Fuel tanks, fuel sending unit and Techron
09-23-2014, 10:52 AM
#1
Le Mans Master
Thread Starter
Fuel tanks, fuel sending unit and Techron
From what I understand the engine is fed from the left tank while the right tank continues to siphon gas to the left tank. Is it correct that the fuel level sending unit that gets corroded is in the right tank? Now when refueling does the left tank fill up first before the right tank? So if Techron is added to a tank low on fuel most of it will stay in the left tank and then the right tank will fill. Correct? Would it be better to add one bottle at the start if filling the tank and another when the tank is full to get Techron to the right tank so it can clean the sensor?
My gauge started acting up last spring and I have been using Techron ever since without results. I was thinking maybe all the Techron is staying in the left tank.
My gauge started acting up last spring and I have been using Techron ever since without results. I was thinking maybe all the Techron is staying in the left tank.
09-23-2014, 11:18 AM
#2
You are partially correct. The EFI pump is in the left tank, as is the sending unit. '97-E2003 the pump and sending unit can be accessed without dropping the tank. L2003-2004 you must drop the tank out to remove/replace the pump and sending unit. As far as refueling the tanks; yes the left side fills first, then the right. However as you drive or even let the car sit Techron will permeate all the fuel. I use Techron about every third fill and pour it in before filling with fuel... Good luck and hope this helps!
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ArmchairArchitect (08-14-2017)
09-23-2014, 12:15 PM
#3
Melting Slicks
From what I understand the engine is fed from the left tank while the right tank continues to siphon gas to the left tank. Is it correct that the fuel level sending unit that gets corroded is in the right tank? Now when refueling does the left tank fill up first before the right tank? So if Techron is added to a tank low on fuel most of it will stay in the left tank and then the right tank will fill. Correct? Would it be better to add one bottle at the start if filling the tank and another when the tank is full to get Techron to the right tank so it can clean the sensor?
My gauge started acting up last spring and I have been using Techron ever since without results. I was thinking maybe all the Techron is staying in the left tank.
My gauge started acting up last spring and I have been using Techron ever since without results. I was thinking maybe all the Techron is staying in the left tank.
Story as given to me by the dealer mechanic at the time is silver solder was used in the fuel sender pickup contacts for 2001 model year. Sulfur in the fuel eventually erodes the contacts, causing the guage to go wonky.
(This happened with more than one model 2001 GM vehicle, BTW.)
The 2002 C5 sender didn't use silver solder, but other than that, the 2001 and 2002 senders are supposed to be identical. But at the time, GM would not allow warranty replacing a 2001 sender w/ a 2002 unit.
Obviously, warranty replacement is no longer an issue...
09-23-2014, 12:28 PM
#4
Drifting
For what it is worth.
I use Chevron gas, it has techron in it.
Once a year I add bottle of Seafoam to gas tank at the 1/4 full mark.
I add Seafoam to all cars and motorcycles once a year.
I use Chevron gas, it has techron in it.
Once a year I add bottle of Seafoam to gas tank at the 1/4 full mark.
I add Seafoam to all cars and motorcycles once a year.
09-23-2014, 12:36 PM
#5
Le Mans Master
Thread Starter
Over time both sending units develop oxidation, not just in the right tank. Yes, fuel first fills the left tank.
Adding Techron Plus to a full tank of fuel is going to result in most of it remaining in the left tank. I suggest that you add the large bottle of Techron Plus to the less than half full system. That way as fuel is pumped into the left tank the "churn" of the gas that occurs from the pressure of the fuel being pumped mixes the Techron and then forces the fuel across the connector between the two tanks. That insures that at least some of the Techron flows to the right tank.
Have you pulled the codes to see what it indicates? There are codes that relate to the sensors in the tanks. Post what you find.
Here is how to pull and post codes:
OR
http://www.c5forum.com/ayc/dtcdic.php
Post ALL your codes including the H or C or HC that follows each 5 character code. If you have any Unnnn codes then list the sensor under which the Unnnn code appears. For example 28-TCS U1016.
The same Unnnn codes can appear under multiple sensors and it is helpful to know which sensor the Unnnn code is associated with.
Adding Techron Plus to a full tank of fuel is going to result in most of it remaining in the left tank. I suggest that you add the large bottle of Techron Plus to the less than half full system. That way as fuel is pumped into the left tank the "churn" of the gas that occurs from the pressure of the fuel being pumped mixes the Techron and then forces the fuel across the connector between the two tanks. That insures that at least some of the Techron flows to the right tank.
Have you pulled the codes to see what it indicates? There are codes that relate to the sensors in the tanks. Post what you find.
Here is how to pull and post codes:
OR
http://www.c5forum.com/ayc/dtcdic.php
Post ALL your codes including the H or C or HC that follows each 5 character code. If you have any Unnnn codes then list the sensor under which the Unnnn code appears. For example 28-TCS U1016.
