Fuel pump relay getting no power
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4th Gear
Joined: May 2021
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Fuel pump relay getting no power
Alrightyyy so I had recently bought an 85 TPI as a project car, I am currently in the process of getting it road worthy so I can enjoy it for a little bit, I would eventually like to do an engine swap is ether an LS or Gen 5 LT, it does have three engine codes, 32 EGR, 33 MAF, and 54, fuel low voltage, I'm currently on code 54, the previous owner replaced the fuel pump so that's brand spanking new, my problem is I am not getting any power to pin A on the pump relay connector for the fuel prime when the key is on, just pin E for oil pressure switch, when the oil pressure builds to close the pressure switch the car will run perfectly! It's just the prime process that's not working for me I have jumped 12v through the relay (which is brand new as well) and the pump will run, I was thinking maybe just as a temporary solution, I can run a manual switch to use as the 2 second priming time, and let the oil pressure switch do the rest of the work as normal. Any advice would be great, I would like to get this done right before I attempt a manual switch, thank you all in advance
Last edited by MYSTERIOUS DRAGON; May 13, 2021 at 04:47 PM.
Thread Starter
4th Gear
Joined: May 2021
Posts: 4
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If you jumper pin A to pin B, does the pump run? If = Yes, the relay can turn on the pump. (The power and pump circuits are functional).
Is there +12 Volts on pin C during the 2 second Prime? (Connect your meter between Pin C and a good ground, and cycle the key). If = Yes, the ECM signal is getting to the relay.
Connect your meter between a (B+) terminal on the alternator or battery and Pin B on the relay. This checks the ground circuit for the relay coil. Is the ground good?
Does the relay "click" on then off for the prime? (This indicates the control-side circuit is functional, but the contacts in the relay may still be bad).
If all of the checks above test good, the relay is bad. In this day and age of "test by substitution", and chain stores honoring returns for any reason, the likelihood of getting a bad (or even the used part returned for credit) has gone way up. Especially from a chain store.
Is there +12 Volts on pin C during the 2 second Prime? (Connect your meter between Pin C and a good ground, and cycle the key). If = Yes, the ECM signal is getting to the relay.
Connect your meter between a (B+) terminal on the alternator or battery and Pin B on the relay. This checks the ground circuit for the relay coil. Is the ground good?
Does the relay "click" on then off for the prime? (This indicates the control-side circuit is functional, but the contacts in the relay may still be bad).
If all of the checks above test good, the relay is bad. In this day and age of "test by substitution", and chain stores honoring returns for any reason, the likelihood of getting a bad (or even the used part returned for credit) has gone way up. Especially from a chain store.
Thread Starter
4th Gear
Joined: May 2021
Posts: 4
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Okay so I just did what you said, jumped pin A to B, and still nothing, I even rechecked pin A for power and there is no power, I checked pin C and there's only 0.04 volts when key is cycled, I checked the grounds from the alternator to pin B and those check out
Safety Car
Joined: May 2001
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From: Fairfax Virginia
Welcome to the Corvette Forum MYSTERIOUS DRAGON!
Start at your battery and be sure it is reading roughly 12 volts minimum without anything turned on. Now go to the battery Positive cable at the battery Positive Terminal. Be sure it is tight and clean. From this point there should be a RED wire that goes off to the drivers side behind the battery under the side panel it attaches to a Point on the frame. The post it attaches to should be easy to find as on my 1988 it has Seven Fusible Links ALL getting their power here. The post is not actually attached to ground and when you put as meter on it you should see battery voltage.
Your 1985 might be different physically but the Fusible Links need +12 VDC fed to them. I have found corrosion on the post that caused a serious voltage drop inside the car. If your Fusible Links are okay and you are getting 12 Volts move on to the fuse box and check for 12V there as well.
The fusible Links were GM's last line of protection from burning the car down. It is wise to check them for continuity if you are having a tough problem. On my 1988 I routinely check that post now that I am aware of the issues it can cause.
One One Corvette I actually found "Bad Fuses" that were causing the problems. They were aluminum and they had no continuity unless you scraped the surface.
Clean battery connections are vital on today's cars.
Good Luck!
Start at your battery and be sure it is reading roughly 12 volts minimum without anything turned on. Now go to the battery Positive cable at the battery Positive Terminal. Be sure it is tight and clean. From this point there should be a RED wire that goes off to the drivers side behind the battery under the side panel it attaches to a Point on the frame. The post it attaches to should be easy to find as on my 1988 it has Seven Fusible Links ALL getting their power here. The post is not actually attached to ground and when you put as meter on it you should see battery voltage.
Your 1985 might be different physically but the Fusible Links need +12 VDC fed to them. I have found corrosion on the post that caused a serious voltage drop inside the car. If your Fusible Links are okay and you are getting 12 Volts move on to the fuse box and check for 12V there as well.
The fusible Links were GM's last line of protection from burning the car down. It is wise to check them for continuity if you are having a tough problem. On my 1988 I routinely check that post now that I am aware of the issues it can cause.
One One Corvette I actually found "Bad Fuses" that were causing the problems. They were aluminum and they had no continuity unless you scraped the surface.
Clean battery connections are vital on today's cars.
Good Luck!
Thread Starter
4th Gear
Joined: May 2021
Posts: 4
Likes: 0
Welcome to the Corvette Forum MYSTERIOUS DRAGON!
Start at your battery and be sure it is reading roughly 12 volts minimum without anything turned on. Now go to the battery Positive cable at the battery Positive Terminal. Be sure it is tight and clean. From this point there should be a RED wire that goes off to the drivers side behind the battery under the side panel it attaches to a Point on the frame. The post it attaches to should be easy to find as on my 1988 it has Seven Fusible Links ALL getting their power here. The post is not actually attached to ground and when you put as meter on it you should see battery voltage.
Your 1985 might be different physically but the Fusible Links need +12 VDC fed to them. I have found corrosion on the post that caused a serious voltage drop inside the car. If your Fusible Links are okay and you are getting 12 Volts move on to the fuse box and check for 12V there as well.
The fusible Links were GM's last line of protection from burning the car down. It is wise to check them for continuity if you are having a tough problem. On my 1988 I routinely check that post now that I am aware of the issues it can cause.
One One Corvette I actually found "Bad Fuses" that were causing the problems. They were aluminum and they had no continuity unless you scraped the surface.
Clean battery connections are vital on today's cars.
Good Luck!
Start at your battery and be sure it is reading roughly 12 volts minimum without anything turned on. Now go to the battery Positive cable at the battery Positive Terminal. Be sure it is tight and clean. From this point there should be a RED wire that goes off to the drivers side behind the battery under the side panel it attaches to a Point on the frame. The post it attaches to should be easy to find as on my 1988 it has Seven Fusible Links ALL getting their power here. The post is not actually attached to ground and when you put as meter on it you should see battery voltage.
Your 1985 might be different physically but the Fusible Links need +12 VDC fed to them. I have found corrosion on the post that caused a serious voltage drop inside the car. If your Fusible Links are okay and you are getting 12 Volts move on to the fuse box and check for 12V there as well.
The fusible Links were GM's last line of protection from burning the car down. It is wise to check them for continuity if you are having a tough problem. On my 1988 I routinely check that post now that I am aware of the issues it can cause.
One One Corvette I actually found "Bad Fuses" that were causing the problems. They were aluminum and they had no continuity unless you scraped the surface.
Clean battery connections are vital on today's cars.
Good Luck!
