Fuel guage accuracy issues

BDRCobra · #1 (**permalink**) 05-12-2005, 06:27 AM

I notice even when I get more than 14 gallons in my tank my fuel gauge never shows more than 1/2 and when it gets close to empty it swings irratically. Has anyone ever dropped the fuel tank? Any tricks I should know about. I have the autometer guages. Is it possible to buy just the sending unit? I appreciate any help.

TedMiller · #2 (**permalink**) 05-12-2005, 06:57 AM

BDRCobra,
Check the gauge first. Remove wire at the sending unit or other access point. Ground the wire, key on engine off, the indicator-needle should go through all range of motion.

Ted.

Ron61 · #3 (**permalink**) 05-12-2005, 09:04 AM

BDR,

I am not sure about the reading when full, but if your tank slopes up in the back like mine does, when you get low on gas and accelerate the gas will move away from the gage and cause it to swing down and them back up. I have had my tank out and my pickup is right at the bottom, but the float follows the movement of the gas. I guess I could have some baffels made and installed which would cost three times the price of the tank, so I just don't let it get completely empty.

Ron

BDRCobra · #4 (**permalink**) 05-12-2005, 09:15 AM

Thanks Ron and Ted,

I guess I have to remove the tank to get to the wires for testing. I wonder if my wires are even hooked up to the sending unit/gauge. I have some wires tie wrapped around the filler neck and if you follow them toward the front of the car they are just stop and are not connected to anything.

In removing the tank did you just put a floor jack under it and disconnect the filler neck and 4 bolts and let it drop down?

I will use my electric fuel pump to pump it emty.

I will take some pictures when I get it out for future reference.

TedMiller · #5 (**permalink**) 05-12-2005, 09:36 AM

If your gas gauge seems to work at all, the wires are connected. Can you get to the fuel sender/wires without dropping the tank? (thru the trunk?). If removal is ness, use the floor jack with a board on the jack saddle to help support the tank. When the tank is down/out pull the sending unit for inspection. Play with the float and verify gauge operation.

Ted.

Rick Parker · #6 (**permalink**) 05-12-2005, 09:52 AM

Be careful of FUMES and potential SPARKS.

Rick

Ron61 · #7 (**permalink**) 05-12-2005, 10:48 AM

BDR,

I used the floor jack and a wide board method with a ground strap attached. But if it wasn't for me already having carpet in my trunk and no upholsterers around here to fix the edges. I would cut the carpet, then cut a hole through the trunk and make a hinged door that I could open to remove the sending unit. Have J.T. toad send you a picture of his. He had to pull it and he hasn't finished the trunk yet so he cut a hole and that makes it much easier. To empty my tank for pulling I just drove it about 20 miles and got on it once.

Ron

Secret Squirrel · #8 (**permalink**) 05-12-2005, 11:23 AM

BDRCobra,

The wires that are zip tied to the filler neck are used for Reverse Lights, if required.
The fuel tank sender wires should be top center, if you look underneath and straight up where the fuel outlet pipe is. I have looked in the trunk and I think it would be underneath the battery tray area. I don't know if an access hole is there or not. I haven't searched that deeply.
My fuel gauge readings will vary as I accelerate and deaccelerate also. I have the Stainless steel tank with baffles.
Just a note on the fuel gauge readings when I first filled my SS tank up in this old thread:

Fuel capacity

Nor Cal Al · #9 (**permalink**) 05-12-2005, 11:45 AM

BDR,
I was told by my dealer that the sender is about center of the trunk just below the trunk deck. I was told to use a Dremel and cut a circular hole about 6" in dia. the sender should be right there. Then use the cut-out piece to fill the hole. Could cut through the wires if not careful.

Mine acts just like everyone elses. Accel and it goes one way and decel and it goes the other. Mine is about 1/4 tank off, ie MT at 1/4 tank indicated. The sender really needs a voltage dampener circuit to slow gauge response.

My car has the stainless tank.

BDRCobra · #10 (**permalink**) 05-12-2005, 01:31 PM

Thanks again everyone. Secret Squirrel fantastic infor on the wires around the filler neck!!!!!!!!!!!!!!!!! I will probably drop the tank, but I will look again tonight and see if I am comfortable cutting a hole. Fantastic info everyone.

