Fuel Pressure
- Disconnect fuel pump harness connector at fuel tank rear side. Start engine. After engine stops by itself, turn ignition switch to "OFF" position. Disconnect negative battery cable. Reconnect fuel pump harness connector.
- Disconnect high pressure fuel hose at delivery pipe. See Fig 1
. Cover hose connection with rags to avoid spraying of fuel. Using the Fuel Pressure Gauge Adapter (31Y050)
, install the fuel pressure gauge to the delivery pipe. See Fig 1
. Tighten bolt to 18-25 ft. lbs. (25-34 N.m). Reinstall the negative battery cable.
Courtesy of HYUNDAI MOTOR CO.
- Apply battery voltage to fuel pump drive terminal. See Figure
. With fuel pressure applied, ensure no fuel leakage is present from the pressure gauge or connection. Disconnect vacuum hose from fuel pressure regulator and plug the hose end. Start engine, measure and record fuel pressure at idle. Reconnect vacuum hose and again measure and record fuel pressure. For fuel pressure specifications, see FUEL PUMP SPECIFICATIONS table. If measurements are not within specification, go to step 4). If measurements are okay, go to step 7).
FUEL PUMP SPECIFICATIONS
| Application |
Pressure psi (kg/cm2
) |
Volume in One Min. Pints (Liters) |
| Sonata |
| With Vacuum |
39 (2.75) |
|
| Without Vacuum |
46-49 (3.26-3.47) |
|
- If fuel pressure is low, check the following items:
- Restricted fuel filter.
- Fuel leaking to the return side. This can be caused by poor seating of the valve in the fuel pressure regulator.
- Low fuel pump discharge pressure.
- If fuel pressure is too high, check the following items:
- Sticking valve in fuel pressure regulator.
- Restricted or bent fuel return hose or pipe.
- If there is no difference in fuel pressure whether vacuum hose is connected or not, check the following:
- Restricted/damaged vacuum hose or fitting.
- Sticking or poor seating valve in fuel pressure regulator.
- 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.
- After testing is completed, disconnect the high pressure hose and remove the pressure gauge from the delivery pipe. Ensure the hose connection is covered with a shop towel to prevent fuel spray. Install a new "O" ring in groove at end of high pressure hose. Connect high pressure fuel hose to delivery pipe.