I bought a 87 Vette a couple years ago and it ran fantastic. Well one day I cranked it up for a quick detail and it started to run rough and it died and hasn’t started since. I did the old starter fluid to the throttle body and she fired up but died after burning off the fluid. So I’m thinking fuel pump so I replaced pump and relay but no good…checked relay voltage and I’m not getting any voltage to the relay at all… when I bought the car the ignition switch didn’t work he had installed a push switch under the dash and when I pulled the dash I noticed a box with wires running from it could this be an alarm or something??? I thought about replacing the ecm but I wanted to get some input before I wasted more money replacing good parts…

 

I would check the fuel pump fuse located at bottom right corner of the fuse box. See attached photo.

It’s the 10 amp 1 marked FP

 

Good morning.

Sorry you're having starting issues with your Vette. Not trying to nit pick but I'm not quite sure why you installed a new pump and relay without doing some electrical testing first. Although its unlikely about the FP fuse I agree to check that first since it's an easy one.

According to your post you are able to get the engine to fire using starting fluid so that rules out an alarm issue unless the PO installed some sort of fuel pump cutoff switch. You may have to dive into the mess of wires under the dash and make sure you didnt inadvertently unhook or know some connection loose.

When you turn the key the power is sent to the fuel pump for about 2 secs to prime the fuel system. If you dont hear the pump kick on then you will gave to trace the wires to the relay and back. You might try and test your old relay in case you got a bad relay. Next put 12 volts on the fuel pump harness and see if the pump turns on.

Whether it is a loose connection, broken wire or aftermarket cut off switch it sounds like electrical to me versus mechanical pump related.

Good luck and post what you find out.

Ted

 

There is a possibility that your Fuel Pump is not getting power due to corrosion that occurs on the post where the battery Positive cable transfers the power to the fusible links. The fusible links are the last line of protection that GM built into the wiring and they supply the power to the fuse panel. I had problems with my Fuel pump not coming on and it was due to the low voltage going to the fuel pump relay.

It is easy to determine if this is the problem in your Corvette. Take a Multi-meter and check the battery voltage and then open the fuse panel and check/measure the voltage getting to the fuses. If they are the same or very close then this is not the cause of your problem. IF the voltage is less at the Fuse panel than the voltage of the battery then it is likely that corrosion on a certain post is the cause of the problem. I have seen several Corvettes with corrosion on this particular point. On my C4 there are 7 fusible links that deliver power to the fuse panel. I would also check all of the fuses when you perform the test. It is possible that one or more of the fusible links could have failed, this is why I test all the fuse positions for power. I like a material called DeOxIt as it removes decades worth of corrosion very quickly and easily.

IF the voltage at the fuse was lower than the battery voltage then try doing this. At the battery there are two red wires coming from the connector at the battery terminal/post. The smaller of the two red battery wires goes behind the battery and towards the panel between the hood and the drivers door. I pulled off the side cover and the post was plainly visible and covered in corrosion. First I disconnected the battery from the car. I removed all the wires on the post and cleaned each one with a wire brush to get rid of the corrosion. After all were clean I then re-assembled the wires and the Red wire back on the post and tightened the nut on it.

The other thing that could cause problems is the oil pressure sensor and the oil pressure switch near the back of the intake close to the distributor. Be sure they are both connected to their appropriate wires as they can be a problem when not connected.

Just so you know, Ether (Starting Fluid) will ignite solely from compression. It works in diesel engines as well as gas engines. If the engine seems to run on the starting fluid it does not rule out problems with the ignition system. If you want to be sure use a timing light and attach it to each spark plug and watch it flash, if it doesn't flash then you might have a problem with your ignition system. Remember to be sure all the electrical connections are Clean and free of any corrosion from the battery to your taillights.

Get a fuel pressure testing tool and hook it to the schrader valve on the passengers side fuel rail. This is a must do test as having the correct fuel pressure is critical on these beasts. Have you ever replaced or serviced the Fuel pressure regulator on your Corvette? There is a vacuum hose that attaches to the FPR, remove it and smell inside. If you can smell raw gasoline then it could indicate a bad FPR diaphragm and that makes the engine tough to start as well. If there is no gas smell then your FPR might be okay. You need the fuel pressure tester gauge to know for sure.

