My Rover SD1 came with factory fit EFI (Lucas) and electronic ignition. The EFI was an addition to the original model and has an entirely self contained feed direct from the battery - the ignition just part of the main loom. So I kept things the same for MS and EDIS8. But ran a heavier gauge wire from the ignition switch for the EDIS. The EFI loom has a main relay switched by the ignition circuit.
The EFI loom (MS) is grounded to the engine block. The EDIS unit locally to the chassis. I've used individually screened co-ax cables for both SAW and PIP with the screens only connected to pin7 on the EDIS8 unit - no connection to the MS grounds on the DB37.
It seems to work just fine - but is this just luck?
Should the EDIS module be grounded at the same point as the MS, ie at the block, and should the screens be connected to the MS ground as well as to the EDIS module? Or something else?
