'04 LeSabre "UNUSUAL" fuel gauge reading.......

[grinder11]

Hello. I'm new to the Forum, but not LeSabre's. My '04 has an unusual fuel gauge issue. When car starts, it goes to Full, then after a 1 or 2 miles of driving, it nosedives to EMPTY. After another mile, or less of driving, the low fuel light then comes on. Happens EVERY TIME CAR IS STARTED!!! Does NOT MATTER where the fuel level is. It can be full, half full, 1/4 tank, etc.. Please HELP!!!!

 

[AviatorFrank]

The fact that your low fuel light comes on tells me it's not the fuel gauge's stepper motor itself but either the sending unit in the tank or a faulty electrical connection. This is a fairly common problem with these cars. Does your driver info center (the dot matrix panel under the tach that has the odometer etc) jibe with the fuel gauge? IOW miles to empty etc. If it does the gauge is 100% OK.

 

[DonP]

I agree with AviatorFrank - And the most likely cause is worn "fingers" on the sender unit in the tank. Many past threads on this topic.

Not a difficult DIY repair, but some risk due to open fuel tank during the repair.

Many folks monitor their miles since last fill-up to estimate remaining fuel until repaired.

 

[gmfugitt]

there is an access panel in the trunk. The sending unit is fairly easy to get to. on my 2000 they had different sending units for different vins.

 

[grinder11]

The fact that your low fuel light comes on tells me it's not the fuel gauge's stepper motor itself but either the sending unit in the tank or a faulty electrical connection. This is a fairly common problem with these cars. Does your driver info center (the dot matrix panel under the tach that has the odometer etc) jibe with the fuel gauge? IOW miles to empty etc. If it does the gauge is 100% OK.

Yes, the DIC jibes with gauge. A little History may help here: I have an '03 LeSabre, too. BUT-Sadly-As much as I loved it, 3 weeks ago I found a DEER who loved it even MORE!!! It had 398,763 (Yes-THREE HUNDRED NINETY EIGHT THOUSAND, SEVEN HUNDRED SIXTY THREE) miles on it! It had the "erratic" fuel gauge problem-Anything under 3/8 to a 1/2 tank of gas, and it went from full to near empty, then back to 1/2, etc.. I bought this car to replace the '03. Drove it 1 week. On the 8th morning, I went out to start it and head to work. I cranked and cranked-But it didn't fire one time!! Took 4 days, but I found the problem: The female "Tangs" in the the underseat fuse block that hold the 20A Fuse for the Fuel pump were spread open way too far. Some tweezers and a jewelers screwdriver, presto-The fuel pump was humming again!!! BUT-As mentioned earlier, now the fuel gauge is not working!!! I've also noticed that the Compressor for the ride level system has not worked since I bought it. BUT-The fuel gauge WAS working before the "loose tang" on the fuse problem reared up. This is all very puzzling, as in nearly 400,000 miles of driving my '03, I NEVER had any of these issues! PLEASE HELP!!!!!

 

[DonP]

The fuel level sender is just a variable resistor (a bit like a volume control on a radio) that is adjusted by a float in the tank. It is passive and is NOT powered by the fuel pump fuse.so the fuse problem should not effect it. You can test the gauge circuit (if you are comfortable with that level of DIY) without opening the fuel tank by replacing the sender connection with a resistor at the connector at the fuel tank (under the access cover in the trunk floor).

The following are from the FSM and are approximate:
90 ohms for empty, (which also means 15% of a tank of fuel remaining)
135 ohms for 1/4
170 ohms for half
204 for 3/4
233 for full (which means 90% full or higher)

Note that over time the contacts in the sender unit wear out and no longer make reliable contact - often it is intermittent contact so it may work at times.

There are two electrical connectors on the fuel pump assembly. One for fuel tank pressure sensor, the other for the fuel level sender and for fuel pump power.

 

[AviatorFrank]

Also if you're replacing the sender do both the pump and sender as well. First, they're often sold together anyway and secondly, why go through the job twice. Despite the easy access panel in the trunk there's a lock ring that's a bit of a fiddle to remove and many people don't like working around open fuel vapors so why not limit the excitement to once instead of twice.

