1984-1996 C4 Corvette Fuel Sending Unit Installation
1984-1996 C4 Corvette Fuel Sending Unit Installation:
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01: In the old days, changing a fuel pump on 1953-1981 Corvettes was a pain in the neck. It was hard to reach. The task was sometimes messy. Because the pump was low in the system, you had to seal off the fuel lines. You had to fuss with the fuel pump pushrod. If you were working on an air car, the HVAC compressor blocked access. Thankfully, with the 1984-1996 C4s, changing what GM calls the “Fuel Sender Assembly” is far less a trying experience.
02: A C4 Fuel Sender is a combination of the electric fuel pump (or, in the case of ’90-’95 ZR-1s, a pair of pumps), fuel pickup, fuel filter, fuel level sensor and fuel level sensor float. Zip Corvette Parts sells reproduction Fuel Sender Assemblies for 1984 (PN GT-293), ’85-’87 (PN GT-292), ’88 (PN GT-291) , ’89-’96 (PN GT-290) and ’90-’95 ZR-1 (PN GT-406) Corvettes. Shown is the ZR-1 Sender Assembly.
03: If you suspect a fuel supply problem, but have not diagnosed the specifics, don’t just start changing parts. Consult the factory Service Manual for your model year. In the majority of cases, the Service Manual’s diagnostic information is the best place to start. 1953-2011 Corvette Factory Service Manuals are available from Zip Products.
04: Once proper diagnosis determines the pump needs replacement and you have a replacement on-hand, disconnect the negative battery cable. Don’t smoke or have the car near any open flame while changing the sender.
05: Next, relieve pressure in the fuel system. With the 1984 model, loosen the fuel inlet fitting on the front throttle body and soak up gasoline which leaks out with shop rags. On ’85-’96 models, connect a fuel pressure gauge having a pressure relief valve to the pressure test port on the engine’s fuel rail then, open the relief and vent the system into a container which can hold at least a cup of gasoline. The ultimate fuel pressure test gauge is an electronic unit made by Waekon which has a pressure relief and uses a transducer to sense pressure and display it on a digital readout. Mechanical gauges with pressure reliefs are available from SPX Kent-Moore, Lisle and MityVac.
06: A gauge without a pressure relief is available from Zip Products, but the process is a little different. Hold the gauge over a drain pan, loosen the fitting at the gauge then drain the gasoline into the pan.
07: The 1984-1996 C4 Corvette’s electric pumps are easily accessible from the top of the gas tank. Start the Fuel Sender Assembly replacement by removing the fuel filler door and the rubber filler housing. You’ll find a drain hose connected to the housing and, you can disconnect it as you lift the housing off the rear deck.
08: With the fuel door and housing removed, the top of the Fuel Sender is exposed. In the old days, draining the tank was required if the sender was installed in the bottom of the tank. Old habits die hard so service manuals still say to drain the tank prior to a sender change. With C4 senders going into the top of the tank, draining is not required to change them. Getting the fuel out of the tank and storing it safely are difficult tasks. Lastly, a fuel tank full of gasoline fumes is more dangerous so, for these reasons, we recommend you not drain the fuel tank.
09: To prevent contamination from falling into the tank while the sender is out, before you remove the tank sender, reinstall the gas cap and clean the area around sender. The best way is flushing with water. Blow the area dry with compressed air or with an electric leaf blower.
10: Loosen the clamps from the fuel feed hose, the fuel return hose and the evaporative emissions control (EEC) system hose.
11: Undoubtedly these hoses have been in place a long time. If you can’t twist them loose, use a set of plastic-jawed pliers to squeeze and rotate to loosen them. If you are going to replace the hoses, remove and save the clamps. Do not use ordinary gas hose, use “fuel injection hose” for the feed and bypass hoses and use EEC hose for the evap system. Both can be purchased from sources such as RockAuto or Goodyear Engineered Products retailers. If you are not replacing hoses, slide the clamps back on the hose until they are clear of the sender’s steel connections. Pull the hoses off the sender connections. A small amount of fuel may leak out of the fuel feed hose which you can soak up with a shop rag.
12: Under the rim of the rear fascia, the fuel sender electrical connection is attached to the fascia. Remove the connector lock then disconnect the three- or four-pin Weatherpac connector.
13: Remove the fuel sender bolts. If the sender isn’t already loose, you might need to tap the filler neck with a rubber of plastic hammer to dislodge it.
14: Remove the Fuel Sender Assembly by pulling up and rotating left or right to free it from the tank. You may have to push on parts of it to get them to clear the edges of the tank. Once the Sender is out, invert it to drain residual gasoline back into the tank.
15: New Senders from Zip include a gasket. This gasket goes on the tank’s sealing only one way. Lay it on the tank such that all bolt holes line up.
16: Reinstall the Fuel Sender Assembly the way it came out. Orient it with the mounting head parallel to the fuel tank top surface and the end of it pointing towards the front of the tank. Lower the Sender Assembly in place, again, pushing on protruding parts to help them clear the edges of the tank. Once the Sender’s mounting head is nearly flush with the tank surface, since the bottom of the assembly rests on the floor of the fuel tank in a baffle, you may need to manipulate the Sender such that it sits in the correct spot in the baffle.
17: Once the Sender is in position, clean the bolts and reinstall them. Proper tightening is critical to correct gasket compression and no leaks. Tighten the bolts to 40-in/lb. (4.5 N/m) torque.
18: Reinstall the fuel and EEC hoses or, if you are installing new hoses, put them in place. To make the hoses slide on easily, spray some P-80 Rubber Lubricant on the steel tank connections. Pure silicone spray, also, works in this situation. Tighten all screw clamps and reinstall the spring clamp you may find on the EEC hose or replace it with a screw clamp.
19: Reconnect the Fuel Sender wiring harness making sure to route the cables as they were previously and to replace the connector locking tab. Before reinstalling the rubber housing and the fuel door, test the system by starting the engine. Let the engine run a few moments while observing all the hose connections. If there are leaks, address those problems, now.
20: Reinstall the rubber housing. Again, some P-80 or pure silicone sprayed on the filler neck and housing edges will ease it’s installation.
21: Just before pushing the housing into place, reach down, grab the water drain hose and attach it to the connection on the housing. If the hose isn’t long enough, install the housing, remove the license plate mount then reach through the opening and push the hose on the connection.
22: Reinstall the fuel cap. Reinstall the fuel door assembly. Take your Corvette out for a road test.
C4 Corvette Fuel Sending Unit Installation: 1984-1996 Fuel Sending Unit
Source: Zip Corvette Parts
Source: Zip Corvette Parts
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