It is best to run a negative cable to the engine block as stock setup.

Add a second battery-to-body or engine-to-body wire. You can ground the fuel pump via the body but it must be an unpainted connection.

great information fella's il take it on board,

question i have Maddat fuel/serge setup tucked up under the tray behind the passengers seat, locating the battery there in the tray,

now with the cable how far from the fuel system must it be? and where do you poke the cable through, can the negative cable be earth somewhere in the tray!, i just want to do this right

Cheers for your help

Make sure to get a breaker switch rather than a fuse, maybe 100amp or so. I'm not sure what the current draw from a datto starter motor is but if you have a battery that is not quite up to scratch the starter will draw huge current and any inline fuse will blow.

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exactly what im doing!

straight through the cabin to the starter motor, the connected everything else off the starter, connected alternator charging wire to same post on starter, works fine

as long as its secure it shouldnt matter i wouldnt think, but thats up to the engineer to say really

in saying that, here in nsw would this route be ok for engineering purposes (through the firewall & under the carpet)

i hole-sawed a hole in the bottom of the firewall, put a gromet in it and ran the cable through there.
Ran the cables through the car under the carpet

I ran cables inside the transmission tunnel.

ok noticing that i have a ute, would putting an hole near starter at firewall, feeding it up over the tunnel inside the cable behind heater unit, down underneath the carpet on passenger side, putting hole through the rear behind seat of car into the tray, then earthing it in the tray area, would that work and pass???