Why are these fitted to some mechanical diesel units ?
![Think :-k](./images/smilies/eusa_think.gif)
I can see that it would be useful with a petrol or HDi unit to cut the in-tank pump off however they appear to serve no purpose with an indirect injection engine at all, unless I've missed the point ?
I can see they are going to control the ECU power (as mine does) however a single relay would suffice for that without an in-tank pump.
So for safety with a petrol engine especially they are essential, I do not question that. I do question why they are fitted to vehicles without any in tank pumping arrangement though.
I suspect its parts standardisation or suchlike as on mine I do have an unused power feed (with a reasonably heavy wire!) present at the sender plug.