Fuel level indicator issues
Thread Starter
CF Senior Moments Member
Joined: Jan 2004
Posts: 1,329
Likes: 1
From: Oklahoma City Oklahoma
Fuel level indicator issues
2000 C5 Fuel gauge shows slightly less than 1/2 tank - so I fill up and it takes 15Gal? 
I've learned to fill up when it gets to 1/2 tank so I don't get stranded.
If I replace the "fuel hat" with the double pump Lonnie's setup - will it also replace the " fuel sender " mechanism that checks how much fuel is left?
Or do I also need to replace the fuel sender in the same (driver side) tank ..when the double pump is installed?
Or do I need to replace the fuel sender in the passenger side tank ?
or... ?
I've learned to fill up when it gets to 1/2 tank so I don't get stranded.
If I replace the "fuel hat" with the double pump Lonnie's setup - will it also replace the " fuel sender " mechanism that checks how much fuel is left?
Or do I also need to replace the fuel sender in the same (driver side) tank ..when the double pump is installed?
Or do I need to replace the fuel sender in the passenger side tank ?
or... ?
Tech Contributor
Joined: Dec 2003
Posts: 19,384
Likes: 87
From: Horncastle Lincolnshire, England
2023 C5 of the Year Finalist - Unmodified
I can't answer the question on the mod. The senders bolt directly into the tank wall so I assume a pump change wont affect the senders.
First thing to try is to run a few bottles of techron through the system to try to clean up the senders. Clear down any fuel codes on the DIC.
If you tried that and have decided that a sender replacement is the only solution, from your symptoms, my guess would be its the left hand tank (drivers side) sender. It seems that the right is working normally down to half contents and the left is then reading full.
First thing to try is to run a few bottles of techron through the system to try to clean up the senders. Clear down any fuel codes on the DIC.
If you tried that and have decided that a sender replacement is the only solution, from your symptoms, my guess would be its the left hand tank (drivers side) sender. It seems that the right is working normally down to half contents and the left is then reading full.
Last edited by DeeGee; Mar 27, 2012 at 02:51 AM.
Thread Starter
CF Senior Moments Member
Joined: Jan 2004
Posts: 1,329
Likes: 1
From: Oklahoma City Oklahoma
I can't answer the question on the mod. The senders bolt directly into the tank wall so I assume a pump change wont affect the senders.
First thing to try is to run a few bottles of techron through the system to try to clean up the senders. Clear down any fuel codes on the DIC.
If you tried that and have decided that a sender replacement is the only solution, from your symptoms, my guess would be its the left hand tank (drivers side) sender. It seems that the right is working normally down to half contents and the left is then reading full.
First thing to try is to run a few bottles of techron through the system to try to clean up the senders. Clear down any fuel codes on the DIC.
If you tried that and have decided that a sender replacement is the only solution, from your symptoms, my guess would be its the left hand tank (drivers side) sender. It seems that the right is working normally down to half contents and the left is then reading full.
Why would the right side be working normally - if I am running out of fuel ?
guess I'm confused...
Thanks for the suggestion regarding the techron ...
Team Owner
Joined: May 2001
Posts: 36,836
Likes: 241
From: Dear Karma, I have a list of people you missed.
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15-'16
If the left side pump assembly has ever been out of the car before, it's possible the sending unit (with float arm attached) was not secured properly when re-inserting the hat assembly and may be caught or hung up on the pump assembly inside the tank.
When removing the pump assembly on the driver's side (ONLY), once the unit is part-way out, the sender/float arm must first be unclipped from the hat/pump assembly and "snaked out" gently allowing for the twists and bends in the float arm, etc and then, with the sender wires still attached, the pump assembly may then be "snaked" (so-to-speak) the rest of the way out. When re-installing, the reverse applies and I think it possible that the sender/float arm may not have been re-attached properly or at least the float arm itself was not checked for free-range of motion up and down and unable to follow the fuel level all the way down.
This "diagnosis" is just theory at this point but would fit the scenario you describe, and would mainly apply only if the driver's side unit has been out before, since this is something I seriously doubt would just "happen" on it's own.
I had to deal with a situation similar to this once before in the driver's tank but in my situation the sender/float arm had come completely off the pump hat and was laying in the bottom of the tank with it's wires still attached.
As to your question on Lonnie's setup, I'm fairly certain you re-use your sending unit, assuming it's working of course.
Thread Starter
CF Senior Moments Member
Joined: Jan 2004
Posts: 1,329
Likes: 1
From: Oklahoma City Oklahoma
FYI, the individual sending units (with float arms) attach to the fuel pump hat assembly in each tank. The right side sender is not available as a separate item, but the driver's side is.
If the left side pump assembly has ever been out of the car before, it's possible the sending unit (with float arm attached) was not secured properly when re-inserting the hat assembly and may be caught or hung up on the pump assembly inside the tank.
When removing the pump assembly on the driver's side (ONLY), once the unit is part-way out, the sender/float arm must first be unclipped from the hat/pump assembly and "snaked out" gently allowing for the twists and bends in the float arm, etc and then, with the sender wires still attached, the pump assembly may then be "snaked" (so-to-speak) the rest of the way out. When re-installing, the reverse applies and I think it possible that the sender/float arm may not have been re-attached properly or at least the float arm itself was not checked for free-range of motion up and down and unable to follow the fuel level all the way down.
This "diagnosis" is just theory at this point but would fit the scenario you describe, and would mainly apply only if the driver's side unit has been out before, since this is something I seriously doubt would just "happen" on it's own.
I had to deal with a situation similar to this once before in the driver's tank but in my situation the sender/float arm had come completely off the pump hat and was laying in the bottom of the tank with it's wires still attached.
As to your question on Lonnie's setup, I'm fairly certain you re-use your sending unit, assuming it's working of course.
If the left side pump assembly has ever been out of the car before, it's possible the sending unit (with float arm attached) was not secured properly when re-inserting the hat assembly and may be caught or hung up on the pump assembly inside the tank.
When removing the pump assembly on the driver's side (ONLY), once the unit is part-way out, the sender/float arm must first be unclipped from the hat/pump assembly and "snaked out" gently allowing for the twists and bends in the float arm, etc and then, with the sender wires still attached, the pump assembly may then be "snaked" (so-to-speak) the rest of the way out. When re-installing, the reverse applies and I think it possible that the sender/float arm may not have been re-attached properly or at least the float arm itself was not checked for free-range of motion up and down and unable to follow the fuel level all the way down.
This "diagnosis" is just theory at this point but would fit the scenario you describe, and would mainly apply only if the driver's side unit has been out before, since this is something I seriously doubt would just "happen" on it's own.
I had to deal with a situation similar to this once before in the driver's tank but in my situation the sender/float arm had come completely off the pump hat and was laying in the bottom of the tank with it's wires still attached.
As to your question on Lonnie's setup, I'm fairly certain you re-use your sending unit, assuming it's working of course.
Much appreciated!! 
Yes the unit had been out recently...
Team Owner
Joined: May 2001
Posts: 36,836
Likes: 241
From: Dear Karma, I have a list of people you missed.
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15-'16
Now you can either drain the L/H tank and re-attach or reposition the float arm so it moves freely, or do the same but replace the sender/float arm instead. If you have recently had the pump assy out, then hopefully your tank gasket is OK and reusable, if not you need a AC Delco G25 gasket kit ($33.xx with new screws on Amazon).
The AC Delco part number for the float/sender is SK1318 (~$80 on Amazon or EBay). If you replace, go ahead and remove the entire assembly again since removing/attaching the two wires with the assy halfway out is really tricky without six hands.
Keep us posted on what you find.