Before you go out and buy another ECM get yourself a set of the Factory Service Manuals for your particular year Corvette. They have very good and useful troubleshooting diagrams and are worth every penny.

 

I checked for voltage at the fuses and the FP fuse is not getting any voltage. I was told that the orange wire at the FP relay should read 12 volt constant and I'm getting zero there too. Could it be a bad fusible link that's cut off power to the fuel pump and relay. Or did the PO install the push button start switch to bypass the Valet alarm that I discovered under the dash... keep the answers coming I'm hoping the something will hepl me

 

I forgot something, Welcome to the Corvette Forum Ceefarmboy! We are glad you have joined us here at the Corvette Forum!!

I would find the post I mentioned earlier behind the battery area and while there you can test the individual Fusible links. Did any of the fuses have the same voltage as your battery? I use a tip with a built in needle probe as they work great to verify that the 12 volts has made it through the Fusible links. If you have the Factory Service Manual it should tell you which fusible link goes to which fuse position, it might be in the schematic but it would not be hard to wire it back to the factory standard way. A Push button starter's wiring might have gone around the original fuse. IF you make any tiny holes in the wire's insulation be sure to put a drop of silicone or something to close it off. Water can get into the tiny holes and cause corrosion inside the insulation which can be a real bear to trace down.

Another test I have done before when the fuel pump was not working was to start at the fuel pump wiring harness and apply 12 volts to the fuel pump directly to make the pump come to life. The harness I speak off is below the gas tank cover in the back of the Corvette. On my 1988 there were three wires. One was Red and then a Purple one and lastly a Brown or Black wire. The Red is the Hot (12+) wire going to the fuel pump. The purple is the return signal from the fuel sender in the fuel tank and the black is the ground (0 Vdc). To test the pump apply 12 Volts Positive to the Red wire and Ground to the black wire and the fuel pump should start right away. If not the pump is a problem. Then I reconnect the wires and go to the fuel pump relay and apply power to the wire that goes back to supply the fuel pump with the +12 volts and again the pump should run. Lastly I would apply power to the relay itself to be sure it is working. On my car the voltage getting to the fuel pump relay was not enough to hold it closed. I fixed the problem in the supply (Dirty Post connection) and the car started right up.

For performing a test like this I used a tool called a Power Probe and it is very helpful when tracing electrical problems. It connects directly to the battery and lets you apply either +12 volts or a Ground at the tip based on the position of the rocker switch near your finger. This tool is one I recommend to anybody trying to solve big electrical problems. The newer version Power Probe 4 has a screen that lets you see the voltage of the circuit or the voltage spike after an Injector Coil releases. It is worth every penny if you tinker much! I used my original Power probe so much that I actually bought a second one, they are that handy....

Good Luck here Ceefarmboy! We are here to try to help you, you are getting very close and it shouldn't be long before the engine makes noise again for you!

Best regards,
Chris

 

I jumped the fuel pump and i could hear it buzzing away in the tank...gonna figure out how to test the fusible links next. the following fuses have 12V (VATS, Radio, INJ2, Gauges, CTSY/CLK, C.Fan)...AC(3.2V) INJ1(1.7V).....The ECM/IGN had 0V. I'm gonna test again with a test light instead of the meter and I'm gonna jump from the relay to see if the pump starts from there so i can rule out that harness as having a bad wire...I have a service manual but its missing section 8A with the wiring diagrams...

 

I'm making a little progress on my 87 Vette...I rechecked the fuses with my test light and I'm getting power to all but 2 fuses(fuel pump and Intr.panel). I checked my fusible link and the one that powers the FP relay was bad i fixed the link and now I'm getting the 12 volts to the pump relay but still not getting any thing to the pump or fuel pump fuse. But now the "service engine soon" light comes on and it didn't before. I did check the fuel pump with my power probe and it's working fine.Also not getting any power to the start enable relay...I'm getting overwhelmed with this but I feel like I am making a little progress BUT ALL HELP IS WELCOMED...