How to Change the Fuel Pump (Fuel Sending Unit)

Fuel System Repair isn’t any more difficult than any other system on a vehicle. Make sure you have the correct replacement part, take your time and inquire within!

On the majority of vehicles you will hear a fairly loud whining noise coming from the area of the fuel pump (gas tank) when the fuel pump is going out. This is your indication something is not right with the fuel pump. Some other common symptoms are:

  • Stalling especially when hot. This is caused in part from the little bit of fuel that is being pumped, evaporates before it can reach the carburetor. If you have stalling your more than likely to also have…
  • Stumbling. If you stall then your engine will stumble as well, especially under acceleration as the fuel pump tries to supply the engines demand it will stumble, heat makes this symptom worse.
  • Great gas mileage….because the engine isn’t getting gas to burn!
  • Surging. As the pump tries to supply fuel the engine surges upon each pump of the fuel pump. This can make you car sick in no time.

Today we are working on the 1989 Chevrolet Silverado 3500. Pull your hair back and remove those acrylic nails and let’s get started!

The truck started having hesitation problems and wanting to stall. It had just become a classic (30 yrs old) and I figured it’s about time to change the fuel pump anyways. I had changed the fuel filter over the years, but never the fuel pump.

I tossed around the idea of drilling an access hole in the bed of the truck like so many people have done just to avoid the challenge of dropping the tank. But I really didn’t want a hole in the bed of the truck.

Fuel System Repair

You can buy a fuel pump rebuild type of kit. It contains a fuel pump and some parts. This runs about $58. I decided on a whole new fuel pump unit which was $112. The truck is old, this is the original pump. If I’m going to drop the tank and go through it, I’m going to put a whole new pump in. I don’t want to have to do it ever again!

I came across one problem, set-back, or chauvinistic move that took more time than necessary to overcome. Before heading out to the parts store I found the pump for $112. That’s why I chose that particular parts store. When I got there and asked for the pump I was told it was $158. I disagreed. I told him I just saw it online. I ended up going out to my car, bringing the item up on my cell phone and showing it to the salesman. He tip-tapped a few more keys on his computer and replied, “Oh, yeah, there it is.” So, I eventually got the pump for the price listed, but it shouldn’t have been that difficult if you ask me. I’m just saying, “Pay attention to the prices.” If I hadn’t known better I would have paid $46 more than necessary.

Back to our fuel pump! Set the pump aside for now.

Prepare to Lower the Tank

Disconnect the negative power cable at the battery. If you have a fuel pressure release on your vehicle by all means use it and release the fuel pressure at this time. This 1989 Chevrolet did not have a pressure release valve. I wasn’t concerned due to the fact I opened the fuel cap and there was no pressure what-so-ever.

Upon inspecting the fuel fill hose I notice a lot of Black Widow webs. Since I’m not big on spiders I decided to remove the screws at the filler and slip it in so it would come out with the tank.

Black Widow webs inside this area made me decide to remove these screws and take the whole set-up out with the tank.

It’s recommended that you drain the fuel from the tank before going any further. It will also make the fuel tank lighter and easier to handle. This truck was already near empty so, again, this was a step I could skip. If you need to remove fuel from your tank make sure to use an approved canister to drain it into.

Lower the Fuel Tank

This is one of the two bolts holding the tank up.

With the fuel pressure released, the tank empty and the rear end raised up and set on jack stands, it is time to lower the fuel tank. To support the tank while I removed the screws, I used two come along’s. I positioned one at each end of the tank and weaved them through the frame in a fashion that the strap would be free to extend or retract without the whole thing slipping through. Photo’s didn’t provide a very good view but this drawing might help.

The red rectangle is the fuel tank. The blue stripped X’s are the come along’s, the grey is the frame and transmission and the red is the filler hose to the fuel tank.

I wedged the come along box between the running boards on the left side of the truck, then weaved the come along strap over the frame, under the fuel tank, under the drive line and attached the hook onto the far side of the frame. I did the same with the second come along.

Come along strap holding tank up.

After I had the come along’s attached to the truck I pulled up the slack so they were setting on the bottom of the tank but not “holding” the tank but ready to hold it.

