matt204

Hi Everyone!

I have a 2003 c5. I recently had both fuel pumps including sending units and crossover pipe changed on my vette by a local shop. When I fill it with fuel it will read to 3/4 max even though its completely full. After driving for a while you can see the gauge slowly going down as it should but shortly after it will drop to empty and the low fuel warning light will come on. If I clear the code the gauge goes back up to 3/4. Everything is new AC Delco parts they have pulled the tanks 3 times to inspect it. Can't figure it out! Does anyone have any ideas? Does it need some type of a flash update? Any help is much appreciated!

Phanni

That type problem is usually indicative of tarnished foils on the sending unit sensor located on the pumps. After time the foil or the pickup gets tarnished and the slide mechanism is not making proper contact. Since you had both replaced, It's likely not the problem, however if the mechanic used your old pick ups or damaged the new ones the problem would be the same.

Why did you have the fuel pumps replaced/
Are you sure they actually replaced them?
Just for drill, I'd dump in a bottle of techron ( you can get it at a Autozone or such store) on you next fill up.
There are many threads on this type problem. Do a search on this forum.

shaggyvette

matt204

Thanks for the info Phanni! They were replaced because I had a no start (bad pump). So I supplied the shop with ac delco pumps, sending units and cross over pipe. Maybe they did damage one? Does it read from both sending units or does the gauge only pick up from one tank?

Thanks for the suggestion shaggyvette but everything is brand new so in theory Techron shouldn't have any effect because there is nothing to clean.

ArmchairArchitect

I'd bring it back to the same shop and have them fix it, and make sure you don't get charged any more than what you already paid.

matt204

ArmchairArchitect the shop has pulled the tanks 3 times and cannot figure it out. They have offered me a refund. I just want it fixed so I'm trying to do some research myself.

Phanni

I suspect they used the same pick ups from the replaced units. They are sorta fragile.
It's likely that they were damaged in the transition. The pick up is simply a rheostat with a wiper arm that contacts different segment of a printed circuit board. there is a float that seeks the level of fuel and the wiper arm reads the level this way. both pumps have them. Any good mechanic that has an ohm meter should be able to check the functioning of the unit. The pumps will have to be removed.

https://www.sailmagazine.com/diy/tes...e-sending-unit

Vetteman Jack

matt204

Update: shop had pulled the tank ohm'd the sending units they are reading correctly. Even used a bore scope to watch the float function. Weird thing is when you clear the code with a scanner the gauge goes back up to 3/4 level. We are stumped!

rrwirsi

When I am faced with computer processing problems that will not get fixed by normal 'fixes', I disconnect everything from the computer and wait 30 minutes. Then I reconnect and many times this cures my issues. Try disconnecting the battery. Sometimes it is a simple fix that does it. Hope you find the problem.

jcgunn

It is very easy to hang the float on the fuel sock, you have to be very careful when installing the sender into the tank

matt204

Update: I have scanned it and the code P1431 Fuel Level (sensor 2) performance. Like I had mentioned before both pumps, sending units, and cross over are new. Would this code be a indication of a defective sending unit? Also when I clear the code the fuel gauge immediately goes from 0 to reading the correct level of fuel

DaveC-98-C5

Did you ever get this solved? Having similar issues.