How To Replace An In-Tank Fuel Pump and Filter Assembly
This article assumes you have determined the condition of the fuel pump and the filter, and concluded that the parts have to be replaced. Nevertheless, briefly, here are some reasons why the pump and filter may need replacement.
Replace the pump if:
- The pump motor is shorted or burned, which is characterized by a blown out fuse.
- The pump motor is open. The fuse is ok, but it just won't run.
- The pump is weak and fails to provide the needed fuel pressure.
Replace the filter if:
- The filter is clogged or dirty, resulting in low fuel pressure.
- The pump was replaced or removed for some other reason after some time of operation, especially if the fuel pump assembly was been turned upside down or shaken during the process of removal. Turning the pump assembly upside down causes the dirt that has accumulated over time at the bottom of the filter sump to spread and further clog the filter element. The dirt could even reach the pump's check valve located at the top end of the pump motor. You will then be surprised to find the fuel system malfunctioning even if it was functioning well before the service procedure was done.
NOTE: This procedure and these pictures are for a 2010 Kia Rio. You may have a different car, but the general idea is more or less the same.
- Work in a well ventilated area, away from open flame and sparks. Also, be sure to have a fire extinguisher ready.
- Do not bench-test the new fuel pump. Doing so may cause damage to the pump. In-tank fuel pumps are designed to operate submerged in gasoline for lubrication and cooling.
Outline of the Replacement Procedure
- Pulling Out the Fuel Pump Assembly (FIG 1,2,3 & 4)
- Disassembling the Fuel Pump Assy (FIG 5 through 12)
- Assembling the Fuel Pump Assy With a New Pump and Filter (FIG 13, 14 and some references to previous FIGs).
- Testing the Installation
- Trouble-Shooting (FIG 15)
- Completing the Fuel Pump and Filter Replacement.
Pulling Out the Fuel Pump Assembly (FIG 1, 2, 3 & 4)
1. Remove the back seat cushion:
- Remove the screw that secures the seat cushion (see FIG 1), using a 12-mm socket wrench, with extension.
- Push the latch at the bottom side in each side of the seat cushion in the direction as shown by the white arrows and at the same time lift the seat cushion.
- Remove the seat cushion.
2. Cover the area surrounding the service window with a rubber mat. You will be pulling out the fuel pump assembly later on and drops of gasoline could discolor or damage the finish of the surrounding surfaces.
3. Remove the service cover using your hand as shown in FIG 2. No tool is needed as the cover is tuck in place with a weather strip gum.
WARNING! – Before proceeding to the next step, be sure to disconnect the negative terminal of the battery. You will be removing the fuel pump assembly later on, thereby exposing the gasoline in the tank. With the battery connected, an accidental electrical spark could occur which could ignite the gasoline.
6. Disconnect the fuel hose by pinching the quick-connect receptacle, and then pulling it off the fuel feed nipple (FIG 4).
7. Do the same procedure as in Step 6 to disconnect the vacuum hose (FIG 4).
8. Disconnect the breather hose (FIG 4).
9. Remove the screws around the ring that holds the pump assembly in place, and then dismantle the ring (FIG 4).
10. Slowly pull out the fuel pump assembly.
IMPORTANT: Cover the fuel tank opening to prevent dust and other foreign matter from falling into the fuel tank.
DISASSEMBLY: Removing the Fuel Level Sender (FIG 5, 6 & 7)
11. Unplug the fuel pump and the lever sender connectors (FIG 5). Each connector has a standard snap-on latch. Just press the latch and pull out the connectors.
12. Remove the fuel level sender assy (FIG 6) by doing the following procedure:
WARNING! - Handle the level sender with care. Its circuitry, though simple, is very delicate.
- 12.1 Referring to FIG 7, push and hold the latch.
- 12.2 While holding the latch down, slide push the sender assy to the right.
- 12.3 Lift the sender casing to completely remove the sender assy.
13. Keep the level sender in a safe place.
DISASSEMBLY: Dismantling the Head From the Filter Assy (FIG 8)
14. Dismantle the head from the filter. Using a flat screwdriver, lift the lid a little bit and pull the filter away from the head to clear the latch (FIG 8). Do the same to the remaining latches to completely detach the filter from the head.
DISASSEMBLY: Removing the Fuel Pump (FIG 9, 10, 11 & 12)
15. Unplug the terminal lug shown in FIG 9 by pushing the detent and pulling out the lug.
16. Remove the fuel pump support. Using a flat screwdriver, lift the lid to free the latch (FIG 10). Do the same to the other remaining latches to completely remove the support.
17. Remove the rubber boot at the bottom of the pump (FIG 11) and set it aside. You might have to reuse it in case the replacement pump has no boot.
18. Pull the pump out of the filter housing. It may be a bit hard to pull the pump out. This is because of the tight fit of the O-ring on the pump nozzle. Turning the pump a bit will help. See FIG 12 for the ejected pump.
DISASSEMBLY: Removing the Pressure Regulator (FIG 12)
19. Pull out the pressure regulator from the filter housing (FIG 12). The tight fit of the O-ring may make it hard to pull it out.
20. Keep the pressure regulator in a clean and safe place. Dust and other particles could get into the regulator's check valve which could cause it to malfunction.
