C4 General Discussion General C4 Corvette Discussion not covered in Tech

need help finding relay

Thread Tools
 
Search this Thread
 
Old Feb 4, 2012 | 12:10 PM
  #1  
90c4convetible's Avatar
90c4convetible
Thread Starter
Instructor
 
Joined: Dec 2009
Posts: 139
Likes: 0
From: Wadley Georgia
Default need help finding relay

Can anyone tell me the exact location of the fuel pump relay in a 90 convertible c4?
Reply
Old Feb 4, 2012 | 01:06 PM
  #2  
oldalaskaman's Avatar
oldalaskaman
Le Mans Master
10 Year Member
 
Joined: Aug 2010
Posts: 9,272
Likes: 17
Default

I dont have a 90 and i may be wrong, but doing a search says its to the right of the winshield wiper motor on one and on the other its behind the i/p. sorry I cant be more clear
Reply
Old Feb 4, 2012 | 05:29 PM
  #3  
90c4convetible's Avatar
90c4convetible
Thread Starter
Instructor
 
Joined: Dec 2009
Posts: 139
Likes: 0
From: Wadley Georgia
Default

Originally Posted by oldalaskaman
I dont have a 90 and i may be wrong, but doing a search says its to the right of the winshield wiper motor on one and on the other its behind the i/p. sorry I cant be more clear
Thanks I am having trouble finding the locations, I have some wiring diagrams but they dont have anything about where it is located.
Reply
Old Feb 4, 2012 | 05:47 PM
  #4  
Hooked on Vettes's Avatar
Hooked on Vettes
Melting Slicks
15 Year Member
 
Joined: Aug 1999
Posts: 2,240
Likes: 41
From: Baltimore, MD USA
Default

Fuel Pump Relay 1 is on the passenger side front edge of the dash.

Fuel Pump Relay 2 is located below the dash cluster and is only used by the ZR1.

You need to remove the plastic panel with the foot well lamp
to get to Fuel Pump Relay 1.

All the relays in that area are the same so you can swap them around.


Last edited by Hooked on Vettes; Feb 4, 2012 at 05:50 PM.
Reply
Old Feb 4, 2012 | 07:09 PM
  #5  
90c4convetible's Avatar
90c4convetible
Thread Starter
Instructor
 
Joined: Dec 2009
Posts: 139
Likes: 0
From: Wadley Georgia
Default

Originally Posted by Hooked on Vettes
Fuel Pump Relay 1 is on the passenger side front edge of the dash.

Fuel Pump Relay 2 is located below the dash cluster and is only used by the ZR1.

You need to remove the plastic panel with the foot well lamp
to get to Fuel Pump Relay 1.

All the relays in that area are the same so you can swap them around.

Thanks for the diagrams they were very useful. I checked fuel pump relay #1 and it was fine. I did not see that you had said relay #2 was only used by zr1 but there was a relay in that spot under the instrument panel and it is shorted. I am not sure if that is the problem, but as soon as the parts stores open back up tomorrow I will be there to get another relay to confirm whether or not that is the problem. Again thanks for all the help!!!!!!!!
Reply
Old Feb 4, 2012 | 11:20 PM
  #6  
Hooked on Vettes's Avatar
Hooked on Vettes
Melting Slicks
15 Year Member
 
Joined: Aug 1999
Posts: 2,240
Likes: 41
From: Baltimore, MD USA
Default

The ECM applies 12 volts to the Dark Green/White wire to turn on the
fuel pump relay.

You didn't say what your problem is. If the fuel pump runs
with the ignition off, it could be the oil pressure switch/sender behind the
distributor on the driverside is bad.



It has two functions. It is an oil pressure sender and it also
has contacts that close if the oil pressure is above 4 psi. When the
contacts close, 12 volts from an Orange wire (hot at all times) passes
through the switch and provides 12 volts to a Red wire that provides
12 volts to the fuel pump fuse and the fuel pump will run. This is a
backup source in case the Fuel Pump relay fails.

If the switch fails in the closed position, the fuel pump will run
all the time. Current path is in Blue for the oil pressure switch.


Last edited by Hooked on Vettes; Feb 5, 2012 at 08:53 AM.
Reply
Old Feb 5, 2012 | 01:03 PM
  #7  
90c4convetible's Avatar
90c4convetible
Thread Starter
Instructor
 
Joined: Dec 2009
Posts: 139
Likes: 0
From: Wadley Georgia
Default

My problem is the fuel pump isnt priming like it did before it was put into storage. This is causing the car not to start. I was hoping it would be the relay because that is much easier to get to than the fuel pump.
Reply
Old Feb 5, 2012 | 01:59 PM
  #8  
Hooked on Vettes's Avatar
Hooked on Vettes
Melting Slicks
15 Year Member
 
Joined: Aug 1999
Posts: 2,240
Likes: 41
From: Baltimore, MD USA
Default

If the ECM can't control the fuel pump relay
if you keep cranking the engine, eventually
4 psi of oil pressure will close the oil switch
and the fuel pump will get 12 volts from the
oil switch.