 

[Terrycabral]

k,it helped me reinstalling it.I replaced my sons,bought one off ebay for about $15. It has been fine for a year now. I did not replace the pump,just the sending unit. A tip would be to take a pic before you remove the assembly from the fuel tanl​

 

[grinder11]

Thank you very much. I am somewhat suspicious that I did the damage somehow, since it worked fine before I "fixed" the fuel pump. I did continuity test the harness/pigtails with a meter, and I'm wondering if I may have damaged a pin/socket with a meter probe. It was working fine before the "fix". I did unplug the "weatherpak" harness behind the rear wheel on passenger side to help find the fuel pump problem. CAR seems to have some sort of electrical issues. Like the keyless entry fob. Everything on that works. EXCEPT the red "horn" button. Also, when unlocking the car after dark, all the external lights come on as they are supposed :-OEXCEPT the headlights!!! These are sorely missed!! They also worked for a few days, but stopped working before I started checking for the the fuel pump, so at least I didn't cause THAT one!!! Seriously, I have had more problems with this car in 2 weeks than I did with my old '03 LeSabre in 8 years and 400,000 miles!!!!!

 

[AviatorFrank]

Don't you just love electrical issues? Makes you yearn for the the likes of an old 66 Dart when the entire electrical schematic fit on the back of a business card.

 

[DonP]

Do the day time running lights work?
How is the key fob battery?
I've seen with other devices that a weak battery can cause some issues with remote controls where some function may work and other not.

When grounds go bad strange electrical things start to happen.

 

[grinder11]

Do the day time running lights work?
How is the key fob battery?
I've seen with other devices that a weak battery can cause some issues with remote controls where some function may work and other not.

When grounds go bad strange electrical things start to happen.

Boy, you got that right, DonP!! I have a 2000 Corvette. ANYONE...Whos familiar with the Corvette electronics knows that when someone says "I've got a 2000 Corvette", they've said it all when it comes to automotive electrical gremlins!! Anyway-Back to the LeSabre....As for the Daytime R.L., I will check that out. As for the key fob battery, it's anyone's guess as to it's age. Now, on the top of the fuel tank itself, there are 2 connectors: I believe that the 4 pin plug is for the Fuel pump, and the 3 pin plug is for the Fuel level sender. My question is this: How do you remove the black, 3 pin Female connector on the top of the tank? I would like to swap it out with the one on my '03, which still lurks in the backyard. Thx, again.

 

[AviatorFrank]

The 4-pin plug is 2 for the pump and 2 for the sender. The 3-pin is for a pressure sensor.

 

[grinder11]

The 4-pin plug is 2 for the pump and 2 for the sender. The 3-pin is for a pressure sensor.

Thank you for clarifying that. I stand corrected. Would you happen to know which is which? Meaning what color are the 2 wires for the sender, and what color for the pump? Thank you very much.

 

[grinder11]

I am also wondering: How many other people have experienced problems with the air compressor for the air shocks/ride level? This air compressor was never was an issue on my '03 in almost 400,000 miles!! Thank you for all your help.

 

[AviatorFrank]

EDIT:

The grey wire is +12V fuel pump, from the fuel pump relay located in the fusebox under the rear seat. The black is fuel pump ground. The other 2 are the gauge sender, according to my 2005 schematic.

 

[jerreich]

You probably have a worn out fuel guage sending unit, which is attached to the fuel pump, a very common problem with these cars. You can replace the unit, or the complete pump. This is accessed thru a hole in the trunk floor, near the front right side of the trunk floor, no need to drop the tank. Mine has been that way for years. I just fill up every 300-350 miles. These pumps are almost bullet proof, but not the sending unit.

 

[grinder11]

Do the day time running lights work?
How is the key fob battery?
I've seen with other devices that a weak battery can cause some issues with remote controls where some function may work and other not.

When grounds go bad strange electrical things start to happen.

To answer your question: Yes-The Daytime Running Lts.
(DRL) WORK FINE. The headlights work properly under the normal situtions that they should: They come on automatically after dark, and they will come on manually using the switch. Seem to work in every situation EXCEPT when you unlock the car with the keyless fob when it's dark!! VERY FRUSTRATING!!!!

 

[grinder11]

You probably have a worn out fuel guage sending unit, which is attached to the fuel pump, a very common problem with these cars. You can replace the unit, or the complete pump. This is accessed thru a hole in the trunk floor, near the front right side of the trunk floor, no need to drop the tank. Mine has been that way for years. I just fill up every 300-350 miles. These pumps are almost bullet proof, but not the sending unit.

You may be right regarding the sending unit. But that would sure is coincidental. I mentioned earlier that I had an '03 model (still do-wrecked-but runs fine) that never have me these same issues. Only trouble I had with fuel gauge Sender was around 275,000 miles, when it started acting like the typical sender problem others here have mentioned. Gauge was reading fine until it neared a half tank. Them it would start going back towards Full again. Then back down towards half full, then up again, etc. VERY erratic. My '04 has not-thus far-done this. When you start it, no matter what the true fuel level is, it goes up to Full for a mile or so, then nosedives to EMPTY and won't move again until you shut off the engine, and re-start the car.