JayBar · #11 (**permalink**) 05-12-2005, 05:35 PM

Check out this thread while you did not mention a burp problem the remedy is the same. Read all the posts.
Fuel Tank Vent

SkipB · #12 (**permalink**) 05-13-2005, 11:11 AM

BDR,

If I remember right, your car is an early model (chassis #thirty something?), so you may need to follow the method indicated in the thread JayBar listed. Some of your problems may go away, but the accuracy may still be in question. Just keep it topped up and don't worry too much about it. On long trips, don't pass up too many opportunities to get gas!

HI Cobra · #13 (**permalink**) 05-13-2005, 12:50 PM

I don't have a BDR but my gauge only goes to about 1/2 when it is full.
It doesn't bounce or anything but for now I use the trip odometer and
zero it everytime I fill it and just go by the mileage to stay out of trouble.
When it gets down to empty I still have about 8 gallons but don't wait
long to fill it. So far, so good.

uncltodd · #14 (**permalink**) 05-15-2005, 05:40 PM

When #139 reads 3/4 full, she's full.

At 1/4, she's almost empty.

I stop at every gas station in between just as a precaution.

Gunrack is a chick magnet...

And UT is crazy, not stupid.

And no matter what pump gas I pour in, and whatever octane booster I use, she diesels.

OH! I have a clock that I can't read thru the steering wheel.

That goes dead when I kill the battery switch.

When it gets below 1/2, I top it off, add octane booster and pray.

No, you don't wanna know.

UT

davidlee · #15 (**permalink**) 05-16-2005, 02:16 PM

BDR
My BDR came with a guage/ sending unit mismach. When the tank was full the gauge read empty and visa versa. I contacted autometer and they gave me the proper ohm readings for the different sending units and then I checked my ohm readings both full and near empty. I then called them back and they gave me the proper part number for the gauge I needed. I contacted Reg and he got me the right gauge . Reg said he had not ever had that problem before.
And yes the first thing I tried was to reverse the wires at the gauge.

I guess the good thing was when the tank was half full the gauge was correct.

Or was that half empty?

BDRCobra · #16 (**permalink**) 05-17-2005, 06:28 AM

Thanks, I shortened the vent line is was way to long. The good news is I got 17 gallons in my tank. The bad news is the guage was reading 1/4 full when I filled up. After filling up it was 1/2 tank. I am beginning to beleive the autometer gauges are for show only. The speedometer is 12 mph off at 60 mph, the fuel gauge is off by see above, The tach is off by 500 rpm, are we sure the clock is accurate?

I still need to drop the tank and play with the sending unit, for now every 200 miles I fill up.

Thanks everyone.

trularin · #17 (**permalink**) 05-17-2005, 10:02 AM

I went through an ordeal setting up my fuel sending unit.

First, I measured the depth of the tank. Divided that by two and centered the pivot of the float at that measurement from the top of the tank.

Then I put the float through the pivot and adjusted it to be at top of the tank and top of travel. Trim the rod until it is short enough.

What I found was the sending unit was much more accurate in reverse. So, I switched the guage to read 0/1 as full and 1/1 as empty.

It is accurate and consistant.

I suggest you pull the sender and adjust it to read top to bottom within your tank.

Hope this helps.

BTW, the guy who has the meter reading backwards, you have the sender backwards on the pivot post.

BDRCobra · #18 (**permalink**) 05-18-2005, 07:06 AM

Thanks Trularin, just when I was thought I was going to live with it you gave me an excellent write-up now I must attempt to fix. Once I run the tank down I am going to remove and play with the sending unit as you describe. What do you mean by switching the guage from 0/1 to 1/1 is there a dip switch or something on the sending unit?

Thanks

oncebitten · #19 (**permalink**) 05-18-2005, 07:05 PM

BDR,
Drop the tank its a breeze. 3 hoses 4 clamps 4 bolts and its in your lap. Easiset is to jack the driver side since the tank has to come down and over toward the drivers side to clear hose connections. Just make sure to empty the tank first. If your tank is equipped with the round extended piece dead center. place your floor jack there when removing. Tank is not very heavt at all. good luck

lomdel · #20 (**permalink**) 11-10-2018, 01:59 AM

I have a new 2018 model BDR with the standard tank and the awesome access hatch on top in the floor of the boot. Its got the tube-type fuel lever sender unit. The fuel gauge is very inaccurate and move around quite a bit during driving. The friendly guys at the Backdraft factory in Durban sent me a Fuel Gauge Wizard (https://www.spiyda.com/fuel-gauge-wizard-mk3.html) to normalize the needle movement. They included comprehensive instructions to install it and I did the connection properly. However it does not have the desired effect. Needle movement is still about a quarter of the range during driving. Any advice?