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Homepage. This page: Ways to start a classic car's engine when the battery is low, or flat.

Starting an engine with a low or flat battery.

Starting a car's engine - simple isn't it?! Leap with the grace of Nuroyev into the driver's seat, apply a spot of choke and retard the ignition (if required), turn the key, and either turn it further to engage the starter, or else pull or push on the starter knob as required. A few moments of churning and the engine will burst into life, settling into a smooth purr.
At least that's the theory, however living with an older car is often not quite that simple. Aged components, perhaps allied to a battery that has seen better days, can make starting a car's engine less than a guaranteed exercise. Here, different methods of starting an engine when the battery has failed in its duties will be looked at, although a glimmer of life in the ignition circuit will be required, at least where a coil rather than magneto provides the spark. Attempt any of these approaches at your own risk, seek advice if you're in any way unsure of what to do.

The starting handle.

Most cars built up to and including the 1950s, and in some cases into the 1960s, will have the provision of a starting handle. That small aperture set into the car's radiator grille, or perhaps in its front bumper, can be a warming sight to anyone faced with a non-starting car on a cold, frosty morning for instance, a common time for any starter component to display its weaknesses.
Using a starting handle on a car engine
Early cars tended to have a starter handle permanently attached to the front end of their engine's crankshaft, so common was the need to use it. Gradually the handle disappeared from the front of the car, spending most of its life nestled away inside a tool roll in the boot, ready to be called upon whenever the need arose.
Starting a car using a handle takes a little practice, and more than a little effort where the engine is of medium or large capacity. The gist of the procedure runs as follows:
  • Apply the handbrake
  • Ensure that the car is out of gear
  • Apply the choke, and retard the ignition if required
  • Turn on the ignition, at the very least a dim glow from the ignition warning light will be required
  • If the car has an electric fuel pump, allow it to complete its job of filling up the carburettor float chamber(s) before attempting a start.
  • Apply the choke, as you would for a normal start
The next point is crucial, and one that I often had to bear in mind when crank-starting my Mk1 A40 on particularly chilly mornings. Do not grab the handle as if you were preparing to wield a tennis racket, say. Curving your thumb around the handle can lead to dire consequences if the engine kicks back, and throws the handle back with it. Instead, ensure that your thumb is ahead of the handle when you use it, ie alongside your knuckles, rather than on the opposite side of the handle to them. This way the handle can kick back, and your hand simply loses grip and you don't risk breaking your thumb.
Turn the handle a couple of times, feeling for when extra resistance is felt, signifying that one of the engine's cylinders is reaching compression. This is when a firm swing on the handle is required, before backing off and seeing what happens. Churning the handle over and over like a (slow) rotary drill isn't the technique to use, better to slowly bring the engine over and only introduce brio to the proceedings when compression is felt. All being well, assuming the ignition system is in good order and no dampness or other outside problems are present, the engine will fire up.
If the ambient conditions are particularly damp, and the engine refuses to fire, then further checks of the ignition and fuel system may well be required.
Assuming the engine fires up, the starting handle will be thrown back slightly from the dog on the end of the crank, so there should be no risk of the handle continuing to flail around once combustion has occurred.

Bump starting.

