1984-1996 C4 Corvette Fuel Sending Unit Installation:
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. 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
8067 Fast Lane | Mechanicsville, VA 23111 | (800) 962-9632
Corvette Parts List Related to Article:
Zip’s kit makes the replacement task a breeze. Very pleased with the whole transaction… JD
I have used your excellent repair guides as a research tool for several projects on my 1996 LT 4 Corvette. The fuel sending unit instructions are equally well done with one exception.
You fail to mention the correct orientation of the fuel pump strainer or filter. Your complete unit has the filter already correctly attached, but some may chose to just change their fuel pump and filter.
Even the FSM fails to give the correct information here. It merely states to install it the way it was removed. Apparently many were incorrectly installed at the factory with the long axis of the filter parallel to the lateral (side to side) axis of the vehicle and this error continues to be duplicated.
If installed in this manner, the filter will be folded up by the sides of the fuel “canoe” or baffle affixed to the bottom of the tank. This restricts the fuel flow because it greatly reduces the available surface area of the filter and places one end of the filter directly under the end of the fuel return pipe outlet. This immediately recirculates the heated fuel being returned by the fuel pressure regulator.
The one tiny graphic in the FSM seems to show the filter oriented side to side.
This was probably due to a cut and paste error from other product lines during production of the manual and no one ever noticed it during editing. Much like the incorrect “you must drain the tank” statement.
If you examine the filter, the mounting hole is offset, therefore it has a short end and a long end. The filter should be attached to the fuel pump with the long end forward and parallel to the longitudinal axis of the vehicle when installed in the tank. This will place the filter in the center of the fuel slosh prevention “canoe” or baffle.
Additionally, the hot returned fuel will now be dumped outside of the canoe instead of into the fuel pump inlet filter.
In one sentence. The fuel pump filter goes front to back with the long end forward as installed in the car.
Safety
If you plan have your fuel sending unit out of the tank for a prolonged period of time or just don’t know, it is very easy to make a fuel tank opening cover plate from 16 gauge sheet metal using your new fuel sending unit gasket as a template. Small pieces of sheet metal are available at most home stores like Lowes or Home Depot in the hardware department.
16 gauge steel may be easily cut to size with metal shears and holes drilled with an electric drill.
An open gas tank can be dangerous, especially in an enclosed area.
Thanks, it makes me feel like it’s not as hard as I thought. John made some good points, I’m sure you were aware of them.
I m having an issue with the fuel evaporation system.according to the DMV in Delaware there is a leak somewhere in the system . I have used my smoke machine on the system and gone through every inch of the system and I can’t find any leak . Does anyone have any suggestions on how to remedy this situation?