Ignition/Starter Issue

[KMD88 2]

Hi everyone,

Had a weird experience with my '69 Mach 1 that I'm trying to pin down. Here's the timeline over the last week: 

• The day after New Year's, I took my girlfriend for a ride for about an hour. Filled up the car and accidentally over-filled the tank; causing some spillage. No issues on the ride back and everything seemed fine. 
• Yesterday I took the car to the gas station to buy something in the convenience store. Come back to the car 2 minutes later, and when I turn the key, it doesn't start. Try it one more time and I get something; almost like the car has just enough juice to ignite one more time. It sounded like the starter was barely providing power to the engine. The car starts, sounds relatively normal (though maybe a little lower than normal for a typical idle) and I drove home to my garage about a minute away. 
• I get in my garage and turn off the car. I try to start the car again right away and there's no ignition at all. The seat belt and car lights are on, just no ignition. Try multiple times with the same result. 
• At first I thought it may be the battery. Tried giving it a jump but nothing happens. So I basically rule out the battery being the culprit. 
• Next Day (about 20 hours later): I go down to my garage to examine the ignition and to take some video for this forum. I turn the key without even putting my foot on the pedal (it's still a carbureted 351 w); just to see if I get any reaction out of the starter...and the car starts right away! Again, I didn't even put my foot on the pedal and this is 20 hours after I last drove the car. 
• Tested the starter a few more times and the car starts every time. Haven't driven it around yet. 

So now I'm stumped. What happened yesterday? As a small note, it's a getting a little colder here, but I live in Southern California and we're talking somewhere in the low 60's, coldest. So don't think that could be a factor at all. 

Any guesses or responses appreciated. 

Thank you. 

[Midlife 814]

Bad connection at the battery terminals, most likely. 

[aslanefe 333]

If it only happens when engine is hot, your starter might be getting heat soak.

[danno 128]

I am wondering if the starter has bad.  A similar thing happened to me.  The brushes in the motor were not making good contact when they were hot, and so it would not start when it was hot.  It would start when the starter motor cooled off.  

If it happens again ( not starting when the engine is hot) have a bunch of water with you.  Dump a bunch of water on the starter to cool it off. Then see if it starts. You have to be careful not to get water on the exhaust or engine block, but just on the starter. 

[KMD88 2]

Thanks everyone for your feedback. It's sounding more and more like the starter. It would also make a bit of sense. When I pulled into the gas station, there was a small pothole that I dipped into on the right side. Maybe that knocked something loose wiring-wise and is causing the heat soak. 

[dmck 3]

On 1/8/2021 at 4:48 PM, KMD88 said:

Thanks everyone for your feedback. It's sounding more and more like the starter. It would also make a bit of sense. When I pulled into the gas station, there was a small pothole that I dipped into on the right side. Maybe that knocked something loose wiring-wise and is causing the heat soak. 

Before you play with the starter, check the solenoid.  When the problem is occurring listen (or have someone listen) for the solenoid to 'click'.  If you are touching it you may even feel it operate.

Dirty connections are also a possibility

1 on the battery, 2 on the solenoid and 1 on the starter motor.   All easy tests before you pull out a starter.

[KMD88 2]

Thanks dmck. I'll be sure and do that first. 

[danno 128]

Yes, I kind of assumed you tried the easiest things first.

1 Good battery

2 Clean battery posts and cables.  .

3 Good solenoid.

4 Good starter wire cable.

5  Good ground from battery to engine.  

These are easy to check and verify they are working before replacing  the starter.  

[harlan69mach 21]

Back in the early days, I had a problem with the stud that the cable attaches to was loose in the starter and caused an intermittent problem.