Engine Controls - Basic Testing: Diagnosis Hyundai Sonata III

VISUAL INSPECTION

Visually inspect all electrical wiring, looking for chafed, stretched, cut or pinched wiring. Ensure electrical connectors fit tightly and are not corroded. Ensure vacuum hoses are properly routed and are not pinched or cut. See L - VACUUM DIAGRAMS article to verify routing and connections (if necessary). Inspect air induction system for possible vacuum leaks.

FUEL PUMP TEST

Turn ignition off. Apply battery voltage to fuel pump drive terminal (Black/White wire on Sonata). (Scheme 1)and (Scheme 2). Remove fuel tank cap and listen for fuel pump operation. Pinch fuel hoses by hand and ensure fuel pressure can be felt.

Scheme 1

Scheme 2

Scheme 3

1. Release fuel pressure. See «FUEL PRESSURE RELEASE»(ref-16486-S41307552982000122900000). Disconnect high pressure fuel hose from top of fuel filter. Cover hose connection using rags to avoid spraying of fuel.
2. Using Fuel Pressure Gauge Adapter (09353-24200 ), install fuel pressure gauge to fuel filter. (Scheme 3) Tighten bolt to 18-25 ft. lbs. (25-34 N.m). Reinstall negative battery cable.
3. Start engine. Ensure no fuel leakage exists at pressure gauge or connection. Disconnect vacuum hose from fuel pressure regulator, and plug hose end.
4. Measure and record fuel pressure at idle. Reconnect vacuum hose, and again measure and record fuel pressure. See «FUEL PUMP SPECIFICATIONS»(ref-16486-S24715862122000122900000) table. If measurements are not within specification, go to next step. If measurements are okay, go to step 8). FUEL PUMP SPECIFICATIONS Engine Application Pressure psi (kg/cm 2 ) Volume In One Min. Pts. (L) With Vacuum 39 (2.8) (1) Without Vacuum 46-49 (3.3-3.5) (1) (1) Information is not available from manufacturer.
5. If fuel pressure is low, check for: Restricted fuel filter. Fuel leaking to return side. This can be caused by poor seating of valve in fuel pressure regulator. Low fuel pump discharge pressure.
6. If fuel pressure is too high, check for: Sticking valve in fuel pressure regulator. Restricted or bent fuel return hose or pipe.
7. If fuel pressure does not differ when regulator vacuum hose is connected or disconnected, check for: Restricted/damaged vacuum hose or fitting. Sticking or poor seating valve in fuel pressure regulator.
8. If measurements are okay in step 4), stop engine and ensure fuel pressure gauge reading does not drop. If fuel pressure drops slowly after engine is stopped, an injector is leaking. If fuel pressure drops immediately after engine is stopped, check valve inside fuel pump is not closed.
9. After testing is completed, release fuel pressure. See «FUEL PRESSURE RELEASE»(ref-16486-S41307552982000122900000). Disconnect fuel pressure gauge from adapter bolt. Ensure hose connection is covered by a shop towel to prevent fuel spray. Remove adapter bolt, install new "O" ring, and replace with original bolt. Apply battery voltage to fuel pump drive terminal. (Scheme 1)and (Scheme 2). Check for leaks.

MFI CONTROL RELAY TEST

1. Remove control relay. On Elantra, relay is located behind left side of driver's dashboard below instrument panel. On Sonata, relay is located under right side of dashboard, near blower motor housing.
2. On all models, apply battery voltage across terminals No. 6 (positive) and No. 8 (negative) while checking voltage on terminals No. 1 and 2. (Scheme 4) Battery voltage should exist. Apply battery voltage across terminals No. 7 (positive) and No. 10 (negative) while checking continuity between terminals No. 3 and 4. Continuity should exist.
3. Apply battery voltage across terminals No. 3 (positive) and No. 9 (negative) while checking voltage at terminal No. 4. Battery voltage should exist. Replace relay if it fails any test.

Scheme 4