It just takes extended cranking time before
the engine will start.

Also under the hood is a wiring harness near the power
brake booster. There is a single Red wire with a female
spade lug. If you apply 12 volts from the Battery
to this terminal the fuel pump should run all
the time even with the ignition off.

If the fuel pump doesn't run most likely the fuel pump is bad.

Last edited by Hooked on Vettes; Feb 5, 2012 at 02:15 PM.
Reply
Corvette Stories

The Best of Corvette for Corvette Enthusiasts

story-0

8 Coolest Corvette Pace Cars (and Replicas) of All Time

 Verdad Gallardo
story-1

Top 10 Corvette Engines RANKED by Peak Torque (70+ Years of Muscle!)

 Joe Kucinski
story-2

Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!

 Verdad Gallardo
story-3

Top 10 Corvettes Coming to Mecum Indy 2026!

 Brett Foote
story-4

Top 10 C9 Corvette MUST-HAVES to Fix These C8 Generation Flaws!

 Michael S. Palmer
story-5

10 Revolutionary 'Corvette Firsts' Most People Don't Know

 Joe Kucinski
story-6

5 Reasons to Upgrade to an LS6-Powered Corvette; 5 Reasons to Stay LT2

 Michael S. Palmer
story-7

2027 Corvette vs The World: Every C8 vs Its Closest Competitor

 Joe Kucinski
story-8

10 Most Common Corvette Problems of the Last 20 Years!

 Joe Kucinski
story-9

5 MOST and 5 LEAST Popular Corvette Model Years in History!

 Joe Kucinski
Old Feb 6, 2012 | 02:43 PM
  #9  
90c4convetible's Avatar
90c4convetible
Thread Starter
Instructor
 
Joined: Dec 2009
Posts: 139
Likes: 0
From: Wadley Georgia
Default

Well the fuel pump is bad and I am getting one to replace it.
Reply

Get notified of new replies

To need help finding relay





All times are GMT -4. The time now is 08:12 PM.

story-0
8 Coolest Corvette Pace Cars (and Replicas) of All Time

Slideshow: Some Corvette pace cars became collectible legends, while others perfectly captured the look and attitude of their era.

By Verdad Gallardo | 2026-05-11 09:50:51


VIEW MORE
story-1
Top 10 Corvette Engines RANKED by Peak Torque (70+ Years of Muscle!)

Slideshow: Ranking the top 10 Corvette engines by torque output.

By Joe Kucinski | 2026-05-05 11:58:09


VIEW MORE
story-2
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!

Slideshow: A Corvette pace car nearly matching IndyCar speeds sounds exaggerated, until you look at the numbers.

By Verdad Gallardo | 2026-05-04 20:03:36


VIEW MORE
story-3
Top 10 Corvettes Coming to Mecum Indy 2026!

Among a rather large group of them.

By Brett Foote | 2026-05-04 13:56:44


VIEW MORE
story-4
Top 10 C9 Corvette MUST-HAVES to Fix These C8 Generation Flaws!

Slideshow: the top 10 things Corvette owners want in the C9 Corvette

By Michael S. Palmer | 2026-04-30 12:41:15


VIEW MORE
story-5
10 Revolutionary 'Corvette Firsts' Most People Don't Know

Slideshow: 10 Important Corvette 'firsts' that every fan should know.

By Joe Kucinski | 2026-04-29 17:02:16


VIEW MORE
story-6
5 Reasons to Upgrade to an LS6-Powered Corvette; 5 Reasons to Stay LT2

Slideshow: Should you buy a 2020-2026 Corvette or wait for 2027?

By Michael S. Palmer | 2026-04-22 10:08:58


VIEW MORE
story-7
2027 Corvette vs The World: Every C8 vs Its Closest Competitor

Slideshow: 2027 Corvette lineup vs the world.

By Joe Kucinski | 2026-04-24 16:12:42


VIEW MORE
story-8
10 Most Common Corvette Problems of the Last 20 Years!

Slideshow: 10 major Corvette problems from the last 20 years.

By Joe Kucinski | 2026-04-14 16:37:05


VIEW MORE
story-9
5 MOST and 5 LEAST Popular Corvette Model Years in History!

Slideshow: 5 most and least popular Corvette model years.

By Joe Kucinski | 2026-04-08 13:25:01


VIEW MORE