GM 19369903 MODULE KIT,F/TNK F/PMP

To check the fuel pump output and pressure, first ensure that there is enough fuel in the tank and relieve the fuel pressure. Then, install a fuel pressure gauge onto the fuel lines or fuel rail using the appropriate adapter fitting. With the ignition switch on but the engine not running, observe the fuel pump running for about two seconds and note the reading on the gauge. After the pump stops running, the pressure should remain steady within the specified range. If the pump does not turn on, check the fuel pump's electrical circuits. Start the engine and let it idle at normal operating temperature, and the pressure should be slightly lower. If all pressure readings are within specifications, the system is functioning properly. If the pressure did not drop after starting the engine, apply vacuum to the pressure regulator. If the pressure drops, repair the vacuum source; if not, replace the regulator. If the fuel pressure is not within specifications, check for vacuum to the pressure regulator and for a pinched or clogged fuel return hose or line. If these are okay, replace the pressure regulator. If the pressure is still low with the fuel return line restricted, the fuel pump may be faulty. After testing, relieve the fuel pressure and remove the gauge. For the fuel pump electrical circuit check, listen for a whirring sound at the fuel filler neck opening when the ignition key is turned on. If no sound is heard, check the fuel pump fuse. If the fuse is okay, remove the fuel pump relay and check for battery voltage to the relay connector with the ignition key off and on. If there is no voltage, check the fuel pump fuse and wiring circuit. If voltage is present, check the relay and then check for battery voltage at the fuel pump connector. If there is no voltage, check for an open circuit between the fuel pump and the relay. If there is power at the fuel pump connector and the pump still does not work, try bypassing the fuel pump circuit and powering it up with battery voltage. Additionally, check the oil pressure and oil pressure switch if the fuel pump fails to operate.

To check the fuel level sending unit, start by removing it and using an ohmmeter to measure the resistance as the float moves from empty to full. Look for a smooth change in resistance. If there is no resistance or very little change, the sending unit needs to be replaced. To remove the sending unit, first relieve the fuel pressure and disconnect the battery cable. Then, remove the fuel tank and the necessary components in the trunk. Disconnect the electrical connectors and quick-connect fittings for the fuel tank pressure sensor and fuel pump/fuel level sending unit. Use a brass punch or water pump pliers to turn the lock ring counterclockwise and remove the fuel pump/fuel level sending unit module from the tank. Inspect the condition of the o-ring and replace if necessary. If replacing the sending unit, separate it from the fuel pump assembly. Installation is the reverse of removal.

On a Cadillac Seville, first check that the fuel tank has enough fuel. Then let out the current fuel pressure before you can measure the pump's output. Hook a fuel pressure gauge to either the fuel line or fuel rail, only using one that has a bleeder valve and works with the fitting type needed for the vehicle. Turn the ignition key to "ON" without starting the engine. Watch how long it takes the fuel pump to run, and make sure the gauge's readings stay within the correct specifications. While running the engine, the fuel pressure should go down by 3 to 10 psi. Also add vacuum to the pressure regulator, check that it works correctly. If you see higher than allowed pressure, make sure the regulator gets vacuum, then look for restricted flow in the return line. Replace the fuel filter if low pressure readings appear. Then test multiple fuel system components with a special valve. After the tests, reduce the fuel pressure and disconnect the gauge. Have the person in charge turn the ignition to ON, and check if you can hear the fuel pump wind up its noises from under the hood when someone else loosens the fuel cap and sits nearby to listen. Under the passenger seat cushion of 1999 and later models, you'll find the fuel pump fuse that needs checking before you can continue. First check the fuel pump fuse is good; if it is, disconnect the relay and measure battery voltage at its connector under both OFF and ON ignition key positions. When the pump isn't working, ensure the fuel pump has battery power at its connector. If the battery current isn't there, look for problems in the electrical circuit between the battery and pump. When the pump isn't working with power, join the pump directly to the circuit to see if it runs. Finally, test your oil pressure switch when the fuel pump won't run, after making sure all electrical circuits are working well.

Start by disconnecting the fuel level sending unit electrical connector from the module cover.