Vehicle wants to start when releasing the key

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ESP47

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The other day my truck went from firing up every time immediately to now turning over and over before sometimes firing up when releasing the key. It'll turn over without even a hint of wanting to start but as soon as you release the key it either fires up or at least tries to.

I got out a volt meter and measured the voltage at the + side of the coil. It has about 8.5v when turning over and when the key is released I can see a real quick 11v on the volt meter before going back down to 6v with the key in "run" without the engine running. I traced the wire back to the bulkhead on the firewall and I'm getting the same voltage readings there. I also went under the dash and checked the voltage going into the ignition switch connector on the ignition switch side and the voltage readings are all the same there as well. I'm not exactly sure what to expect but shouldn't the voltage be at 12v when cranking and not 8.5v? Before I start blaming it on the ignition switch, I'd like to know what you guys think. This is on a 75 D100 with a 318. Thanks!
 
Had the same problem. Check the reluctor to pickup gap inside the distributor. Use a brass feeler gauge and set the gap to .008, make sure it's clean and not rusty.
 
You should have about 12v cranking because the BR is grounding out, and 8 to 9v running at the coil.
 
Ballast resistor problem kind of presents itself opposite of what you are experiencing. Starts until you release key, instead of what you describe as firing up as soon as you release key.
 
lsm360 said:
Ballast resistor problem kind of presents itself opposite of what you are experiencing. Starts until you release key, instead of what you describe as firing up as soon as you release key.
Click to expand...

It can work either way.
On a four wire ballast it can go bad on one side and act completely the opposite.
Since there is voltage in both start and run positions but low on the start side it's most likely the ballast.
They do go bad inside and give low voltage, and the trick is to get the right one to replace it with.
 
Thanks fellas. Good info here.

TrailBeast, when you say the trick is to get the right ballast to replace it with... Is there something I should know before I go to Napa and grab one from them?
 
I replaced the ballast resistor and that didn't work. Replaced the ignition module and that didn't work. Gapped the distributor to .008 and that didn't work. Threw in a known good working coil from my Duster and that didn't work. Also replaced the rotor because it was looking a little beat up. Can't get the thing to fire up at all.

Under the dash at the ignition switch connector I have 12.5v going to the ignition switch with the key off and when the key is cranking I have 8.5v going out on the ignition start wire. Does that mean I have a bad ignition switch?
 
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It randomly fired up and I systematically put every old part back in and it fires right up every single time now. No freakin idea what the deal is!
 
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