Slant Six Forum :: losing spark after letting go of key

The car sounds like it is trying to start while cranking, but it has an uneven coil pattern. For example, when cranking with a timing light attached, it doesn't always fire on number one. I put the light onto the main coil wire on the secondary side. It should have fairly consistent pulses of light... it doesn't. It seems almost completely random.

It seems to have spark whilst cranking, yet never quite fires enough to the point where it will run. Advancing the distributor fully in the slot for the hold down causes the starter to catch. The distributor is installed in the exact same spot as it was when it ran.

We get almost 12v to the ballast feed, ~6 v on coil output and ~ 1.5v on the other in "RUN", and it has full 12 volts to the coil when in "START" . As stated before, we replaced the ballast resistor. The old ballast and the new one read the same. The car ran just fine on the old one.

The ignition switch and ballast are thus removed from the equation.

We tried jumping the battery to the coil, it made no improvement. Jumped the battery to the feed side of the ballast, showed no improvement. We replaced the EI module with a known good one, also made no difference.

So the EI module is thus removed from the equation.

The only thing that I think could have failed would be something in the distributor, or if the cheap chinese coil died. If the pickup in the dizzy died, then it may be causing our intermittent spark issue. I need to get over there, yank the distributor and check to see that the pickup is working ok.

With the cap off, the distributor rotor seems to turn with the engine just fine, and the new timing set was nice and tight when I installed it, so I am going to rule out mechanical issues as well, at least for now.

I wish I owned a DSO... that would tell me if there is something wrong with the ignition system right off the bat.

Merf...

~THOR~

Author:	DonPal [ Sat Mar 07, 2009 6:12 am ]
Post subject:
I bought a 68 Dart GT off a dealer lot that had the same symptom; the dealer tried jumping the coil to the battery with no improvement. With the money saved off the price of the car I bought a new ignition switch and replaced it. The car ran immediately. An ignition switch that is grounding the run circuit would cause a car not to start even if you run power from the coil to the battery. It's a "kill" switch Test the switch for that possibility also as well as checking the run circuit wiring for a short to ground.

Author:	Aggressive Ted [ Sat Mar 07, 2009 12:07 pm ]
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Slantsixbob, Yes, you should be seeing 12 volts to and from the key switch. Then only time you should see a drop is after the resistor and at the coil. Reference my earlier post.

Author:	slantsixbob [ Sat Mar 07, 2009 2:08 pm ]
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taken and noted ted, i will get in there today and take the ignition out. thanks for all the helpful posts i will try and get to make a post as soon as possible once i find some results.

Author:	THOR [ Tue Mar 17, 2009 1:36 pm ]
Post subject:
The car sounds like it is trying to start while cranking, but it has an uneven coil pattern. For example, when cranking with a timing light attached, it doesn't always fire on number one. I put the light onto the main coil wire on the secondary side. It should have fairly consistent pulses of light... it doesn't. It seems almost completely random. It seems to have spark whilst cranking, yet never quite fires enough to the point where it will run. Advancing the distributor fully in the slot for the hold down causes the starter to catch. The distributor is installed in the exact same spot as it was when it ran. We get almost 12v to the ballast feed, ~6 v on coil output and ~ 1.5v on the other in "RUN", and it has full 12 volts to the coil when in "START" . As stated before, we replaced the ballast resistor. The old ballast and the new one read the same. The car ran just fine on the old one. The ignition switch and ballast are thus removed from the equation. We tried jumping the battery to the coil, it made no improvement. Jumped the battery to the feed side of the ballast, showed no improvement. We replaced the EI module with a known good one, also made no difference. So the EI module is thus removed from the equation. The only thing that I think could have failed would be something in the distributor, or if the cheap chinese coil died. If the pickup in the dizzy died, then it may be causing our intermittent spark issue. I need to get over there, yank the distributor and check to see that the pickup is working ok. With the cap off, the distributor rotor seems to turn with the engine just fine, and the new timing set was nice and tight when I installed it, so I am going to rule out mechanical issues as well, at least for now. I wish I owned a DSO... that would tell me if there is something wrong with the ignition system right off the bat. Merf... ~THOR~

Author:	slantsixbob [ Tue Mar 17, 2009 5:43 pm ]
Post subject:
Quote: The car sounds like it is trying to start while cranking, but it has an uneven coil pattern. For example, when cranking with a timing light attached, it doesn't always fire on number one. I put the light onto the main coil wire on the secondary side. It should have fairly consistent pulses of light... it doesn't. It seems almost completely random. It seems to have spark whilst cranking, yet never quite fires enough to the point where it will run. Advancing the distributor fully in the slot for the hold down causes the starter to catch. The distributor is installed in the exact same spot as it was when it ran. We get almost 12v to the ballast feed, ~6 v on coil output and ~ 1.5v on the other in "RUN", and it has full 12 volts to the coil when in "START" . As stated before, we replaced the ballast resistor. The old ballast and the new one read the same. The car ran just fine on the old one. The ignition switch and ballast are thus removed from the equation. We tried jumping the battery to the coil, it made no improvement. Jumped the battery to the feed side of the ballast, showed no improvement. We replaced the EI module with a known good one, also made no difference. So the EI module is thus removed from the equation. The only thing that I think could have failed would be something in the distributor, or if the cheap chinese coil died. If the pickup in the dizzy died, then it may be causing our intermittent spark issue. I need to get over there, yank the distributor and check to see that the pickup is working ok. With the cap off, the distributor rotor seems to turn with the engine just fine, and the new timing set was nice and tight when I installed it, so I am going to rule out mechanical issues as well, at least for now. I wish I owned a DSO... that would tell me if there is something wrong with the ignition system right off the bat. Merf... ~THOR~ thanks for putting it into detail, im not always good at that. so maybe the others can take a look at this and think about it a little more/differently than i originally posted.

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Author:	AndyZ [ Thu Mar 19, 2009 7:19 pm ]
Post subject:
I think you are right suspecting the coil or the dist at this point. Are the electronics attached well to the distributor? Is the side play in the distributor shaft excessive? Is the wire from the coil to the distributor damaged, worn? I would still be most suspicious of your Chinese coil though

Author:	THOR [ Thu Mar 19, 2009 8:03 pm ]
Post subject:
Quote: I think you are right suspecting the coil or the dist at this point. Are the electronics attached well to the distributor? Is the side play in the distributor shaft excessive? Is the wire from the coil to the distributor damaged, worn? I would still be most suspicious of your Chinese coil though Yes, they have the factory connectors and are in great shape. Distributor was in great shape upon installation and subsequent fussing around trying to find the right spot. Wire from ballast to coil is new. Replaced it when we found the original to be bad. I went over today to work on a different car... maybe I will get over there sometime this weekend to get it looked at. ~THOR~

Author:	slantzilla [ Fri Mar 20, 2009 3:20 am ]
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Make sure the distributor doesn't have a couple teeth knocked out of the drive gear.

Author:	THOR [ Fri Mar 20, 2009 4:32 am ]
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Last time I yanked it, the gear looked fine. I will definitely check it again when I pull it next. ~THOR~

Author:	Aggressive Ted [ Fri Mar 20, 2009 6:37 pm ]
Post subject:
Gents, Another thought........ Measure to be sure the pick up coil in the distributor is reading around 300 ohms. If not, replace it with the more expensive unit, not the $12 version. I believe they may run from $24 to $30. The cheap ones are sometimes bad right out of the box. To be sure you get a good one take your volt meter with you. The more expensive one should have better potting on the coil and better wires and plug.

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