Before lowering the tank at all I removed the ground wire for the filler hose as pictured.

Remove tank ground wire before trying to lower tank or it may rip out.

The straps holding the tank only need the two bolts on the passenger side removed. The other side of the straps are slip-fitted so they can just hang down once the bolts are removed on the one side.

I began lowering the tank by unscrewing the two bolts holding the straps of the fuel tank. As I unscrewed the bolts I could see the tank visibly lean on the come along straps just as planned.

The bolts were long with a fine thread so the unscrewing was slow, unless you have a drill that you can attach to your socket and just go for it! I used the drill method when I put it back up, but bringing it down I wanted to make sure my straps were going to hold the tank before dropping so I did the slow ratchet.

Once the screws are out and the tank is resting on your straps slowly release the straps, lowering the tank further, until you can reach all the hose lines coming out of the top of the tank. They should come out the top of the fuel tank and hang over slightly on the drivers side. They attach to lines that run up the frame rail to the engine.

There is a fuel feed like, a return line and a drain. The drain has a rubber hose pressed onto it. The other two are screw pressure fittings. Make sure to note which line goes to which. I put a red mark on one of the screw pressure bolts across to it’s matching hose.

Once these are removed there is an electrical connection and another ground wire in this same area. Disconnect the electric wires and remove the ground.

Now you can lower the tank to the ground and slide it out from under the truck. If it won’t fit out from under the truck you will have to raise the truck higher. Forcing the tank out from under the truck will damage the fuel lines on top.

Fuel tank with gas line still attached.

To remove the fuel pump you need to remove the locking tab at the top of the tank. In the photo below I have outlined the piece that needs to turn until the slots line up with the open slots. In other words knock of the locking tab and twist the part that is outlined in red in the picture below counter clockwise.

Twist the ring outlined in red to release it and then the fuel pump will lift out.

Once you get the locking ring to turn and release, you can pull the fuel pump up and out of the tank. WARNING: Use care when removing the fuel pump. There is a leveling roller and a screen on the bottom half of the pump. So you may need to tilt the pump to get the bottom part out safely.

If you opted for the rebuild kit, this is the time to start removing parts that are contained in the kit and replacing them on the pump. My truck’s pump looked so tired and worn out I just went for a complete new one as I mentioned above. The kit costs around $56. Twice that for a new one.

Now is the time to do a thorough cleaning of the inside of the fuel tank. There are fuel tank cleaning products available at auto parts stores and online.

Install the New Pump

Removing the wrapping, if any, that is on the new pump. Lower it into the tank carefully. There is a large O ring that sets down first, then the fuel pump, then the locking device. Compressing the O ring enough to get the locking ring on can prove to be challenging. Use some Vaseline on it to help. Use a good gob of Vaseline! Make sure the locking ring is set onto the pump lip and twisted to the right until it is fully locked. The pump should not have a wiggle to it at all once it is locked in.

Aint it perty!

Now transfer the mark you made on the old pump to indicate it’s match on the truck onto the new pump.

  1. Slide the fuel tank back under the truck. I used my feet to get it into position, shoving and sliding it around with just my feet worked fine.
  2. Slide your come along straps under the tank and re-attach to the frame in preparation for lifting the tank.
  3. Start ratcheting the come along’s evenly until you can re-attach the lines on the fuel tank to the one’s on the truck rail.
  4. Re-connect the electrical.
  5. Re-connect the ground wires (2 of them).
  6. Lift the tank further guiding the fuel tank filler hose up over the frame towards it’s outlet on the side of the truck (If you took it out like I did).
  7. When you can get a jack under the fuel tank trade the come along’s for jacks. One at each end, centered under the fuel tank well.
  8. Jack the tank up until the straps can be screwed back in. Again, a socket with electric drill works best if you can get the drill in there. There’s a lot of space.
  9. Re-attach the fuel fill hose to the filler hole. Tighten all hose clamps you loosened or removed.
  10. Re-attach the negative battery cable.
  11. Turn the key to the “ON” position. Can you hear the pump start up? You should.

Start it up! It may take just a few seconds for fuel to reach the carburetor.

Awesome! You’re good for several thousand miles now!

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