IMPCO Type
IMPCO carburetors are used on low pressure gas fuel systems and high pressure gas fuel systems.
The jets and the valves are interchangeable on the carburetor. A change in the jets and the valves will allow the carburetor to burn a variety of fuels. The system can burn natural gas, propane gas, or fuels with low Btu. The jets and the valves can also be changed in order to be used with an air/fuel ratio control when a catalyst is used.
Operation of a carburetor with a single diaphragm is described below. Carburetors with more than one diaphragm operate in the same manner.
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| Illustration 1 | g00812091 |
Flow of air and gas into the carburetor (1) Filtered air (2) Gas | |
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| Illustration 2 | g00813770 |
Section view of the carburetor and the throttle in the open position (1) Filtered air (2) Gas (3) Spring (4) Valve (5) Jet (6) Diaphragm (7) Passage (8) Load control valve (9) Throttle body | |
When the engine is stopped, spring (3) presses the O-ring seal of valve (4) against jet (5). No air or fuel can enter the mixing chamber of the carburetor.
As the engine is started, the intake strokes of the pistons generate a vacuum in the cylinders. The vacuum draws filtered air (1) into the carburetor. A vacuum pulls through passage (7) so that the vacuum pulls on top of diaphragm (6). When the vacuum's pull on top of the diaphragm is greater than the force of spring (3), the diaphragm moves toward the cover of the carburetor and valve (4) moves away from jet (5). This allows filtered air and gas to enter the mixing chamber. The mixture of air and gas goes past the throttle plate in throttle body (9) into the air inlet manifold.
When the engine is operating at a constant load and speed, the position of the diaphragm is constant. The diaphragm only moves when the demand for fuel varies.
Load control valve (8) is used to adjust the air/fuel ratio at full load. The position of the valve determines the quantity of gas that enters the carburetor. The valve causes the air/fuel ratio to be rich or lean. The exhaust emissions are adjusted with this valve.
Deltec Type
Deltec carburetors are used in low pressure gas fuel systems only.
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| Illustration 3 | g01046780 |
(1) Filtered air (2) Gas | |
Filtered air (1) is drawn into the carburetor through the air inlet. Gas (2) is entered through the gas inlet. The air and the gas are mixed as the two are drawn through the carburetor. The air and gas pass through the outlet of the carburetor and the two are drawn into the inlet of the turbocharger compressor.
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| Illustration 4 | g01416886 |
Typical example (3) Turbocharger compressor (4) Air cleaner (5) Throttle (6) Carburetor (7) Carburetor venturi | |