[svsantosh]

Originally Posted by Petrolhead_97

Does that happen for both manuals and automatic?

I knew Automatics lock the shaft with a parking pawl which locks the drivetrain from any sort of rotation, but depending on it could stress it, I believe.

What about Manuals?

Forget about stresses on a non-moving car that is exerted on a cold drive train - its nothing to worry about a lot.

But you made an interesting point that reminded me - the P on a Automatic (torque convertor or CVT) will hold the car in position even if the engine is removed from the car, that is because the P engages a locking pin mechanism inside the gearbox that locks the output shaft of the GB.

But in manual (& AMT) you cannot hold the car still in any Gear without the engine connected to the GB - the GB will free roll without engine vacuum.

[Auto_guy_101]

Originally Posted by Rehaan

To do that in petrol cars, you need a spark + fuel.
- In carbureted cars, you might get fuel but you won't get spark unless the ignition is active.
- In MPFI cars, you won't get either unless the ignition is active.

For push-starting a car, the ignition needs to be active (ie. the last possible position of the key turn where it stays put).
This will not be the case for a parked car.

This brings me a to dangerous experiment I had in mind during my college days (a curiosity that was fueled by textbook knowledge of engines and the starter system). I request mods to excuse me if the content is not relevant to this thread.
The experiment: If a car on the top of a sloping road is turn off, put in 1st gear (manual), the clutch is depressed and the brake is released, the vehicle should start rolling down the incline. If the clutch is slipped, it should allow the car to be jump started, right?

Assumptions:
1. Electricity: Once the car is running, the ignition coils get power from the generator (which also charges the battery). So, slipping the clutch should result in enough crankshaft rotation to generate power
2. Engine: Instead of the motor running the crankshaft and the engine at start, the wheel's rotation should do it

Why it may not work:
- If the key being in off works as a circuit breaker, this wouldn't work. I don't know much about this aspect.
- This would be cranking the engine without fuel supply (as the pumps, especially in MPI cars) won't be working. I don't know if the electricity generated from this cranking is sufficient for this.

Why is it dangerous?
Too many reasons, including lack of brake boosters, clutch wear out etc.

As I don't have the courage, risk appetite or safe environment to try this (and nor would most people), I would like to know if it would work, theoretically.

[dhanushs]

Originally Posted by Auto_guy_101

...
The experiment: If a car on the top of a sloping road is turn off, put in 1st gear (manual), the clutch is depressed and the brake is released, the vehicle should start rolling down the incline. If the clutch is slipped, it should allow the car to be jump started, right?
...

Well, if you have a car with a dead starter thats what you do right? Even push starting the car is the same.

[Auto_guy_101]

Originally Posted by dhanushs

Well, if you have a car with a dead starter thats what you do right? Even push starting the car is the same.

I have (*touchwood) not had to push start a car. While I have seen it done, I wasn't sure of the key position and slipping of the clutch.

Wouldn't this also allow for a car to be stolen? And the only way to stop said car would be by stalling it, right?

[dhanushs]

Originally Posted by Auto_guy_101

I have (*touchwood) not had to push start a car. While I have seen it done, I wasn't sure of the key position and slipping of the clutch.

Wouldn't this also allow for a car to be stolen? And the only way to stop said car would be by stalling it, right?

Oh, you were pointing out to a situation where you dont have the keys/switched off position. Then, no it wont start.

In Petrols you dont get spark/Fuel and in diesels your FIP wont work. Basically fuel is cut off when the Key is Off. However, in older gen diesels where one needed to mechanically cut off the fuel pump pulling a cable, the engine will start of turned over at sufficient speed.

[RunGaDa]

I never ever got this problem in the US. It seems cheap skating on parts or service the only reason when the car does not stay in place even when the hand brake is engaged.
Whoever has driven in SFO and parked their cars on 30 degree slopes and inclines can relate this. I lived in SFO for a year and regularly parked both manual and automatic cars in parallel parking on road sides. Not a single time did my car leave its place. Though CA DMV makes it compulsory to turn the wheels inwards while parking. Regardless no way would the car move.
I remember my VW serviceman explaining to me the way they adjust the handbrake. This is a crucial point and would lead to dangerous conditions if the car slips off on its own.
Now in India I had this issue with my Ecosport on several occasions. The incline was not great, may be 15 degree, sometimes the car refused to stay parked even when I pull the hand brake to its limit. I had to engage a gear to make sure it doesn’t roll down.

[Cresterk]

Parking in gear is not some magic brake that locks the wheels completely. It just transfers the force to the engine via the gearbox. If the slope is steep and the force is enough to rotate the engine, the wheels will move.

Parking in P in an automatic is just a engaging the gearbox to a cog / locking pin that doesn't move. This cog isn't some invincible piece of metal either. Put enough force on it and it will break off and you car will start moving. Naturally this will lead to a hefty repair bill for your transmission.

Engage the handbrake and only then put it in gear or P to ensure as much force as possible rests on the actual brakes. The gear is just an additional failsafe. Turn the steering as much as possible to ensure even if the car does roll, it only rolls away enough to turn sideways and come to a stop instead of hurtling down the hill. Put a rock under the tyre if the slope is too much.

A decent handbrake would be able to lock the rear wheels completely. For some reason, this is rather rare in India despite the service center's best efforts at "adjusting it".

[x-o-b]

Originally Posted by Petrolhead_97

I have a 2022 Suzuki 1.5L Petrol Ertiga with only 7.5k kms on it, almost 1 year 5 months old

Recently I had parked my car, in my apartment drive-through, which is a ramp leading to the basement, in first gear, and I tried to leave the car.

Time for an engine compression check, which could lead to further inspection of the engine (engine bore, piston and piston rings).

Bottom line: this isn't normal, and your car should not have rolled down.

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