A mechanical pump is used on all GLC models, 1983-85 626s, and carbureted 323s. The pump is located on the right side of the engine block on rear wheel drive models and on the left rear side of the cylinder head on most front wheel drive models.
REMOVAL & INSTALLATION
See Figures 1, 2, 3, 4, 5, 6, 7 and 8
Be sure to obtain new fuel pump gaskets before installation.
- Open the hood and disconnect the negative battery cable.
- Mark the fuel inlet, outlet and (if applicable) return lines near the fuel pump connections, to avoid confusion during installation.
- Slide the fuel line clips back off the pump connectors. Then, twist and pull the fuel lines off the pump. Note that the 323 and 626 have inlet and return lines on the top of the pump and an outlet on the side.
- Unfasten the mounting bolts (usually two) from the block or cylinder head, then remove the pump, gaskets, and spacer.
- Position new gaskets with the spacer and fuel pump on the block or cylinder head, then install the mounting bolts.
- Attach the inlet, outlet and (if applicable) return lines to the appropriate connections on the pump and secure them with the line clips.
- Connect the negative battery cable. Start the engine and check for fuel leaks.
- Disconnect the fuel inlet line going to the carburetor. Install a calibrated pressure gauge into the line coming from the pump. Be careful not to spill any fuel, but if you do, remove all spillage before starting the engine.
- Start the engine and run it at idle using the fuel still in the carburetor float bowl. Allow the engine to run until the pressure gauge reaches a maximum reading. Note the pressure reading. Normal specifications are 2.84-3.84 psi (20-26 kPa), except for the 323, whose specifications are 3.98-4.98 psi (27.4-34.3 kPa) for the Sedan or 3.91-4.93 psi (27-34 kPa) for the Wagon.
- Stop the engine. Remove the pressure gauge, reinstall the fuel line into the carburetor, and run the engine until the carburetor float bowl is full of fuel.
- To test the volume of fuel discharged by the pump, the engine must be run at idle for one minute. Position a durable container (preferably metal) with a capacity of at least 1 1 / 2 qts. near the carburetor fuel inlet line. Disconnect the fuel line at the carburetor, and put the open end into the container. Idle the engine until it stops (or for one minute) and time how long it has run. Then, reconnect the fuel line to the carburetor and run the starter or idle the engine until the float bowl is full. Repeat the fuel discharge and timing operation until the engine has run for a total of one full minute at idle speed and all the fuel discharged by the pump has been collected. The pump must discharge at least 1.1 qts. per minute.
- The pump should be replaced if it fails either the pressure or volume test.