Still new to the forum and to the C5.
I have a strange issue. My new to me C5, when it reaches just under 3/4 of a tank the gauge goes to E all at once.
The C5 has a 19.5 gallon fuel tank.
So today I and riding knowing I had plenty of gas. After a couple hundred miles I ran completely out of gas.
I knew there was no way I had burned 19.5 gallons.
Luckily and gas station was close by and had to push it to the pump.
I could only put 12 gallons in it.
My questions start with, Has anyone else had this issue? This is more than the typical C5 Gauge problem.
I know there is a lot of knowledge here so I am looking to you guys for direction. Thank you in advance.

 

I, and many others have this problem. In a nut shell, the C5 has saddle tanks. Each tank has a gauge. When the two sending units from the gauges sends their data to the computer, and they don't match, the computer sends the gas gauge to "No Gas."

Some people have reported success in fixing the problem by removing the passenger side wheel, wheel well, and cleaning the contacts on the sending unit. I've heard that others have had success fixing the problem by putting 20 oz of Techron in the gas tank just before filling up the tank. I tried that and it didn't work for me. The 20 oz bottle is available at Auto Zone, and other parts houses.

If you find another easy fix, me and a bunch of other people will appreciate your telling us about it.

I went to the dealer and they told me that I could spend thousands of dollars on trying to fix it, and not really getting it fixed.

I've never had my car quit running when the gauge went to the zero. I've driven it further than 20 miles before I gave in and stopped the car at a gas station, and took a ten minute break. When I restart the car, the gauge works for awhile and then it goes to zero again. The speed I drive doesn't seem to make a difference.

 

Search the forum, there are a bunch of threads about fuel tank/gage problems.

 

Thanks for the info and I will try the somewhat easier fixes first and see how it goes. I actually drove about 2 hundred miles after the gauge went to E. Usually if I fill up when it falls to E it only takes 5-6 gallons to refill. Today it took 12 but it completely ran out of gas. I just wonder where the other 7.5 gallons of gas o am suppose to have is at.

 

Thanks for the information and the advice. It sounds like the siphon pump is a good place to start. The car is a 2000 model.

 

If the siphon pump were out, I doubt you could have driven 200 miles! Sounds to me like the sensor contacts are fowled on one or both sensors. I would try a couple tanks of Techron first (although I have better luck with BG BK 44).

 

I guess it is possible, but I don't get 400 miles per fill-up (of course I do not generally drive on the highway). If he is getting that kind of mileage and actually ran out, then I agree that it is probably the jet-pump. I actually did not read the OPs post closely enough. Apologies!

 

that the siphon pump would be the best place to start looking for the problem. I can get 200+ miles from a half a tank of gas (26-27 mpg) and my tank holds 18.5 gallons of gas.

 

im surprised everyones getting into these complicated diagnostics and theories

You most likely have what so many of us have, which is a wonky fuel gauge sensor

it is easily fixed with a fuel system cleaner, like techron (so ive heard), or regane Gumout (which ive personally used and works like a charm)

 

The car ran completely out of gas. I could only put 12 gallons in it which filled it completely. That means there was 6 1/2 to 7 1/2 gallons of gas in there somewhere that is not usable.
I know the fuel gauge problem is common but i don't see how a gauge alone could cause this.
The siphon pump sounds more like the root problem. But it seems I would have ran out of gas around 9-10 gallon mark unless the tanks are different sizes.
Are both tanks the same size?
Again, thanks everyone for your input.

 

After owning my C5 04 vert for 3 months and reading the Forums info on the gas tank/fuel gauge problem, I decided to only use top grade premium gas (Shell was my choice - no Chevron or Texaco in my area), add a can of Techron every other fill-up, and never let the tank get below 1/4 hoping I will not have the gage/tank issues.

 

8Vette 7 is giving you good advice. You need to start with the siphon pump. Fix it first and see what happens with the fuel gauge.

 

It is the jet pump, not the gauge. The key is running out of gas, and only being able to put 12 gallons in.

It has happened to me. The gas gauge went to zero because PCM was sensing incorrect quantities between tanks, I thought it was the typical gauge problem, so I kept going and ran out of gas.

The reason that you are able to use a bit more than 9 gallons of gas is that the fill crossover is not all the way at the top.

Some members have had success in cleaning the jet pump, but what gets clogged is the internal motive flow nozzle which is very tiny.

You cannot buy the jet pump alone, just the complete assembly including the sender, mounting plate and internal plumbing.

 

Thanks for all of the replies.
I will try running Techron through is for a few tanks and see what happens. I guess that is the easiest and cheapest attempt for now. However I will be filling up every 200 miles. I don't feel like that will fix this particular problem but at least I tried.
Meanwhile I will be looking into what it takes to replace the complete Jet pump assembly and sender as I believe that is probably the problem.
Has anyone priced the parts?

 

Try this for parts http://www.gmpartsdirect.com/ and there are others listed on search engine.
I just moved and found the local Chev dealer has a great Corvette tech. Had them replace both fuel sensors. Parts dept gave me 35% off when I told him I could get them for 41% online. With 86k on the car, it's needing parts replaced.

 

https://www.corvetteforum.com/forums...-on-gauge.html

 

Also try techtron - seemed to work in my friends ride when he first got his ride. The contacts might also be dirty ?

 

Right, but at this stage, more than one tank full will probably be required. possibly 3-4 tanks worth.

 

Update: It seems my problem is getting even stranger! My initial problem was the fuel gauge quit working when it reached 3/4 tank. I would refill with gas (about 5-6 gallons) then the gauge would go back to full. Then one day I ran out of gas and was able to squeeze 12 gallons in it. So I knew it was not using all the fuel on board.
I have ran several Techron treatments with no luck yet. It was worth a try.
Yesterday I filled the car with gas and drove about 150 miles. The fuel gauge quit about 100 miles into the trip. Being 150 miles from home I decided to stop for gas. The gas pump (at the station) tripped at 2 gallons. I waited a few seconds and could pump another 2-4 10ths of a gallon in. I did this for several minutes until I had but almost 6 gallons in. When I got back in the car the fuel gauge did not work. First time this has happened.
I then drove the 150 miles back home. I stopped at my local station to refill the tank. Same thing. Kicked off at about 2 gallons. I spent the next 10 minutes pumping in 2-4 tenths of a gallon and wait. After about 10 minutes I had managed to get almost 6 gallons in and it finally ran over.
So I am at a complete loss as to where to start.
I was sure the siphon pump in the right tank was plugged or partially plugged. But if after 150 miles, way could I only get 2 gallons in the tank. It seems to be working.
So again, I have no idea where to start right now and praying you guys sled some light on where I need to go with this. Thanks for any help you can provide.

 

Sounds like you have multiple issues to me:

1) The fuel filler hose in some of these cars is too narrow. There's a TSB on it, details here:

http://www.superchevy.com/how-to/add...filler-nozzle/

That could be your refill issue

2) You could have a wonky sending unit causing your fuel gauge to act up. I'd keep putting in the techron. Also I recommend Costco gas for it's high level of detergents.

3) Jet siphon pump may or may not be bad.