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ProblemsCarburetor doesn't adjustproperlyCarburetor floodsFuel leaks at shaftInternal fuel leakMisses or surgesStumbles or loads upEngine won't idleRough idleBackfiresBogsHard startingLack of powerPinging at moderatecruise just off idleEngine stalls on hardbrakingLow fuel economyPossible SolutionsFuel pressure too high. Fuel regulatormay be needed. See #3 belowXXXXCheck for dirt or metal in needles andseats.
Choke staying closed. Or partly closed. 1) Fix choke or heat source. Slow flooding. 2) Fix cause of flooding. Carb Trouble Shooting Guide.xls 4. Carburetor Troubleshooting Guide. Problem CONDITION POSSIBLE CAUSE CORRECTION. Ford& Holley Only. Power valve blown out. Spitback up through carb. Observe the pump jet in the carburetor, and with your hand, work the carburetor throttle to the wide-open position. You should observe a healthy squirt of fuel from the pump jet. A single barrel carburetor will normally squirt a single stream; while a two or four barrel carburetor will normally squirt 2 streams.
Needles and seats may need replacement. See #1 belowXXXCheck for air leaks. Make surecarburetor and manifold gaskets seal properly.
All outlets must beplugged or connected.XXXXXXXXXCheck ignition system. Replace parts asnecessary. Adjust timing to proper specifications.XXXXXXXXCheck choke adjustment.XXXXXXXChange carburetor fuel filter and/orin-line fuel filter.XXXXXToo lean.XXXXCheck float level and drop.XXXXXCheck idle mixture screw adjustment.XXXXToo rich.XXXIncrease accelerator pump stroke.
Pumpsquirter size change may be needed.XXOff-road vehicle may need spring-loadedneedle and seat kit.XXCheck for dirt blocking the low speedcircuit. Clean unit and apply air pressure.
Install in-line fuel filter.XXXXCheck floats for leakage. Replace ifnecessary.XXXXCheck air horn gasket. Replace ifdeterioration or breakage is present.XXXXFuel is boiling due to excessive underhood temperature.
See #2 below.XXXXFuel pressure too low. Check fuelsystem.XXCheck secondary latching device and rodfor proper movement.XLower float level Slightly.X#1 Dirt/metal shavings between the needle and seat or a 'stickingfloat': To correct either of these problems, lightly tap thecarburetor fuel inlet area with the handle of a screwdriver. If floodingcontinues, pinch the fuel line (if possible). Start the engine and let it rununtil it stops.
Release line and restart engine. If flooding persists examinethe needles, seats, float level, and float drop. Adjust or replace parts ifnecessary.#2 Excessive under hood temperature: Ensure fuel line is not locatedtoo close to heat sources such as the exhaust or block, causing expanding fuelto be forced past the needle and seat. Fuel can also boil inside thecarburetor due to missing gaskets, spacers, or heat shields. Also check to seeif the exhaust heat riser is stuck, allowing excessive heat under thecarburetor.#3 Excessive fuel pump pressure: Avoid extremes in fuel pressure. AtIDLE, there should not be any more than 5.0 psi; if the vehicle has anadjustable fuel-pressure regulator, set it to 4.5 psi. With most fuel pumpsthe minimum fuel pressure is encountered at high rpm and WOT.
Fuel pressureshould not drop below 2.0 psi. If it does, a fuel pump with more capacity maybe required.