I used to kick start my old VW by rolling down a hill and popping the clutch. Can you do that with today’s cars with electronic fuel injection?
I use to “kick” start my old VW by sticking my foot out the door and getting it rolling backwards before putting it in gear. I did not even need the hill.
Yes you can still kick start modern cars, but the electrical system must be working and the battery can not be totally dead.
The reason the battery cannot be totally dead is, the alternator field needs to be engergized by the battery so it can produce voltage to power the ignition etc. If there is enough power left in the battery to at least light up the dash lights when the key is turned on it will kick start ( manual trannies only ) as newer automatics past the early to mid 60’s cannot be push started
due to removal of the rear transmission pump which was driven by the drive shaft
which would supply enough pressure to engage the clutches in the tranny and spin the engine.
My 59 T-bird ( auto ) will push start. You have to get it up to 20mph, turn on the ignition and drop it into “L”. Being that this car uses a generator instead of an alternator it will start with a “dead” battery as the generator usually has enough residue magnetism left hanging around for the field.
The reason they removed the rear pumps were because they were redundant once the engine was running as the front pump did all the work and the rear pump went into by-pass mode and very few people used the push start capabilities as it was easier to jump start unless your starter bit the dust.
The reason that there must be a certain level of voltage in the battery is not to power up the alternator alone, as powering up the alternator is not 1st or second in line. First you must still have power for the electric fuel pump and the ignition.
While the engine is cranking the alternator is not turning fast enough to help even if it is adaquately energized. Alternators do start to output much earlier than a generator but an alternator still needs to at least break idle speed (preferably 1000 rpm) for any kind of output and cranking speed or the speed developed from a leg push start is much lower than that.
Some alternators will self energize with residual magnetism but you have to spin it really fast. The reason they don’t self energize as easily as generators did is the forward voltage barrier of silicon rectifiers. A silicon diode does not conduct forward until 0.7 volts is obtained. Since the current has to go through at least two diodes, the stator has to generate more than 1.4 volts before self exitation even begins to happen.