Impco HHI, Service Manual

Page: 465 / 485

465
Contamination of the HEGO sensor can re-
sult from the use of an inappropriate RTV
sealer or silicone spray products. Do not
use silicone sprays or hoses which are as-
sembled using silicone lubricants. Always
use “oxygen sensor safe” RTV sealant for
repair procedures. Silicon contamination
will cause a high but false HEGO signal vol-
tage (rich exhaust indication). The ECM will
then reduce the amount of fuel delivery to
the engine, causing a severe driveability
problem. If silicone contamination is sus-
pected, remove and visually inspect the
sensor element. If contaminated, the portion
of the sensor exposed to the exhaust
stream will have a white powdery coating.
Always be sure to eliminate the cause of
contamination before replacing the sensor.
3. Reinstall Port Fittings on both ends of the hose
and secure with retaining pins. Make sure
hose is correctly positioned and not twisted or
kinked.
4. Reconnect negative battery cable.
5. Open valve on the LPG tank.
6. Turn Key to the ON position for several
seconds, then turn back to OFF. Using a liquid
or electronic leak detection tool, inspect the
EPR, fuel hoses and all serviced fittings for
leaks.
7. Start the vehicle and check for leaks. Let run
until it reaches normal operating temperature.
8. If a DTC code is found, refer to the Electrical
Section for further diagnosis.
XIII. LPG FUEL SYSTEM PRESSURE CHECK
1. Turn ignition to OFF.
2. Disconnect negative battery cable.
3. Remove plug on EPR listed as “PRIMARY
PRESSURE TEST.”
4. Install Pressure Gauge.
5. Reconnect negative battery cable.
6. Start engine and note value on gauge.
7. Turn engine OFF.
8. Relieve the LPG fuel system pressure. Refer to
III. LPG Fuel System Pressure Relief.
9. Disconnect negative battery cable.
10. Remove Gauge.
11. Replace Plug.
12. Reconnect negative battery cable.
13. Turn ignition to ON for approximately 30
seconds, then OFF.
14. Check for leaks.
XIV. GASOLINE FUEL PRESSURE CHECK
ITK-3 or ITK-4 test kit gauge or J 34730-1A fuel
pressure gauge or equivalent.
Fuel Pressure Gauge
1. Turn ignition to OFF.
2. Disconnect the negative battery cable.
3. Refer to the
Fuel Injection Pressure Tester
Owner’s Manual supplied in the IMPCO Test Kit
for instructions on relieving gasoline fuel pres-
sure for fuel systems without a Schrader valve or
test port.
Systems without test ports require that fuel
lines be removed or disconnected. Be aware
that these lines may be UNDER PRESSURE and
when remove could cause fuel to spray and/or
leakage onto hot engine parts.