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| Engine starts when ignition key is released https://slantsix.org/forum/viewtopic.php?t=65473 |
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| Author: | Jester [ Wed Oct 28, 2020 10:54 am ] |
| Post subject: | Engine starts when ignition key is released |
The slant in my '72 does not want to fire while the starter is engaged. It starts as soon as the key is released. Any ideas what it could be? This happened with the old and new ignition switch. Electronic ignition with 2 wire ballast. Possibly a weak battery... |
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| Author: | THOR [ Wed Oct 28, 2020 3:46 pm ] |
| Post subject: | Re: Engine starts when ignition key is released |
As I recall the ignition switch should bypass the ballast and put full power to the coil while cranking. I'd be willing to bet you'll be lacking voltage at the coil while cranking. My guess, bulkhead connector needs a thorough cleaning, or the wire which supplies said power has a bad connection/broke somewhere. ~THOR~ |
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| Author: | GTS225 [ Wed Oct 28, 2020 6:27 pm ] |
| Post subject: | Re: Engine starts when ignition key is released |
It sounds like you're missing your bypass for the start circuit. That ignition switch routes a full 12VDC around the ballast resistor in the "start" position, then routes that same 12VDC through the resistor in the "run" position. That aids in starting, then the resistor drops the voltage to around 8VDC for running conditions. Follow Thor's advice to troubleshoot. Roger |
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| Author: | Greg Ondayko [ Fri Oct 30, 2020 6:38 am ] |
| Post subject: | Re: Engine starts when ignition key is released |
I had a similar situation recently where it was the corrosion on the Firewall electrical bulkhead pass thru. I cleaned the wires and terminals there and it was fixed. Test light showed coil power with key on (run) but I couldn't' start the engine as there was no power to the coil in the (start) position. took me a while to figure it out with a test light on the coil + feed and an assistant working the key. Greg |
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| Author: | Jester [ Fri Oct 30, 2020 7:30 am ] |
| Post subject: | Re: Engine starts when ignition key is released |
Thanks, guys. I have a few things to check, but recently cleaned the bulkhead connectors and they looked to be in great shape. |
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| Author: | Louise76 [ Sun Nov 01, 2020 8:45 pm ] |
| Post subject: | Re: Engine starts when ignition key is released |
With the key on, it is building up a coil charge, then the charge collapses when your open the primary circuit by letting the start switch go to off. The collapse of the primary is what fires one spark plug once, but gives the engine enough kick around to fire more spark plugs weakly. That has been my analysis on our family daily drivers (1975's). First choice: ignition module is weak, or has a very bad case ground. Second choice, off the cuff, the start-run relay contacts are dirty inside. For us, we always have a spare ignition module on the shelf, as they are now aftermarket and made poorly in a foriegn neverland. So that is the easiest thing to change, and not very spendy $$. |
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| Author: | Jester [ Tue Nov 03, 2020 9:14 am ] |
| Post subject: | Re: Engine starts when ignition key is released |
From pouring over my shop manual schematics, it looks like Ign 2 runs through the firewall (Q) and bypasses the ballast resistor. If I'm not mistaken, the wire may be on the wrong side of my ballast resistor. I will have to get a better look after work. |
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| Author: | Jester [ Sun Nov 08, 2020 2:39 pm ] |
| Post subject: | Re: Engine starts when ignition key is released |
After going through chassis wiring diagrams, and testing with a meter, tracing from coil back to ign switch, all the wiring is correct. With a volt meter on the + side of coil and good ground, I was getting 5-6 volts with ignition on, and zero volts when ign in start position. Was about to get mad, when I turned the ign switch a little further, and got 12 volts on the meter while cranking. The new ignition switch just takes a little extra oomph to hit the ign 2 circuit.  Starts right up now... |
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| Author: | GTS225 [ Sun Nov 08, 2020 8:09 pm ] |
| Post subject: | Re: Engine starts when ignition key is released |
BRAVO!! New parts will sometimes require new expectations, as you just learned. It's good that you did find that all your tested circuits are in correct working order. It's that much less that could be a concern for you. Thanks for updating this. Roger |
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