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Fuel delivery system for 1989 Corvette

I love my Chevy Chevette!
Posts: 3
Joined: 04/12
Posted: 09/14/12 07:18 AM

You all have been real helpful in the past and I just want to thank you in advance.  I am having a fuel issue with my 1989 Vette. Not getting any fuel to the fuel rail. When I check the pressure at the Schrader valve there is nothing.  About two years ago I replaced the fuel pump and it's doing the same thing again.  Is there any thing else it could be? Help!  Dale  Confused  

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My first time was in a Chevy
Posts: 181
Joined: 04/12
Posted: 09/14/12 02:00 PM

the fuel pump is powered by 2 devices...

there is an ORANGE wire that supplies power to both.. this orange wire is NOT switched.. there is power all the time..

the fuel pump relay and the oil pressure switch are wired in parallel...

so either can control the fuel pump..

take a look at this kinda confusing wiring diagram...

86 165V8tpi 4

first ...  while you have somebody turn the key from off to ON... listen to the fuel tank at the gas cap...  you might also pound lightly on the gas cap.. to giggle the pump in the tank.. this will sometimes get the pumps to restart..     but this has to be done with the engine cranking...

i would like you to check the fuel filter.. that its not clogged...  you will probably want to replace the fuel filter..  the filter could be inside the frame behind the right front wheel.. could also be back by the back of the car..  i don't know for sure on an 89..

another way to test the pump...   use a jumper wire from the positive battery .. to the G terminal on the aldl connector..  with the key off.. thats the prime the pump connector..  powers the fuel pump directly through the relay when the relay is not powered...

if you can get the fuel pump to spin by sending positive power to the G terminal.. then you can continue...

lets look again at the wiring diagram... start at the top of the page... see the fuse... do you have power on that fuse in the fuse box inside the car???

the fuel pump relay is up on the firewall.. probably next to the power brake booster.. sort of near the wiper motor..

there is also a 3 wire oil pressure switch...  lets take a look inside those...


see the single terminal sticking out.. thats just for the oil pressure gauge... when the oil pressure comes up.. the bar moves up to contact the terminals inside the cap..


see the contacts inside the cap.. this is what the bar moves up and touches...  the problem.. the area where it touches may get some burning marks on it and prevent it from sending all the power...


this is the inside of a later GM fuel pump relay...

you can on some.. pry the cover off without damaging it..

you can then squeeze the contacts closed to see if the fuel pump runs at that point...

i came up with a test... i get the car or truck running.. i pull the fuel pump relay or connector... if the engine does NOT die..  i know that the oil pressure switch contacts are working properly..


how it all works... when the key is first turned on..  the ECM turns on the fuel pump relay for 2 seconds... this builds up fuel pressure... when you start cranking. the ECM commands the fuel pump relay on again...  

once the engine oil pressure comes up.  the oil pressure switch takes over.. most cars still keep the fuel pump relay turned on..  later models with the smaller pins on the relay.. don't have enough amperage to properly supply the fuel pump for very long. the relay socket terminals will get hot.. melt.. loosen up. . melt the relay undersides also..

i hope this gives you enough to get your fuel pump running..

feel free to ask questions..

lastly ... PLEASE DO NOT PROBE THE FUEL PUMP RELAY SOCKET.. if you manage to touch the wire to the ECM.. you can burn out the ECM and really ruin your day...

the grounds are important also..  its usually next to or behind the battery..  

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V-6 Camaros rule!
Posts: 83
Joined: 01/12
Posted: 09/14/12 05:26 PM

Ghostwalker: Thanks for the attaboy:

I'm sure the fuel pump is he problem, or the check valve in the pump itself....If you have to replace the pump see if they make a Hi Performance pump for your application. Sometimes the pumps overhaet and stop picking up and pushing fuel. Check I don't know it that year had a sock on the inlet. Thats a filter. If your new pump doesn't come with a new filter get one.


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