In Tank Pump

In tank Fuel Pump Replacement


Testing Procedure

Before we replace a pump that we think is bad we should test to be sure that it is. Several tests will assure us that the pump is bad before we proceed with its removal and replacement. What will be needed to do these test is as follows:

1) Digital multi meter.

2) Phillips screwdriver.

3) Mechanics Stethoscope

4) 12v source other than car.

5) Dremel Tool with sanding drum.

6) Soldering Iron

7) 18 gauge bare copper wire.

8) Heats shrink tubing.

At this point we must open the hood. Next open the trunk and remove the flooring carpet to gain access to the Fuel Tank inspection cover. Removal of the inspection cover is next by removing the 3 Phillips head screws. Once the cover is removed this should expose the Fuel Pump and Sending assembly. 

We can now test to see if the pump is running buy starting the car. With car running place tip of Mechanics Stethoscope to top of fuel. When we touch the top of the fuel unit we should hear the pump running. If not then we need to check for voltage.

Unplug the pump wire from the pump plug. (This is the plug with only 2 wires going to it.) Next while car is running (pump will only operate after car is started) touch the meters probes the ends on the plug. If showing 12 volts then the pump must be removed for further testing. If no voltage then we need to go to the Fuse/Relay Box located on drivers side fender under the hood.

The Relay located on the outside of the Fuse/Relay Box is for the in tank pump. Remove this relay and replace with a new one. Now repeat above test for voltage. We should now have 12 volts for the pump. If pump is not running after replacing the relay and being sure that there is 12 volts to the pump plug then we must remove the Pump assembly for further testing.

Pump Assembly Removal

We must first remove the fuel tank sending unit from the fuel pump assembly to facilitate its removal from the tank. Removing the 4 screws located on top of the send unit itself does this. Remove securing nuts and flat washers using a 8mm socket. Once all 4 nuts are removed then you can begin to slide the fuel-sending unit out. Just before the unit clears slightly cock it to one side and let it hang in the hole. This will allow fuel to drain from the unit. Allow at least 5 minutes for this (depending on how full the tank is) as the slots in the unit to allow fuel in and out are quit small. Once removed set this unit to the side in a safe place.

Next remove the band clamp that is securing the hose to the outlet line (larger hose) and then the band clamp from the return line (smaller hose). You may find that you can take a screwdriver and separate the clamp slightly so it will pull off. If not then large pair of cutting pliers is in order. Once the clamps are off be sure to save the inside band on each hose from the old clamps as they should be used again with the new clamps.

Now remove the hoses from their respective tubes. Once removed rotate the in tank pump assembly to the left. This will then allow you to lift out the pump. You will have to twist and slightly lean over the pump to work it out of the tank hole locking notches. Once you get to the fuel pickup screen be very careful, as you will be using this again. Also be careful as residual fuel will be in the pump and will spill when lifted out of the tank.

Pump replacement

As stated the pump replacement will be done using a in tank fuel pump from a 1976 Chevrolet 2.3 liter Vega. These can be had at most auto parts stores for about $35.00. Its not quite an exact replacement but it is very close and takes little modification.

First we must remove old pump from the original assembly. This is done by looking on the bottom of the fuel pickup screen and removing the small screw that is holding it to the pump. Next place the pump in a vice so that you can securely hold it as we are going to grind off the heads of the rivets that hold the wires to the pump. I do this with a Dremel tool and a sanding drum. Lightly sand off the head of the rivets until you can pull off the positive wire and the negative ground strap. At this point the ground wire strap screw must be removed, as this will allow you to keep the copper strap and to remove the pump from the tubes. Be careful not to loose the clip nut, as you will use this again. 

You can now attach the strap the negative side of the pump. Place the rubber hose supplied with the pump on the pickup tube and press in place. At this point you will have to check the positive wire and see if it is long enough to reach the terminal on the pump. On my install it was barely long enough to reach but was OK. If not use only bare copper wire covered by heat shrink tubing. This will have to be soldered at the top of the tank cover. Make sure the nuts are secure on the terminals and use clip nut to secure ground strap back on the pump tube.

At this point it will be necessary to do a little work to the old pickup screen for reuse. Since there is not a way to screw the pickup screen back on we must be split the return tube side of the pickup screen (dremel tool again) and clamp it with a full fuel hose type clamp. I also used a nylon tie rap to help hold things together. Once the clamp is tight to the pickup screen the unit is ready to put back in the tank. Reinstall using the reverse of above and install new hose clamps on fuel and return lines using the center ring portion from each of the old pinch type clamps.

Hopefully the pictures included with this will help further your project along. This is much cheaper than the original and the pump has enough fuel flow to power a Chevy V8 350 cid engine.