is it possible to start a car by just rolling it ?? with a key?? and without??.. is it possible??.. manual of course.. etc.. blah blah.

 

with a key, you can pop the clutch to start it.

 

You need the key to be in the on position to get the electrical stuff working when the car finally gets moving, but other than that, yeah.

Its call bump starting or push starting.
http://en.wikipedia.org/wiki/Bump_starting

 

I can start my car without the ignition key, using only the power of my mind.

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0==WW==0
"…axles of evil…" - george w. bush

 

There's one inaccuracy in Wikipedia's wiki - you won't be able to push start a vehicle if the battery is completely dead. The ignition system requires a minimum amount of power to fire the system and the alternator will not provide a sufficient amount during a push start.

--
0==WW==0
"…axles of evil…" - george w. bush

 

I don't think it has to do with minimal power.. they used to hand cranck cars way back in the day without any batteries, especially old diesel engines. If i'm not mistaken it has to do with turning the engine over and the alternator should provide enought to spark the plugs and then it just prepetuates itself on its own.. i believe that the system will make 14volts with or without a battery.. i may be mistaken though>

I have to park on hills all the time because my battery drains and sometimes, i don't even bother trying to strat nrmally. I actually just got home from buying a new battery.. 90 bucks out the window.. should have just poured some water into the old one..

 

Disconnect the negative lead on your battery, and try to push start your car on alternator output alone. You wouldn't be able to push your car fast enough on level ground to start your vehicle.

--
0==WW==0
"…axles of evil…" - george w. bush

 

well, wouldn't disconnecting a terminal cause an incomplete circuit in which case it won't spark anyway? To be honest, I don't think you can push start on level ground regardless of the juice.. i always needed a hill or a push from another car.. its too heavy and needs to go too fast to kickover..

 

older cars it's no problem cuz a points distributor style ignition doesn't need much at all to fire the plugs... also those old carbureted motors didn't need any juice to fire the injectors either... just the minimal air flow through the carb would draw a little fuel...

 

Yes, the older and simpler the car, the easier it is to roll-start. I imagine with a lot of new cars, roll-start would be impossible even on a hill; the ECU or some other element of electronics would prevent it. I used to drive a '71 Rabbit with a weak alternator and a fuel pump that would keep running after the car turned off, which meant the battery was dead 3-4 times a week. I just got used to parking it facing downhill. Let it roll to 10 MPH, put it in 2nd, turn the key and pop the clutch -- start!

If you can push a car to 10+ mph on a flat surface, it is time to cut back on the steroids.

 

sweeeet.