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Change the fuel pump and sending unit

Posted on Jan 28, 2009 by Josh Merva in How To

This article was originally submitted in 2004 by Tom Fraley aka MountaineerTom. Thanks Tom!

This guide covers changing the sending unit on the fuel filter of a 1999 Chevrolet S-10 Blazer. While not all procedures will be the same, they will be similar for S-10 trucks and full-size trucks/SUV’s.

Here’s a look at the parts that come in the kit from GM.

Park the vehicle in a place where you’ll have plenty of room to work. If you have access to a lift, that would be great. We didn’t, so we just backed the vehicle’s rear tires up on some ramps. Having the least amount of fuel in the tank helps too; less weight to deal with. Also, if you have a truck, it may be easiest to remove the bed from the truck rather than lowering the fuel tank. Obviously we couldn’t do that with the Blazer, but after doing by removing the tank, I have to believe that removing the bed would be easier. Once the bed would be removed, you would have access to the fuel pump right on top of the tank without having to lower it. Removing the bed would be fairly simple too; removing the bolts that hold the bed on, removing any electrical/ground wires that are connected, and having a few extra bodies to help lift and carry the bed to sit on stands or saw horses. If you do remove the bed, it would be wise not to sit the bed directly on the ground. While it doesn’t weight a lot, it could be just enough to cause the sheet metal on the sides to bend.

Relieve any fuel pressure by removing the fuel cap. Disconnect the negative battery terminal. Pre soaking any required bolts/nuts with WD-40 prior to the job will help also. We removed what lines and connectors we could from the fuel pump and tank but it’s tight in there and we couldn’t get them all at that time. There are 3 lines and 2 electrical connectors to be removed from the fuel pump, and the filler and vent hoses that need to be removed from the back of the tank. There was also a small hose on the front part of the tank that needs to be removed, but we didn’t see it until we actually started lowering the tank. Just remember where everything hooks back up. Label the lines, if needed.

Start by removing the skid plate, if equipped.

Once the skid plate is off, you’ll have access to the straps that hold the fuel tank on.

The forward strap on the Blazer was pretty rusted and not very stout. It was basically formed as a strap that ended in a threaded bolt. It was not coming off easily in our case and ended up breaking trying to remove it. We supported the tank with a floor jack with a transmission removal assembly on it.

We easily fixed the broken strap problem by welding a bolt to the strap.

Once all the straps were loose, we lowered the tank just enough to get better access to the lines and connectors leading to the fuel pump. This is where removing the bed of a truck would make the job so much easier. There is not much room to get in there, at least on a Blazer. If you had the bed of a truck off, it would only take a couple minutes to remove the lines. In our case it took an hour or so of messing with it.

Once the tank is off, it’s a good time to look around in that area to see if there are any other problems that may need to be addressed.

Before removing the fuel pump, be sure to clean off all the junk that has collected around it.

Replacing the float and sending unit is fairly simple. Just pay attention to how the old parts are removed, and install the new parts in reverse order. Be sure to get the wiring routed correctly and install the new seal that comes with the kit. The sock filter on the bottom of the pump was just a little bit clogged, so we made a trip to the auto parts store to get a new one. Luckily they had one that would match up.

While we had the tank off, we siphoned what fuel was in there and cleaned out the tank really well.

The installation is basically just a reverse of the removal. Be prepared to take quite a bit of time for this project. It took much longer that I expected. Somewhere around 8-9 hours, but that’s including several little problems, lunch, and making a trip to the parts store for a new sock filter for the bottom of the pump. In comparison, we changed the sending unit in my sister-in-law’s Dodge Neon right after, and it took about 1 ½ hours total.ing unit on the fuel filter of a 1999 Chevrolet S-10 Blazer. While not all procedures will be the same, they will be similar for S-10 trucks and full-size trucks/SUV’s.

Here’s a look at the parts that come in the kit from GM.

Park the vehicle in a place where you’ll have plenty of room to work. If you have access to a lift, that would be great. We didn’t, so we just backed the vehicle’s rear tires up on some ramps. Having the least amount of fuel in the tank helps too; less weight to deal with. Also, if you have a truck, it may be easiest to remove the bed from the truck rather than lowering the fuel tank. Obviously we couldn’t do that with the Blazer, but after doing by removing the tank, I have to believe that removing the bed would be easier. Once the bed would be removed, you would have access to the fuel pump right on top of the tank without having to lower it. Removing the bed would be fairly simple too; removing the bolts that hold the bed on, removing any electrical/ground wires that are connected, and having a few extra bodies to help lift and carry the bed to sit on stands or saw horses. If you do remove the bed, it would be wise not to sit the bed directly on the ground. While it doesn’t weight a lot, it could be just enough to cause the sheet metal on the sides to bend.

Relieve any fuel pressure by removing the fuel cap. Disconnect the negative battery terminal. Pre soaking any required bolts/nuts with WD-40 prior to the job will help also. We removed what lines and connectors we could from the fuel pump and tank but it’s tight in there and we couldn’t get them all at that time. There are 3 lines and 2 electrical connectors to be removed from the fuel pump, and the filler and vent hoses that need to be removed from the back of the tank. There was also a small hose on the front part of the tank that needs to be removed, but we didn’t see it until we actually started lowering the tank. Just remember where everything hooks back up. Label the lines, if needed.

Start by removing the skid plate, if equipped.

Once the skid plate is off, you’ll have access to the straps that hold the fuel tank on.

The forward strap on the Blazer was pretty rusted and not very stout. It was basically formed as a strap that ended in a threaded bolt. It was not coming off easily in our case and ended up breaking trying to remove it. We supported the tank with a floor jack with a transmission removal assembly on it.

We easily fixed the broken strap problem by welding a bolt to the strap.

Once all the straps were loose, we lowered the tank just enough to get better access to the lines and connectors leading to the fuel pump. This is where removing the bed of a truck would make the job so much easier. There is not much room to get in there, at least on a Blazer. If you had the bed of a truck off, it would only take a couple minutes to remove the lines. In our case it took an hour or so of messing with it.

Once the tank is off, it’s a good time to look around in that area to see if there are any other problems that may need to be addressed.

Before removing the fuel pump, be sure to clean off all the junk that has collected around it.

Replacing the float and sending unit is fairly simple. Just pay attention to how the old parts are removed, and install the new parts in reverse order. Be sure to get the wiring routed correctly and install the new seal that comes with the kit. The sock filter on the bottom of the pump was just a little bit clogged, so we made a trip to the auto parts store to get a new one. Luckily they had one that would match up.

While we had the tank off, we siphoned what fuel was in there and cleaned out the tank really well.

The installation is basically just a reverse of the removal. Be prepared to take quite a bit of time for this project. It took much longer that I expected. Somewhere around 8-9 hours, but that’s including several little problems, lunch, and making a trip to the parts store for a new sock filter for the bottom of the pump. In comparison, we changed the sending unit in my sister-in-law’s Dodge Neon right after, and it took about 1 ½ hours total.

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Tags: Fuel Pump, Maintenance, Sending Unit