Fuel Gauge question
Thread Starter
Melting Slicks
Joined: Mar 2009
Posts: 2,300
Likes: 115
From: Odessa FL
St. Jude Donor '10-'12-'13-'14-'15-'16-'17
Fuel Gauge question
My fuel gauge seems to work fine. I use only Chevron 93 octane and will on occassion also add a bottle of Techron as well. The gauge doesnt stick and runs downs to empty at a pace that seems normal. But heres where I am confused. When the gauge reads empty it has never taken more than 10 gallons to fill it up. I know that the C5 has two tanks and that total capacity is about 19 gallons. So why would my gauge seem to only be reading 1/2 the capacity or just one of the tanks? Anyone else experience this?
Thanks for any information.
Thanks for any information.
Melting Slicks
Joined: Dec 2009
Posts: 2,504
Likes: 66
From: Louisville, KY
fuel problem
Your are right, 19 gal divided into two tanks, left and right. My guess would be you are not getting fuel from the right tank because of a problem with the fuel transfer system. Your engine gets fuel from the left tank only. The Fuel Pump in the left tank feeds fuel to the engine and also sends some fuel to the right tank to energize the right tank Jet Pump. That Jet Pump pumps fuel from the right tank to the left tank. In your case the Jet Pump may be clogged or for some reason it is not getting the fuel from the Left Fuel Pump to energize it.
Team Owner
Joined: May 2001
Posts: 36,836
Likes: 244
From: Dear Karma, I have a list of people you missed.
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15-'16
Your are right, 19 gal divided into two tanks, left and right. My guess would be you are not getting fuel from the right tank because of a problem with the fuel transfer system. Your engine gets fuel from the left tank only. The Fuel Pump in the left tank feeds fuel to the engine and also sends some fuel to the right tank to energize the right tank Jet Pump. That Jet Pump pumps fuel from the right tank to the left tank. In your case the Jet Pump may be clogged or for some reason it is not getting the fuel from the Left Fuel Pump to energize it.
Also, the right side fuel tank has it's own separate fuel level sending unit (which is electrical of course) and the BCM or DIC relies on both sending units to determine the actual fuel level.
HTH
Melting Slicks
Joined: Dec 2009
Posts: 2,504
Likes: 66
From: Louisville, KY
fuel problem
Lone Star is correct, the jet pump is not electrical. The fuel from the left side only "energizes" the Jet pump to work thru the Venturi effect to suck the fuel out.
There are two sending units, one in each tank and that was the confusing part to me in your situation. It seems if the left tank was going down and the right tank was not you should get a "Check Gages" and the fuel gage going to Empty because the computer would not know how much fuel you had. Cannot explain why that is not happening. Seems like I remember it taking like up to only 1-2 gallons difference to cause that.
There are two sending units, one in each tank and that was the confusing part to me in your situation. It seems if the left tank was going down and the right tank was not you should get a "Check Gages" and the fuel gage going to Empty because the computer would not know how much fuel you had. Cannot explain why that is not happening. Seems like I remember it taking like up to only 1-2 gallons difference to cause that.
Instructor
Joined: Jan 2006
Posts: 246
Likes: 4
From: Denton County Texas
When you fill the tank it first fills the left tank and then overflows into the right tank via the transfer tube that connects the tanks together. Best guess is that you have a fuel level sensor that is inaccurate and giving false readings to the pcm. You could run the fuel out of the fuel rail into a gas container with the engine running and watch your fuel gauge. If it shows empty and you can still pump out the 9 gallons your missing then your fuel level sensor is skewed. Could be either the right or left level sensor. Looking at a scanner will show approx 0.7 volts when the tanks are empty.
Thread Starter
Melting Slicks
Joined: Mar 2009
Posts: 2,300
Likes: 115
From: Odessa FL
St. Jude Donor '10-'12-'13-'14-'15-'16-'17
OK, had to leave for a business trip overseas and just am catching up with all the responses. First thanks to all for the input.
First, I am not getting any "check gauges" or any other indicators that something is wrong. So it may be that the sending unit while faulty is still sending a signal.
So my next step is to check pumps, tranfer tube, and sending units. I will wait until the tank reads empty once again to validate that there is still approximately half of the capacity still actually left within one of the tanks.
Thanks again.
First, I am not getting any "check gauges" or any other indicators that something is wrong. So it may be that the sending unit while faulty is still sending a signal.
So my next step is to check pumps, tranfer tube, and sending units. I will wait until the tank reads empty once again to validate that there is still approximately half of the capacity still actually left within one of the tanks.
Thanks again.
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