The Walbro 255lph fuel pump is a must for any heavily modified and/or swapped 240sx. They are inexpensive, reliable and flow more than enough fuel to satisfy the thirsts of even heavily boosted motors.
Note: These procedures should be performed in a well ventilated area away from open ignition sources. (i.e. gas fumes are harmful to breath and they can ignite)
Depressurize the factory pump
First things first, the fuel system needs to be depressurized. With the car parked on level ground, the transmission in neutral and the parking brake engaged, open up the hood and locate the EGI Pump fuse in the fuse box near the battery. Remove this fuse and start the car. The car will idle for a short period and then will die. The fuel system is now depressurized and the fuse should be reinstalled. Now, disconnect the ground (black (-)) cable from battery and proceed to the rear of the car.
Remove the stock fuel pump
With the trunk open, remove the trunk liner until the two metal plates are visible. Using a philip’s head screwdriver, remove the two screws on the smaller plate and unplug the fuel pump from the wiring harness. Next, use a 10mm wrench to remove the 4 bolts that hold the larger plate to the trunk floor. Once removed the top of the fuel tank will be visible.
Remove the right (smaller) plate to unplug the fuel pump from the harness. Remove the left (larger) plate to gain access to the fuel tank.
Once the main lid is removed, the top of the fuel tank is easily accessible. Note the 2 fuel lines.
Now slide the two fuel lines off. (pictured above) Keep some shop towels ready in case there is still some residual pressure in the fuel system. Remove the 6 bolts from the top of the fuel pump assembly (a.k.a. the lid) and slowly snake the fuel pump assembly out of the fuel tank. Cover the exposed hole with a shop towel to prevent debris from entering the fuel tank.
Once the fuel pump is removed from the 240sx, the fuel in the tank is exposed. Cover this area up with a shop towel to avoid getting debris in the tank.
Compared to the Walbro taking its place, the stock fuel pump in a 240sx is actually quite large.
Disassemble the factory pump
First, the factory pump needs to be removed from the fuel pump assembly. Simply remove the clamps from the fuel line at the top of the pump and then twist the pump housing about 1/4 turn and the fuel pump will slide out of the bracket. Now cut the red and the black wire about 1 and 1/2 inches from the top of the lid. The factory pump is now removed.
Assemble the Walbro pump
The Walbro pump installs in the same exact manner as the factory pump. First, install the filter onto the bottom of the Walbro and use the small metal lock ring to secure the filter. Next, Install the rubber grommet onto the bottom of the new pump. The grommet is notched and is made to sandwich itself between the lower bracket of the fuel pump assembly and the fuel pump. Now slide the new fuel line onto the Walbro pump and slide the other end of the line up and onto the the lid. (This is the same location the factory unit attached to.) Before tightening the clamps on the short fuel line, ensure that the fuel pump is sitting snugly against the lower bracket with the rubber grommet’s lip contacting the lower bracket. Now, use the plug in harness that came with the new pump and splice the red and black wires on the harness to the red and black wires previously exposed from the bottom of the lid. Use the butt splice connectors that came with the new pump, connecting red to red and black to black. If the wires on the new harness are too long, cut them to the appropriate length.
The Walbro pump assembled and ready for install into the 240sx.
Install the new pump
Snake the newly assembled pump back into the fuel tank, taking care not to damage the fuel level float. Tighten the lid using the 6 bolts previously removed. Insert the two fuel lines back onto their respective nipples and clamp them back down. Before reinstalling the metal cover, it is recommended to plug the fuel pump back into the harness, reconnected the battery ground and then start the car. Once the car is started, walk to the back of the car and give the two fuel lines a visually inspection to ensure that fuel is not leaking near the clamps. If a leak is found due to bad clamps, replace them. Once satisfied that no leaks are present, reinstall the large cover and the plug cover and you are done.
Additional notes: I would like to take a minute and mention one problem that can arise when installing a high volume fuel pump such as the Walbro into a 240sx. Although not always the case, this fuel pump on some older cars will overrun the factory fuel pressure regulator and over-pressurize the fuel rail. This results in the injectors dumping more fuel into the cylinders, causing an overly rich condition. To remedy this, an adjustable fuel pressure regulator will need to be installed in place of the factory unit in order to dial the fpr down. As such, I will write a tutorial on installing a Nismo FPR onto the CA18DET soon.