1970 LT1 No Spark
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Joined: Feb 2011
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1970 LT1 No Spark
Hi Guys, I need help trying to figure out what is wrong with my 1970 LT!. Car was nut and bolt restored with all new wiring, ignition system complete to stock back in 2018. Original K66 transistorized ignition with new circuit board etc.. Car has always run fantastic and is a three time Top Flight Car. Now for some reason it will not fire. TI ignition system, ignition harness, new coil, distributor rebuilt, etc.. Now when I go to start the car I only get a spark from the coil when I turn the key on and off but no spark when cranking. Car sounds like it would start when you stop cranking and the key goes to on--which is when you only see the spark. No spark a plugs when cranking? Also tried leaving the key in the on position and putting power directly to starter and would only spark from coil when igniting starter and disengauging starter. Any input appreciated.
Dr. Detroit
Joined: Mar 2012
Posts: 10,097
Likes: 4,027
From: New Braunfels Texas
Does the transistor ignition have an "R" side to the starter solenoid with a wire going to it? If so...this is the wire that becomes hot while cranking.......common thing on points cars but I never played with a K66.....
Jebby
Jebby
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This is the wiring diagram, shows the R terminal, upper right, and a ignition switch feed, lower left.
http://tispecialty.com/articles/64-65diagram.htm
http://tispecialty.com/articles/64-65diagram.htm
Melting Slicks
Joined: Oct 2001
Posts: 2,065
Likes: 1,395
From: Halifax, Nova Scotia, Canada
I had a very similar problem, however it would sometimes start when you released the key from cranking.
After much checking I discovered that if I DISCONNECTED the wire from the starter to the TI harness it started fine. Drove it about a year this way and the TI Amp then it finally died.
In the C2 section of the forum, someone reported a similar problem as well. I suggested he disconnect the wire from the starter to the TI harness and the engine started up immediately.
He replaced the TI Amp board and that cured his problem.
Some of these upgraded TI Amp boards fail in a strange way.
Not saying this is your problem, however it only takes a minuite to disconnect the plug, worth a try.
After much checking I discovered that if I DISCONNECTED the wire from the starter to the TI harness it started fine. Drove it about a year this way and the TI Amp then it finally died.
In the C2 section of the forum, someone reported a similar problem as well. I suggested he disconnect the wire from the starter to the TI harness and the engine started up immediately.
He replaced the TI Amp board and that cured his problem.
Some of these upgraded TI Amp boards fail in a strange way.
Not saying this is your problem, however it only takes a minuite to disconnect the plug, worth a try.
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Verdad Gallardo
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St. Jude Donor '22
Hi Guys, I need help trying to figure out what is wrong with my 1970 LT!. Car was nut and bolt restored with all new wiring, ignition system complete to stock back in 2018. Original K66 transistorized ignition with new circuit board etc.. Car has always run fantastic and is a three time Top Flight Car. Now for some reason it will not fire. TI ignition system, ignition harness, new coil, distributor rebuilt, etc.. Now when I go to start the car I only get a spark from the coil when I turn the key on and off but no spark when cranking. Car sounds like it would start when you stop cranking and the key goes to on--which is when you only see the spark. No spark a plugs when cranking? Also tried leaving the key in the on position and putting power directly to starter and would only spark from coil when igniting starter and disengauging starter. Any input appreciated.
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Race Director
Joined: May 2006
Posts: 18,737
Likes: 2,583
Thread Starter
Intermediate
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Race Director
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Melting Slicks
Joined: Jan 2000
Posts: 3,326
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From: home
Couple of things to check: Damn good module housing ground wire connection at the radiator support. Check resistance of the pickup coil while slowly moving the advance plate with a mityvac. Alsomcheck for breaks in the 2 wires to the pickup coil. If you aren't too concerned about originality, you could use a 4 pin hei module and eliminate the factory module. This is the way I'm going if my t.i. ever fails again and going to mount the hei module inside the distributor box so it won't be seen while retaining the wire harness and t.i. module to look correct.What you are describing sounds like a blown t.i. module. are you using a GM t.i. coil and not a repro coil?
Tech Contributor
Joined: Jun 2004
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From: I tend to be leery of any guy who doesn't own a chainsaw or a handgun.
Something is amiss here. With a TI system you should only see about three volts at the ignition coil positive terminal. Any chance the starter R terminal is incorrectly hooked up, and feeding the coil C+ when cranking? This would prevent the engine from starting, but does not answer why there is also 12v at the coil while in the key-on/run position.
Thread Starter
Intermediate
Joined: Feb 2011
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Something is amiss here. With a TI system you should only see about three volts at the ignition coil positive terminal. Any chance the starter R terminal is incorrectly hooked up, and feeding the coil C+ when cranking? This would prevent the engine from starting, but does not answer why there is also 12v at the coil while in the key-on/run position.
yes I do have about three volts at coil with key in start or on position. I was assuming it was 12 volts because I was checking with a text light.
Tech Contributor
Joined: Jun 2004
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From: I tend to be leery of any guy who doesn't own a chainsaw or a handgun.
An oscilloscope hooked to the coil C+ terminal will tell you what, if anything, is happening at the coil during cranking. Or, a simple 100 ohm resistor and an LED in place of the coil will give you a sharp visual indication of voltage and switching pulses during key-on and cranking.
(I'm holding my nose while typing this: Does your test light, when hooked between coil C+ and ground, flicker while the engine is being cranked?)