ASSEMBLY: Installing the Sock Filter (FIG 13)
NOTE: In some cases the new sock filter will interfere with the float of the level sender, and so you will have to reuse the old one.
21. Press fit the sock filter onto the pump as shown in FIG 13.
22. Install the clip to lock the sock filter in place.
ASSEMBLY: Installing the Fuel Pump
23. Transfer the nozzle spacer from the old pump to the new pump (FIG 12).
24. Install a new O-ring on the nozzle. The new O-ring must be similar to the old one. Check the old filter, the old O-ring might have been left inside when you pulled out the pump.
IMPORTANT! Make sure that the O-ring can provide the needed sealing to avoid unnecessary rework later. A leak from this area could cause the fuel being pump out by the fuel pump to escape back to the fuel tank, resulting in low or no pressure in the fuel system.
25. Transfer the wiring harness from the old pump to the new pump (FIG 12).
26. Insert the new pump into the new filter. Make sure that the wiring harness is properly laid out through the filter casing.
27. Fit the rubber boot on the pump (FIG 11).
28. Install the spout (FIG 12).
29. Install the pump support. Make sure that the boot is properly fitted in place.
ASSEMBLY: Installing the Pressure Regulator
30. Install a new O-ring for the pressure regulator (FIG 12).
31. Insert the pressure regulator into the filter casing (FIG 12).
ASSEMBLY: Installing the Head
32. Insert the terminal lug (FIG 9).
33. Install a new O-ring to the feed spout (FIG 14).
34. Snap the filter into the head.
ASSEMBLY: Installing the Fuel Level Sender
35. Install the level sender (FIG 6).
36. Plug the pump and the sender connectors to their respective receptacles (FIG 5).
ASSEMBLY: Installing The Fuel Pump Assy Into the Tank
37. Install the fuel pump assy into the fuel tank.
38. Re-connect the hoses and the pump's electrical connector. To re-connect the fuel and vacuum hoses just insert the quick-connect fittings to their respective nipples. These are self-sealing fittings and no further action is necessary to ensure proper sealing.
TESTING THE INSTALLATION
NOTE: Please note that this replacement procedure is carried out on the assumption that it has already been determined that the fuel pump and/or filter are defective. Therefore, this testing procedure and the trouble-shooting that follow are solely focused on testing the integrity of the installation.
39. Re-connect the negative terminal of the battery.
40. Check to see if the pump motor is functional. Listen very closely to the sound that the pump motor will produce once you turn on the ignition switch the first time. The first time you turn on the ignition switch the Engine Control Unit (ECU) energizes the pump motor to pressurize the fuel line, then it will be turned off once the fuel line is pressurized. So it could be possible that in the subsequent turning on of the ignition switch you won't be hearing any sound from the pump motor, as the fuel line may still has enough pressure.
- If you hear a humming sound, proceed to Step 41, else check the power connection to the pump. If something is wrong with the connection, fix it. Then go back to Step 40.
- If there is nothing wrong with the connection it could be possible that the new pump is defective. However if you are using genuine replacement parts, the possibility of a defective fuel pump is very unlikely and the problem could lie elsewhere. Trouble-shooting in this area is beyond the scope of this procedure. Re-install all the remaining parts that have been disassembled then go to Step 44, and be prepared to perform the needed trouble-shooting.
41. Start the engine.
- If engine won’t start or runs roughly, go to Trouble-shooting (Step 42).
- If engine starts and runs ok, go to Step 44.
42. Connect a pressure gage to the fuel feed spout (FIG 15).
43. Turn the ignition switch on. You should hear a humming sound coming from the fuel pump for a while, then it will stop. The Engine Control Unit (ECU) of the car energizes the fuel pump the first time you turn on the ignition switch to pressurize the fuel lines. You may not hear this sound again in the subsequent turning on of the ignition switch for the reason that there could still be enough pressure in the fuel lines. Read the pressure gage. The reading should be around 49 psi.
- If the pressure is ok, then the problem is not the in the fuel pump assy. Install the remainng parts that have not yet been installed and consider the replacement job complete. Then go to Step 44.
- If the pressure is low (causing the engine to run roughly) or if there is no pressure at all (causing the engine not to run), it is very likely that there is a leak in the fuel pump assy. The leak could come from the pressure regulator O-ring (FIG 12), the pump nozzle O-ring (FIG 12), or the feed spout O-ring (FIG 14). A leak from any of these locations causes some or all of the fuel being pumped out by the fuel pump to escape back to the fuel tank, thus, producing low or no pressure at all in the fuel lines. Check these locations and repeat Step 43.
- If after checking the O-rings the fuel pressure is ok, go back to Step 41. If not, install the remaining parts that have been disassembled and condider the replacement job complete. Go to Step 44, and prepare yourself for your next trouble-shooting job.
COMPLETING THE FUEL PUMP AND FILTER REPLACEMENT
44. Return the service cover (FIG 2) and install the seat cushion (FIG 1).
45. CONGRATULATIONS! You’ve just done a nice replacement job. But if the replacement job you’ve just completed didn’t solve your problem, this means that there’s something wrong with your initial trouble-shooting that led you to conclude that the pump is defective. Let me just say goodluck on your next trouble-shooting job and I sincerely hope that you will be able to find the solution very soon.
"Usually, the thing that makes a job difficult is our lack of understanding of the principles involved."
This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.