Torque Shop

Can I push-start a car with an automatic transmission? How about a car with dual-clutch transmission like what many Volkswagen models have?

Push-starting a car with a manual gearbox is feasible. If the battery is dead or too weak to power the starter motor, one way to ignite the engine is to get the car in motion with the help of a couple of strong people.

Meanwhile, the person in the driver's seat should have the car in second or third gear, hold the clutch pedal in and have the ignition key in the "on" position. Once the car reaches a reasonable speed, which need not be much more than jogging pace, a sudden release of the clutch will fire up the engine.

The manual friction clutch provides a positive coupling between the driven wheels and engine.

This is not the case with an automatic transmission, which has a fluid coupling. Also, with most automatic transmissions, you need the engine to be turning first before "Drive" can be hydraulically engaged.

Although the dual-clutch gearbox uses a friction plate clutch arrangement, the selection for "Drive" is controlled by a sophisticated mechatronic system which needs both electrical power and hydraulic pressure from an engine-driven pump.

Hence, should the car have a dead battery, even if you select "D" with the gear lever, the mechatronics will not actuate the gearbox shifter.

In such a case, the only way to start the engine is to jump-start using another battery. One method is to connect a battery from another vehicle to the dead or weak battery with a jump cable. This may not be feasible or safe on a fast-flowing highway.

These days, you can purchase compact lithium-ion power banks specially designed to provide the required starting voltage to start up an engine that has a dead battery.

Shreejit Changaroth

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A version of this article appeared in the print edition of The Straits Times on August 15, 2020, with the headline Torque Shop. Subscribe