|
I used to think the speed relay had to be there because the fuel pumps stop if you disconnect the multi pin plug from it or just disconnect the brown ground wire or the white wire in the multipin plug on it while leaving the rest in place... but, a friend of mine with an '87 930 removed everything under the driver seat including the whole wire harness that goes from all that stuff and then down along side the driver side longitudinal, then under the rear carpeting through to the engine compartment and ends at the multipin plug on the rear shock tower cross member and his fuel pumps run fine without any of it.
I guess having that harness in place creates a ground loop or whatever you call it that makes it so the speed relay has to be hooked up for the punps to run. I was real surprised to hear his fuel pumps run with the ignition on and white overboost wire grounded without any of the crap under the seat or that harness in place.
All the lambda stuff under the seat is an afterthought. 930''s before 1986 had none of it so it appears removing the harness and all the stuff under the seat sort of backdates part of the engine wiring safely.
The 2 CIS warm up devices get their heater element 12 volts from the rear fuel pump relay so it appears they are independent of the relays and ECU under the driver seat but I don't know which harness their 12volt supply wire travels through - the one on the shock tower cross member behind the air flow meter or the other one that goes to the rear relay panel. He switched to EFI so the WUR and AAV are no longer.
I don't know... you can't see electricity unless it sparks or arcs so whats going on with it is usually a partial mystery.
|