First post. Used the search looking under hesitation and intermittent no start with no help. Here is the situation. The car was running normally before it was overheated. A heater hose blew due to a cooling fan that wasn't coming on. The heater hose was replaced and the engine cooling switch replaced fixing that problem. Here's the drivability issue I'm having.

When the car is cold I turn the key to on . Fuel pressure goes to about 25psi, so the fp is running. When the key is turned to start the engine turns over, fuel pressure goes to 35-38 psi. If a timing light is hooked up, it will flash merely. The engine turns over evenly, no combustion takes place. It doesn't buck or snort or anything. The check engine light is not on. If I pull the plugs, there is fuel on them. They are not black at all. They are new, but the insulators don't have carbon on them. A boroscope inspection reveals a coating of fuel in the cylinders. No puddles, just shiny.

If I put the plugs back in, and try to start it, sometimes it will fire right up and idle nice as you please. Other times it will start normally so I haven't figured out why it won't start sometimes. When I could get it to start I have put the shorting wire in the service connection and allowed it to run long enough to turn the cooling fan on. Then I checked the timing and adjusted the distributor as it had been removed and I wanted to make sure the timing was good. A vacuum gage will show about 15" at idle.

Once you get it to start, if you try to drive the car, or even give it gas with your hand, you can do so if you accelerate VERY gently. If you try to accelerate normally, the engine stumbles badly and sometimes dies. The longer it runs the worse it gets. The fuel pressure stays steady, unless the throttle is blipped. Then it goes from around 38 up to 42 which I think is normal.

I have checked the compression cold, throttle wide open. 190/195/190/200. I have checked the fuel pump per the manual and with the vac line on the regulator pulled and capped it sits right at 42 which is in spec.

When it was in it's no start mode, I pulled a plug wire and put a spare plug in it grounding it to the valve cover and turned the engine on. The spark looked yellow to me so I started into the distributor. I checked the coil and the primary didn't measure per the manual, so I replaced it. The new coil measured just like the original and had no effect on the problem. I am still su****ious of the yellow spark.

Some parts had been replaced prior to the car coming to me, but here's whats replaced.

Fuel Filter
Plugs
Wires
Cap
Coil (me)
Engine Temp Switch (Cooling Fan Switch) (me)

I would entertain any ideas y'all have.
Thanks

 

Have you check out the ignitor in the distributor?

 

Possible fix! Thanks for the suggestion of the ignition module. I bought one ( all the dizzies are gone from the cars in the local junk yard), and was taking the rotor off of the shaft to get at the module when I remembered the owner said she had not replaced the rotor, just the cap. Looked down inside the rotor and what do I see? A carbon crater! Checking the end of the dizzy shaft I have corresponding evidence of arcing which I will share. No way the image of the rotor would turn out. After I replace the rotor I'll give it a try. I held off on the ignition module for now. The red circle didn't come out to well in my edit job, but I think you can pick out the arc spot. Stay tuned! (pardon the pun!)

 

Ok, confirmed. Fixed it with the rotor!