Cars that don’t start because of a dead battery or a failing starter are not so rare cases and that can happen when drivers least expect it. If this happens when you are in a rush, or you don’t have some quick help at hand, the first thing that you can do is to push start the car.
This might come in handy if you find volunteers to help push your car or if you find another car to tow you. This will work well if the car has a manual transmission, but does push starting a car also work on a car with an automatic transmission?
The answer is, in most cases, no. You won’t be able to push start a car that has an automatic transmission because its design does not allow starting the engine in any other way than the traditional one.
But, if your car’s automatic transmission is among the few exceptions, push starting can be possible. More details on that will be given below.
Even if some car manuals claim that this does not work for an automatic car, the situation is not that clear regarding this method, because this depends on the type of automatic transmission that your car has.
To better understand why in most cases we won’t be able to push start a car with automatic transmission and how to do it in exceptional cases, we need to add other arguments that are linked to this topic.
How push starting a car works?
To get the engine to start working, the crankshaft should be turned. This task falls on the shoulders of the car starter. However, if there is a problem with the starter, it can become useless. Thus towing or pushing will help to start the engine because the drive wheels in motion transmit torque to the crankshaft, after which the car starts.
It is possible to push start a car with an automatic transmission?
If you opt for towing, a necessary condition is that the towing car has a rigid connection with the towed car’s wheels. On a manual gearbox the crankshaft is connected to the input shaft with the help of the clutch friction disc and driveshaft with the driven shaft, and it with the wheels is connected via pinions which are connected by the couplings. This rigid link does not exist in most types of automatic transmissions.
Thus, certain limitations appear, because the operating principle of this method is based on the torque that is transferred by the rotating wheels to the engine. On automatic cars, if the engine is not running, the transmission also does not function, because the oil pump only adds oil when the engine is running.
To put it simply, if an engine on a car that has automatic transmission is stopped, there is no connection between the wheels and the engine through the transmission. So, when towing or pushing a car, the torque will not be transmitted to the engine, and the piston group will be immobile. As a result, the car will not be able to start.
Gear shifting in automatic transmissions is not carried out by rigid mechanical rods, but by hydraulic mechanisms. The automatic transmission fluid must be under pressure for the gear to be activated.
The pressure there is created by the pump on the input shaft, which is rotated by the motor. While there is no pressure, the friction gears are disengaged and the output shaft, which transmits the rotation to the wheels, is not connected in any way to the primary one.
The required condition to push-start an automatic car
Above I said that there are still some exceptions when push starting an automatic car do work, but they are very few and very rare. The requirement needed is an extra oil pump that is located on the transmission’s output shaft.
Unlike the primary oil pump that is located in the input shaft, there are old automatic transmissions that have that second pump on the output shaft. Taking advantage of that second pump, when the car is towed the wheels are able to create the necessary pressure there to start the car.
But these AT models are very old. You can find them in cars like Mercedes-Benz W124, W126, W140, W460, old Japanese cars like Toyota and Mitsubishi before the 1990s, and some American cars between the years 1980 and 1990.
These car owners are lucky, the cars can tolerate this starting method without much negative consequences due to the presence of a second oil pump.
The theory of push starting a car with automatic transmission
There is a theory that you can start an AT car, but for that, another car is needed for towing. Pushing it will not help.
- Connect the cars;
- Switch on the ignition by setting the key to the second position;
- Set the automatic transmission lever to neutral;
- Start to move the car;
- Gaining a speed of about 30 km/h, or 18 mph for a cold transmission or 50 km/h, or 31 mph, for a warm one, and keep this speed for about about 5 minutes.
- After building up the pressure, put the lever in the second or third gear (lower position of the lever) and press the gas pedal to the middle.
- As soon as the engine starts, put the lever back to neutral and tell the driver that tows you to stop the car.
If it didn’t work the first time, give the car a little rest for 10 minutes and try again. If it didn’t work out the second time, you should stop trying, because you can damage the transmission.
Sounds better in theory, right? In practice, it is hard to achieve not only the speed itself, but also it takes attention and skill to set the lever in several positions. This method may work on cars mentioned above, but not in other cases.
Unfortunately, referring to the cars present on the streets today, you won’t be able to push start a car that has an automatic transmission. As an advice, do not try using this method, because doing so may cause serious damage to the transmission, and repairs will cost a lot.
Try as much as you can to fix this starting issue by changing the battery, or the starter since these two parts are the most common cause. And if you need to transport the car, call a tow truck and take the car to a workshop to begin the repairs.