Fuel Gauge

P3AHE · 15th September 2017, 08:29

Been to put in petrol this morning because gauge was showing quarter of tank. Filled with £35.00 of unleaded but gauge is still showing quarter of tank. Gauge goes to zero when ignition is off but slower than normal to register when ignition is on. Is something sticking in tank or is it electrical fault?

T-Cut · 15th September 2017, 08:54

Has any work be done in the tank recently? To fit the FOC for example?
The usual cause is a mechanical issue in the tank. There are two level floats which operate together and they must be clear of any obstructions (there are some). Each float operates a rheostat which causes a voltage variation proportional to their respective level. You can check the rheostat readings to see if there's any obvious problem. This means removing the rear seat and the offside tank access panel on the floor.

The panel gives access to the pump module on top of which is the cable conection for all the tank gubbins. Using a multimeter, check the rheostats as below.

There's also a simple test for checking the functions of the IPK. The fuel gauge is also tested independently of the rheostats. This tells you if the gauge itself is OK.

YouTube: https://www.youtube.com/watch?v=VrG0VQETlEI

TC

HarryM1BYT · 15th September 2017, 08:58

It is likely that the float in the fuel tank, is sticking on something. Has the pump in the tank been disturbed in the past?

You could run the dash diagnostics - the built in ones (or the ones provided by Phil-T4 for use with the OBD), to confirm it is not the needle on the gauge which is sticking.

P3AHE · 15th September 2017, 09:18

FOC has been fitted but that was 9 months ago. No IPK or on-board diagnostics. It's a MG ZT SVP. (Entry level with added extras!) Would using an OBD11 Reader be of any use?

HarryM1BYT · 15th September 2017, 10:01

Quote:

Originally Posted by P3AHE

FOC has been fitted but that was 9 months ago. No IPK or on-board diagnostics. It's a MG ZT SVP. (Entry level with added extras!) Would using an OBD11 Reader be of any use?

I would suspect the float is almost certainly getting caught up on wiring inside the tank. It is no biggy to remove the seat squab, remove the covers and take a look in with a mirror and torch. Make sure the fuel level is low in the tank.

No matter which model, the basic dash diagnostics are built in, just a matter of pushing the button in the right sequence on the dash. Search the forum for 'dash diagnostics'.

No, a normal OBDII reader will not do it, nor will the usual OBDII type interface. Look up TOAF, the TOAF type interface (VAG) and the free IPK software posted on here by Phil-T4. Phil's software can exercise the gauges, the dash lights, plus do a few more useful things. One very cheap interface which works with both TOAF and Phil's software, just needs a laptop.

P3AHE · 15th September 2017, 14:48

Thanks for all the replies and advice but when I went back out to car to investigate as per suggestions .........The fuel Gauge is working again! Found the Dash Diagnostics- no mention in owners handbook! Having owned the car for more than 2 years this is the first time I was aware that there was Dash Diagnostics. Now going to read up & learn.

Avulon · 15th September 2017, 14:56

Quote:

Originally Posted by HarryM1BYT

I would suspect the float is almost certainly getting caught up on wiring inside the tank. It is no biggy to remove the seat squab,

Pedantic note (as already discussed on this forum in the past) The squab is the seat back**. It'd be more convenient to lift the seat cushion/base/

**many sources differ.

15th September 2017, 08:29	#1
P3AHE Regular poster MG ZT 1.8 Turbo & MG TF Join Date: May 2015 Location: Tonypandy Posts: 99 Thanks: 8 Thanked 23 Times in 18 Posts	Fuel Gauge Been to put in petrol this morning because gauge was showing quarter of tank. Filled with £35.00 of unleaded but gauge is still showing quarter of tank. Gauge goes to zero when ignition is off but slower than normal to register when ignition is on. Is something sticking in tank or is it electrical fault?

15th September 2017, 08:58	#3
HarryM1BYT This is my second home 75 Contemporary SE Mk II 2004 Man. Sal. CDTi 135ps, FBH on red diesel, WinCE6 DD Join Date: May 2010 Location: Leeds Posts: 17,273 Thanks: 2,160 Thanked 2,061 Times in 1,586 Posts	It is likely that the float in the fuel tank, is sticking on something. Has the pump in the tank been disturbed in the past? You could run the dash diagnostics - the built in ones (or the ones provided by Phil-T4 for use with the OBD), to confirm it is not the needle on the gauge which is sticking. __________________ Harry How To's and items I offer for free, or just to cover the cost of my expenses... http://www.the75andztclub.co.uk/foru...40#post1764540 Fix a poor handbrake; DIY ABS diagnostic unit; Loan of the spanner needed to change the CDT belts; free OBD diagnostics +MAF; Correct Bosch MAF cheap; DVB-T install in an ex-hi-line system; DD install with a HK amp; FBH servicing. I've taken a vow of poverty. To annoy me, send money.

15th September 2017, 08:54	#2
T-Cut This is my second home Rover75 and Mreg Corsa. Join Date: Nov 2006 Location: Sumweer onat mote o'dust (Sagin) Posts: 21,754 Thanks: 341 Thanked 3,660 Times in 2,924 Posts	Has any work be done in the tank recently? To fit the FOC for example? The usual cause is a mechanical issue in the tank. There are two level floats which operate together and they must be clear of any obstructions (there are some). Each float operates a rheostat which causes a voltage variation proportional to their respective level. You can check the rheostat readings to see if there's any obvious problem. This means removing the rear seat and the offside tank access panel on the floor. The panel gives access to the pump module on top of which is the cable conection for all the tank gubbins. Using a multimeter, check the rheostats as below. There's also a simple test for checking the functions of the IPK. The fuel gauge is also tested independently of the rheostats. This tells you if the gauge itself is OK. YouTube: https://www.youtube.com/watch?v=VrG0VQETlEI TC

15th September 2017, 09:18	#4
P3AHE Regular poster MG ZT 1.8 Turbo & MG TF Join Date: May 2015 Location: Tonypandy Posts: 99 Thanks: 8 Thanked 23 Times in 18 Posts	FOC has been fitted but that was 9 months ago. No IPK or on-board diagnostics. It's a MG ZT SVP. (Entry level with added extras!) Would using an OBD11 Reader be of any use?

15th September 2017, 14:48	#6
P3AHE Regular poster MG ZT 1.8 Turbo & MG TF Join Date: May 2015 Location: Tonypandy Posts: 99 Thanks: 8 Thanked 23 Times in 18 Posts	Thanks for all the replies and advice but when I went back out to car to investigate as per suggestions .........The fuel Gauge is working again! Found the Dash Diagnostics- no mention in owners handbook! Having owned the car for more than 2 years this is the first time I was aware that there was Dash Diagnostics. Now going to read up & learn.