Question about 1988 Chevrolet Corvette

3 Answers

Help. I have replaced the Fuel pump relay and the fuel pump on an 88 Corvette. I still don't hear the fuel pump pressurizing the system.

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  • Tom Moore Apr 27, 2010

    I do not have a pressure guage. When I hold down the relief valve on the fuel rail I'm not getting any fuel delivery.



    I am getting voltage at the pump. I am also getting voltage at the relay. And I checked the the fuse (assuming it's the right one). Bottom right hand of the block marked FP.



    Fuel pump is brand new and I replaced the relay.

  • Tom Moore Apr 27, 2010

    Quick question. If the fuel filter is clogged would the fuel pump disengage and not pressurize the system?

  • Tom Moore Apr 27, 2010

    Advice was sufficient but we are still waiting for an answer.

  • Tom Moore Apr 27, 2010

    Im getting 10 + volts at the plug. When we turn it over it drops to about 8. The fuse is ok but can you verify that I'm looking at the right fuse?



    Bottom right hand corner labeled FP.

  • Tom Moore Apr 27, 2010

    How do I use a jumper to bypass the relay?

  • Tom Moore Apr 27, 2010

    I can't hear/feel a click on the relay. It's a brand new relay.

  • Tom Moore Apr 29, 2010

    Ok. The ground was bad at the collar on the tank which is why the relay was not clicking. I cleaned it up, tested it with a multimeter, reinstalled a NEW fuel pump in case we got a bad one.



    We still are not getting fuel and we are not hearing the fuel pump pressurize the system.



    So....the relay is good, we are running with a new fuel pump.



    Help!

  • Tom Moore May 03, 2010

    Would I have voltage at the plug to the fuel pump if the inertia switch were out?



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3 Answers

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  • Master
  • 1,297 Answers

Not a problem... lets find out if its a power or ground issue

I need you to go to the fuel pump connector with an old fashion automotive testlight

using the test light I want you to verify power to the pump when someone turns the key to the on position.

if you do not have power, update me personally on your post, my name is Sean, and I'll tell you how to diagnose the power supply concern

if however, you have power then your concern is ground related.... just run a new ground wire and you'll be fine!

Posted on May 03, 2010

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  • Master
  • 1,796 Answers

Hi!!

Did you check fuel pump FUSE, if OK, Check plug by fuel pump, it may not be plugged in all the way, if OK, have sombody turn key to RUN (Take all safety measures) while you check if juice is going to the pump. Remember that about 85% of the electrical problems is because a faulty - GROUND not +12V.

Good Look!

Posted on Apr 27, 2010

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  • Rene J Solis Apr 27, 2010

    If you have 10+ volts at the Fuel Pump plug, when you plug it in you should hear a buzzing noise that lasts about 2 secs.coming from the fuel pump when you turn the Ignition key from OFF to RUN. Also, you should be able to hear a CLICK from the FUEL PUMP RELAY. If buzzing or no click, check for ground to relay or use a jumper to bypass relay.



  • Rene J Solis Apr 27, 2010

    There is two diagrams in the relay top, one shows an open circuit and has a number on each end, that's the coil, in one end it should have ground and the other 12V to activate, when you energize the coil is when you hear the clck. The second diagram shows the contactor, on one end you should have 12v and on the other nothihng until you energyze the coil and hear the click, then both ends should have 12v.



    Now, when you turn the relay, each leg is mark with a number which corresponds to the one in the diagram. Do wherever is easier for you, use a paper clip to jump the terminals of the contactor, you won't hear a click by you will be bypassing the relay and should be able to hear the buzzing coming from the fuel pump. If you want to check the relay, apply 12v to one end of the coil and ground on the other, if you hear the click, there should be continuity between the contactor sides (the one with the continuous line.



    Any doubts just post a note.

  • Rene J Solis Apr 29, 2010

    Ok, we are in the right track now. I am assuming that the fuel pump RELAY is clicking when the key is turned ON. If you run a wire straght from the RELAY OUTPUT (the one that gets HOT when the relay is energyzed), to the 12V + in the fuel pump. Will it make the pump run?

  • Rene J Solis Apr 29, 2010

    You can practice with the old fuel pump. And then try it on the installed one.

  • Rene J Solis Apr 30, 2010

    Also, check the Inertia Switch, is the one that cuts power to the Fuel Pump when involved in a collision. Depends where it is located, it can activate by just letting the car jack drop too fast after you worked on the pump. To reset it, just push the button.

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  • Master
  • 661 Answers

Ok lets see if I can help. couple of things.
Sometimes a pump may be so quiet you don't hear it. Do you have a gauge to check the actual pressure? You really need one because there are pressure minimums.

Most pumps do make noise and if you cant hear yours then it may not be working. Have you checked the voltage at the pump? Have you checked the voltage at the relay? Have you checked the fuse for the fuel pump?
These are all things we would check in the shop to fix your problem.
One of them will leave you a clue as to where the problem lies.

Posted on Apr 27, 2010

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  • Bryan Fullerton
    Bryan Fullerton Apr 27, 2010

    Id have to say that a clogged fuel filter would definitly slow things down. so would a bad ECM.

  • Bryan Fullerton
    Bryan Fullerton Apr 29, 2010

    Unfortunately having the right tools is very important to be able to diagnose and fix a vehicle properly. For a fuel injected system these days it is very important to have a fuel pressure tester since the injectors need a certain pressure to operate properly.
    If your relay is working then your pump should work unless the pump is bad or the wiring has a problem from the pump to the relay. Grounds are very important. FP should be the fuse but check the other fuses as well.
    You said you had voltage to the pump? or was it the relay. thanks fixya for not showing the comments on a reply.lol It seems low but it is normal to have a voltage drop while cranking. Ultimatly you need to pressure test the system.



  • Bryan Fullerton
    Bryan Fullerton May 03, 2010

    ok lets back up a bit here.
    If you have voltage at the pump then the pump will run and if you have gas it will pressurize the system.
    You do have gas don't you? Don't assume so because the gauge says you do. It is possible the pickup tube rusted off.. OR the pickup filter is totally plugged. It doesnt make sense to have current at the pump and still not have pressure. If you feel the pump lines when the key is turned on you should feel the vibration of the pump running and possibly hear it to depending on what type of pump it is.
    Another thing that could cause a no pressure situation is a kinked hose.
    Or if someone recently worked on the fuel system and slipped a hose over a metal tube that had sharp edges that could cut into the rubber effectively making a one way valve. The chances of that isn't very good unless there has been recent work done.
    To check just unhook the pump and unhook the line at the engine and see if you can blow air through it.. Obviously you should be able to pretty easy.

    Another thought, I dont recall if that year had a pressure regulator or not. Someone may have added one. those do go bad sometimes.
    Ponder those thoughts and check and make sure they don't apply. ;)



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