Low fuel-check gauges

[Lakotah]

Well here's something I haven't seen come up on my DIC for while. Quite a while. Even with a full tank of gas, driving around, all of sudden I hear that warning bell (the one you hear when you leave your keys in the ignition and open the door). Then "Low fuel Check Gauges" comes up on the DIC then the gas gauge needle goes to E and stays there until I stop and re-start the engine. I have gotten into the habit of re-setting "trip-A" to "0" so I can monitor how many miles I've driven each time fill up the gas tank and make sure I'm really not out of gas (Trip "B" I reset each time I change the oil). Seeing as how cleaning as many grounds as I could find resolved a number of issues with my C-5, I was pretty surprised to see this happen. Not that I expected it to be included with my previous grounding problems. Any ways, does any one have any idea where this problem could be coming from? I have to mention that I sometimes drive quite a few thousand miles in-between the times this happens.

 

[BigJimZ16]

Well here's something I haven't seen come up on my DIC for while. Quite a while. Even with a full tank of gas, driving around, all of sudden I hear that warning bell (the one you hear when you leave your keys in the ignition and open the door). Then "Low fuel Check Gauges" comes up on the DIC then the gas gauge needle goes to E and stays there until I stop and re-start the engine. I have gotten into the habit of re-setting "trip-A" to "0" so I can monitor how many miles I've driven each time fill up the gas tank and make sure I'm really not out of gas (Trip "B" I reset each time I change the oil). Seeing as how cleaning as many grounds as I could find resolved a number of issues with my C-5, I was pretty surprised to see this happen. Not that I expected it to be included with my previous grounding problems. Any ways, does any one have any idea where this problem could be coming from? I have to mention that I sometimes drive quite a few thousand miles in-between the times this happens.

Sounds lie its time to run some Teckron concentrate through the fuel system and clean the sulfur deposits off of the sending unit!

 

[dadaroo]

I agree that sulfur deposits could be your issue and is very common. I still want you to pull your codes and see if they show anything. There is a sender in each tank. Here is the design for your car. 2003 and 2004 is similar but with some plumbing changes from the earlier years..

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.

 

[dadaroo]

I got a like on my post so I thought I would also provide the 2003 and 2004 info since it includes pictures that can help in understanding since the two designs are very similar. I am also posting a video of how to remove a fuel sender. It is done on a C6 but the basics are the same.

Info is at the bottom of post 2.

Guys I forget the big difference between c5 and c6 fuel system - Corvette Forum


The C5 does not require all of this to remove the pumps/senders, just access and draining the tank as much as possible.

https://www.youtube.com/watch?v=32nvOlj9ZFg


PS: The right side sender design was changed in 1999 and has 3 wires not 4. I think the senders for the 2003-04 are also different, just don't have the parts manual.


Here are the earlier schematics:





If anybody can think of anything else I can add to this Thread let me know and I will try.

 

[Lakotah]

I agree that sulfur deposits could be your issue and is very common. I still want you to pull your codes and see if they show anything. There is a sender in each tank. Here is the design for your car. 2003 and 2004 is similar but with some plumbing changes from the earlier years..

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.

dadaroo,
Bringing up this issue with the gasoline deposits made me think back that I haven't had this problem since I changed to a different brand of gas and running a can of Sea Foam through the tank, thinking it was the cause of my stalling problems. For various reasons I decided to go back to Shell and coincidence or not there was that "low fuel check gauges" again on the DIC and the performance has dropped off a noticeable amount with shell gas. Today I'll run another can of Sea Foam through the gas tank and try to use up as much of that shell gas as I can in the next few days as long as my back can hold up. Thanks, BigJimZ16 and dadaroo.

dadaroo I have to say that's quite a process the sending units and PCM go through just to let us know how much fuel we have in the tank.

 

[Otter]

I got a like on my post

Have a 99 and appreciate you taking the time to explain the methods behind the madness.

 

[Lakotah]

P1431h

dadaroo,
Bringing up this issue with the gasoline deposits made me think back that I haven't had this problem since I changed to a different brand of gas and running a can of Sea Foam through the tank, thinking it was the cause of my stalling problems. For various reasons I decided to go back to Shell and coincidence or not there was that "low fuel check gauges" again on the DIC and the performance has dropped off a noticeable amount with shell gas. Today I'll run another can of Sea Foam through the gas tank and try to use up as much of that shell gas as I can in the next few days as long as my back can hold up. Thanks, BigJimZ16 and dadaroo.

dadaroo I have to say that's quite a process the sending units and PCM go through just to let us know how much fuel we have in the tank.

dadaroo,
Thought I'd let you know I found P1431H on the DIC. I'm guessing it arose from the shell gas affecting the fuel level sensors. I don't know about you, but I really think all the sensors on these C-5's have too close of a tolernce just to make them run. Seems like there is a lot less moisture coming out of tail pipes from both of our cars by not using shell gas. It's anybody's guess what they put in it here in California with all the regulations and all. So I'm going back to using Arco again.

 

[dadaroo]

Strange that Shell would cause you issues. Seems like few things are normal in California anymore.

 

[Lakotah]

shell

Strange that Shell would cause you issues. Seems like few things are normal in California anymore.

dadaroo,
I just think it's unusual since I switched from shell to arco I haven't seen that " Low fuel-check gauges" come up on my DIC. It's been a number of months since I did, then before using even a 1/4 of a tank of shell gas there it was again. Coincident? I don't know. Like I mentioned using shell gas, there was always quite a bit if moisture coming out the tail-pipes. Somewhere years ago I read they have a way to suspend moisture in the fuel for environmental purposes. In California I can imagine they do anything they can think of to enforce more regulation on everyone. I guess they think our air never goes outside the California border and no outside air ever comes in. I'll keep using arco for a while with an occasional can of sea foam and see what happens.

 

[RLDaily]

Had the problem a couple years now and have run out of options so I'm going to perform surgery on my right tank and sending unit

 

[tankman]

An option .. . .
I had this problem with my 98 many years ago. I had some free time so I thought I would see what kind of fun I could have. I took out the main tank pump/sensor/float contraption and was able to take some very fine sandpaper and sand down the contact area. I was very careful and I rinsed them off before reinstallation, but it worked. At least for a few years, then I changed the fuel pump and it has never reared it's ugly head again. So, if you have some free time, give it a whirl, new fuel pumps are expensive.

Good Luck
Tank