My car backfires? when engine is shut off..

syncview

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My little 3 cylinder suzuki alto has started backfiring when the engine is being turned off.. It doesn't do it every time, but it was more frequent yesterday.. its been almost three days it has started to do this.. its carburetted.. and has no electronics whatsoever, so what am I looking at? What could be wrong?
 
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LeVeL

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I'm guessing its running too lean... maybe advance is messed up for some reason :dunno:
 

airmenair

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Sounds like the timing is too far retarded. Have access to a timing gun? If not mark the position of the distributor with the block (as a reference point) then rotate the distributor slightly clockwise (generally all cars I am aware of advance the timing by rotating the distributor clockwise but you might want to double check this before proceeding), tighten and see if there is any change. You can play around with this until you have the car running well.

Otherwise it could be a carb problem.
 

syncview

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But why would the timing retard itself for no apparent reason? I mean, I haven't got anything done to the car within the last few days.. related to timing actually..

If we're looking at the carb, how can it be fixed if it can be fixed at all?

People here say, most of them anyways, that cars running on CNG (Compressed Natural Gas) have to have carby problems sooner as when compared to the cars which are run on Petrol.. my car has been run till 65000 kilometers on CNG and since then its been on Petrol only, removed the CNG kit / tank / wiring / all of it actually.. its now at about 90K kilometers now.. Why do they say so, if you have any idea?

And oh, when I press my accelerator, the engines tends to die but gets back up again.. really notable when started in the morning.. this wasn't much noticeable until three days ago. :(
 

argatoga

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I would hazard a guess it is a carburetor issue if it starts dieing when you press down the accelerator.
 

Nabster

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Isn't it generally a backfire out the carb meaning lean, and a backfire out the tailpipe being rich? If it happens when you turn it off I'm guessing it's out the rear because you'd have the engine pushing some unburned fuel out after you cut off the spark. It's possible some of the seals/gaskets in the carb have degraded and allowed some gas to seep or flow through as it shouldn't. Could be as simple as some gunk holding something in the carb open, too. Try a bit of carb cleaner, see if it helps, if not perhaps rebuild the carb. If that doesn't fix the issue, well you've got a fresh carb that should provide better service once you've fixed the issue, so there's no loss. Alternately take it by a mechanic who knows older cars, and I'd be willing to bet he could tell you exactly what the problem is and have a simple fix for it. Hard for us to say without first hand experience what's going on.
 

syncview

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it pops at the front, so its coming out of the carby?
Anyways, I will try that carb cleaner thing, how long should I spray it in? And is it bad in any way? I'll go for a carb rebuild anyways..
 

Nabster

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Follow the directions on the can for the carb cleaner. And no, it shouldn't be bad for it, but if the carb does have some holes or gaps in the gaskets, the cleaner may open them up some after cleaning out the gunk, so there's a chance it could make things worse, in which case you know you'd need a rebuild.
 

airmenair

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Isn't it generally a backfire out the carb meaning lean, and a backfire out the tailpipe being rich?
it pops at the front, so its coming out of the carby?
Anyways, I will try that carb cleaner thing, how long should I spray it in? And is it bad in any way? I'll go for a carb rebuild anyways..
When I was timing my mustang, the first time I went to start it I shot fire up through the carb. All I did afterwards was advance the timing slightly and it fired up fine with no more scary flames.

I have heard of cases happening where the timing can work itself "loose" so to speak. Just as a sanity check, take a look at the hold down nut on the distributor it may not be all that tight.

As far as the carb cleaner goes, it's pretty straightforward and should have directions on the can. I've never heard it being 'bad' in anyway. I mean it's flammable and not good to breathe but shouldn't hurt the car. Just keep it away from painted surfaces.

EDIT: Beaten to the punch!
 
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InfernalVortex

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Get a gasket set for that carburetor and pull it off the car and disassemble it, clean everything, and put it back together. Spray out all the little passages and holes in it with the carb cleaner. You may want to dunk it in some parts cleaner overnight and do that afterwards.

I'm betting the carb is just gunked up.
 

syncview

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airmenair: I checked the distributor, I couldn't move it.. neither clockwise nor anti-clockwise..

Is it really that simple to clean a carby, or should I get it done by someone who does that job? :p I've cleaned throttle bodies myself.. but they are well.. easy to do so :p
 
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