Fuel and temperature gauge go max when ignition is switched on

Hello,

Just to clarify, when you first start the vehicle the temperature gauge and the fuel gauge got all the way to max? Or does it happened when you turn the key to the "on" position?

It does sounds like an issue with the temperature sensor and it is sending wrong signal to the gauge. Please keep in mind this can also be due to faulty gauge.

https://www.2carpros.com/articles/how-a-coolant-temperature-sensor-works
https://www.2carpros.com/articles/symptoms-of-a-bad-coolant-temperature-sensor

The fuel level reading can also be due to a bad sending unit or the gauge. There is float in the tank with the fuel pump that measures the fuel level and sends that information tot he gauge.

Please let me know of any questions.
Thank you.

So this could be due to a weak or bad ground (earth).
Unfortunately I do not have the wiring schematics for the Tazz, as this was not sold in North America.
However you should be able to check the temperature sensor wiring and see if its getting power and if the sensor has the correct resistance value.

https://www.2carpros.com/articles/how-to-check-wiring

Sounds good. Let me know what you find.