Engine Controls - System/component Tests: Diagnosis Chevrolet Sportvan G20

A/C ON SWITCH SYSTEM TEST

1. Turn ignition switch to RUN position. Move mode selector switch to OFF position. With A/C control assembly connector connected, measure voltage between mode selector switch Dark Green wire and ground. For wiring schematics, see mini-schematics in A/C CLUTCH under «MISCELLANEOUS ECM CONTROLS»(ref-10153-S04789922632001010200000) in this article.
2. Battery voltage should be present. If battery voltage is present, mode selector switch is operating normally. If battery voltage is not present, check Dark Green wire from selector switch to fuse for an open circuit.
3. Check voltage between mode selector Dark Green wire and ground. Voltage should not be present. If voltage was present, replace mode selector switch.

PRELIMINARY GLOW PLUG DIAGNOSIS

1. If system does not operate as described in «NORMAL GLOW PLUG CIRCUIT OPERATION»(ref-10153-S29201984562001010200000) , ensure glow plug system is correctly installed. Check that all connectors are properly attached, clean and tight. Inspect engine harness ground connection. Ensure nut securing 4-wire connector at controller is tightened to 96 INCH lbs. (11 N.m), with connector fully seated and latched.
2. Ensure controller copper stud upper nuts are tightened to 96 INCH lbs (11 N.m). Do not tighten lower nuts. Ensure temperature switch connector in water crossover near front of engine is tightened to 48 INCH lbs. (5.4 N.m). Inspect WAIT lamp on instrument panel for tight connection and operation.

INJECTION PUMP HOUSING LEAKAGE TEST

1. Remove injection pump and drain all fuel. Connect an air supply line to fuel inlet fitting. Ensure air supply is clean and dry. Seal off return line fitting. Completely immerse pump assembly in a container of clean test oil.
2. Apply 20 psi (1.4 kg/cm 2 ) to pump. Leave pump immersed for 10 minutes to allow trapped air to escape. Watch for leaks after 10 minutes. If no leaks are observed after 10 minutes, reduce air pressure to 2 psi (.14 kg/cm 2 ) for 30 seconds.
3. If there are still no leaks, increase pressure to 20 psi (1.4 kg/cm 2 ) again. If no leaks are observed, pump is ready for use. If leaks are noticed, pump must be replaced.

TEST PREPARATION

1. Remove injector nozzles from engine. Clean carbon from tip area of nozzle with soft brass wire brush. DO NOT use steel brush or motorized brush to clean nozzle tip. Damage to nozzle tip may result. CAUTION: Use Nozzle Socket (J 36142) to remove and replace injection nozzle. Attach socket to 30mm hex portion of nozzle. Failure to do so will result in damage to the injector nozzle.
2. Connect injector nozzle to injection nozzle tester. Place clear plastic tubing on both fuel return fittings to prevent bleed-off from being confused with leaks. Close tester shutoff valve to pressure gauge.
3. Fill tester with test fluid. Fill and flush nozzle assembly with test fluid by operating tester lever briskly and repeatedly. This purges air from injector nozzle and coats all parts with test fluid.

OPENING PRESSURE TEST

1. Open tester shutoff valve 1/4 turn from closed position. Slowly depress tester lever and observe gauge. Note pressure at which needle of pressure gauge stops. Some injector nozzles may pop while other injector nozzles may drip (this is not a leak).
2. Injector opening pressure should not fall to less than the lowest limit of 1500 psi (105 kg/cm 2 ). Replace any injector nozzle which does not meet lowest acceptable pressure. Release tester pressure.

LEAKAGE TEST

1. Open tester shutoff valve 3/4 to 1 3/4 turns from a closed position. Blow dry injector nozzle tip. Slowly depress tester lever until pressure gauge reads 1400 psi (98 kg/cm 2 ). Maintain pressure for 10 seconds and observe injector nozzle tip.
2. A drop may form on end of injector nozzle, but should not drop off within a 10 second period. Replace injector nozzle if drop of test fluid drops from tip during the 10 second period. (Scheme 84) Release tester pressure.

Scheme 84

CHATTER TEST

Chatter for new and used injector nozzles may vary. With some used injector nozzles, chatter is difficult to detect during slow actuation of tester lever. Some injector nozzles may chatter louder than others. As long as there is chatter, the injector nozzle is acceptable.

1) Close tester shutoff lever at pressure gauge. Slowly depress lever and note whether chatter can be heard. If no chatter is heard, increase speed of lever movement until it reaches a point where injector nozzle chatters.

2) At fast lever movement, injector nozzle may emit a "hissing" or "squealing" sound rather than normal chatter. This is acceptable. These sounds indicate that injector nozzle needle moves freely and injector nozzle seat, guide and pintle have no mechanical defects. Replace any injector nozzle assembly which does not chatter.

SPRAY PATTERN TEST

The injector nozzles used with this system have several features which make pattern testing difficult. These features include longer nozzle overlap, greater pintle to body clearances, and an internal wave washer between injector nozzle nut and injector. Typical injector nozzle tester cannot deliver fuel with sufficient velocity to obtain proper spray patterns. DO NOT replace injector nozzle(s) based on spray pattern.

SYSTEM TEST

Start and run engine to normal operating temperature. With engine at idle, RPM should drop as EGR valve is opened by pushing up on underside of EGR diaphragm.