3/4 Fuel, to LOW FUEL warning, need help
#1
Racer
Thread Starter
3/4 Fuel, to LOW FUEL warning, need help
Hey guys, so randomly during my trip my warning light comes on saying low fuel. I stop to check for leaks, none. I shut off the car and turn it on again, it works for a short while then gives me the error again.
I put in a bottle of Techron, and waiting for it to kick in. What else could I do to help before resorting to replacing the sending unit?
I put in a bottle of Techron, and waiting for it to kick in. What else could I do to help before resorting to replacing the sending unit?
#3
Racer
Thread Starter
It's not a silly question since one of my exes made this mistake before Would running the car speed up the process? I'm in the process of selling the vehicle, but refuse to sell it if it's not in pristine condition
#4
Le Mans Master
When my '01 gets to half a tank the gauge goes to E and the low fuel warning light comes on. I have been using Techron all summer and it hasn't helped. It is a factory defect and lots of C5s experience the same problem. If Techron doesn't cure it you may have to replace the fuel sending unit and that is pretty expensive.
#5
Le Mans Master
Found this:
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."
This estimating strategy and the physical layout of the system results in an unusual fuel gauge characteristic that may be noticeable to some people. When the fuel level is at or near half tank, the right hand tank is empty and the left hand tank is full, so the system is estimating the actual fuel level. Because of the siphoning system, when the car sets without running, the fuel level equalizes in the two tanks. When the car is first started, the system is actually reading the fuel level in both the right and left hand tanks. After running for several minutes, the fuel in the right hand tank has been transferred to the left hand tank, leaving the right hand tank empty and the left hand tank full. The change in the fuel levels results in the system changing from reading the actual fuel level to estimating the fuel level. This change results in the fuel gauge reading actually indicating more fuel than when the car was first started.
One of the common concerns with the Corvette is the fuel gauge goes to "empty" intermittently. First, let's discuss why this happens. As previously mentioned, the system estimates the fuel level at certain times. When the signal from the left hand sender is above the preset voltage limit, the system estimates the left hand tank fuel level to be full. When the signal from the right hand sender is below the preset voltage limit, the computer estimates the right hand tank fuel level to be empty.
In this situation, left tank full and right tank empty, the computer estimates the fuel level and sets that gauge at half tank. Once the fuel level in the left hand tank goes below the preset voltage limit, less than full, the computer begins reading the actual fuel level and setting the gauge accordingly. At this time the computer expects to see the voltage signal from the right hand tank stay below the preset limit that indicates empty. The problem comes from the fact that the signal from the right hand tank does not stay below the preset limit. When the computer sees the right hand signal voltage exceed the preset empty limit, it assumes that there is a problem in the fuel transfer system, which is a possibility. When this condition exists, the computer software turns on the Check Gauges light and commands the fuel gauge to the empty position. The logic for this is, if there were a problem with the fuel transfer system and fuel was not being transferred from the right hand tank into the left hand tank, you could have the gauge indicate half tank, when then the left hand tank would be empty and the right hand tank would be full. In this situation you would run out of gas and be walking.
On some Corvettes the situation that is occurring now is the result of the right hand sending unit being attacked by compounds within reformulated gasoline. This condition manifests itself as an erratic voltage signal from the right hand sending unit. In the above scenario, left tank full and right tank empty, gauge at half, the computer looks for the voltage signal from the right hand tank to stay below a preset level. The erratic voltage signal caused by the reformulated gasoline causes the computer to think there is fuel in the right hand tank when there is not. When this happens the computer software turns on the Check Gauges light and commands the fuel gauge to empty. GM has issued a revised computer software, for 1999 through early 2002 models, that raises the right hand preset voltage empty limit to prevent the erratic voltage signal from causing this situation. While it has proven to be an effective solution, it has not corrected the concern in all instances.
Another possible resolution is to use Techron fuel system cleaner. This has also worked in many, but not all cases.
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."
This estimating strategy and the physical layout of the system results in an unusual fuel gauge characteristic that may be noticeable to some people. When the fuel level is at or near half tank, the right hand tank is empty and the left hand tank is full, so the system is estimating the actual fuel level. Because of the siphoning system, when the car sets without running, the fuel level equalizes in the two tanks. When the car is first started, the system is actually reading the fuel level in both the right and left hand tanks. After running for several minutes, the fuel in the right hand tank has been transferred to the left hand tank, leaving the right hand tank empty and the left hand tank full. The change in the fuel levels results in the system changing from reading the actual fuel level to estimating the fuel level. This change results in the fuel gauge reading actually indicating more fuel than when the car was first started.
