C5-2003

2003 C5 16k, Chevron premium used forever and Stabil used for storage......At startup today fuel gage indicated 1/2 full with a full tank. Added Techron Plus at a 20gal concentration and drove the car about sixty five miles with no change......still inaccurate. During the 65miles the gage did indicate that fuel was being used but quantity remained wrong. No codes or lights at anytime. Any suggestions???

(1)Does the gas tank have to be full in order to have the fuel quantity probes and sending units fully submerged in fuel? Trying to determine the best way to get the Techron Plus to the probes/sending units to remove the sulfur from them......full tank or partial? (2)Would using a higher concentration of Techron Plus than the 20 gallon help or could it damage things? (3)How bad of a hit($$$) to replace the probes and sending units if it comes to that? Thanks for any help on this.....

Phanni

The units sit in a horizonal position within each tank. You do know that there are two tanks in a C-5 right? They are pretty much submerged until the tanks get quite low. There is a 'float' that measures the fuel and works a pickup along a etched reostat on each sending unit. You particular problem sounds like (but does not always mean) that one of those unit may be malfunctioning. I'd fill the tank and see what happens. A resistance check at the plug might give you a clue, however it's not all that easy to 'get' to. As for replacement, it isn't cheap, and isn't easy to do. the tanks will need to be almost empty, (or you'll lose a lot of gas) and I'd only let a qualified servicetech do it since you're dealing with a very explosive situation.

that's my opinion anyway.

black match box

I have not had this problem with the vette but on my wifes pacifica. Took it to the dealer and they checked it out. I was told that it was the right sending unit. Make a long story short, paid them the 94$ for inspecting it and I told them that I would think about it. Gas tank was low so I stoped on the way home and bought 2 bottles of techron, put one in, filled the car. 1 week latter filled and added the techron again. Befor the 3rd fill up the gauge started working again. Thanks to this forum, saved me 995$ in repairs, this is what they wanted to fix the problem. Good luck

srs244

Techron treatment usually takes more than one application. I would try filling the tank again and adding a bottle and do it again once that tank needs refilling. Certainly cheaper to try before the expense (and yes it is about a 1400.00 job at a dealership)

LoneStarFRC

Actually it's the other way around. Driver's side replaceable as a separate item.

That's the first thing I noticed when he posted.

Vetteman Jack

Give it another bottle or two of Techron concentrate and see if it helps before taking it in for any repairs.

oh1vette

When it first happened to me it took 3 tankful treatments to clear it up...

Now I'm on preventive maintenance w/ Techron...

94centennial

i had issues. added one bottle to a nearly empty tank and it corrected the reading with 2 minutes of driving. i filled thetank after 15 miles. that was 3 years ago. i've not had a problem since and i have not added more Techron. i mostly use Marathon or Bp gasoline.

C5-2003

Thanks to everyone for this excellent information....very much appreciated................ My only remaining question is regarding the Techron Plus concentration. I already put one bottle of Techron Plus at a 20 gallon concentration into an already full tank..............do I have to run that tank to near empty before adding another 20gallon bottle or can I add more Techron Plus before running the tank to near empty. Somewhat worried about a too high of a concentration of Techron Plus could cause possible damage.
With a full tank with a high level of Techron Plus concentration is the Techron Plus also doing its job or does the car need to be driven for an extended period of time(3 tankfuls & 900 miles) to really allow the techron to do its job? I ask that because I am trying to determine if this is an internal problem of the system requiring the car to be driven or if it is an external problem of the probes/sending units where just physically sitting in fuel highly concentrated in techron plus would take care of the problem given time . Looks to me that it could be a possible combination which would dictate that the car has to be driven to cover all bases. You guys are the expert.......what do you think???

C5-2003

Car does have FSS RPO(must drop both tanks) so this could get very expensive if Mr Techron Plus does not come through...

leet13

Glad I saw this... My gauge never quite reads FULL after a fill up.

reath1

I have no idea on the concentration of Techron doing any damage to your system but I can tell you that with every vehicle I buy no matter new or used..I run the tank down to near empty. I like to see just where empty is and then I add 4 cans of Seafoam and 4 cans of Chemtool. Then I push my luck driving with that in the tank for about 20-30 miles. Then go and fill back up with fuel. My guess is that I have somewhere around 20-40% "cleaner" in the fuel tank while doing this. Never has caused a problem and yes, I did do it to the vette I bought about a month ago. I do this about every 6 months. Even do it with my lawnmower.

In fact, I would like the more knowledgeable guys to tell me what exactly the Techron does that Seafoam and Chemtool can't.

BG is really the best stuff as far as I'm concerned but I never think to buy it online and it's a little pricey. Not bad compared to the above concoction that I named though. Seafoam is about $8/per can and the Chemtool is about $4/can.

But again, I really don't think you have to worry about getting too much Techron in there.

CCA Corvette Parts

Yup



Peace
Chip

C5-2003

UPDATE: At the start of this the car was full of fuel but at startup the fuel gage suddenly showed 1/2 full so I added some Techron to the full tank and drove the car. Car has always had Chevron premium as well as stabil during storage times which have been about four months a year.
1. Ran the fuel down until the reserve fuel light came on and then added the 20gal concentration of Techron along with a 5gallons of chevron premium. Drove the car until the car ran out of fuel.
2. This was the only way to confirm that no fuel was being transfered from the FULL right tank to the left.
3. Added another 20 gal concentration of Techron and filled the left tank and have continued to drive the car but only able to use the fuel in the left tank which limits the range to about 150 miles.
Not sure where to go from here other than continuing to drive the car and using the techron while hoping that things come back. My only diagnosis is that the sending unit(incl venturi pump) in the RIGHT tank has failed. If that is the case then my only remaining option is to drive to the dealer and hand him a credit card. This car has received the most meticulous care of any vette but unfortunately it looks like that was not enough when it comes to avoiding these infamous fuel system problems with the C5s. I knew about the problems and I did my best to prevent them but apparently it was not enough. Unfortunate.