What happens on my 1990 Jaguar you put the battery in wrong what will it cause problems on

What happens when you put the battery in wrong on a xj6 1990

one tank has too much gas in it. I keep filling the other up. is it a pressure valve malfunction? I found a canister on the right passenger side that has nothing in it and has a bottom plate that is falling off. it has a hose at the top that isn't attached to anything.

ambient air temp the worse it gets and must stay above 2K RPM on really hot days and about 12K to 15K RPM in cooler air.

There is a clicking noise under the hood ,coming from the relay switches behind the headlights,under the hood,at the same time the lights flash.It clicks about every 5 seconds.It doesn't do it when the car is running.Any idea what this can be?Thanks.

My rear passengers window is stuck. Both the drivers door switch and passenger switch will lower the window but will not make the window go up. I hear the motor when it goes down. There is a click when you hit both switches.

Crank sensor 3 yrs old cap rotor and coil same age wires are old

I think that isn't the problem, because once in a while if you turn the engineoff and on it will goe into four for a little while. any suggestion would be appeciated, it was showing it was the throttle body sense but that wat replaced.

Do the low beam head lights have a fuse relay as like the blower motor.

The actual year is 1988

if i have on were is it located on the car and cand u show me a diagram

i have a 1981 xj-6 i replced a leaking valve cover gasket. and now when i start it races up to 2500 rpm and dont come down the linkage is fine.i removed the breather to gain more access and returned it to its place. ????

intermittently while driving but the headlights work fine? Hazard lights work too. Fuses are o.k. Are relays involved? Which one/s and where located?