Fuel sender issues. Any ideas?

[MGOracle]

I replaced my intank pump with a second hand unit back in January.

I'd noticed that according to my fuel guage I was using more diesel than normal, but put that down to the cold spells.

Anyhoo, last week, I had an 1/8th of a tank showing, no red light and the car wouldn't start. It turns out the tank was dry.

Now this is quite worrying and to top it off, today, the guage and range indicator were all over the place. Started out with a range of 147 miles and by the end of 1 mile it was showing 39miles. Gauge just fluctuates between less than an 1/8th and 1/4

Garage chap said the senders were not in sync. Could this be because of the second hand replacement pump?

I've check on IPK tests and under section 6 I have the following results

6.0 Fuel level averaged; --0187 - Left half sensor input=0 liters;
Right sensor input=18.7 liters
6.2 Indicated value and diagnostics:
last digit: (which means) 2 - sensor error;

Is there a way to remedy this?

Garage chap said the senders were like £300 each. One of them is on the pump.

[crofts]

Surely that's rubbish. The whole assembly, pump & all is not £300.
Can just the sender be replaced anyway ?

[Phil]

Not had one out before, but I know on Honda cars, when replacing the intank fuel filters, there is a little arrow that has to be perfectly lined up with the tank and the top of the filter assembly and if these aren't lined up properly you get a very innacurate fuel gauge.

[sworks]

I had a 75 with the gauge reading incorrectly (can't remember what engine / model etc) When i removed both units from the tank the o/s/f sender unit had become detatched and was floating in the fuel. The gauge takes an average reading from both sender units

[Greeners]

The fuel level sensors consist of a float and lever-operated variable resistors. One of the fuel sensors is included as an integral part of the fuel pump assembly. The sensors are connected in series, so if one of the sensors fail (open or short circuit) the fuel gauge will default to zero and the low fuel warning light will turn on.
The instrument pack receives an analogue voltage from the fuel level sensors, which is converted to a digital value by an analogue to digital converter integral to the instrument pack. The instrument pack's microprocessor uses the digital value to compute the fuel volume in the tank and drive the gauge pointer to the respective position on the scale.

I'd take them both out and give them a wiggle.....