mg zt petrol fuel sender unit

Billyuk1 · 17th April 2017, 11:17

hi all,
got a problem with my fuel gauge.
1st time i have filled her up and went a ride to wales.
on the way back the fuel gauge got to half and don't move any further towards empty.
if i turn the ignition off the gauge goes to rest.
sounds like a duff sender unit in the tank to me.
my question is is there a write up on how to remove the sender unit from the tank.
am thinking it might be linked to when i fitted the orange clip due to brakedown.

cheers all

T-Cut · 17th April 2017, 13:55

There are two float arms (senders) in the tank. Any work done in the area often causes this sort of issue. The floats have to be orientated exactly right so they don't rub/foul anything. The first thing I'd suggest is to measure the rheostat readings with an ohm meter.

To do that, you have to access the top of the pump module under the rear seat on the off side. Under the seat/carpet there's a circular hatch which gives you access. Under there you'll see the pump connector. This diagram shows you the sort of readings to expect.

You may have to test these with the tank reasonably full and then reasonably low. This will tell you if a float arm isn't working right and which one. You can then delve deeper into the mechanicals. There's a HowTo service the float arm rheostats in the Engine & Technical subsection of the HowTo forum.

TC

Billyuk1 · 17th April 2017, 17:41

thanks for the reply great help.
with a ohm meter i got 149ohms for the n/s and 48 ohms for the o/s which sounds like something is amiss with the n/s
i know i have roughly £15 worth of petrol in the tank.
next step is to take the n/s out and look if something is wrong since i did the orange clip mod due to non start a while back.
will post back with my findings and post some pictures.
thanks again you are a great help.
cheers...

Billyuk1 · 19th April 2017, 09:47

just a quick update. haven't had time to take the tank units out yet looks like a weekend job.
this is what readings i get using the onboard diagnostic on the dash..
strange readings...

T-Cut · 19th April 2017, 10:09

There have always been some ambiguities in the Section 6 section. Assuming my interpretation of it is correct, the 6.0 display '--0223' indicates the left side sensor is malfunctioning and 22.3 litres in the RHS. It may be that the left signal is missing completely rather than a stuck float. Did you check the 6.1 and 6.2 displays?

The resistance readings suggest the rheostats are working so it's rather unclear how to interpret it. A physical exam may give more info.

TC

Billyuk1 · 19th April 2017, 11:11

looks like the dash isn't getting a reading from one side

T-Cut · 19th April 2017, 15:32

Yes it looks that way.
You'll have to check the wiring on the rheostat to ensure nothings been broken off or bent out of shape during the earlier tank work. This Howto might help with the latter: http://www.the75andztclub.co.uk/foru...d.php?t=194156

TC

Billyuk1 · 19th April 2017, 21:49

Great big thanks for the link will come in useful.
Won't be doing the job till weekend due to work. But I will post back with pictures of my findings in case its of use to others on the forum.
Thanks again
Billy.

The Rovering Member · 8th September 2020, 02:13

There's no point adding another thread to the many concerning this common problem so I've just tacked onto one of the later ones.
Mine recently starting stopping on 3/4 when l filled up (as l always do) then carried on downwards as normal so l had a sort of accurate reading of fuel level & l always zero the trip anyway working on 400 miles (more or less) per tank. When my slave cylinder started playing up a couple of weeks ago l parked her up & when l did so the needle was at the bottom with the fuel light on giving me 100 miles in the tank.
Today l used her for work after successfully squirting some fluid down to the slave cylinder at the weekend, my first stop being the garage to fill up as l had briefly forgotten the gauge problem. Despite filling the tank though, the needle stayed down the bottom & the fuel light on. The needle is still moving down as the fuel is used & l assume it will carry on until it hits the 'stop'. I just did the IPK cluster test (most impressive

) & the gauge travelled it's full range.
So l guess my next stop will be the connector plug down on the tank. I'll just add that the tank hasn't been interfered with since l fitted the orange clip & 'O' ring three or four years ago.

17th April 2017, 11:17	#1
Billyuk1 Avid contributor zt saloon 1800cc Join Date: Apr 2013 Location: in my car Posts: 234 Thanks: 277 Thanked 63 Times in 48 Posts	mg zt petrol fuel sender unit hi all, got a problem with my fuel gauge. 1st time i have filled her up and went a ride to wales. on the way back the fuel gauge got to half and don't move any further towards empty. if i turn the ignition off the gauge goes to rest. sounds like a duff sender unit in the tank to me. my question is is there a write up on how to remove the sender unit from the tank. am thinking it might be linked to when i fitted the orange clip due to brakedown. cheers all

