As with the T5 swap, I'm no pioneer when it comes to installing an aftermarket fuel pump. I'm just offering some directions and guidance for people who are interested in doing the installation. In this article, I will only cover the swap into a 700-series Volvo, since the swap into the 200-series has some differences and I have no experience in that regard. I am not a mechanic, and I disclaim any liability for anything you do to your car.
The 700-series uses two fuel pumps. The first is the main pump, which sits in a cradle underneath the car, alongside the fuel filter. This pump does most of the work in supplying the fuel to the engine. In addition, there is an in-tank pre-pump. This pump, located inside the fuel tank, lessens the burden on the main pump by doing part of the work. If your in-tank pump fails, the main pump has to work much harder. You may experience some symptoms of fuel starvation. If either pump fails, they are expensive to replace. However, the Walbro high-pressure 255lph pump is around $100-$120. It provides enough fuel to replace both the in-tank pump AND the main pump. If either of your pumps has died, it's cheaper, and perhaps smarter to use a Walbro as a replacement. I've included the separate steps for removing the main pump after the Walbro installation instructions. You may or may not need to remove the main pump. I experienced problems when I left mine in place, though. First, the fuel hose before the main pump burst, which was probably due to the higher pressure from the Walbro pump. This indicates that you may want to replace any worn fuel line at the same time as the Walbro installation. I also removed the main pump and left only the fuel filter in the cradle. Again, the Walbro can be used as a single pump, and is being used in that manner by a number of folks in the Volvo community without any problems, including myself.
The Walbro is a high-pressure, high-flow aftermarket pump used by many people in motorsports. The particular model we want is the Walbro GSS340. I purchased mine from a website that advertised it as a replacement pump for Mustangs. The pump came with an "installation kit". Much of this kit is useless, as the parts are designed for the Mustang replacement procedure. However, it is necessary to at least get the pump itself, the wiring harness, the filter sock and the crimp connectors. You could probably make do with your own crimp connectors and wiring, but the stock Volvo sock filter does NOT fit the Walbro pump.
These are the things you'll need for the ideal installation.
Please buy a Haynes manual. If you have one, you should be able to figure this whole swap out for yourself. Still, it helps to have one even if you're following my directions. It has nice pictures. You can also look at the tips in the 700-series FAQ at the Brickboard. I'm going to assume that you have all the tools you need. We're just talking about some screwdrivers, a wire stripper/crimper, etc.
1. Starve the fuel pumps of fuel to relieve fuel system pressure. In the 700-series, remove fuse 11 for the in-tank pre-pump and fuse 1 for the main pump. Crank the engine a few times. Now pop the hood and disconnect the battery. Sparks will kill you when you're working in the gas tank. Avoid them at all costs.
2. My life was easier because there is no carpet in my trunk. If your carpet is still there, peel it back from the left back corner of your trunk. Find the cover plate and remove the four bolts holding it in place. Remove it from the car.
3. You should now be able to see the top of the pump/sender assembly sticking out of the gas tank. Trace the wiring harness inside the trunk and disconnect it. Remove the ground screw as well. Feed the wiring harness through the hole and into the same area as the pump/sender assembly.
4. There are four hoses going to the top of the assembly. Have some rags ready to catch spilling fuel. I also had a roll of duct tape to use for sealing hose ends temporarily. Unscrew the hose clamps. Remove all four hoses.
5. Unscrew the retaining ring that holds the pump/sender assembly in place. If it is stuck, use a piece of wood and hammer to carefully get it started with some light taps. Remove the ring and give it a good cleaning.
6. An old toothbrush works well for removing some of the dirt from the pump/sender assembly top plate. Don't get dirt in your gas tank!
7. Pull the pump/sender assembly out of the gas tank. You will need to rotate the assembly as you go. Be gentle. I covered the open tank with a "cap" of duct tape.
8. Remove the entire assembly from the car and set it on your work bench. The pump is the piece with two wires running to it: one black and one red. The black ground wire is screwed to the sender portion of the assembly. The red power wire goes through the cover plate.
9. Remove the old filter sock. Remove the pump from the holder.
10. The Walbro pump does not fit in the holder. Remove the holder, leaving the one metal strap that is attached to the sender assembly. You will attach the Walbro pump to this strap with two hose clamps.
11. Attach the wiring harness to the new pump. Crimp a connector for the ground wire onto the harness.
12. Unscrew the old ground wire from the sender assembly clamp. Attach the new ground wire.
13. Cut the old power wire. Using a butt connector, attach the old power wire to the new wiring harness.
14. Attach the new pump to the hanging metal strap with two large hose clamps.
15. Use a wire tie to bundle the wires to the sender assembly.
16. Remove the old o-ring from the pump/sender assembly. Install the new ring.
17. Install the sock filter on the new pump, as firmly as possible.
18. It's now time to reinstall the entire assembly. The Brickboard, again, as good instructions for this procedure. Some rotation of the assembly is necessary to get the pump into the proper position inside the tank. Use a flashlight (not your Zippo!) to look inside the tank before you reinstall.
19. A little Vaseline is a very helpful aid to getting the assembly and o-ring properly seated in the tank.
20. Reinstall the retaining ring. Torque down by hand.
21. Reconnect your wiring inside the trunk, and don't forget the ground strap.
22. Reinstall the cover plate and trunk carpet. Put the fuses back (if you haven't already) and reconnect the battery.
23. Start it up and check for leaks.
1. The main pump is beneath the car, under the driver's seat. Along with the fuel filter, it is held in a cradle secured by 3 12mm bolts. Remove the bolts and let the cradle hang down.
2. Snip the power and ground wires for the pump.
3. Remove the fuel filter, as now is a good time to replace it anyway.
4. Disconnect the fuel line from the main pump as well, and remove it from its clamp.
5. On the upstream (gas tank) side of the new fuel filter, JB Weld a 1/2" hose barb into place. The JB Weld is needed for sealing, since the Volvo filter uses copper crush washers to seal.
6. Wait the full cure time for the JB Weld!
7. Put the new fuel filter in the clamp on the cradle.
8. Reattach the upstream banjo bolt using new copper crush washers.
9. Use a 7/16" fuel hose to connect the upstream (gas tank) hose nipple to the hard line. Tighten down the hose clamps!
10. Reinstall the cradle.
11. Cap the ends and push the pump wiring up through the floorboard.
11. Optional: Instead of just capping the main pump wiring, you can run a long power lead from the red wire to the red wire that supplies power to the in-tank pump. The ground wire doesn't need to be extended--you can use the old in-tank pump ground wire. This means that the in-tank pump is now on the main pump circuit. Make a note of this on your fuse diagram. I found that a good place to tie in to the wiring for the in-tank pump was at the connector near the fuel filler neck inside the trunk.
