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Old 13th August 2009, 23:01   #1
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Default Starting and idling problem in Carb Zen

Hi,
I have a carb Zen (1999) with 83000Km on ODO. The car has 3 problems which I'm describing below:

i) In the morning the when I start the car I generally have to push the accelerator a little to keep the idle RPM stable at 800. Without the accelerator - the RPM goes as low as 500 and the engine dies sometimes. After a minute or two , the engine becomes stable and the RPM is stable at 750-800. The car starts in half self though.

ii) Recently another problem has started - the car starts fine in the morning (as described in point no. 1). But after driving for a few KM when I switch off the engine at the signal and try to restart I usually have to crank the engine for longer - sometimes have to try twice. But if I slightly tap the accelerator twice before cranking - the engine starts immediately. Fuel pump was changed about 3000Km ago, fuel filter has also been checked and found to be O.K.

iii) The idling has also become rough now-a-days. The RPM at idle varies from 700-900 (sometimes goes to 600) and the engine vibrates. The change in RPM is erratic and not constant and does not follow any pattern. I reported the problem to my local mechanic (not MASS) and he checked for fuel pump, fuel filter and vacuum tubes and didn't find any problem. Also cleaned the carb and the throttle body with spray.

I asked him to do a carb overhaul - but he suggested that since I'm getting a good mileage (17 KMPL) - no need to open the carb. The car was tuned about six months ago with the help of a PUC machine.

Although the problems are not hampering any of my normal activity with the car - I'm wondering what needs to be checked to get the problems solved?

Help me guys.

Last edited by archat68 : 13th August 2009 at 23:10.
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Old 13th August 2009, 23:11   #2
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17 km/l on a carb Zen is just terrific, especially in Kolkata. I think you are running an extra-lean mixture, which is the root of all your problems.
Quote:
...if I slightly tap the accelerator twice before cranking - the engine starts immediately.
Doing that solves the lean mixture problem by sending in a few drops of extra petrol into the manifold from the acceleration pump of the carb.

Enjoy the mileage - fixing your current issue will reduce the FE you are getting.
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Old 14th August 2009, 02:53   #3
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Quote:
In the morning the when I start the car I generally have to push the accelerator a little to keep the idle RPM stable at 800. Without the accelerator - the RPM goes as low as 500 and the engine dies sometimes. After a minute or two , the engine becomes stable and the RPM is stable at 750-800. The car starts in half self though.
Dont worry. This is not an issue. Usually carb engines behave this way.


Quote:
The idling has also become rough now-a-days. The RPM at idle varies from 700-900 (sometimes goes to 600) and the engine vibrates. The change in RPM is erratic and not constant and does not follow any pattern. I reported the problem to my local mechanic (not MASS) and he checked for fuel pump, fuel filter and vacuum tubes and didn't find any problem. Also cleaned the carb and the throttle body with spray.
This is tuning problem. Take it to a tuner/mechanic who is good at carb engines. He can resolve it within a minute.
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Old 14th August 2009, 09:49   #4
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Quote:
Originally Posted by SS-Traveller View Post
17 km/l on a carb Zen is just terrific, especially in Kolkata. I think you are running an extra-lean mixture, which is the root of all your problems.

Enjoy the mileage - fixing your current issue will reduce the FE you are getting.
My driving is about 30-40% within city rest is on E.M. Bypass where 70-80 KMPH is possible. Earlier with 100% city driving without AC I used to get around 12-13 KMPL.

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Originally Posted by adi99 View Post

This is tuning problem. Take it to a tuner/mechanic who is good at carb engines. He can resolve it within a minute.
O.K I'm also thinking of it - will try it tomorrow.

Anything other to be checked out? Does the carb needs to be overhauled?
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Old 14th August 2009, 09:52   #5
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I think you should go in for a carb-overhaul, even if you are getting good mileage. I feel the problems you are facing are carb related.
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Old 14th August 2009, 10:01   #6
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Quote:
Originally Posted by archat68 View Post
My driving is about 30-40% within city rest is on E.M. Bypass where 70-80 KMPH is possible. Earlier with 100% city driving without AC I used to get around 12-13 KMPL.
Anything other to be checked out? Does the carb needs to be overhauled?
From 12-13 to 17 is a big jump. If you can live with the rough idle, don't fiddle around with the settings. Or just get them tweaked slightly to make things slightly better.

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I think you should go in for a carb-overhaul, even if you are getting good mileage. I feel the problems you are facing are carb related.
I beg to disagree... don't open up a carburettor which is working so excellently. It's a tricky job to clean and assemble back a carb, and in not-so-expert hands it could be quite a mess. That said, I used to know some really expert mechanics in Kolkata some years ago, but have lost touch nowadays. With MPFi in the market, I suppose the art of fixing carbs is a dying one.
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Old 14th August 2009, 10:03   #7
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I think you need to tune the carb's its running lean and mostly idle circuit is lil chocked. For rectifying you dont need to open the whole carb and can check the idle jet separately, will take 10 mts for a good mech.
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Old 14th August 2009, 10:08   #8
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Quote:
Originally Posted by musicmanaman View Post
I think you should go in for a carb-overhaul, even if you are getting good mileage. I feel the problems you are facing are carb related.
I dont think there is a need for a carb overhaul. Plus its i feel the reason could be the detuning done during PUC check as mentioned below.

Quote:
Originally Posted by archat68 View Post
The car was tuned about six months ago with the help of a PUC machine.
.
I remember during my Carb esteem days as well these PUC guys usually used to make my car run lean to get the PUC cleared how ever i used to get it set back to normal as my car used to jerk at high RPM. just get the idling jet set properly. That should solve the problem.

Thanks,

Pramod
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Old 14th August 2009, 12:37   #9
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Thanks guys.

Yes, I'm very happy with the mileage this 10 year old car is giving. Apart from the rattles that Maruti specializes in - the car is giving me excellent service.

I've a friend in Kolkata who runs a service centre. I get the car serviced from his garage only. He also advised me not to open the carb since the mileage is excellent.


Will check the tuning tomorrow. Will also check the idle jet as suggested by Jaggu.
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Old 14th August 2009, 15:06   #10
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Please get the vacuum hose that connects to the carb checked as well. I vaguely remember such a problem in my old zen and that was resolved when the vacuum hose was connected properly.
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Old 14th August 2009, 15:25   #11
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Quote:
Originally Posted by mtnrajdeep View Post
Please get the vacuum hose that connects to the carb checked as well. I vaguely remember such a problem in my old zen and that was resolved when the vacuum hose was connected properly.
Already done that and it is O.K.
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Old 14th August 2009, 15:25   #12
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Quote:
Originally Posted by mtnrajdeep View Post
Please get the vacuum hose that connects to the carb checked as well.
I agree - the thin tube that connects the inlet manifold/carb to the vacuum timing advance mechanism. A leaky tube can also cause similar idling problems.

EDIT: We posted exactly at the same time, archat68! Fine, so that's not the culprit.

Last edited by SS-Traveller : 14th August 2009 at 15:26.
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Old 14th August 2009, 15:28   #13
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O.K. I will get the vacuum tube changed. It doesn't cost much. Let's see if there is any change.
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Old 14th August 2009, 15:41   #14
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will cost 10 bucks at the most, since the car is old maybe a good idea to check all those tiny rubber tubes and plastic parts and get them changed if required.
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Old 19th September 2009, 19:05   #15
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Man you have busted solenoid of carburator! or the wire connecting it to +side of battery is broken! hard starting and not settling on idle! Typical solenoid death!
else your induction system is leaking air from somewhere,hence its drawing more air and leaner mixture is the problem!
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