earthing problems

[joe winkfield]

i recently took my 1098 engine out to replace the oil pump. however when the engine was put back in the whole engine is live when tested with a test screw it lit up on any part of metal on the block. this only happened when the starter motor was trying to start the engine. so basically why isnt the engine earthing. also the radiator is not
on, not sure if that effects the earthing.

[Neil MG]

Sounds like the starter motor is wired incorrectly or the insulation has broken down. The engine should have an earth strap!

[joe winkfield]

were can i find the earth strap to check this?

[mike.perry]

There should be a braided strap between the engine/gearbox and the gearbox crossmember/chassis (or somewhere in that area)

[IslipMinor]

With no earth strap connected and switching the starter will produce around 6-9 volts at the engine I would think? The resistance of the starter motor itself is very low, so it would be quite normal to see a 'voltage' on the engine without an earth connection. The usual path that the earth tries to take is the choke cable or maybe the throttle cable (neither is a good idea!).

As Mike says, the earth strap originally was a braided wire about 8" long that connects between the back of the gearbox and one of the gearbox crossmember mounting bolts. If it is missing or lost, a short length of starter cable will do the job just as well (it needs to have 5/16" or 8mm ring connections on both ends).

[MarkyB]

There is often another earth strap that bridges the front engine mount.
Much easier to fit and keep an eye on.