The way to Clean and Rebuild Carburetors (1)

With this issue we begin a series on making the fine adjustments so that a carburetor will operate at its optimum ability. But before any adjustments can be made, problems have to be solved, and that includes locating and sealing air and vacuum leaks anywhere in the engine, and cleaning the carburetor thoroughly, replacing damaged or questionable parts, and reinstalling the carb on the car.

If the car shows symptoms of poor idling, hesitant acceleration, stalling, lack of power, rough running or backfiring, the problem must be isolated and corrected. Begin with the electrical system. Check the wires, the points, the grounds, the condenser, the distributor cap and the spark plugs to be sure that all parts are in good condition and performing as expected. Often an electrical problem will manifest itself in a way similar to a fuel problem. When you are assured that all is well with the electrical, move on to the fuel.

First thing to check is that there is an uninterrupted supply of gasoline to the carburetor. Irregular or interrupted fuel delivery can be caused by a clogged pick-up filter within the gas tank, a plugged or dirty in-line or in-carburetor filter, a crimped fuel line, a defective or leaking fuel pump, a leak at the vacuum tank, or even an empty, or near empty fuel tank.

Check the entire engine for vacuum leaks.  An open vacuum line – a cracked line, a line plug that has come loose, a disconnected line – can all allow air to enter the engine and cause a lean condition. You can often locate vacuum leaks by sound - a ‘whooshing’ sound - or by selectively spraying engine starting fluid or brake cleaner around the suspected leak [Editor’s note: be very careful with these flammable sprays, which also dissolve paint. Don’t neglect the intake manifold gasket, the carburetor base, and joints between sections of the carb and the windshield wiper line.

Check and tighten the lines and screws on the vacuum tank. Follow each vacuum line to be sure that it is connected or plugged. If it feels loose, hard, or is otherwise suspect, replace the line and then again check with the aerosol spray. You may find that the entire rough idling problem is not the carburetor but just an open vacuum line. (Editor’s note: this is especially true in the 1970s-1980s engines.)

Okay, you’ve checked, and everything seems to be in order, but the engine still doesn’t run properly. Let’s check the carburetor. Before reaching for the wrenches, carefully examine the carb for cracks, a warped mounting base, or other evident problems. Try the air adjustment screw(s). There should be a definite change in the way the engine is idling as each air screw is turned in or out. If not, it’s a pretty good indication that there is an air leak. It may be internal and only repairable when the carb is disassembled, or it may be that the mounting gasket(s) are leaking, the carburetor is not securely mounted, bolts are loose or other easy fixes.

Find out more aboutToyota 1RZ carburetor by visit miparts.com.