'81 930: No power to WUR

[B. Elliott]

We recently got an '81 930 in the shop with an excessively run-rich issue. After testing the pressures and doing some probing around I found the WUR is not receiving power.

I stumbled across conflicting info stating that the WUR does receive power when the fuel pumps are running and also that the WUR does NOT receive power until the engine is running. I jumped terminals 30 and 87a then cycled the key on and the pumps run, but no power to WUR. I then re-installed the relay and started the engine... still no power to WUR but the pumps and engine are running.

Is there anything else that can secure or affect power to the WUR?

[tops911]

I had an issue with power to the WUR and it was caused by the fuel pump relays. I had black relays and read that they should be the red relays. So I bought new red relays and changed to the red relays and I had over rich conditions with no power to the WUR, put the black relay in and all was well. I have 1 red relay and 1 black for the fuel pumps, I just never bought another red relay after buying a bad relay.

[B. Elliott]

Well, looks like we're dealing with a hack job. Unbeknownst to my associate I removed the fuel pump relay, and when he turned the key on to check that both pumps were running.... they turned on!

[B. Elliott]

Is there supposed to be a second relay next this one?

[mark houghton]

Originally Posted by B. Elliott

Is there supposed to be a second relay next this one?

Your two fuel pump relays are up front in the main fuse/relay panel. The rear pump relay is the one that energizes the WUR and the AAR. And no, the WUR will not be energized unless the engine is running, but let's qualify that: Presuming everything is stock wiring, what I just said is true.

The red relay (later years use a rectangular yellow relay) you show in the picture is part of the system that interlinks with the overboost sensor switch and with the micro switch that trips when the air metering arm deflects far enough (as when cranking the engine). Rather than going into a lot of discussion, if your fuel pumps run when you turn the key to "on" - but without the engine running - then yes the WUR will have power to it. If your pumps don't run with the key on, then they won't run unless and until you crank the engine and draw air past the metering plate, tripping the micro switch/engaging the relay/ and engaging the fuel pump relays/and sending power to the WUR. If you hear both pumps running, you should see power to the WUR.

[RarlyL8]

All of the CIS components are in a daisy chain that is energized through the rear pump relay.
The rear pump relay is in the trunk fuse box.
The pumps will run with the key in the "on" position if you unplug the cutoff switch behind the air meter assembly.
Turn the pumps on and trace continuity back to the rear pump relay.
I'd start by cleaning the electrical leads to the WUR.

[B. Elliott]

Lots of good info. Thanks guys. Just to clarify, here's the steps I took previously...

#1: Unplugged the WUR and cutoff switch to take fuel pressure measurements. Got 15psi (way low) cold pressure and 85psi and 15C with the WUR blocked. No change in pressure when the WUR was plugged in.

#2: Verified both pumps are running.

#3: Used a test light to check for power at the WUR plug with a multimeter... no power.

#4: Started the engine and checked again for power at the WUR plug... no power.

#5: Checked for power at AAR... no power.

It looks as though the power leg that feeds the AAR and WUR has an issue. I only have a shotty copy of the wiring diagram for the vehicle, so I cant read the labels for each component. Can anyone identify 1 through 4 in this picture?




And just to give you an idea of what i'm dealing with up front...

[JFairman]

These cars are known for poor solder connections that don't have good continuity after time. You may have to unsolder some connections, scrape the copper wires clean and resolder them with good quality rosin core solder.
Good luck with it. Electrical problems can be frustrating.

[B. Elliott]

We've definitely isolated the issue to the leg that supplies power to the WUR, AAR, Thermovalve and EGR. The issue now is that we cannot locate where the power leg ties into the RED/GRN fuel pump power wire.

Does anyone know where the pin circled in red is located? Someone on here has to of checked this pin at some point in the past. The wiring harness is very tight in this area and i'd hate to have to remove everything just to find out that it's actually in a easy-to-reach location.

[B. Elliott]

Well, got her up and running. Something in the luggage compartment snagged the wire feeding the rear fuel pump and pulled it loose.

Another grey-market 930 back on the road.

Thanks for the help guys.

[heliolps2]

You quite the wire mess,

[Alan L]

Amazing what happens to them over the years - esp when someone doesn't want to spend $s and looks for a cheap fix - it it works it's good enough. My 930 was like that when I bought it - absolutely full of crap wiring - relays jumped, o/boost bypassed, burnt wiring under dash.....
Took me about a month to get wiring back to stock, because as I fixed something it would expose another elec problem.
Its a wonder they still go. Well, sometimes not.
Alan

[B. Elliott]

I've talked the owner into letting us go through it and return as much as possible back to stock. Ditching the grainger boost controller, the inoperative aftermarket alarm system and aftermarket subwoofer.

She should clean up very nice. Plus, making any future troubleshooting MUCH easier.

[B. Elliott]

Well, the WUR ended up crapping out on him. Ordered an adjustable one from Brian Leask with the heavy duty diaphragm. Fast turnaround and excellent documentation included with it. He even included a copy of the adjusting values for the pressures.

Brian Leask is the man.

[Alan L]

I just ordered a rpm solenoid unit off Brian - he had it in the post in 2 days - before I even transferred the funds. Big thumbs up to him.
Alan

[mark houghton]

Originally Posted by RarlyL8

All of the CIS components are in a daisy chain that is energized through the rear pump relay.
The rear pump relay is in the trunk fuse box.
The pumps will run with the key in the "on" position if you unplug the cutoff switch behind the air meter assembly.
Turn the pumps on and trace continuity back to the rear pump relay.
I'd start by cleaning the electrical leads to the WUR.

So true, being all daisy chained. On my list for the Phoenix, since both my pumps run with the switch to the air fuel metering arm still connected, and with both relays yanked from the fuse box. No wonder I don't have any power to the WUR or the AAR, with the rear relay having no function what so ever. Funny, though, is that part of the "daisy chain" includes the yellow relay and overboost switch....both of which still work (i.e., yank either of them and the pumps stop running). Some really funky re-wiring went on in her past somewhere.