Spark, then no spark
Thread Starter
Racer
Joined: Feb 2012
Posts: 333
Likes: 2
From: Aurora Colorado
Spark, then no spark
Parked my 71 Sunday. Went to start it yesterday nothing?
Cranks and every now and then tries to start but won't. Sort of like timing is WAY off. Checking spark while wife turns the key and no spark then when it very briefly tries to start there is spark. Cap and rotor look fine. Car has Mallory unilite mechanical drive tac dizzy and a Mallory promaster coil. Car came with that set up. The only thing I found wired wrong was that they had the coil wire and the ignition switch wire on the same side of the ballast and the dizzy wire on the other side by itself. According to the Mallory instructions the dizzy wire and ignition wire should be on the same side and the coil wire by itself on the other side of he ballast. It ran just fine the way it was wired but I changed it to how it is suppose to be wired but still won't start. The ignition wire when tested alone off the ballast is 12.5v when connected to the ballast with the dizzy or the coil on the other side, both sides of the ballast read 5v, and at the coil it also reads 5v. Could the coil have been ruined over time when it was wired wrong? Would a bad coil produce spark / no spark (mostly no spark) condition? Thanks!!
Cranks and every now and then tries to start but won't. Sort of like timing is WAY off. Checking spark while wife turns the key and no spark then when it very briefly tries to start there is spark. Cap and rotor look fine. Car has Mallory unilite mechanical drive tac dizzy and a Mallory promaster coil. Car came with that set up. The only thing I found wired wrong was that they had the coil wire and the ignition switch wire on the same side of the ballast and the dizzy wire on the other side by itself. According to the Mallory instructions the dizzy wire and ignition wire should be on the same side and the coil wire by itself on the other side of he ballast. It ran just fine the way it was wired but I changed it to how it is suppose to be wired but still won't start. The ignition wire when tested alone off the ballast is 12.5v when connected to the ballast with the dizzy or the coil on the other side, both sides of the ballast read 5v, and at the coil it also reads 5v. Could the coil have been ruined over time when it was wired wrong? Would a bad coil produce spark / no spark (mostly no spark) condition? Thanks!!
Race Director
Joined: May 2006
Posts: 18,740
Likes: 2,583
a stock 1970 ignition wire to the coil + side should consist of two wires connected to a single spade connector, a regular wire for cranking and a resistance wire for running. Cranking voltage reading should be just about full battery voltage and with the key in the on position a few volts less. Do you have that?
I dont think it will start with 5 volts.
I have a Mallory Unilite conversion kit in the original Delco distributor and do not run any additional ballast. It has been in the car for a couple of decades.
I dont think it will start with 5 volts.
I have a Mallory Unilite conversion kit in the original Delco distributor and do not run any additional ballast. It has been in the car for a couple of decades.
Last edited by MelWff; Apr 6, 2012 at 03:57 PM.
Thread Starter
Racer
Joined: Feb 2012
Posts: 333
Likes: 2
From: Aurora Colorado
a stock 1970 ignition wire to the coil + side should consist of two wires connected to a single spade connector, a regular wire for cranking and a resistance wire for running. Cranking voltage reading should be just about full battery voltage and with the key in the on position a few volts less. Do you have that?
I dont think it will start with 5 volts.
I have a Mallory Unilite conversion kit in the original Delco distributor and do not run any additional ballast. It has been in the car for a couple of decades.
I dont think it will start with 5 volts.
I have a Mallory Unilite conversion kit in the original Delco distributor and do not run any additional ballast. It has been in the car for a couple of decades.
Thread Starter
Racer
Joined: Feb 2012
Posts: 333
Likes: 2
From: Aurora Colorado
I wanted to test the coil itself for spark, not sure if you are suppose to do this or not, I disconnected the the coil to cap wire from the coil and put in a spark tester into the coil and grounded the other side, cranked the engine over and had plenty of spark. Reconnected the coil wire to the cap and cranked the engine over and it started right up! For about 30 seconds then died, no spark at plug again, repeated the coil spark test, had spark, reconnected the coil to cap ant it started up for 30 seconds? Every time I test the coil it starts up after the test but runs out of spark about 30 secs later? What's my deal??!
Thread Starter
Racer
Joined: Feb 2012
Posts: 333
Likes: 2
From: Aurora Colorado
Thanks, I can't find anything grounding out? Thought I fixed it last night but was too late to start it up. GM uses a resistor wire instead of a ballast reaistor. With the ballast in line ir was getting twice as much resistance. I removed it last night and fired it up this morning, it started right up! About a minute later it died and no longer have spark at the plug wire. When it was running I measured 9v at the + side of the coil, and from what I have read that is now correct. So far I have replaced cap rotor and coil, luckily I had planed the cap and rotor anyway, Mallory is very proud of those components, $50 at local auto store. Only thing left is unilite modual and wires. Any other thoughts?
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Melting Slicks
Joined: Mar 2007
Posts: 2,520
Likes: 11
From: Hinckley OH
Does the engine fire until you release the key from the start position? If it does, then the problem is in the resistor or resistor wire. If the engine does not fire at all, then I would look at the coil or points or condensor. If you have a condensor, you can disconnect it temporarily because it could be shorting to ground internally.
Thread Starter
Racer
Joined: Feb 2012
Posts: 333
Likes: 2
From: Aurora Colorado
Does the engine fire until you release the key from the start position? If it does, then the problem is in the resistor or resistor wire. If the engine does not fire at all, then I would look at the coil or points or condensor. If you have a condensor, you can disconnect it temporarily because it could be shorting to ground internally.
Thread Starter
Racer
Joined: Feb 2012
Posts: 333
Likes: 2
From: Aurora Colorado
The unilite module that came in the car when I bought it passes the troubleshooting test provided by Mallory but apparently was bad even though it passed the test. I received the new module and filter today, put just the filter inline and still no spark, threw in the new module and it fired right up, took it for about a 5 mile ride and no problem. The date on the old module was 1993, 19 years of service, I'll take it!
