Replacing The Fuel Pump & Sending Unit On A 1987 C4 Corvette
This weeks Corvette Question comes from Kris who owns a C4 Corvette.
How do I replace the fuel pump & sending unit on my 1987 Corvette?
C4 Corvette Fuel Pump
Answer: Once you have troubleshooted your Corvette’s Fuel System and determined it is time to install a new fuel pump & sending unit on your Corvette you will first need to disconnect the negative battery cable and relieve the pressure in the fuel system. To relieve the fuel system pressure on a C4 Corvette you can simply remove the gas cap and let the car sit for 15 minutes. Once the pressure is relieved drain your Corvette’s fuel tank and remove the tank filler door attaching screws and bezel. Next, lift the fuel tank filler pipe housing and disconnect the drain hose from the nipple. Before disconnecting the fuel tank filler pipe housing, clean all fuel connections and surrounding areas to avoid contaminating the fuel system. Next disconnect the fuel hoses and EVAP hose from the fuel sender assembly. Plug or pinch the fuel feed and return hoses and remove the fuel sender electrical connector. To finish removal of your C4 Corvette’s fuel pump and sending unit remove the fuel sender assembly attaching screws, assembly, and gasket. You can re-install the old gasket but first check to see if your new C4 Corvette Sending Unit came with a new gasket. If it did then discard the gasket and thoroughly clean the gasket sealing surfaces. If you just purchased a new C4 Corvette Fuel Pump you will need to purchase a gasket separately or re-install the old gasket. Finally, cuts, nicks, swelling, or distortion is common on the fuel feed, fuel return and EVAP hoses so be sure to inspect these hoses before proceeding.
Once you are ready to install your new C4 Corvette Fuel Pump & Sending Unit begin by positioning the gasket on the fuel tank with the notch facing forward in the right hand corner of the tank. Carefully fold the strainer to allow it to fit through the opening in the tank. Next, install the fuel sender assembly into the fuel tank and re-connect the fuel sender electrical connector. Then connect the EVAP hose and tighten the hose clamps. Re-connect the fuel drain hose to the nipple on the filler pipe housing and place the housing around the filler pipe. Now you can re-install the filler door bezel, add fuel, and re-connect the negative battery cable. Before driving your Corvette away, be sure to turn the ignition switch on, off, then back on and check for any possible fuel leaks. If no leaks are recognized your Corvette fuel pump replacement was a success.
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This procedure is very good and will result in a successful installation. It’s not necessary to completely drain the fuel tank, but it is advisable to run the fuel level down as far as possible. I had never changed a fuel pump & sending unit on a Corvette before. The procedure took about two hours, start to cleanup and was 100% successful!
The fuel pump replacement details for the 1987 Corvette? Is this procedure the same for all C4 Corvettes?
Mike,
Yes you can follow this procedure to remove the fuel pump and sending unit from all C4 Corvettes.
I installed a new pump and sending unit on my Corvette and I cant get the float to stop hanging on the plastic bladder. Do I need a new fuel tank or can anything be done?
Rick,
The bladder should not be anywhere near the sending unit float. If it is then you need a new fuel tank.
I just installed a fuel pump in a c4 Corvette, it took about half an hour. I found it to be a very simple job. I dont see what the problem is in fitting one.
I can not get the sending unit/pump assembly out of the tank on my 1989 Corvette. Something blocks it when it is about 2 inches out. I tried to pull, twist, turn…no way it will come out. Any suggestions? The gas gauge won’t go higher than 2 bars, just don’t want to force it and break the assembly.
Dan,
You have to rotate the sending unit out. The pump and arm have to come out. You should be able to see which way to rotate the unit as it comes out.
I’ve changed the sending unit and pump on my 1985 Corvette but I still need to replace the two hoses connected to the fuel lines? Any idea what type of hose is needed or where to find?
Rob,
You may have to do some fabrication. The fuel hose that hooks up to the sending unit is 3/8 fuel line and 5/16 line. The problem is the line is crimped into the steel line. You will either have to use a splice to splice the rubber line or cut the metal line and attach the new hose to it.
Great article on replacing a C4 Corvette fuel pump. My 1989 Corvette has been sitting for over a year because water got into the gas tank. I siphoned all the fuel out and filled it with fresh fuel but I am pretty sure the fuel pump is toast. I can’t hear the fuel pump nor get any fuel to the schrader on the injector rail… This article is going to make my Corvette fuel pump replacement easy. THANKS!
