# US 5,706,774 A · Carburetor start pump circuit

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- Number: US 5,706,774 A
- Document ID: US5706774A
- Status: Granted
- Kind: A
- Application number: 08/653,679
- Filed: 1996-05-24
- Granted: 1998-01-13
- Earliest claimed: 1996-05-24
- Assignees: U.S.A. Zama, Inc.
- Inventors: Scott R. Shaw
- Web page: https://patentgrep.com/patent/US5706774A

## CPC

- F02M 37/046: {Arrangements for driving diaphragm-type pumps}
- F02M 1/16: Other means for enriching fuel-air mixture during starting; Priming cups; using different fuels for starting and normal operation
- F02M 37/12: fluid-driven, e.g. by compressed combustion-air
- F02M 37/16: characterised by provision of personally-, e.g. manually-, operated pumps
- F02M 49/00: Fuel-injection apparatus in which injection pumps are driven or injectors are actuated, by the pressure in engine working cylinders, or by impact of engine working piston
- Y10S 123/05: Crankcase pressure-operated pumps
- F02M: SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
- Y10S: TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS

## Abstract

A carburetor start pump circuit, for starting an engine, has an auxiliary fuel pump mounted on a relatively standard carburetor body, a pulse passageway extending through the carburetor body to the auxiliary fuel pump, and a fuel circuit having an intake side extending from a metering chamber in the carburetor body to the auxiliary pump where it is interconnected to a discharge side extending from the auxiliary pump to a throttle bore in the air intake of the carburetor body. To facilitate control of fuel flow, the fuel circuit includes inlet and discharge check valves and a metering jet.

## Claims

### Claim 1

A carburetor comprising
a body,
a first fuel pump mounted on said body,
a starter circuit including
a second fuel pump mounted on said body, and
a first pulse passageway extending through said body to said second fuel pump.

### Claim 2 (depends on 1)

The carburetor of claim 1, wherein said second fuel pump is only operational during engine start-up.

### Claim 3 (depends on 1)

The carburetor of claim 1, wherein said starter circuit further comprises
a first fuel passageway interconnecting said second fuel pump to a metering chamber in said body, and
a second fuel passageway interconnecting said second fuel pump to a throttle bore in said body.

### Claim 4 (depends on 3)

The carburetor of claim 3, wherein said starter circuit includes a check valve interposing said first fuel passageway and a pumping chamber in said second fuel pump.

### Claim 5 (depends on 3)

The carburetor of claim 3, wherein said starter circuit includes a check valve interposing said discharge fuel passageway and a pumping chamber in said second fuel pump.

### Claim 6 (depends on 5)

The carburetor of claim 5, wherein said outlet check valve is spring loaded.

### Claim 7 (depends on 1)

The carburetor of claim 1, wherein said starter circuit comprises a metering jet.

### Claim 8 (depends on 1)

The carburetor of claim 1, further comprising
a second pulse passageway extending through said body to said first fuel pump, and
a channel interconnecting said first and second pulse passageways.

### Claim 9 (depends on 1)

The carburetor of claim 1, wherein said second fuel pump includes a diaphragm.

### Claim 10 (depends on 1)

The carburetor of claim 1 wherein said first pulse passageway has an open mode during engine start-up and a closed mode during all other modes of engine operation.

### Claim 11 (depends on 1)

The carburetor of claim 1 further comprising a primer bulb interconnected to said second fuel pump.

### Claim 12

A carburetor comprising
a body,
a start circuit including
a fuel pump mounted on said body and driven by a pulse from an engine's crankcase during start-up of an engine,
a pulse passageway extending through said body to said fuel pump,
a first fuel passageway operably interconnecting said fuel pump to a metering chamber in said body, and
a second fuel passageway operably interconnecting said fuel pump to a throttle bore in said body.

### Claim 13 (depends on 12)

The carburetor of claim 12, further comprising a second fuel pump mounted on said body.

### Claim 14 (depends on 13)

The carburetor of claim 13, further comprising a second pulse passageway extending through said body to said second fuel pump.

### Claim 15 (depends on 14)

The carburetor of claim 14, wherein said pulse passageway is interconnected to said second pulse passageway.

### Claim 16

A carburetor comprising
a body,
a first fuel pump mounted on said body, and
a second fuel pump mounted on said body, said second fuel pump being operably interconnected to an engine's crankcase during engine start-up when said body is mounted to an engine.

### Claim 17 (depends on 16)

The carburetor of claim 16 further comprising a pulse passageway extending through said body to said second fuel pump.

### Claim 18 (depends on 17)

The carburetor of claim 17 wherein said pulse passageway includes a valve member mounted in said passageway.

### Claim 19 (depends on 18)

The carburetor of claim 18 wherein said valve member is positionable to a preset engine start-up position wherein said pulse passageway is open.

### Claim 20 (depends on 19)

The carburetor of claim 19 wherein said valve member comprises a throttle valve shaft having a hole drilled therethrough, said hole being aligned with said pulse passageway when said throttle valve shaft is rotated to a preset engine start-up position.

### Claim 21 (depends on 17)

The carburetor of claim 17 further comprising
a first fuel passageway operably interconnecting said second fuel pump to a metering chamber in said body, and
a second fuel passageway operably interconnecting said second fuel pump to a throttle bore in said body.

### Claim 22

A method of enriching the air-fuel mixture in a carburetor mounted to an engine during start-up of the engine comprising the steps of
transmitting a pulse from an engine's crankcase to an auxiliary fuel pump mounted on a carburetor body,
drawing fuel from a metering chamber in the carburetor body into a pumping chamber of the auxiliary fuel pump,
discharging the fuel in the pumping chamber in the auxiliary fuel pump into a throttle bore in the carburetor body, and
terminating the transmission of the pulse from the engine's crankcase after the engine has reached a desired operating temperature.

### Claim 23 (depends on 22)

The method of claim 22 further comprising the steps of
opening a pulse passageway in the carburetor body that is interconnected to the auxiliary pump and the engine's crankcase, and
closing the pulse passageway after the engine has reached a desired operating temperature.

### Claim 24 (depends on 23)

The method of claim 23 further comprising the step of
rotating a throttle valve shaft in the carburetor past wide open throttle to a preset position wherein a hole drilled through the throttle valve shaft is aligned with the pulse passageway to open the pulse passageway, and
reverse rotating the throttle valve shaft to close the pulse passageway.

### Claim 25 (depends on 22)

The method of claim 22 further comprising the step of
metering the fuel into the auxiliary pump.

### Claim 26 (depends on 22)

The method of claim 22 further comprising the step of
metering the fuel out of the auxiliary pump.

### Claim 27 (depends on 22)

The method of claim 22 further comprising the step of
priming the auxiliary fuel pump with fuel.

### Claim 28 (depends on 22)

The method of claim 22 further comprising the step of
purging air from the metering chamber in the carburetor body.