Carburetor Main metering system works at idling

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Dumindu
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My tercel:: 1987 Toyota tercle 4wd DX Wagon 1452CC
Location: Sri Lanka
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Carburetor Main metering system works at idling

Post by Dumindu » Sun Aug 25, 2019 6:41 am

My car is a 1987 Toyota Tercel DX Wagon RHD 1452cc manual driven car.

When the car is idling, I can see puffs of petrol emitted through the main metering system. I can hear a "shhhh" sound coming through the carb.

My car is having a fuel economy around 8km/l now.

Also I cannot gain the RPM below 900. That RPM value is changing. Digital RPM meter shows 1040, 1350, 900, 1100, 3100 with its each change.

Car is Idling even the Fuel Mixture Adjustment screw is fully closed with little opened throttle. When the throttle fully closed, car stops.

What could be the problem?

I there any Intake to Exhaust valve located inside the manifolds that could be leaking ? (Because if presents, I have to disassemble the manifold assembly to see it)

EXTRA DETAILS:

Carb was rebuild few days ago with new gaskets, jets, Plungers, Balls added. Lines were cleaned. Gaskets were fully tightened (without adding gum or grease)

I have tested the vacuum booster. No leak could be found. Vacuum check valve is also ok.

No vacuum source is connected to any carb component (AAP pump ect.). Vacuum connections are fully sealed with caps.

PCV valve connection doesnt have apparent vacuum leak. Valve is opened to a one direction.

I sprayed carb cleaner around the hoses and gasket connections including manifold gasket to catch a leaking point. Engine RPM increased only when spray to the carburetor upper gasket area. It is possibly due to little bit of carb cleaner entering through the carburetor mouth. I couldnt find any Increment in RPM at other areas.

At lowest attainable RPM which is 900, engine vacuum is 17 inHg with little shaky (within 1 inHg range).

Engine is hard to start. After start and warm-up it is easy to start.

Slow running jet was tested. Clicking sound can be heard.

NO EGR or Canister system is there in my car. Their connections are also properly sealed.
Last edited by Dumindu on Mon Aug 26, 2019 7:01 pm, edited 1 time in total.

xirdneh
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Posts: 1966
Joined: Thu Aug 04, 2005 11:38 am
My tercel:: 87 tercel 4x4 wagon w/reringed engine, 83 tercel 4x4 wagon w/salvaged engine and 4.1 Diff's
Location: seabeck, washington, USA

Re: Carburetor Main metering system works at idling

Post by xirdneh » Sun Aug 25, 2019 12:58 pm

I would try another carb. I keep several around for ruling out or in a carb. Might have missed something on the rebuild.
Love those Tercell 4x4 wagons but they sure suffer from road noise.

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Dumindu
Top Notch Member
Posts: 167
Joined: Wed Aug 02, 2017 12:34 pm
My tercel:: 1987 Toyota tercle 4wd DX Wagon 1452CC
Location: Sri Lanka
Contact:

Re: Carburetor Main metering system works at idling

Post by Dumindu » Fri Aug 30, 2019 11:12 am

Finally found the simple cause.

Throttle positioner which was not supplied with vacuum was blocking the full closure of the throttle. The lag was just a small degree angle. But it could cause a huge change.

when see it from the eye level It is not noticeable the effect of the throttle positioner arm.

I could learn the how much change can result the minute turn in the throttle.

Now Idle fuel consumption of the car nearly 0.8 l/hour. I can gain the RPM even below the 650 which is recommended.

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