Fuel gauge not accurate in Santa Fe Forum Forum

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Fuel gauge not accurate

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DSHornet	Fuel gauge not accurate	Lead	[-]
Posts: 3 (10/07/08 18:16:29) Reply Quote More My Recent Posts	Tags : fuel gauge, fuel sender Remove this ad I have a problem on my '01 Santa with the fuel gauge showing empty after about 180-200 miles and the tank being full when I put only about ten gallons in it. I understand from a post on another message board that the Santa Fe has two fuel level sending units, one each in the right and left sides of the fuel tank, because of the "saddlebag" shape of the tank. It looks like one of the two fuel level sender units has gone bad, or maybe a bad connection. Where are the fuel sender units located? How are they accessed? I'm hoping the Santa isn't one of those cars that needs the gas tank dropped to access the sending units!
sbr711		#1	[-]
Posts: 180 (10/07/08 18:40:58) Moderator Reply Quote More My Recent Posts	Easy way to access is to remove the rear seats. Looking at the carpet, you will be able to visual a partial square cut-out lines in the carpet. Take a new sharp razor blade and cut the carpet and pad to make a flap to fold toward rear, I usually just the square chunk of foam out and set it aside. Remove the floor plate, and there is the top of the sender on the passenger side, and the driver side reveals the complete fuel pump/sender module. Unplug the units, and remove the plastic lines from the fittings (use 2 fingers, squeeze the pads to release,,, might find easy to push tube down, squeeze and lift) The driver side module will be a rather tight fit throught the hole in the floor, and watch the rubber ring upon re-assembly, if out of place or get cut, you will end up with an evap code the next time the PCM does a self test on the system, as the leak will not allow the tank to hold vacuum when it is tested. I cannot offer too much as far as the senders, seems we have never really had much luck getting the bum sender figured out, I can see if I can find some specs for testing.
DSHornet		#2	[-]
Posts: 4 (10/08/08 02:50:00) Reply Quote More My Recent Posts	Thanks for the procedure. I folded the right rear seat up and removed the plastic trim yesterday afternoon but didn't see anything obvious. So there is some wrench work to remove the seat cushions? It would be interesting to put an ohmmeter on the sensor connector pins, rock the car to slosh some gasoline in the tank, and see which one changes resistance with the changing fuel level. Or maybe one will be fully open or shorted while the other will show a plausible resistance reading. It looks like this will be this coming weekend's project. While my sweetie is grubbing in the flower bed, I'll be playing with the car and listening to the football game.
sbr711		#3	[-]
Posts: 181 (10/08/08 02:54:49) Moderator Reply Quote More My Recent Posts	Raise/tilt the seat bottom, remove the plastic tray via the handfull of "phillip" screws. There is (4) bolts that hold seat to floor, (2) at front lower along the floor pan, and (2) at rear of seat frame, seen when the plastic tray is removed.
geopa		#4	[-]
Posts: 35 (10/10/08 18:07:01) Reply Quote More My Recent Posts	I'm seeing the same thing with my 03 Santa Fe, one minute the gauge shows half, then it drops all the way to empty and the fuel light turns on. When i fill up the tank it only takes about 11 gallons . Funny thing is that this started right after my 60,000 mile service. Any chance that changing the fuel filter triggered this problem, until then never had a problem with the gauge.
DSHornet	Update: Problem worked around	#5	[-]
Posts: 6 (10/11/08 14:47:33) Reply Quote More My Recent Posts	My Friday evening project was to find the problem with my fuel gauge reading wrong. Here's what I found. The right hand sending unit is mounted with six Phillips head screws and was easy to remove after pulling the seat out. I measured the resistance of the strip in it and found it to be about 40 ohms. When reading the variable resistance between the connector pins, which shows the signal coming from the sender that is used to control the fuel gauge, I saw that the resistance change was not smooth as the float was moved. It had a couple of "dead" spots where the movable contact wipes the length of the strip. I VERY carefully cleaned the resistance strip with some very fine sandpaper, about 600 grit, and that solved the problem. I also found a fuel pickup tube and filter sock that is piped to the fuel pump on the left side so the pump can draw fuel from both sides of the tank. I reinstalled the sender and turned to the left hand unit. The left hand sending unit and the sensor for the low fuel light are a part of the fuel pump assembly. I saw that the head of one of the eight Phillips head screws that mount it was almost stripped out. I also saw that a screwdriver had been on the remaining seven screws, so it looks like the fuel pump had been changed some time in the past. I removed it (spilling some gasoline in spite of my effort to relieve fuel pressure by running the engine to stall with the connector off) and checked the resistance strip on its fuel level assembly. Surprise: The resistance strip measured 80 ohms, not 40 as the right one did. It also had some dead spots on it, so I carefully used the fine sandpaper on it, too. I reinstalled it and went back to the right hand sensor. I jumpered the pins on the connector from the wiring harness to short them together. The next paragraph will explain why. The level sensors are wired in series with the fuel gauge, so they add their varying resistance readings to show fuel level in both sides of the tank. My problem with my gauge dropping too fast was consistent with TOO MUCH resistance in the gauge circuit (minimum resistance = full, open circuit = empty). I hypothesize that the original fuel pump was replaced with one that was designed for single point fuel level sensing, not dual point. That is why it has an 80 ohm resistance strip in it. The total resistance of the circuit should probably be 80 ohms divided between two 40 ohm devices, but I had a 120 ohm sensing circuit. That explained what I was seeing. I jumpered the pins on the connector for the right sensor to make the gauge work properly. The only downside is the fact that I now have single point (left side) fuel level sensing, but the gauge now seems to work right. So that's what I found. Any questions? I'll be glad to help if I can.

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