A friend that works on aircraft at UPS and said Rolls Royce requires triple torque method. Torque loosen, torque ... 3 times. This heats up the fitting slightly for a more secure fit.
Oil will either just below and behind the distributor or port side rear of block tee with oil pressure gauge sender.
Water will be on thermostat housing
Exhaust one each will be on elbow
Might think about installing a ACR, then no need to move the switch unless needed to parallel to start motor. If weak one won't come up might also be time to replace
Welcome, it's a GXI what?
Being a GXI fuel pressure at the rail should be 50-60 psi
Injectors are turned ON by the ECM applying a ground to one side, the other side should have full 12V with key ON not cranking
Gauges go bad all the time and so long as your measuring 14+V you should be good.
Now the other Bat being low can be the issue for the Bat. Look at how it gets charged. Is it charged from a ACR, Isolator or just the Bat switch?
Each model can have different sensors. This is a E model and it has 4 switches that can turn on the alarm
Oil pressure
Water Temp
Port and Starboard Temp