Minimum Cranking Volts to Start a Gas Engine?
- Thread starter SubLGT
- Start date
There is no one number, rather the condition of the starter, the size the manufacturer chose relative to engine size, the voltage needed to create spark from the particular ignition system while under the load of cranking. Then there is the condition of the battery and starter terminals and cable between them, how much loss, and in the solenoid.
Realize that as battery health drops, you can have a battery get up to full charged voltage but it loses capacity so drops during the cranking.
There is also where you measure voltage, the temperature of the engine, and temperature of the battery if measuring before rather than during cranking.
If you'd like a number that I pulled out of thin air, 10.03417V.
Realize that as battery health drops, you can have a battery get up to full charged voltage but it loses capacity so drops during the cranking.
There is also where you measure voltage, the temperature of the engine, and temperature of the battery if measuring before rather than during cranking.
If you'd like a number that I pulled out of thin air, 10.03417V.
Also the condition of the engine, whether it's a new high compression engine with 200 psi per cylinder v-12 or a spent inline 4 barely making 40 psi.
*Numbers are made up and may or may not match reality.*
*Numbers are made up and may or may not match reality.*
MolaKule
Staff member
Depends on the temperature as others have stated.
My experience is that at around 55F a minimum of voltage of 9.5V@95 Amps is required for my 1999 S-10 V6.
Below 30F the current requirement goes up to 120 Amps.
During starting it is normal to see the battery voltage drop temporarily. How much voltage drop one will see is highly dependent on battery condition.
Dont forget it isnt just about firing the injectors and cranking ...ECU's can get wonky with just a marginal battery or corroded ground strap. I dont think youre gonna find a specific V that this happens at. So an engine that turns over may still not fire up if the ECU is glitched out.
This is so very true. When my battery started to go it would crank the engine and it would start but the dash would go nuts and it ran rough and threw codes. Just putting a charger on the battery for an hour would solve the issue temporarily. When I put my meter on the battery the cranking volts would drop to about 7.5 but on a digital meter the readings are not instant so it could have been lower. After charging for an hour it only dropped to 9v and I did not have any issues.
This! I had a battery go bad on my Cherokee and it seemed to crank only a bit slow, but would not fire. Someone told me to try jumpstarting it. I thought they were nuts, but sure enough, it started right up. And died as soon as I unhooked the cables. The battery wasn't providing enough voltage to keep the sensors and computers working.
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It’s not the Volts as much as it’s amps.
A battery that dips to a low voltage usually can’t supply enough amps to crank.
I’ve found that most cars will start even if things dip quite low (7.x) volts but usually if the battery dips that much it drops almost to zero instantly and can’t crank (click click click)
A battery that dips to a low voltage usually can’t supply enough amps to crank.
I’ve found that most cars will start even if things dip quite low (7.x) volts but usually if the battery dips that much it drops almost to zero instantly and can’t crank (click click click)
Wrxsixeight said his vehicle took about 150-200 amps to start his vehicle at modestly cool temperature. I think the temp was in the 40s...
Each vehicle is obviously going to have different requirement.
I'd bet mine is somewhere between 100-150 amps. Wild donkey guess but I'd bet it is likely not too far off.
Each vehicle is obviously going to have different requirement.
I'd bet mine is somewhere between 100-150 amps. Wild donkey guess but I'd bet it is likely not too far off.
JHZR2
Staff member
Its always interesting to me how much of a voltage drop I observe just by setting the vehicle to "on", even without lights, blowers, etc. Some of that I think is due to a relatively high voltage drop across the conductors to the consumer bus in the car, but its still can be a decent load. Someday Ill put a meter on and get that real value...
Control modules generally shut off below 9 volts. Voltage may drop lower at peak inrush current as the starter begins to spin but 9 volts cranking is where I call a battery doing a starting and charging system test assuming that the charging system is charging properly and I dont have excessive starter current draw
It depends. My mom had a 1994 Cadillac Sedan deVille back about 16 years ago. It was getting harder to start in the cold. I checked the battery, and it was about 12.4 volts. Many times, we had to hook up some jumpers to get it started first thing in the morning. It would be ok, but slow cranking, the rest of the day. It would repeat the next day.
Having ruled out the battery, I checked output from the alternator... 14.6 volts.
The starter was worn out, and was drawing more amps to turn its gummed up innards (but still starting). I’ve never before, or since, had a starter fail this way. They either work, or they don’t start no matter how much power you put to it. We changed out the starter for a parts store reman (before RockAuto), and it (probably) lasted until the next owner junked it (around 2012).
Having ruled out the battery, I checked output from the alternator... 14.6 volts.
The starter was worn out, and was drawing more amps to turn its gummed up innards (but still starting). I’ve never before, or since, had a starter fail this way. They either work, or they don’t start no matter how much power you put to it. We changed out the starter for a parts store reman (before RockAuto), and it (probably) lasted until the next owner junked it (around 2012).
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