900 L4-1985cc 2.0L SOHC Turbo VIN S FI (1984)
Evaporative Emissions System: Technical Service Bulletins
Evaporative System - Leak/Pressure Testing
June 1980
Issue: 6
Volume: 1
REMINDER OF THE MONTH
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A pressure test per S.I. 01/79-343 (see page 84 of Section 2 of the Saab S.I. Supplement No. 1) is the only sure way to pinpoint evaporative loss
system leaks. The bayonet-type filler cap on late model 900's is not as easily modified into an adapter tool for pressure testing as the earlier
threaded cap. Instead, it is easier to disconnect the smaller tank vent hose at the tank and insert a short hose and tee-fitting to which you can
connect the cooling system test pump. As described in the S.I., do not use high pressure (3-6 psi is enough for a leakage test, vent line removed
and plugged at canister). Locate leaks with a stethoscope or CO meter.
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In the rare case that a tank sucks in on a long drive or spits back when the filler cap is released after a short drive, suspect a crimp or blackage in
the vent line between the canister inlet (check the inlet too) and filler housing. NOTE: From M80 the canister has a purge valve at the outlet.
Basically, this is a non-return valve that opens at the slightest engine vacuum. This valve cannot block the system or cause too high pressure (the
canister is open at the bottom to draw in fresh air).
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New car won't start? If the cold start injector isn't operating during cranking, check that the harness connector plug at the thermo-time switch is
not wired backwards. If it is, reverse the green and yellow wires.