I have a 2005 C6 Z51 Corvette. The engine has had some major upgrades including a Magnuson Supercharger w/water cooler, MSD coil packs on each plug, new spark plugs, major air box, computer reset, 160 degree thermostat, and numerous other small changes. The first and only problem that I’ve had is with the fuel pump going out. The builder offered to replace it for free but the trip was too expensive all things considered. He indicated to me that the fuel pump problem was common on “those” Corvettes? Have you gathered enough information to make any assumptions like that? If so at what oil temperature? Thanks for your time and effort and thanks for the new set of wheels and tires you just supplied me with! I’ll be calling with more feedback as soon as I get to drive it some.
Sam,
No fuel pumps have not been an issue when they are used in the correct applications. If you are using a boost-a-pump, then yes that could be an issue. If so the problem is that the boost-a-pump supplies more than the recommended amount of voltage (14v) to get the pump turning fast to supply more fuel. With this you are operating the Corvete’s fuel pump out of its design parameters and yes you will eventually fail it. The proper way would be to have the new C6 Z06 Corvette Fuel Pump or even the C6 ZR1 fuel pump installed, this should correct the problem. You may have some programming that would be required depending on how the old setup was programmed to operate.
Thank you for asking us about your Corvette’s fuel pump and how to fix a failing fuel pump on a C6 Corvette.
Thanks for your time and your answer. If it should happen again, I’ll know how to fix it and keep it fixed.
Regards,
Sam Tucker
Nice description, seems straightforward and not too difficult. However, I can’t disconnect the sending unit electrical connector. Does it pull up from, or slide off the assembly? I don’t want to break it when trying to remove it.
I just discovered that one of the rubber hoses above my 1996 Corvette’s fuel sending unit has a small pinhole that spews fuel when the engine is running. I looked high and low for a way to replace the hose and found that a replacement hose with crimp a connector is not available anywhere. I’m going to insert a metal tubular splice into the hose and clamp it on both sides of the splice.
JoMo,
The electrical connector on top of the sending unit does not come off, it is permanently attached. You unplug the harness end (orange connector).
We have a 1987 Corvette that was running fine. The car was parked for a few days at a body shop, the doors were left open and battery connected while they were working on it… now it can not be started no gas is reaching the engine? Is there a fuel pump relay to check or how can we make sure it’s the fuel pump before we try to change it?
Mike,
Well there is a fuel pump relay located on the firewall between the wiper motor and brake booster. If your car is a 4+3 you will have two of these and one is for the O/D on the transmission. You can use a test light to see if it is getting power to the pump. Also listen to the pump when you first turn on the key, it should run for about 3 seconds. If you do not hear it, then more than likely it has failed.
My Vette has been sitting about a year and a half and it started and run fine when taken off the road. Now there is no pressure at the schrader valve. It starts easiely with starting fluid shot into intake but burns that up and stops. No fuel at the fuel rails. It acts like it is trying to run. Was wondering if there is a way to help un-stick a stuck pump that has been sitting? Thanks.
I am putting a TPI system on my 1980 Corvette and want to install an in-tank pump. I bought a pump for a 1990 Corvette. My concern is the electrical connections are in the fuel and are not liquid tight. Is that right?
The C4 Corvette factory fuel pumps did not have any type of cover or seal over the connections. I don’t understand that but it still works just fine. As long as your connections are correct you should be ok.
I have a 1991 Corvette Convertible. I replaced the entire fuel assembly (indicated in the picture). It had rusted out and required replacement. Now I have to pinch the fuel return line for it to start. Once it starts, if I immediately pinch the line, it stutters and sometimes will shut off. Once it warms up, it runs fine. Any help is most appreciated.
I have a 1985 Corvette which has been sitting and not run for a few years (always inside), I put a battery in it and when I try to start it it will fire but not run. I can’t hear the fuel pump over the noise of the cooling fan(it comes on with the key). Hmm, just thought..I could unplug IT. Anyway is the pump prone to fail from sitting for an extended period or where would I begin? Seems like fuel issue of some sort to me.
I have a dumb question, I have an 89′ corvette, fuel pump is out and I’m getting ready to replace the fuel pump. Where does the new strainer go. I didn’t watch when the fuel pump was taken out of the gas tank.
