Operational Tests
Fig. 3 Diagnostic connectors:
Fig. 5 Control relay connector:
Fig. 6 Airflow meter connector:
Fig. 7 Throttle position switch connector:
Fig. 8 Electronic control unit connector:
Fig. 9a Bosch LU Electronic fuel injection wiring schematic.:
Fig. 9b Bosch LU Electronic fuel injection wiring schematic.:
Fig. 9c Bosch LU Electronic fuel injection wiring schematic.:
Fig. 9d Bosch LU Electronic fuel injection wiring schematic.:
Fig. 10a Bosch LU Electronic fuel injection wiring schematic.:
Fig. 10b Bosch LU Electronic fuel injection wiring schematic.:
Fig. 10c Bosch LU Electronic fuel injection wiring schematic.:
Fig. 10d Bosch LU Electronic fuel injection wiring schematic.:
The wire terminals have been assigned reference numbers to facilitate electrical checking. These reference numbers do not appear on the electrical connectors but are used in combination with the electrical schematic. Refer to Figs. 3 and 5 through 8 for electrical connector reference and Figs. 9 and 10 for electrical schematics.
Fig. 3 Diagnostic connectors:
FUEL SYSTEM TESTS
Fuel Pump Pressure
1. With engine off, disconnect cold start injector input fuel hose or injector ramp assembly and pressure regulator hose, then using ``T'' connector, connect pressure gauge.
2. Connect jumper wire between terminals D1-5 and D1-6, Fig. 3.
3. If pressure is not approximately 70 psi, check fuel pump, electrical circuit, and fuel filter and repair or replace as necessary.
Pressure Regulator Operation
1. Using a vacuum pump with engine off, apply 16 in. Hg to pressure regulator.
2. Connect jumper wire between terminals D1-5 and D1-6, Fig. 3.
3. If pressure is not between 17 and 23 psi on Alliance and Encore models, or 27 and 33 psi on Fuego and Sportwagon models, replace pressure regulator.
Injectors For Leakage
Note: The following test is to be performed on Alliance and Encore models only.
1. With engine off, disconnect injector wire connectors.
2. Remove injector ramp assembly with injectors and cold start injector.
3. Connect a jumper wire between terminals D1-5 and D1-6, Fig. 3.
4. If injectors leak, replace them.
Injector Operation
Note: The following test is to be performed on Alliance and Encore models only.
1. With engine off, position injector ramp assembly so that each injector in turn may be placed in a suitable container.
2. Connect a jumper wire between terminals D1-5 and D1-6, Fig. 3.
3. Apply 12 volts and ground to each injector for short period of time.
4. Each injector should atomize when energized and output should stop when voltage is removed. If not, replace injectors.
Fuel Pump Output
1. Disconnect fuel tank return hose from pressure regulator and place it in suitable graduated container.
2. Connect jumper wire between terminals D1-5 and D1-6, Fig. 3.
3. After 1 minute, there should be a minimum of approximately 1 quart in container. If not, check fuel pump, pressure regulator, fuel filter, and electrical circuit and repair or replace as necessary.
Fig. 3 Diagnostic connectors:
Fig. 9a Bosch LU Electronic fuel injection wiring schematic.:
Fig. 9b Bosch LU Electronic fuel injection wiring schematic.:
Fig. 9c Bosch LU Electronic fuel injection wiring schematic.:
Fig. 9d Bosch LU Electronic fuel injection wiring schematic.:
Fig. 10a Bosch LU Electronic fuel injection wiring schematic.:
Fig. 10b Bosch LU Electronic fuel injection wiring schematic.:
Fig. 10c Bosch LU Electronic fuel injection wiring schematic.:
Fig. 10d Bosch LU Electronic fuel injection wiring schematic.:
SYSTEM OPERATIONAL TEST
Voltage and resistance values given are nominal and actual value may vary slightly from unit to unit.
1. Ensure that ignition is on, engine is off, and coolant temperature is less than 77°F.
2. Check control relay and ECU grounds by connecting ohmmeter probes between terminals D1-3 and D2-7, Fig. 3. Ohmmeter should read zero ohms.
3. Check battery voltage by connecting voltmeter positive probe to terminal D1-5 and negative probe to terminal D1-3, Fig. 3. There should be approximately 12 volts.
4. Check ignition voltage by connecting voltmeter positive probe to terminal D1-2 and negative probe to terminal D1-3, Fig. 3. There should be approximately 12 volts.
5. Check coolant temperature sensor by connecting ohmmeter probes between terminals D2-12 and D2-7, Fig. 3. With Electronic Control Unit (ECU) disconnected, there should be 2.5k ohms at 68 degrees F or 320 ohms at 176 degrees F. With ECU connected, there should be 1.5k ohms at 68 degrees F.
6. With ECU connected, check injectors by connecting ohmmeter test probes across pins A and B of injector wire harness connector, Figs. 9 and 10.There should be a resistance value of 4 ohms.
7. Check fuel pump by applying 12 volts with jumper wire between terminals D1-5 and D1-6, Fig. 3. Noise should be heard from fuel pump.
8. Check throttle position switch as follows:
a. Connect ohmmeter test probes between terminals D2-13 and D2-6, Fig. 3. There should be infinite ohms.
b. Connect ohmmeter test probes between terminals D2-4 and D2-13 with throttle at idle position. There should be zero ohms.
c. Connect ohmmeter test probes between terminals D2-4 and D2-6 with throttle wide open. There should be zero ohms.
9. Check thermo-time coolant switch by connecting voltmeter positive probe to terminal D2-9 and negative probe to terminal D2-7, Fig. 3. Operate starter motor. There should be 8 to 12 volts present, then drop to 0 volts after a few seconds, depending on temperature.
10. With engine temperature below 77 degrees F, check starting voltage by connecting voltmeter positive probe to terminal D1-4 and negative probe to D1-3, then operate starter, Fig. 3. There should be 8 to 12 volts present.
11. With engine temperature below 77 degrees F, check tach voltage by connecting voltmeter positive probe to terminal D1-1 and negative probe to D1-3, then operate starter, Fig. 3. There should be oscillating voltage available.
12. With coolant temperature below 77°F, and oxygen sensor temperature below 480°F, start engine. Check integrator voltage by connecting voltmeter positive probe to terminal D2-2 and negative probe to D2-7, Fig. 3. There should be approximately 6.8 volts. Note reading.
13. With engine running at 750 to 850 RPM, wait until coolant temperature exceeds 104°F and oxygen sensor temperature exceeds 480°F. Check integrator voltage by connecting voltmeter positive probe to terminal D2-2 and negative probe to terminal D2-7, Fig. 3. Voltage should vary ± .5 volts with that noted in step 12.
14. Increase engine speed to 3500 RPM and rapidly close throttle plate. Check fuel cut-off during deceleration by connecting voltmeter positive probe to terminal D2-2 and negative probe to terminal D2-7, Fig. 3. Voltage should be the same as that noted in step 12.
FEEDBACK FUNCTION DIAGNOSIS
1. If, with conditions described in step 12 of previous test, voltage was 12 volts, check for short circuit in sensor or check for air leak and repair or replace as necessary.
2. If voltage was zero volts, check temperature sensor and airflow meter and replace as necessary.
3. If, when conditions are as described in step 13 of previous test, voltmeter does not move from position achieved when conditions were as described in step 12, check that oxygen sensor is securely connected. If so, check for break in wiring.