Fuel gauge problems

[pug7]

Cally in the knowledge of blat chat!

My new 7 is giving me problems with the fuel gauge 10% of the time it works the other 90% it's showing around the full mark. Since the last fill up its showing just below full but I've done 130 miles and I know a 7 isn't that economical! I've got the floor up but a bit lost with the wiring as to what is the sensor. There a large white tank cover left hand side of tank with fuel hose and block connector with black, grey green, green black, and yellow green wires. No obvious sensor or is it all under the large white cap held in with the black ring? Don't want to risk breaking the gasket unless I have to. Guage end is 3 wire connector yellow,green and black wires so not sure what's between the sensor and Guage?

Any offers as to where the problem may be? Checked the earth black wire at Guage and off the tank both fine

[pug7]

Just to add, checking earth black to yellow on Guage connector gives me 207 ohms, give cara good wobble ie slosh the fuel and I get readings 192 to 208 then settles v quick to around 207 again Guage fault then?

[Roger Ford]

Fuel level sender is on top of tank. Not sure if that's what you mean by "large white cap with the black ring". Common fault is for the sender wire to short through the boot floor - if you've got that out you're not going to find the fault! Is the gauge working at the moment?

[pug7]

theres a large cap laft hand side of the tank on the top maybe 20cms across? its got the fuel pipe outlet on it and a long thin connector 4 wires and 2 blanked off. other than the filler pipe on the other side of the tank thats all i can see on the top of the tank...which is why im lost on the sender or just being thick and missing something obvious ?

[CharlesElliott]

The fuel pipe you can see will be the return from the low pressure end of the injection rail. The pump is on the right hand end of the tank which drives the high pressure side of the rail. The sender is on the top under the plate. As Roger says, the fault is often the wire shorting to earth on the boot floor - you can see a cut out on the floor which should sit over the sender wiring. Check the wiring carefully, I suspect there is a nick in it somewhere.

[CharlesElliott]

I take some of that back. Looks like on EU4 cars the pump and sender are all in one module, that is under that large cover. You can see the module here. The comment on the wiring shorting is probably still right though, especially if you are measuring a variable resistance with the floor out.

[pug7]

thanks charles thats the top i was tring to describe looks like a big lump. As its only been finished a few days i shall give caterham a call tomorrow see what they say as ive still got 9 months warrenty. They can advise suggestions. along with why has the speedo now died ... no readout on the display looks dead to me !