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Old 09-17-2013, 09:12 PM   #1 (permalink)
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Lightbulb Engine Off Coasting Damaging My Car?

Sometimes I like to turn the engine off if I'm going down a hill and then use the clutch to start the car again instead of putting more wear on the starter, but is that hurting something? Is the sudden jerk of the engine and transmission turning over again damaging something? Should I be concerned? Will having worn out motor mounts make it worse? This is something I have always wondered about but was never able to really find a good answer for. Thanks!
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Old 09-17-2013, 09:27 PM   #2 (permalink)
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This has been discussed several times if you do a search, but I'll sum it up.

Bump starting is not going to cause excessive wear or other problems if it is done properly. You shouldn't feel a sudden jerk. Essentially you need to double clutch in order to bump start. You should pick the highest gear that it will start in. When you want to bump start, let off the clutch slightly until it grabs, then push back in. Once the motor is running, rev match and let out the clutch to drive in gear.

The only difference between using the starter and bump starting is that one uses the starter to rotate the flywheel instead of using the forward movement of the car to rotate the flywheel.
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Old 09-17-2013, 09:54 PM   #3 (permalink)
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When I EOC in my truck, I bump start by dropping into top gear and easing the clutch out for a smooth uptake. The truck has finally burned out its clutch, and it only burned out because it's
1) the original clutch from 1987,
2) got over 200,000 miles on it and
3) been teaching the last son how to drive stick. THAT is what killed it more than anything.

Seriously, I've been driving my truck like this for yeeeeaaaarrrrs. It shouldn't hurt anything.

Also sometimes I'll do EOC without taking the truck out of gear, just let your momentum carry the engine along. It keeps your accessories spinning so you don't run out of vacuum for brakes or pressure on the power steering. You lose a lot of distance on your coasts but when you key back on there is no shock whatsoever.
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Old 09-17-2013, 10:02 PM   #4 (permalink)
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Quote:
Originally Posted by elhigh View Post
Also sometimes I'll do EOC without taking the truck out of gear, just let your momentum carry the engine along. It keeps your accessories spinning so you don't run out of vacuum for brakes or pressure on the power steering. You lose a lot of distance on your coasts but when you key back on there is no shock whatsoever.
Forced DFCO?
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Old 09-17-2013, 10:27 PM   #5 (permalink)
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Quote:
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Forced DFCO?
It's an '87 and carbureted. Yeah, forced. One click, not two. Two locks the steering = Very Very Bad.
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Old 09-18-2013, 01:59 PM   #6 (permalink)
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Old 09-18-2013, 02:07 PM   #7 (permalink)
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since it's relevant... thought i've had about bump-starting lately is putting the throttle on the floor(or at least, opened significantly) before letting the clutch out to prevent the instant engine braking that would happen with a closed throttle plate when going from 0RPM to whatever the engine would spin up to when in gear.

seems like it would be less strenuous on both the clutch and engine.
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Old 09-18-2013, 02:18 PM   #8 (permalink)
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Quote:
It's an '87 and carbureted.
Aren't you still using* fuel?

*)Wasting.
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Old 09-18-2013, 03:17 PM   #9 (permalink)
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Quote:
Originally Posted by jakobnev View Post
Aren't you still using* fuel?

*)Wasting.
Depends on the carb. If it has a fuel cutoff solenoid, you will not be wasting the fuel.
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Old 09-18-2013, 03:50 PM   #10 (permalink)
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Yes not recomended with wore out engine mounts. can cause bad results. The torque loading shouldnt be too much if done in a correct gear for speed you are traveling though. I kick over in 4th mostly again depends upon speed and I have not had much probblems. you may have things to fix if it is hard starting and bucks when engaged.
Something else Most dont conscider is compression ratio high compression engines bump harder. And if your using the key it is possible it restarts in clear flood mode thinking it has stumbled or stalled previously. due to ignition flash times. try counting to 3 from key off b4 returning to run position. "unless steering lock is an issue". Then I dont recomend you do it at all! install a shut off switch. Hope this answers all your concerns.

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