[mitiempo]

It's for the engine control panel wiring. Installing a relay between the panel wiring and the solenoid will boost the voltage and it'll start every time you push the button.

I disagree. The starter solenoid doesn't use much current. That is why there is a solenoid there to start with. If the voltage at the solenoid isn't as high as it should be there is a wiring problem to or from the panel, either gauge, connections corroded, or age of wire. Adding a relay (really another solenoid) will not solve the problem only mask it and add more connections at the same time.

Now if there are glow plugs and they are powered off the panel a relay does make sense as they do use a lot of current.