When a Poulan chainsaw has fuel and a spark but won’t start, serious engine problems may be to blame. Two-cycle engines operate with three main areas of functionality: spark, fuel and compression. If the spark is being fired at the right time and the proper amount of fuel is reaching the carburettor, that leaves compression as the main culprit. Loss in compression can be caused by worn seals and gaskets on the carburettor or crankshaft, or around the piston and cylinder. These major problems may not be fixable.
- Skill level:
- Moderately Challenging
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Things you need
- Needle-nosed pliers
- Carburettor cleaner
- Compression gauge
Dump out any old or bad gas. Fill the saw with freshly mixed fuel. Make sure fuel is reaching the carburettor. Disconnect the main fuel line from the carburettor with the needle-nosed pliers and hold the engine upside down. A small amount of fuel should dribble out of the carburettor and fuel line.
Replace fuel lines and the fuel filter, or clean your carburettor with carburettor cleaner if fuel isn’t properly reaching your carburettor.
Make sure the spark plug is clean, gapped and firing at the right time. Replace the spark plug if it’s corroded or dirty. Check the ignition wires to make sure they aren’t touching metal on the engine. Make sure the ignition switch isn’t faulty.
Test the engine with the compression gauge. Disconnect the spark plug’s rubber boot and unscrew the spark plug with the socket wrench. Remove it from the engine. Insert the tip of the compression gauge into the spark plug hole.
Pump the compression gauge to required engine pressure. Common Poulan chainsaw models use from 90 to 110 psi in their engine (see model’s service manual for specific pressure). Make sure the pressure doesn’t drop below the required amount during the testing period. If pressure falls, compression is being lost in the engine.
Unhook the air filter cover and cylinder cover from the top of the engine body. Remove the air filter from its mounting post. Unscrew the two retaining screws above and below the air filter’s mounting post. Pull off the choke cover plate and throttle screws.
Unscrew the carburettor from its mounting gasket. Remove it from the engine. Remove the gasket below the carburettor. Inspect the intake manifold on the engine. Replace the gasket. Disassemble, clean and service your carburettor.
Reinstall the parts in reverse order. Test the compression again. If compression is still being lost, you likely have a problem in your bore, piston or cylinder, or the gaskets on both sides of the crankshaft need to be replaced. These repairs should only be made by a qualified professional.
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