17th April 2017, 13:55	#2
T-Cut This is my second home Rover75 and Mreg Corsa. Join Date: Nov 2006 Location: Sumweer onat mote o'dust (Sagin) Posts: 21,752 Thanks: 341 Thanked 3,660 Times in 2,924 Posts	There are two float arms (senders) in the tank. Any work done in the area often causes this sort of issue. The floats have to be orientated exactly right so they don't rub/foul anything. The first thing I'd suggest is to measure the rheostat readings with an ohm meter. To do that, you have to access the top of the pump module under the rear seat on the off side. Under the seat/carpet there's a circular hatch which gives you access. Under there you'll see the pump connector. This diagram shows you the sort of readings to expect. You may have to test these with the tank reasonably full and then reasonably low. This will tell you if a float arm isn't working right and which one. You can then delve deeper into the mechanicals. There's a HowTo service the float arm rheostats in the Engine & Technical subsection of the HowTo forum. TC Last edited by T-Cut; 7th January 2021 at 11:50.. Reason: Updated resistance data

8th September 2020, 02:13	#9
The Rovering Member I really should get out more....... Rover 75 saloon Join Date: Feb 2014 Location: London Posts: 2,953 Thanks: 263 Thanked 538 Times in 431 Posts	There's no point adding another thread to the many concerning this common problem so I've just tacked onto one of the later ones. Mine recently starting stopping on 3/4 when l filled up (as l always do) then carried on downwards as normal so l had a sort of accurate reading of fuel level & l always zero the trip anyway working on 400 miles (more or less) per tank. When my slave cylinder started playing up a couple of weeks ago l parked her up & when l did so the needle was at the bottom with the fuel light on giving me 100 miles in the tank. Today l used her for work after successfully squirting some fluid down to the slave cylinder at the weekend, my first stop being the garage to fill up as l had briefly forgotten the gauge problem. Despite filling the tank though, the needle stayed down the bottom & the fuel light on. The needle is still moving down as the fuel is used & l assume it will carry on until it hits the 'stop'. I just did the IPK cluster test (most impressive ) & the gauge travelled it's full range. So l guess my next stop will be the connector plug down on the tank. I'll just add that the tank hasn't been interfered with since l fitted the orange clip & 'O' ring three or four years ago. __________________ Reducing the size of my Rover fleet by adding a 75 to it.

17th April 2017, 17:41	#3
Billyuk1 Avid contributor zt saloon 1800cc Join Date: Apr 2013 Location: in my car Posts: 234 Thanks: 277 Thanked 63 Times in 48 Posts	thanks for the reply great help. with a ohm meter i got 149ohms for the n/s and 48 ohms for the o/s which sounds like something is amiss with the n/s i know i have roughly £15 worth of petrol in the tank. next step is to take the n/s out and look if something is wrong since i did the orange clip mod due to non start a while back. will post back with my findings and post some pictures. thanks again you are a great help. cheers...

19th April 2017, 09:47	#4
Billyuk1 Avid contributor zt saloon 1800cc Join Date: Apr 2013 Location: in my car Posts: 234 Thanks: 277 Thanked 63 Times in 48 Posts	just a quick update. haven't had time to take the tank units out yet looks like a weekend job. this is what readings i get using the onboard diagnostic on the dash.. strange readings...

19th April 2017, 10:09	#5
T-Cut This is my second home Rover75 and Mreg Corsa. Join Date: Nov 2006 Location: Sumweer onat mote o'dust (Sagin) Posts: 21,752 Thanks: 341 Thanked 3,660 Times in 2,924 Posts	There have always been some ambiguities in the Section 6 section. Assuming my interpretation of it is correct, the 6.0 display '--0223' indicates the left side sensor is malfunctioning and 22.3 litres in the RHS. It may be that the left signal is missing completely rather than a stuck float. Did you check the 6.1 and 6.2 displays? The resistance readings suggest the rheostats are working so it's rather unclear how to interpret it. A physical exam may give more info. TC

19th April 2017, 11:11	#6
Billyuk1 Avid contributor zt saloon 1800cc Join Date: Apr 2013 Location: in my car Posts: 234 Thanks: 277 Thanked 63 Times in 48 Posts	looks like the dash isn't getting a reading from one side

19th April 2017, 15:32	#7
T-Cut This is my second home Rover75 and Mreg Corsa. Join Date: Nov 2006 Location: Sumweer onat mote o'dust (Sagin) Posts: 21,752 Thanks: 341 Thanked 3,660 Times in 2,924 Posts	Yes it looks that way. You'll have to check the wiring on the rheostat to ensure nothings been broken off or bent out of shape during the earlier tank work. This Howto might help with the latter: http://www.the75andztclub.co.uk/foru...d.php?t=194156 TC

19th April 2017, 21:49	#8
Billyuk1 Avid contributor zt saloon 1800cc Join Date: Apr 2013 Location: in my car Posts: 234 Thanks: 277 Thanked 63 Times in 48 Posts	Great big thanks for the link will come in useful. Won't be doing the job till weekend due to work. But I will post back with pictures of my findings in case its of use to others on the forum. Thanks again Billy.