The same Unnnn codes can appear under multiple sensors and it is helpful to know which sensor the Unnnn code is associated with.
09-23-2014, 12:41 PM
#6
Le Mans Master
Thread Starter
Over the winter when I put it away for storage I am going to put 2 bottles in it.
09-23-2014, 01:14 PM
#7
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Regarding adding Techron directly, should you add it when the tank is very low, per instructions, or add it at 1/4 or 1/2 full to make sure the Techron gets flushed into both tanks? (I don't think the Techron directions took into account the dual tank system of the C5)
Last edited by MSG C5; 09-23-2014 at 02:13 PM.
09-23-2014, 01:58 PM
#8
Le Mans Master
Thread Starter
That's what I was wondering..
09-23-2014, 02:53 PM
#9
Le Mans Master
Thread Starter
You are partially correct. The EFI pump is in the left tank, as is the sending unit. '97-E2003 the pump and sending unit can be accessed without dropping the tank. L2003-2004 you must drop the tank out to remove/replace the pump and sending unit. As far as refueling the tanks; yes the left side fills first, then the right. However as you drive or even let the car sit Techron will permeate all the fuel. I use Techron about every third fill and pour it in before filling with fuel... Good luck and hope this helps!
The C5 Corvette has two fuel tanks, left and right hand. The left hand tank contains the electric fuel pump that supplies fuel to the engine. The right hand tank has a pump, which transfers fuel from the right tank to the left tank. The pump in the right hand tank has no moving parts and is not really a pump. It is a siphon device that uses fuel pressure from the left hand pump to start a siphon that transfers fuel from the right hand tank to the left hand tank. In order to create this siphon, the fuel line that goes to the engine splits and a small amount of pressure is routed to the right hand tank to start the siphoning. The fuel that is being siphoned is routed through another hose to the left hand tank. If the left hand tank is full, the fuel transfers back to the right hand tank through the large filler tube located at the top of the tanks.
The idea is to always keep the left hand tank full whenever there is fuel in the right hand tank. When the fuel gauge reaches a half tank, the right hand tank is empty and the left hand tank is full. Both tanks have a float and sender that measures the fuel level in the tank. These signals go to the Powertrain Control Module (PCM) which interprets the information and sends a signal to the Body Control Module (BCM) which then sends a signal to the fuel gauge in the Instrument Cluster.
Because of the variation in tanks and sending units, the PCM doesn't always read the actual fuel level in the tank. Above or below preset voltage limits, the fuel level is estimated. The voltage limits for each sending unit, right and left, are set to represent "full" and "empty." When one or both tanks have exceeded the preset limits, either "full" or "empty," the system is estimating the actual fuel level. This happens when both tanks are full, gauge is "full;" when the right tank is empty and the left tank is full, "half" on the gauge, or when both tanks are empty, gauge is at "empty."
The idea is to always keep the left hand tank full whenever there is fuel in the right hand tank. When the fuel gauge reaches a half tank, the right hand tank is empty and the left hand tank is full. Both tanks have a float and sender that measures the fuel level in the tank. These signals go to the Powertrain Control Module (PCM) which interprets the information and sends a signal to the Body Control Module (BCM) which then sends a signal to the fuel gauge in the Instrument Cluster.
Because of the variation in tanks and sending units, the PCM doesn't always read the actual fuel level in the tank. Above or below preset voltage limits, the fuel level is estimated. The voltage limits for each sending unit, right and left, are set to represent "full" and "empty." When one or both tanks have exceeded the preset limits, either "full" or "empty," the system is estimating the actual fuel level. This happens when both tanks are full, gauge is "full;" when the right tank is empty and the left tank is full, "half" on the gauge, or when both tanks are empty, gauge is at "empty."
Last edited by JR-01; 09-23-2014 at 02:55 PM.
09-23-2014, 03:22 PM
#11
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To clarify, the "left" tank is the driver's side tank and the "right" tank is the passenger side tank correct?
09-23-2014, 03:23 PM
#12
Le Mans Master
Thread Starter
09-23-2014, 05:20 PM
#14
Le Mans Master
Thread Starter
09-23-2014, 06:18 PM
#16
Drifting
09-23-2014, 07:27 PM
#17
Le Mans Master
Thread Starter
09-27-2014, 07:00 PM
#18
Le Mans Master
Thread Starter
Success. After spending a hundred bucks on Techron this summer I finally figured out none of it was getting into the right tank which must have the dirty sensor. So a few days ago I filled the tank first and then added the Techron to get it into the right tank and today the gas gauge started working normally again. From now on I will put one bottle in before I fill up and a bottle in when it's full. Something to try if your gauge isn't working properly.
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ArmchairArchitect (08-14-2017)
09-27-2014, 07:47 PM
#19
Drifting
Good tip, I'll give that a go!