C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

Relay!!!!!!!!!!

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Old Apr 28, 2017 | 10:17 PM
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Default Relay!!!!!!!!!!

Neighbor has a 1984 corvette, cranks but will not start. I looked it over and found that a relay had exposed and frayed wires, and that when two wires touched the cooling fan came on, the dash lights worked and if the battery was charged it would have started. My issue is that #1 - I do not know what the proper name of this relay is, it is located above the brake booster and has a total of 6 wires, two of which go to one terminal. The wire colors in order are tan, red, green, black and two large red wires. #2 - He got a replacement connector and relay, the new relay only has 5 terminals (im gonna guess this is the wrong part), and the connector has the two wires going into the 4th spot instead of the 5th.
The connector is labeled a-b-c-d-e- and the wire colors go a-tan, b-red, c-green, d-black, e-2 red wires. If the a and b wires are connected all of the =dash light function correctly and I think it will start. Im not sure where to go from here - any advice would be appreciated a great deal.
Thanks!!
Wayne
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Old Apr 29, 2017 | 08:56 AM
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First step is to get an FSM (Factory Service Manual) for the 84 model year.
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Old Apr 29, 2017 | 09:10 AM
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Maybe post the information from the old relay! The fuel pump relay for an '84 is to the right of the booster on a bracket I believe. If it were original I'd expect maybe 14078915. Post also the brand/number of what was purchased.

Maybe "fade" has over come the wire ID.

I'd expect for fuel pump 2 - RED @ A, BLK/WHT @ B, GRN/WHT @ C, RED @ D and ORNG @ E

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Old Apr 29, 2017 | 02:15 PM
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Originally Posted by WVZR-1
Maybe post the information from the old relay! The fuel pump relay for an '84 is to the right of the booster on a bracket I believe. If it were original I'd expect maybe 14078915. Post also the brand/number of what was purchased.

Maybe "fade" has over come the wire ID.

I'd expect for fuel pump 2 - RED @ A, BLK/WHT @ B, GRN/WHT @ C, RED @ D and ORNG @ E

Attachment 48088061
There is no visible information on old relay, im just trying to help out a friend. Would this have an effect on dash lights and turn signals? All of the aftermarket connectors I see for sale have two wires coming from the second terminal, not the first. im confused by this.
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Old Apr 29, 2017 | 04:31 PM
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That's generous of you to help out a friend with his electrical problems. The fuel pump relay shouldn't have anything to do with the lighting circuits or the fan operation. It sounds like you have several problems. Do you know the history of this car? I'd suspect some bad ground connections.

WVZR-1 is giving you the right information. The relay socket you have may be a universal application. Are the two wires on the second (B) terminal black/white? Here's the overall diagram for the '84 fuel pump wiring:



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Old Apr 29, 2017 | 05:00 PM
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Originally Posted by 81c3
First step is to get an FSM (Factory Service Manual) for the 84 model year.
Do you buy them for your neighbors?
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Old Apr 29, 2017 | 05:16 PM
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Originally Posted by Hot Rod Roy
That's generous of you to help out a friend with his electrical problems. The fuel pump relay shouldn't have anything to do with the lighting circuits or the fan operation. It sounds like you have several problems. Do you know the history of this car? I'd suspect some bad ground connections.

WVZR-1 is giving you the right information. The relay socket you have may be a universal application. Are the two wires on the second (B) terminal black/white? Here's the overall diagram for the '84 fuel pump wiring:



Thanks for the diagram! Yes, this car was converted back to carb. There are many what I would call "questionable" wiring wonders under the hood of this thing ...lmao. The cooling fan is wired to ignition sw rather than sensor. I guess I need to look for a bad ground somewhere - which I thought of when i shorted two wires (orange and blk) and the fan and all dash lights came back on. I'll give him a bit more of my time but i'm no electrical pro, especially when someone else has been in there monkeying around.
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Old Apr 29, 2017 | 05:19 PM
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Originally Posted by Wayne Larson
Thanks for the diagram! Yes, this car was converted back to carb. There are many what I would call "questionable" wiring wonders under the hood of this thing ...lmao. The cooling fan is wired to ignition sw rather than sensor. I guess I need to look for a bad ground somewhere - which I thought of when i shorted two wires (orange and blk) and the fan and all dash lights came back on. I'll give him a bit more of my time but i'm no electrical pro, especially when someone else has been in there monkeying around.
Also - regarding the wiring to the relay, the wires are red and they both go to pin A.......The connector however has them going to B.
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Old Apr 29, 2017 | 05:37 PM
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Originally Posted by Wayne Larson
Also - regarding the wiring to the relay, the wires are red and they both go to pin A.......The connector however has them going to B.
Edit...................the two wires when jumped that produce a good running vehicle are d & e red/orange
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Old Apr 29, 2017 | 06:17 PM
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Originally Posted by Wayne Larson
Edit...................the two wires when jumped that produce a good running vehicle are d & e red/orange
That makes perfect sense. That way you get power to the fuel pump without any signal to the relay.

When the relay engages the A pin gets connected to E instead of D as it is drawn in the schematics.

If the relay is good then your problem is with B or C pin.
B should be ground.
C should get power from the ECM, but as the the engine is converted to carb this could be modified. Do you know if the ECM is still in the car? ECM should prime the pump when ignition turns on. Then it should run the pump then it detects ignitition reference pulses anf probably during cranking also.
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Old Apr 29, 2017 | 07:06 PM
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You will find the wires looks bare on allot of relays, they only crimp the wire. With time and heat the plastic shell shrinks and pulls away, and since only the wire is holding, they can break and fray.
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Old Apr 29, 2017 | 08:42 PM
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Originally Posted by Dt86
Do you buy them for your neighbors?
Use your head man.... Like I meant HE should get one... good grief!
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Old Apr 30, 2017 | 12:36 AM
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Originally Posted by JoBy
That makes perfect sense. That way you get power to the fuel pump without any signal to the relay.

When the relay engages the A pin gets connected to E instead of D as it is drawn in the schematics.

If the relay is good then your problem is with B or C pin.
B should be ground.
C should get power from the ECM, but as the the engine is converted to carb this could be modified. Do you know if the ECM is still in the car? ECM should prime the pump when ignition turns on. Then it should run the pump then it detects ignitition reference pulses anf probably during cranking also.
dont know if ecm is present, im curious how this wire grounding would make the dash lights work?
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