Jim Grant's Tech Tips
'98 Chevy S-10 Blazer, Gas Tank Pop
Q:
I
have a '98 Chevy S-10 Blazer, 4WD. My gas tank has started to "POP".
This is a loud pop that can be heard for half a block. It happens each
time I use the car. Usually when I first turn the motor off. What would
cause this and what should I do?
- Leroy G.
A:
The next time you turn
your vehicle off try loosening the gas cap. Why? If your gas tank is making
a popping noise it may be under pressure. Pressure can come in two forms:
high pressure and low pressure. The low pressure is commonly called vacuum.
Either form of pressure can be occurring and causing unnatural movement
of the gas tank.. It is common for fuel vapor pressure to build in a gas
tank as the vehicle is driven. This vapor pressure is suppose to be controlled/released.
There is an on-board storage device called a charcoal canister and the
engine's emissions controls allow these gas vapors to be pulled in and
burned by the engine. In '95 the manufacturers started to phase in control
systems that would monitor gas tank pressures. The first phase started
with passenger cars. As many of you know a loose gas cap will turn the
check engine light on. This phase in continued with light trucks and SUV's.
Your vehicle may not have the ability to monitor gas tank pressure and
would not turn on a check engine light if there was a problem. If loosening
the gas cap stops the pop then there is a pressure control problem.
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