Hi Randy -
There could still be several issue here. Let’s start with the fan, it should not turn on when the key is immediately in run, could be a bad ECM or a fan Relay. The initial start of the engine is because the injectors are priming the engine for startup when you first turn the key on. So if you have a bad ECM it is possible that it is not commanding the injectors to fire after that. You can check those with a noid light, it would also be a good time to check the fuel pressure, it should be about 38lbs. You can also have a ignition problem, although the system if firing, it is not giving off a engine speed to the ECM. It needs an engine speed to tell it that it is turning over and needs the injectors to fire. These are a couple of things to check. Remember – it takes compression, fuel and spark – if it has those it will run. Good Luck!
My 85 Corvette will not start. I have determined it has spark and it will start if you spray starting fluid
in the the throttle body. I have also noticed I cannot hear the fuel pump come on, I am thinking its the fuel pump,but after reading Mike’s issue with his 87 do you think it may be a fuel pump relay?
Where is the relay located?
Bernie -
The fuel pump relay is located on the firewall on the drivers side of the wiper motor. If this car is a 4+7 there will be two relays there, one for the fuel pump and one for the over drive.
@Zip Corvette Parts
Thank you for the advice. I believe years back my Dad had the fan hooked up direct as we had an overheat issue at one time. But when I get back at it I will certainly check into what you have told me. Is there a way to directly check the ECM?
Thanks again!
No such thing as a dumb question, Chris!
Check out the picture in our corvettemagazine.com article: C4 Corvette Fuel Tank Sending Unit Replacement You’ll find full directions for installing a fuel tank sending unit with the fuel pump.
Randy-
There is no way of checking the ECM in your car. You need to check the three things I explained earlier. If the car has spark then you should be good. Check your fuel pressure – is the pump running at all? You will need an external guage to hook up onto the rail. If this car has been sitting, the injectors could also be locked up – are they firing? You can get something called a noid light and hook it into the harness to see if the injector is getting power. Don’t suspect the ECM until it can be nothing else. There are too many Corvette Parts that can go bad from sitting that are bolted to the engine. The Corvette Fuel System is probably going to be the culprit. If you would like to send us the injectors, we can clean and flow them to make sure they are working properly. Call us at 1.800.962.9632 if you want to give that a try.
Ok, so previously I heard the fuel pump, but only after I shut the key off (odd), and nothing when the key was on. Today I did some checking, no sound from the fuel pump at all now and connected noid light…no light. I have a fuel pump relay coming tomorrow. Is it possible to have a bad ground somewhere? Isn’t fuel and electrical fun?! Not!
Thanks again for your time and advice!!
Eddie:
Have you replaced the Corvette Fuel Injectors? You should not have to pinch a return line, you are increasing your fuel pressure on the injector when you do this. I would try having the injectors cleaned and rebuilt, they have a screen in the top of them that could be clogged up with rust debris that was in the line.
Randy -
If the noid light did not light off you may also not have a bad fuel pump or relay. What happens when you try and start the car? Does the tach do anything during cranking? If so, and the noid light did not light, then try unplugging all of the injectors and then try the noid light again. If it does not light up then the ECM is bad. This could also keep the fuel pump from turning on.
@Corvette Parts
I put a new fuel pump relay on and the pump runs as soon as I crank, checked with fuel pressure guage and it goes right up to 38lbs. The digital dash isnt working so not sure about tach. I’m thinking ecm is bad.
Randy-
Well it is hard to say, really need to see if there is an RPM signal or you are just throwing parts at it. You can try the ECM and see what happens. Good Luck!
I just replaced a fuel sending unit on a 1987 vett and the first time i turned over the engine it started. 30secs later it stalled. I tried to starting the car again and nothing happend. Over the 5 trys and still nothing but now the abs relay (silver Bosch) clicks after putting the key on run… I NEED HELP PLEASE! The car sat for about a year and I have fuel problems before it sat. And even after replacing the sending unit the gas gauge still reads full and I removed about 2.5 gallons.
Orlando:
If the car sat for over a year, I would suspect that any trash in the fuel system has been forced forward into the injectors. These will probably at least need cleaning.
I would also strongly recommend cleaning each and every electrical connection you can get to. Clean the grounds, take each connector apart and put them together again a couple of times to scrape off any corrosion, and smear some dielectric grease into each of them when you finally put them together for good. This would be a good all weekend project, as there are many, many connections.
This may or may not solve the problem you are having, but it will be difficult to accurately diagnose the electrics if they are ‘fuzzy’ from sitting. Good Luck!
Hi Terry:
You could always TRY reversing the wires on the pump, and run it backwards for a second or two.
Or take the pump out and hit it with a hammer while energized. What year is your Corvette?