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Starlight Silver MG TF 135
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Discussion Starter · #1 ·
I always switch-off at traffic lights or when bought to a halt by heavy traffic etc. I also select neutral and switch off when trundling slowly downhill towards any stationary traffic ahead: Saves fuel, reduces pollution etc. etc.

If still moving when traffic ahead starts moving, I have used bump-starting in an appropriate gear to save the starter motor. Always did this on my kit car, (1960's carburettors - no problem) HOWEVER, with EMS, Lambda sensors and all that clever wizardry, am I causing a problem?

The car in question is a 2002 TF135 Mk1
 

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Bump starting is a bad idea for any motor vehicle due to the extra strain exerted on the gearbox and transaxle. Think about the components you are asking to rotate, in both scenarios. Far less friction on an engine that on the whole caboosh ! It should be used as a last resort only.
 

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I agree with statement that bump-start is different way of rotating the engine to start it.
However I would like to point out that in case of starting the engine by starter motor you have controlled way of doing it as in case starter motor "engine" wil force starter teeth to come out and you will hear them if you leave ignition key in starting position longer period then needed.
If you are starting the engine by bump-start you do not have controlled way of starting the engine since you are depending on your clutch, your clutch pedal and in the end your foot in order to be able to release your clutch from the engine when engine starts. In bump-start you realy are risking timing belt tooth jump.
 

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mg_tf
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OK you like to respect the environment by switching off the engine at lights etc. and when coasting. Your choice of course, but it’s interesting that the consensus of opinion is don’t do it.
I would join that band, and it would be more advantageous to sell/ scrap your current not-as-environmentally- friendly- as could - be TF, and buy a modern euro-box with this detestable ( in my opinion) stop/start system.
Switching off the engine in a coasting situation may accelerate the demise of the TF, when you loose your brake servo assistance and run up the posterior of the car in front!
What area are you in, so I can hopefully keep my distance?
Kind regards,
Austin.
 

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Starlight Silver MG TF 135
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Discussion Starter · #8 ·
It can dump unused fuel into the cat damaging it, that is why the manufacturers advise against it.
Thanks, Chris T, That is exactly why I asked the question. I will not use bump-starting again.

As for quite correct comments regarding loss of brake servo: I know that there is enough vacuum stored in the servo to allow 3 gentle bake application/release cycles before the servo stops assisting. I therefore NEVER cycle the brakes when coasting.

BEFORE starting coasting, I ALWAYS have foot already on the brake pedal, so can react MORE quickly and stop SOONER than someone who has to move from accelerator to brake before commencing braking.

ALSO I should have mentioned that when switching off, I immediately switch back to ignition on, so that all instruments are live, and I know that I have not accidentally gone too far with the ignition key, resulting in steering lock, which WOULD be very dangerous (and stupid!)

As I said above, I will NOT be using bump-starting again, but I do not understand the Physics of:
In bump-start you realy are risking timing belt tooth jump.
I can understand that turning the engine in the wrong direction would probably pull the tensioner side of the belt "straight-ish", and the opposite side (which should be straight) loose, thus risking belt-jump, but as long as the engine is driven forwards, what is inducing jumping? Anything to do with the rate at which the engine is accelerated?
 

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For the tooth jump I see potential problem in force and momentum you are providing in case of bump jump since that is not controlled way as in case of starter motor. Problem which I see are in the moments of start and the end of the process itself.
 

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'06 MG ZR +120 (HQM) '04 MG ZR 105 (IAB)
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Remembering the advice that was given out during the 'energy crisis' in 1973, it was not recommended to shut off your engine if it was only going to be stopped for a very short time because (we were told) it uses an increased amount of fuel to restart and this would cancel out any saving made by switching off (an engine at idle uses very little fuel).
 
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