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Discussion Starter · #1 ·
Ok, I have a 31 Ford roaster. 351 Cleveland. When I first go to start. The voltage reads 14. When firing up the car drops to 12. After I shutdown a few minutes later. I go to fire r up again. The voltage reads 12. Drops below 10 and won’t fire the car up. Thoughts on what I should check
 

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The battery should start the engine three times with ease. Both the alternator and battery need testing. Before you take them out start the engine and test the voltage at the battery...should be 14.2 volts. Shut engine down and test voltage again, should be less than when running.
 

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Discussion Starter · #5 ·
Thanks. Let me try the load test. The battery is new as well as the starter. It’s random which is a bit odd. I keep a trickle charge on it when not in use. When this happens. I have to connect a battery charger and hit the 90 second start which does allow me to fire the car up. Been dealing with this for a long time so appreciate the advice. I did replace the alternator voltage regulator awhile back
 

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You can load test the battery your self by checking voltage, which should be 12.6 or real close, crank the engine for 15 seconds (Igntion disabled) and watch the battery voltage. It will drop, but shouldn't drop more than 10.5. If it does, replace it.

The 14v is a surface charge and normal straight off the charger, the 12v is normal after a start up because the surface charge is gone and the battery has stabilized, although it should be 14 running as the alternator is doing its thing, 12v is normal with the engine NOT running. The 10 tells me the battery can't keep up with the amp draw and is likely worn out.
 

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Short side note, I had two newer batteries die on me. Both were replaced without cost because they were defective. One in my 33 Willys and the other in my '32 roadster and both were within several weeks of each other! On the other hand my '39 Chevy was cranking very slow but started each time. Was going to get the starter tested, almost got a new one but had the battery tested and discovered it was bad...also 11 years old! Do the easy stuff first.
 

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Did you replace the alternatior before all this began?

This all could be because a 50 cent diode is fried or was installed backward(easy).

When the alternatior and battery are tested outside the car they test good.

But inside in the car that diode is keeping the sense wire from telling the alternatior to start charging.

Look at your wiring. Always check the cheap fixes first.
 

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Discussion Starter · #10 ·
Short side note, I had two newer batteries die on me. Both were replaced without cost because they were defective. One in my 33 Willys and the other in my '32 roadster and both were within several weeks of each other! On the other hand my '39 Chevy was cranking very slow but started each time. Was going to get the starter tested, almost got a new one but had the battery tested and discovered it was bad...also 11 years old! Do the easy stuff first.
Let me try that. The battery is less than a year. The draw is
Sounds like the battery is only taking a surface charge. This goes away very quickly to reveal there is no reserve. A load test should reveal this, the likely answer will be battery replacement.
battery is 9 months old. Just had it checked and passed. Alternator is new. Tested load when fired up. Right at 14v on battery and alternator. Checked out good. When ignition is on but motor not started. Checks out at 12v. Go to start, drops to about 10v. Still won’t turnover the starter. Still have to put the charger on it and press 90 second start. Fires right up.
 

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Discussion Starter · #11 ·
Let me try that. The battery is less than a year. The draw is

battery is 9 months old. Just had it checked and passed. Alternator is new. Tested load when fired up. Right at 14v on battery and alternator. Checked out good. When ignition is on but motor not started. Checks out at 12v. Go to start, drops to about 10v. Still won’t turnover the starter. Still have to put the charger on it and press 90 second start. Fires right up.
What should be the load at the starter, same? Around 12v. Or should I be check amps. Thoughts
 

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Charge the battery
Run a 10 gauge wire from the S terminal to a push button/flip switch then from that switch to the battery.

Or if the solenoid is on the firewall then jump the S terminals with a switch in between them

This eliminates the wiring going to the key. Now with the key off the thing should not start as the coil is not energized. But I disconnect the coil plug anyway for good measure.


We are just checking cranking here.

Once your switch is hooked up(and your away from rotating stuff) flip it up and the starter will crank. Let it go for 3 or 4 turns before flipping it down then stop wait 10 seconds and do it again(2nd time) for 3 to 4 more times then stop for another 10 seconds and this 3rd time it should be slower but still crank.

If the thing does not crank the 2nd time then your left looking at the starter, solenoid, battery, or wiring between them. If it does then your left looking at the rest of the ignition/charging wiring and then can move on to eliminating the charging wiring.
 

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When you say it doesn't start, are you saying that it cranks real slow?.. or cranks fast "as normal"? Is the symptom temperature related? I had the same problem if that's your symptom.. and easy fix if you have the same issue...let us all know.
 

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Discussion Starter · #14 ·
Charge the battery
Run a 10 gauge wire from the S terminal to a push button/flip switch then from that switch to the battery.

Or if the solenoid is on the firewall then jump the S terminals with a switch in between them

This eliminates the wiring going to the key. Now with the key off the thing should not start as the coil is not energized. But I disconnect the coil plug anyway for good measure.


We are just checking cranking here.

Once your switch is hooked up(and your away from rotating stuff) flip it up and the starter will crank. Let it go for 3 or 4 turns before flipping it down then stop wait 10 seconds and do it again(2nd time) for 3 to 4 more times then stop for another 10 seconds and this 3rd time it should be slower but still crank.

If the thing does not crank the 2nd time then your left looking at the starter, solenoid, battery, or wiring between them. If it does then your left looking at the rest of the ignition/charging wiring and then can move on to eliminating the charging wiring.
Thanks I went through the process. Ended up finding two things. A wire that required replacing and the starter was buggy. It’s a high performance stater which reading online. Its has issues with the solenoid. Replaced with a heavy duty OEM starter. It cranks over. Appreciate everyone and all the advice. It allowed me to walk through several steps eliminating possible issues.
 

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The battery should start the engine three times with ease. Both the alternator and battery need testing. Before you take them out start the engine and test the voltage at the battery...should be 14.2 volts. Shut engine down and test voltage again, should be less than when running.
What kind of battery ? AGM...Optima, or standard wet cell ?
 

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A stand alone full charged battery s/b 12.6 to 12.7 volts. If at 12 volts it is only at 50%.
It my start the car a couple times but borrowed time is coming.

This simple chart shows the small range between good and bad battery.
617360
 

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There are three separate battery levels to test, one is standby, second is actual load/cranking and third is running/charging mode. A decent digital multi-meter should have a Max/Min function that will catch and hold the battery voltage as it swings between minimum and maximum levels. Standby should read 12.5vdc to slightly higher, cranking mode voltage drop can read 11vdc to 10.5vdc and charging mode should read high 13's to 14vdc. I own a Amprobe AM-530 digital multi-meter (with max/min) it was around 70 bucks and there are others similar. Check for loose connections which can cause a lot of intermittent issues. Auto batteries generally last about 36 months and some do last longer.
 

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I would get new battery. You have 14 volts at battery with alternator charging. So charging by alternator is good. But you say the battery is 10 volts (after you shut down,….. I assume). But the drop to 12 volts is key. The battery s/b 12.6 to 12.7 volts on it’s own with engine off. Accordingly the battery is at 50%. And at 10 volts it’s dead. Just because it takes a charge does not indicate the battery is good. It must also retain a charge. 12 volts is not enough to sustain repeated starts. Even at 12.2 volts battery will not repeatedly start. A jump box would be a handy thing to have with you……..
 
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