Fuel gauge never reads full

[mtb_gary]

My fuel gauge is not getting past about 7/8 on the gauge. Initially I thought it was the sender that was faulty or dirty, but after changing the fuel pump a few weeks back that theory was put to rest as both senders give the same readings. I can confirm that the tank is full of petrol because having the access hatch cut in the floor I have removed the pump to visually check the fuel level. I physically cannot get any more fuel in there!

So where to next? Is there a calibration procedure that I am not aware of? Any ideas gratefully accepted....

1996 4.6 HSE

Gary

[rangerdanger]

Dejavu
I've got the same problem, which continued after replacing the fuel pump as well. My only thought was to find and clean the earth but it is more of an annoyance so have never quite got there yet.

[Hoges]

I agree re. a possible earthing problem. It occasionally happens when I haven't driven the vehicle for a couple of months and the tank is only half full. A dose of efi cleaner in the tank and a couple of refills on a long trip and it tends to right itself. An early tech bulletin noted this was an issue on vehicles using ethanol mix fuel... ethanol caused problems with the sender unit causing errors in the resistance measurements which drive the gauge. Not saying you use ethanol, but it supports an earthing gremlin as a feasible reason for a resistance error. Also, have you tried filling the tank well past the cutoff level (then go for a long drive:D) to force the sender to the top?
EDIT Pls disregard the last sentence, didn't properly read yr post...
IIRC, if you have a faultmate (not sure about the Nanocom) you can 'force' the fuel gauge to read full or empty as a test...

[redandy3575]

Dejavu
I've got the same problem, which continued after replacing the fuel pump as well. My only thought was to find and clean the earth but it is more of an annoyance so have never quite got there yet.

Trejaviu

Me too.

I didn't bother trying to repair it. Just accepted it as the norm.

I found mine was accurate enough below half to know when you're close to empty.

[FANTOM P38]

Sounds like a more common fault than I first thought. I had same issue but worse as it would only read between 1/4 & 3/4 full so was guessing as to how much I really had, estimated by speedo most of time.
So I CHANGED FUEL PUMP & SENDER FOR NEW - GUESS WHAT - NO DIFFERENCE. Then I picked up anew set of dial gauges & replaced those - you guessed it still same. Posted up on here a while ago but no responses as to what to try next. Ive had fuel tank out to replace sender etc & while at it I cyt access hole - Thinking I may need it at some point again to resolkve this issue or some other.
Earth is looking more probable so will need to look into that.
Anyone traced the earth from the tank?
Is there something in Becm that may contribute to this problem?
Or maybe an earth behind dash although you would thinl that would affect other gauges!
Anyone that may have solved similar issue most welcome to hear your views.

[rangerdanger]

I did research this a while ago in readiness for some troubleshooting which still hasn't happened.


The sender needs to have resistances of 19 ohm when tank full, less than 175 ohm the fuel light will come on. >19 ohms when full suggests a sender problem.
Measure resistance between connector C114, pin 10 and earth. C114 is the plug at the front of the BECM. Check rave for pin location if not numbered on the plug.
The earth for the fuel pump and gauge is next to the coolant reservoir. My plan was to clean every earth in the general area and see if it is fixed it first.


I vaguely remember reading of issues of the float on the sender sinking if E10 fuel was used, and that a float from an EA falcon fuel pump could be used to replace it.


Interesting to see if anybody has success.

[mtb_gary]

Thanks rangerdanger. Given both the old and the new senders read pretty much identical I suspect the problem is somewhere different. I will check the resistance though. There is also a digital to analogue converter that may be potential cause. Then Thera are the various plugs and connectors I also need to check to verify they are clean connections. Not high on the priority list but I will get around to it ;).

Gary

[RoverHse]

I also have a fuel gauge problem at the moment.i don't think it ever really shows full, and will intermittently drop to empty, with the light coming on. I also get a fuel gauge error on the dash display. thought it might be fuel tank sender.

At the moment. I zero the odometer on filling the tank and fill up again a around 500km.

[rc42]

Mine has a similar problem that started a few weeks ago.
The guage will periodically drop to about half way to where it should be but sometimes it reads correctly so I can never be sure if the amout of fuel left is what it says or twice that.
Zeroing trip odometer is a habit I've had for a long time so that helps but when we go off road it's less useful.

It's on my things to do list, I'm hoping it's corrosion around the earth connector for the sender unit and a problem outside the tank that's easy to find and fix. (has to be a first time for everything).

[TheTree]

It seems I have now joined this illustrious club, so far no flicking to empty and back , which would indicate a dodgy connection somewhere. But I am in the 3/4 full club ;) which to me indicates a high resistance connection somewhere

Steve

[mtb_gary]

Welcome to the club Steve ;)

[TheTree]

When I had the tank out today to clean the fuel pump pre-filter I cleaned both the tank connector and the connector on the body near the wheel arch with deoxit and now my fuel gauge reads much higher but not quite to F yet!

So corroded connections are the root of the issue here:(

Steve

[Dougal]

Is the tank dented? On my rrc the dented bash plate pushed the sender up, thus it thinks the bottom of the tank has risen and the top is unattainable.

[TheTree]

Is the tank dented? On my rrc the dented bash plate pushed the sender up, thus it thinks the bottom of the tank has risen and the top is unattainable.

My tank has no dents, I now get the gauge up to the notch before F whereas before it only went to about 3/4 of the way

Steve