason for weak sparks.
The TI-Amp has only 3 transistors inside (i mean the original unit from back then. Dont know newer circuits.).
The spark is generated by cutting off the voltage from the coil.
Well as your only problem is the a weak spark, i guess the distributor and the amp are working good. Cant imagine the amp pulls the coil only 3 volts down, what could also cause a weak spark.
But what is very important is, that you have the right polarization at the coil! If you twist it wrong, you will have less spark power.
Maybe you try this first, its no big deal to change the connections
If you have no spark afterwards, it was already right. If its stronger, you got the root cause.
Question 1 Is that 7 volts on the plus side of the coil while I'm cranking the engine or while I just have the ignition on?
According to ti specialty that voltage with just the ignition on should be 2.5 - 4.5. My car had 3 v
Question 2 You mentioned the right polarization of the coil. Are you talking about me putting the white big wire to the ground side and the black wire to the plus side?
Last edited by georgeculolias; Dec 23, 2011 at 12:59 PM.
Thread Starter
Instructor
Joined: Jan 2006
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From: brea california
Am I missing any?
Pro
Joined: May 2011
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From: Karlsruhe (Germany)
i cant remember if i measured the 7 volts with just the ignition on, or the engine running. i guess it was just with the ignition on, because i was looking for a problem too.
4V seems to be to low, check if 12V coming out of the amp to the coil.
The difference gets lost at the resistor wire between them.
(i hope your car battery is loaded ;-) )
Next thing about the wiring of the coil: just make sure that the (-) negative marked conncetor is connected to the ground of the car.
Measure the voltage between the ground of the coil and the engine (ground). Ignition must be on.
If there is a drop higher than 1 volt thats not good. The (+) side of the coil must deliver a higher voltage against the engine block.
With this test you check for a good ground connection too.
And to come back to the 7 volts of the coil: this voltage depends not only on the supply voltage. (caused by ground or supply connection problems)
It depends also on the coil resistance!
If lower resistance, lower voltage will be measured because of a higher current that is more limited by the resistor wire before the coil.
Yeah its not that easy to find the root cause if you have no good electric background
4V seems to be to low, check if 12V coming out of the amp to the coil.
The difference gets lost at the resistor wire between them.
(i hope your car battery is loaded ;-) )
Next thing about the wiring of the coil: just make sure that the (-) negative marked conncetor is connected to the ground of the car.
Measure the voltage between the ground of the coil and the engine (ground). Ignition must be on.
If there is a drop higher than 1 volt thats not good. The (+) side of the coil must deliver a higher voltage against the engine block.
With this test you check for a good ground connection too.
And to come back to the 7 volts of the coil: this voltage depends not only on the supply voltage. (caused by ground or supply connection problems)
It depends also on the coil resistance!
If lower resistance, lower voltage will be measured because of a higher current that is more limited by the resistor wire before the coil.
Yeah its not that easy to find the root cause if you have no good electric background
Last edited by zuendler; Dec 23, 2011 at 02:26 PM.