One of the common concerns with the Corvette is the fuel gauge goes to "empty" intermittently. First, let's discuss why this happens. As previously mentioned, the system estimates the fuel level at certain times. When the signal from the left hand sender is above the preset voltage limit, the system estimates the left hand tank fuel level to be full. When the signal from the right hand sender is below the preset voltage limit, the computer estimates the right hand tank fuel level to be empty.
In this situation, left tank full and right tank empty, the computer estimates the fuel level and sets that gauge at half tank. Once the fuel level in the left hand tank goes below the preset voltage limit, less than full, the computer begins reading the actual fuel level and setting the gauge accordingly. At this time the computer expects to see the voltage signal from the right hand tank stay below the preset limit that indicates empty. The problem comes from the fact that the signal from the right hand tank does not stay below the preset limit. When the computer sees the right hand signal voltage exceed the preset empty limit, it assumes that there is a problem in the fuel transfer system, which is a possibility. When this condition exists, the computer software turns on the Check Gauges light and commands the fuel gauge to the empty position. The logic for this is, if there were a problem with the fuel transfer system and fuel was not being transferred from the right hand tank into the left hand tank, you could have the gauge indicate half tank, when then the left hand tank would be empty and the right hand tank would be full. In this situation you would run out of gas and be walking.
On some Corvettes the situation that is occurring now is the result of the right hand sending unit being attacked by compounds within reformulated gasoline. This condition manifests itself as an erratic voltage signal from the right hand sending unit. In the above scenario, left tank full and right tank empty, gauge at half, the computer looks for the voltage signal from the right hand tank to stay below a preset level. The erratic voltage signal caused by the reformulated gasoline causes the computer to think there is fuel in the right hand tank when there is not. When this happens the computer software turns on the Check Gauges light and commands the fuel gauge to empty. GM has issued a revised computer software, for 1999 through early 2002 models, that raises the right hand preset voltage empty limit to prevent the erratic voltage signal from causing this situation. While it has proven to be an effective solution, it has not corrected the concern in all instances.
Another possible resolution is to use Techron fuel system cleaner. This has also worked in many, but not all cases.
#6
Le Mans Master
I recently had been having the fuel gauge problem. It took more than just a couple of bottles of Techron, even trying doubling up on Techron using two in one fill up. Fortunately I stocked up when Advance had a BOGO sale. When at Carlisle they had a C5 problem seminar headed by Paul Koerner from GM. He also suggested in addition to trying Techron, to change your brand of gasoline. He said that using the same brand constantly seems to cause the possibility of the problem occurring. So I switched a tank of gas to a different brand than I typically use, tried Shell. Problem seems to have cleared up all of a sudden. BTW, you should only use Top-Tier gasolines. Google it tof ind out what brands are near where you live.
#7
Racer
Thread Starter
I recently had been having the fuel gauge problem. It took more than just a couple of bottles of Techron, even trying doubling up on Techron using two in one fill up. Fortunately I stocked up when Advance had a BOGO sale. When at Carlisle they had a C5 problem seminar headed by Paul Koerner from GM. He also suggested in addition to trying Techron, to change your brand of gasoline. He said that using the same brand constantly seems to cause the possibility of the problem occurring. So I switched a tank of gas to a different brand than I typically use, tried Shell. Problem seems to have cleared up all of a sudden. BTW, you should only use Top-Tier gasolines. Google it tof ind out what brands are near where you live.
#8
Intermediate
Bad fuel level sending units is a common problem with gm vehicles across all makes and models,I had the same issue on my 06 trailblazer,and my vette. (Hopefully they finally put the updated unit in my 11 suburban). Best to change them and be done with it.
#9
Melting Slicks
Hey guys, so randomly during my trip my warning light comes on saying low fuel. I stop to check for leaks, none. I shut off the car and turn it on again, it works for a short while then gives me the error again.
I put in a bottle of Techron, and waiting for it to kick in. What else could I do to help before resorting to replacing the sending unit?
