Question about 1999 Jeep Grand Cherokee
Engine idle speeds, odd, hot? any real symptoms?
can be lots of things, the FSM covers it.
I think the ratio to real EVAP faILuers TO BAD CAP , IS LIKE 1000000:1 its so bad , new cars put , gas cap failure on dash !! display.
Give that fact, check cap first, and reset the ECU.
the EVAP system can be simple or hard.
Visual check the vacuum lines to all EVAP components
check all fuses.
then make sure gas cap is tight. (if cracked its no good) or a bad seal.
the reset the codes, using any scan tool. ($9 tool)
drive for a week see if it comes back, if comes back then its REAL.
if there is breach in the EVAP or bad VSV, (vacuum sol. valve)
then that takes the testing steps in the FSM.
or the EVAP system needs pressure testing, like they do
in all smog stations , at the cap.
if the leak down test fails, then you simply find that leak.
On can use any rubber tube held to the ear to hear a leak (after using a pressures source to the system.
if you have no tools, take it in. if DIY , buy them.
read the FSM. under this code, and the EVAP sections carefully.
there are 2 paths, it really is failing the EVAP or the OBD2 testing parts
lots of guessing here, no tests...
the EVAP system , keeps gas fumes from polluting the air we breath.
it seals the tank vents and burns off all fumes as you drive.
that is what it does.
and is tested, all the time by the OBD2 system.
its very reliable in finding, any failure.
Your system fails the first step, it checks to see if the system
even holds pressure, and fails. the FSM explains how this
test is conducted, the steps and checks.
my current jeep , the cap ratchet was dead. and would not get fully tight.
or the vacuum breaker inside is bad. (stuck open)
or the sealing ring is bad.
or someone put wrong cap on car.
or a locking cap that is wrong.
the cap holds pressure, and never a vacuum.
the vacuum breaker prevents fuel tank collapes (photos avail)
Posted on Dec 25, 2013
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Posted on Jan 02, 2017
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