This procedure can require outside assistance, unless you happen to be parked at the top of a hill or reasonable decline.
The theory of bump starting is that the engine is churned over, not by a handle, but by the movement of the car while it is in gear, thus pulling the engine over and over until it fires.
How the movement takes place is the tricky part. If you can avail yourself of a useful hill descent, then gravity can do the work. Otherwise a group of willing pushers will be required. Theoretically it could be possible to bump-start a car on one's own, hopping in just as the engine catches, but the risk of the un-manned car darting off into the sunset with its owner stood looking slightly foolish at the side of the road, means that this should not be attempted. Something similar happened to a friend of mine. His Spitfire had a stuck starter motor, on a day he'd planned taking the car out for a spin. He'd heard that rocking the car backwards and forwards, while in gear, would help free it off. This he did, with great success. However he'd left the ignition on and the choke fully extended. The starter freed off a treat, but alas the engine fired while he was at the rear, and the Triumph proceeded away in an easterly direction, its progress only being halted by his mother's Volvo that happened to be parked 50ft or so away down the road. An embarrassing, but potentially lethal, state of affairs.
Bump-starting a car
Anyway, back to bump starting. Typically this will only work on a car with a conventional manual gearbox, my Standrive-equipped Standard 10, with its centrifugal clutch, couldn't be started this way. Fortunately the handle got me out of trouble with that one.
With a willing band of pushers poised at the rear of the car, hop in, turn on the ignition and apply some choke. The car can be left in neutral as the pushers swing into action. With momentum achieved, depress the clutch pedal, select second gear and gradually lift off your foot from the pedal, engaging drive and causing the engine to turn over. Do this too early, or try using first gear without sufficient speeds achieved, and likely as not the car will judder to a halt, so some practice may be required.
All being well with the car in gear and forward momentum in progress, the engine will fire up. As soon as it does, depress the clutch once again and bring the car to a smooth halt. Don't do this and the car will leap towards the horizon, quite possibly leaving your pushers in a heap on the road.
If neither hill nor pushers are in evidence, then the use of a tow car can achieve the same results. Whoever is in the car being started will need to be lively with depressing the clutch pedal when the engine fires, as there's a risk of towed car making contact with the rear bumper of tow car. For this reason, using a very short rope isn't a good idea, and it's crucial to ensure that the rope is only attached to sturdy points on both vehicles - the end of a bumper, or a steering track rod, will not do. Keeping a weather eye open for young children, and indeed all pedestrians, while attempting a bump start is also a wise plan, as anyone tripping over your tow rope while start-up attempts are being made are likely to be an unwelcome distraction.

Jump starting.

This method requires the use of a known good battery, of the same voltage, to "jump start" the stranded vehicle, and a pair of jump leads. Good quality leads are essential here. A few moments thought will need to be given to the car being started, and also the one doing the jumping. The electronics on more modern cars do not always take kindly to ham-fisted jump-start attempts, so a perusal of either car's handbook, if one or both are of recent manufacture, could save a lot of wallet-ache. Don't jump start a car equipped with six-volt electrics with one using a twelve-volt system, for obvious reasons.
Jump-starting a car from another
Jump leads are coloured, one red, the other black. The red is typically used for the positive (+) connection, the black for negative (-). Both cars need to be parked close to each other for this to work, but they must not touch. Also bear in mind where the battery in each car is situated, and also the length of leads available, and park them up accordingly with their bonnets raised as necessary.
At this stage, the "good" car's engine should not be running.
On a negative-earth car, connect the positive terminals of both cars' batteries together using the red jump lead, ensuring that neither lead is anywhere near to components (fan belt, power steering pulleys etc) that will be rotating once the engines are operating. Now connect the black lead to the stranded car's negative battery terminal. At no point must red and black lead connectors touch once connections are made. The remaining end of the negative (black) lead can then be clamped to an earth on the good car, this could well be the engine block which is preferable to using the battery connection directly, in case of sparks.
With all the connections made, the good car can now start its engine, and should be kept at a fast idle to give the "dead" car a good chance of starting. All being well, the dead car will be receiving sufficient donor charge for it to fire up.
Once running, disconnect the negative lead from the "good" car and then from the other. The red lead can then follow suit, the idea being that any spark caused by attaching the final lead in the circuit, and later removing the first from a circuit, may cause a spark, and this spark should be well away from the battery receiving the most charge, in this case the dead one.
Whichever method is used to get the car running, ensure that the engine is allowed to run at a fast idle for say ten minutes minimum, with no lights on, to give it some charge and half a chance of being usable next time it's called upon to start the engine. As soon as is practical, give the battery a full charge and if symptoms persist, then either the battery is on its way out, or perhaps the charging system in the car isn't as fit as it once was.
If you're not particularly mechanically-minded, and all this sounds just a little too risky, please don't attempt any of the above. Instead call out someone who knows what they're doing, whether this be a breakdown company, or a trusty individual from a local garage.

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