I put in a bottle of Techron, and waiting for it to kick in. What else could I do to help before resorting to replacing the sending unit?
Seems to be worst on < 2001s
#10
Racer
Thread Starter
#11
Race Director
I recently had been having the fuel gauge problem. It took more than just a couple of bottles of Techron, even trying doubling up on Techron using two in one fill up. Fortunately I stocked up when Advance had a BOGO sale. When at Carlisle they had a C5 problem seminar headed by Paul Koerner from GM. He also suggested in addition to trying Techron, to change your brand of gasoline. He said that using the same brand constantly seems to cause the possibility of the problem occurring. So I switched a tank of gas to a different brand than I typically use, tried Shell. Problem seems to have cleared up all of a sudden. BTW, you should only use Top-Tier gasolines. Google it tof ind out what brands are near where you live.
using 20-40oz on a fill is maintenance
#12
Le Mans Master
Is it safe to use that much Techron? Could it cause damage? I put a bottle in my truck with only a quarter tank of gas and the Check engine light came on.
Last edited by JR-01; 09-21-2014 at 10:14 AM.
#13
Make sure you use Techron Plus
They sell Techron and Techron Plus. Make sure you use Techron Plus since of the two it is the only one that cleans sulfur compounds off the fuel level sensor.
https://www.corvetteforum.com/forums...wintering.html
https://www.corvetteforum.com/forums...wintering.html
#14
Melting Slicks
fuel guage
My fuel gauge on my 2001 coupe was going crazy like other members here. I had purchased a new right side jet pump and level gauge. I got the new unit at a local AC Delco wholesaler for a closeout price of $124.00. I had tried techtron to no avail several times and at 5.00 a bottle had spent more than half of what the new unit cost. I went ahead and change the unit out today and the fuel gauge is now working properly. The gauge was reading a little less than half a tank when I started. After changing the unit out I was showing on reserve fuel just a little above empty. I went and filled the tank and added 16 gallons of fuel. The gauge, for the first time since I owned the car went right to full the way it should after fill up instead of going nuts and finally ending up on full. I do believe the gauge contacts could be cleaned just as well and not replace the whole thing. The contacts on the removed unit were covered in black gunk and seemed to clean well with brake cleaner and 600 grit sand paper. I wish I would have tried that just to see if the results were the same. It is not that hard of a job so I would tackle it to stop using the techtron. I also had the dealership do the service bulletin update where the PCM is reprogramed to help with the voltage problems that sulfur content causes with some of todays fuel, it did not seem to help before the replacement, but it may help now that the unit has been changed.
Hope this helps someone else who is fighting a fuel gauge issue.
Hope this helps someone else who is fighting a fuel gauge issue.
#15
Le Mans Master
My fuel gauge on my 2001 coupe was going crazy like other members here. I had purchased a new right side jet pump and level gauge. I got the new unit at a local AC Delco wholesaler for a closeout price of $124.00. I had tried techtron to no avail several times and at 5.00 a bottle had spent more than half of what the new unit cost. I went ahead and change the unit out today and the fuel gauge is now working properly. The gauge was reading a little less than half a tank when I started. After changing the unit out I was showing on reserve fuel just a little above empty. I went and filled the tank and added 16 gallons of fuel. The gauge, for the first time since I owned the car went right to full the way it should after fill up instead of going nuts and finally ending up on full. I do believe the gauge contacts could be cleaned just as well and not replace the whole thing. The contacts on the removed unit were covered in black gunk and seemed to clean well with brake cleaner and 600 grit sand paper. I wish I would have tried that just to see if the results were the same. It is not that hard of a job so I would tackle it to stop using the techtron. I also had the dealership do the service bulletin update where the PCM is reprogramed to help with the voltage problems that sulfur content causes with some of todays fuel, it did not seem to help before the replacement, but it may help now that the unit has been changed.
Hope this helps someone else who is fighting a fuel gauge issue.
Hope this helps someone else who is fighting a fuel gauge issue.
#16
Melting Slicks
#17
Drifting
This is why I only get gas at Chevron or Shell (both have Techron) in all my performance vehicles.
#18
Le Mans Master
#20
Race Director
i've done it multiple times, techron is similar to acetone, very flammable. you may not want to go racing with that high of loadout but it's not going to hurt the engine