Fuel issue
Thread Starter
7th Gear
Joined: Jul 2022
Posts: 7
Likes: 1
Fuel issue
Hello Everyone,
I am having an issue with my 03 z06. It seems that my fuel pump is working intermittently (sometimes I will get pressure and other times I wont). I did voltage testing on the relay and saw that the car would start and run fine while at battery voltage, but after a short amount of time would drop voltage by half. After dropping voltage the engine would stop preforming optimally and soon stop running. I have replaced the relay, but that didnt fix the issue. I have also ordered a new (used) fuse box in hopes that might be the issue. After disconnecting the old fuse box, I dont see any corrosion or burning on the harness connectors. I will update the post once I get the new fuse box in place and tested. I am not savvy in electrical work, but I am tired of throwing new parts at the car to see if it will be the fix. Any help or reply is very much appreciated.
I am having an issue with my 03 z06. It seems that my fuel pump is working intermittently (sometimes I will get pressure and other times I wont). I did voltage testing on the relay and saw that the car would start and run fine while at battery voltage, but after a short amount of time would drop voltage by half. After dropping voltage the engine would stop preforming optimally and soon stop running. I have replaced the relay, but that didnt fix the issue. I have also ordered a new (used) fuse box in hopes that might be the issue. After disconnecting the old fuse box, I dont see any corrosion or burning on the harness connectors. I will update the post once I get the new fuse box in place and tested. I am not savvy in electrical work, but I am tired of throwing new parts at the car to see if it will be the fix. Any help or reply is very much appreciated.
Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,319
Likes: 3,927
From: Cape Coral, Florida
Being that yours is an 03 is your fuel pump at the bottom of the tank…if on top your RPO code in your glove box will say “FFS”…do you know ??..I may want to hold off on replacing the fuse box…where and how were you checking for this voltage drop ??
Last edited by C5 Diag; May 8, 2023 at 03:16 PM.
Thread Starter
7th Gear
Joined: Jul 2022
Posts: 7
Likes: 1
Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,319
Likes: 3,927
From: Cape Coral, Florida
Your fuel pump should be at the bottom…RPO codes go in alphabetical order and I don’t see it…where are how did you check for this voltage loss ??…you can also go by the VIN to check for which system you have…just easier to look at the RPO’s…they changed halfway through that model year.
Thread Starter
7th Gear
Joined: Jul 2022
Posts: 7
Likes: 1
I tested at the relay with a multimeter a small pin touching the connectors of the relay. Would that be a sufficient way and location to test for the drop? Like I said, im a newbie to voltage testing so im not 100% sure.
Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,319
Likes: 3,927
From: Cape Coral, Florida
Well what you can do is hook up one lead of your voltmeter to battery positive and with the engine running touch the other lead to the fuel pump fuse #13…don’t worry if you see a minus just look at the number…I don’t know how long it takes for the voltage to drop but here we are making sure we are not dropping voltage through the ignition switch…if you see 0.2 to 0.3 volts you’re good…if you see 5 or 6 volts…bad…you would just continue on down the circuit till go get to the pump…the negative side of the pump will also have to be checked…video below !!
Last edited by C5 Diag; May 8, 2023 at 04:02 PM.
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Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,319
Likes: 3,927
From: Cape Coral, Florida