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flightlead404 flightlead404 is offline
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Join Date: May 2015
Location: Secret lair deep underground
Posts: 914
How I wired my FCIS Power

After a couple of iterations of wiring my FCIS in my 86 930 I think I've found the optimum solution.

I had originally wired to the WUR power with a Y cable I made, however I found that the millisecond blip in the power as the key goes from "crank" to "run" caused resets and lost programming in the MS. Additionally WUR power is only on when the engine is running, ie the airflow plate is displaced and all other conditions met for fuel pumps to run. That means the MS is firing up during the start process and as part of MS start up takes its ambient air pressure sample from the intake manifold when there is vacuum there. This probably affects both starting and mixture for the duration of that run.

Then I wired to the delay relay for the CDI, which solved the above problems but I found that due to the warm up delay in the 14point7 Spartan controller I'm using it was no good for diagnosing startup problems, AFR was only useful 10-30 seconds after start.

So, where I've ended up.

I'm taking power from the lower unused position of the three fuses in the engine compartment. This is unswitched power, its always on regardless of the engine/ignition key state. I made an extra jumper and have a 15A fuse in that position.

I'm running that to a standard automotive relay and using a wire spliced into the power for the CDI to power the relay coil, grounding the other side to the ground location right by that panel. This turns on the relay coil and provides power when the ignition is in the run position, and further the delayed off feature of the CDI power prevents the reset issues I had originally and lets me get complete logging of engine shutdown as well. Power goes from the relay to a 6 position ATC style fuse block that I've mounted on the RHS manifold on an aluminum plate that also holds the MS and the MAP sensor. That fuse block provides separate fused power to the MS, injector, lambda valve, WBO2.

Now I can turn the key to on, wait a few seconds for the WBO2 to come alive, then crank and get full logging of the the startup sequence.

I have currently got the stock WUR plumbed in (MAP sensor is T'd into the vacuum line) and am not using the replacement eWUR. I have found the eWUR unnecessary.

I am also using a VW oil pressure fitting to be able to install the digital fuel pressure sensor into the control pressure line from the WUR.

So far working well.

Last edited by flightlead404; 10-11-2017 at 03:06 PM..
Old 10-10-2017, 07:03 AM
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