Walbro 340M fuel pump Installation

This install was completed on a 1998 Grand Prix GTP and will be exact on all 98-2001 Grand Prix GTP's. This method should be similar on all other W-body vehicles.

Step 1: Disconnect the vehicle's battery. Remove your spare tire, jack, and pull back or remove the carpeting in your trunk. You will see a plate at the front of the trunk right behind the rear seat.

Step 2: Remove the seven 10mm nuts on the plate and gently use a flat-blade screwdriver to pry the plate up.

Step 3: Remove the two electrical weatherpack connectors and the three fuel line connections. Remove the two outside fuel lines by squeezing the clear plastic retaining clips together and pulling outward. The middle fuel line is removed by applying a gentile squeeze to the black ring and pulling outward. Remove the retaining c-clip around the pump assembly.

Step 4: Remove the in-tank assembly by pulling up and sliding the whole assembly up and out of the tank. Be careful as you remove the assembly because you will have to maneuver the end of the assembly to the side to remove it due to the tank level sender and fuel sock. DO NOT FORCE THE ASSEMBLY OUT. Rotate it and tilt it to the side until the assembly slides out.

Step 5: Slide the large blue seal ring back into its position at the top of the assembly if it was moved during removal.

Step 6: Remove the red retaining clip and weatherpack connector on the underside of the assembly, the weatherpack connector on the top of the pump, and the small black fuel return hose from the pump. Push in the two clip-style latches on each side of the assembly and separate the two halves of the assembly.

Step 7: Pull off the sock from the bottom of the pump; you will not be using a sock on the new walbro. Not the sock on the lower assembly but sock on the pump itself, and slide the pump out of the upper assembly. Remove the translucent ribbed fuel hose from the top of the pump. You will most likely need to exert great force onto the hose to remove it from the pump so be VERY careful not to damage the hose. If the black rubber sheath came out with the pump remove it from the pump also.

Step 8: Remove the brass return fitting from the top of the stock pump. You will have to pry and use great force to remove the brass fitting but be careful not to ruin it. Set this aside for later use.

Step 9: Clip the black and gray wires on the stock pump wiring harness as close the pump-side weatherpack connector as possible. Strip 1/4" of the jacket off of the wires and using the supplied connectors crimp the red wire on the new harness to the gray wire on the stock harness and the black wires together.

Step 10: If the black rubber pump sleeve came out of the upper assembly attached to the pump; then remove the pump from the sleeve and place the sleeve back into the upper assembly. Note the ring on the outside of the sleeve. This ring should just be visible on the bottom of the upper assembly.

Step 11: Set the brass return fitting into the smaller return hole on the top of the walbro. It will not be an exact fit but it should just sit inside the hole.

Step 12: Generously lube the Walbro with petroleum jelly and slide it halfway inside the rubber sleeve in the upper assembly.

Step 13: Slide the upper assembly back into the lower assembly but do not allow the two side latches to engage and secure the two together.

Step 14: Attach the stock ribbed fuel line to the outlet on top of the walbro by sliding it onto the outlet. Slide the back return line back onto the brass fitting. Using the supplied hose clamps use one on the outlet of the walbro to clamp and secure the fuel line. Arrange the clamp in such a way that it also will place some leverage on the brass fitting to hold it in place. The fitting does not need to be clamped or held down hard to secure it in place. You only want leverage on it so it does not pop out of the return hole. You may also choose to use the other clamp for security of the lines as in the pictures.

Step 15: Slide the Walbro all the way into the sleeve until it bottoms out. You should be able to see the inlet of the Walbro protruding from the bottom of the rubber sleeve if you pull the upper and lower assemblies apart.

Step 16: Re-attach all wiring harnesses and slide the upper and lower assembly together and allow the two side latches to secure together.

Step 17: Lube the blue o-ring with petroleum jelly and carefully maneuver the assembly back into the fuel tank and push it in place. Re-install the retaining c-clip and reattach the three fuel lines by sliding them into the outlets of the assembly until they click into place. Reattach the two weatherpack connectors, cover plate, and seven 10mm nuts.

Step 18: Prime the fuel system with the key in the on position for a few seconds and then start the car.

If you need assistance or have any questions about the Walbro 340M fuel pump Installation please email Sales@INTENSE-Racing.com






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