ignition wiring

nickjggreen · Post by **nickjggreen** » 01 Jun 2016, 16:14

I have fallen in love with these 850's for use many might seem silly. I have been using them in demolition derbies and they are destroying everything in their way my problem is now I have had two cars that I have lost all spark in and cannot for the life of me get back change all the sensors trace as much wiring as I can figure out everything tests and seems good but still zero spark at the coil. has anyone tried to make their own wiring harness for these cars? a way to bypass all the extra junk I know a lot of guys have been using these "white blocks" in 240's as swaps but I cant find out their wiring harness ideas I need nothing except for the motor to run.. I don't even really need the trans to do much more then first and reverse. manily I need to get theses car to maintain spark. any help is greatly appreciated!

Post by **Ozark Lee** » 01 Jun 2016, 18:06

The way the car is set up it can't really run without the ECU getting power. There is a bunch of stuff that you can strip away from the electrical system and basically put a toggle switch in its place. I, as a moderator, can't post any schematics since Volvo's legal department got bent out of shape over it but they can be downloaded from here:

http://www.volvowiringdiagrams.com/

There is one very exposed and really important electrical item and that is the master fuel system relay. Volvo intentionally places it on the radiator shroud so that power will be removed from the system when the car is crunched in a head on collision. The relay is a gray relay that is mounted on the fan shroud. You can wire around that one and it should improve the reliability right out of the box.

The important stuff to keep the engine running is power to the fuel pump, the injectors, and the ECU. Without power to the transmission and the transmission control module it goes into limp mode which will give you reverse and 3rd gear only. The ECU/TCU box is also fairly exposed and it could be relocated further back towards the firewall but there will be a fair amount of cutting and splicing of the wires involved.

...Lee