Why Does My Chevy Truck Exhaust Smell Like Gas?by David Reber
Gasoline odor in auto exhaust indicates that gasoline vapor is passing through the engine without being burned. This can signal one of three basic problems with the engine's performance: misfire, too rich a fuel mixture or leaking exhaust valves.
If the fuel taken into the engine is not burned, it will pass out through the exhaust, causing a gasoline odor in the exhaust. This may be caused by fouled spark plugs, faulty ignition wires or malfunctioning ignition system components.
Excessively rich fuel mixture.
Proper burning of fuel requires the right proportions of fuel and oxygen. If the vehicle fuel system delivers too much gasoline, there will not be sufficient oxygen in the mix to burn it all. This will cause some unburned fuel to exit through the exhaust system.
Leaking exhaust valves.
All engine valves must create a tight seal for good compression and power from each cylinder. If any exhaust valves are not seating properly, fuel mixture will be forced into the exhaust system during the compression stroke of the piston.
- "Chevy & GMC Shop Manual 1970-1987"; Lahue, K.; 1987
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