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Crank-starting your car: The perfect duration & knowing when to stop

I've seen a lot of people "over-crank" to start their car, and the unpleasant sound makes me cringe every single time.

BHPian PearlJam recently shared this with other enthusiasts.

How do you figure out the right duration to crank start a car having manual key-based ignition systems?

A lot of us have learnt to drive in an era where Keyless engine start systems were unheard of. In a keyless system (on a separate note, it's the wrong terminology because you still need a key fob. But that's a separate topic!) all you need to do is to have the key fob in your pocket, depress the clutch pedal, and press the Start button - and the engine magically comes to life with perfect timing. The keyless engine start system has been discussed in detail here:

But a lot of cars from the lower segments, as well as cars like the Polo, come only with manual key-based ignition systems even today.

One of the big challenges I faced while learning to drive, many many years ago, was how to perfectly crank start the car. I could never get the timing or duration right for a few months.

If you crank for too short a duration, the engine will not come to life, and it's an effort wasted. If you crank for too long, you hear the unpleasant sound where the starter motor still tries to drive the engine even after the engine has started. Both these situations are undesirable since they could reduce the life of the ignition system over the long term.

I've seen a lot of people "over-crank" to start their car, and the unpleasant sound makes me cringe every single time. While some cars prevent you from attempting to re-crank the engine unless you turn the key back to the "switch off" position first, it still doesn't help you in the right timing duration.

And if this is not enough, there are more challenges:

  • In a noisy environment, you can't really hear the engine, so it's difficult to know if the engine has started.
  • The time taken to crank a cold engine is slightly longer than a warm engine - and this is true even for the latest MPFI or turbocharged-based systems.
  • Some older non-MPFI cars need the accelerator to be pressed a bit (not too much though, otherwise it will flood the engine and the crank duration changes) while starting
  • Diesel engines usually need a little longer cranking duration.
  • A weaker battery leads to slower cranking and hence a change in duration
  • So cranking duration across different cars becomes more of an art, gut feel, or instinct, whatever you might call it. You cannot have a fixed duration in mind every time and expect it to work perfectly.

I simply cannot explain how I came to the point where I can now start a car most of the time by the precise duration of cranking. I think it just comes from experience. Probably it's the slightly different engine sound a few milliseconds before the actual start? A slight change in the speed of rotation of the engine just before starting?

While this thread discusses the right sequence to start a car, it doesn't discuss the crank duration.

How did you learn to start your car perfectly? Did you figure out a practical formula for this? Or, did you not care about this at all? team-bhp is the only perfect place to start such niche discussions.

Here's what BHPian alpha1 had to say on the matter:

I am surprised that I have never given a thought to this topic.

And I am even more surprised that I have hardly heard any novice learner over-crank the starter.

Perhaps all of us have an instinct (honed by being passengers most of the time) for doing it for the right duration just by listening to the subtle changes in engine sound and vibrations.

Here's what BHPian kosjam had to say on the matter:

The duration of the starting sequence is generally too short for one to actively make a decision to end it once the engine has started. It basically boils down to a mix of:

  1. Muscle memory
  2. Reflexive reaction based on sound
  3. Reflexive reaction based on the vibrations (the sequence being: still-plenty vibrations-steady vibrations)
  4. Experience

While I have started many scores of vehicles and engines, so I believe I am reasonably experienced in the same, I still get confounded when I come across a vehicle which does not start as per a preconceived time frame assigned basis knowledge of the type/age/general condition of the vehicle/engine in question.

The latest example was a two-wheeler during TD, which took noticeably longer (again, measured in milliseconds, if one actually bothers to measure it) than what I expected it to, explained away by the sales advisor as being a characteristic of the engine in question...

Here's what BHPian Gypsian had to say on the matter:

In vehicles equipped with engines like the Mahindra DI, the engine sound clearly emanates from the stages of cranking and starting, whereas, in the insulated modern cars, the chances of over cranking are more, especially at the hands of newbies.

Check out BHPian comments for more insights and information.

 
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