924Board.org

kcoyle · Joined: 15 Jan 2011 Posts: 712 Location: Long Island, NY

Doing a CIS test and checking the injector spray pattern today for no reason other than a baseline reading. 1982 931. The car runs well.

FP jumpered. Key out of ignition. Injectors out.(for injector testing only) WUR and AAV disconnected.

System pressure-5.8 bar. (5.8-6.5 spec)
Cold control- 1.8 bar (2-2.4 spec at 68 degrees, ambient temp is 45 degrees)
Hot control pressure-3.6 bar*******
Leakdown after 10 min-2.1 bar
Leakdown after 20 min 2.0 bar

***** This reading is with WUR and AAV re-connected and heat gun on WUR- I couldn't get the WUR to warm up even with key in ignition. Pressure just stayed at cold pressure.
Apparently WUR won't heat up unless the car is actually running? Does it need signal/voltage from ignition?

I will check hot pressure again after I button up the injectors.

KC
_________________
1982 931- Stock with MBC at 8psi

Relax, all right? My old man is a television repairman, he's got this ultimate set of tools. I can fix it.

Rasta Monsta · Joined: 12 Jul 2006 Posts: 11733 Location: PacNW

I don't understand your post. Did control pressure increase from 1.8 to 3.6 or not?

The only thing warming up with 12v attached is a bimetal strip inside the unit, unlikely to be detectable externally.
_________________
Toofah King Bad

WeiBe (1987 924S 2.5t) - 931 S3

kcoyle · Joined: 15 Jan 2011 Posts: 712 Location: Long Island, NY

Sorry, that was a sh*tty post.

Yes, pressure went up but only with heat applied to the WUR from a heat gun(earlier today because I had the injectors out and couldn't start the car), or with the car running.( which I did an hour ago after putting the car together again)

I guess what I'm trying to ask is that it appears the car need to be running for the WUR to warm up.

Is this correct and why?
_________________
1982 931- Stock with MBC at 8psi

Relax, all right? My old man is a television repairman, he's got this ultimate set of tools. I can fix it.

Paul · Posted: Mon Mar 12, 2012 12:15 pm Post subject:

Check the resistance of the heating element, sounds like it will be infinity.

When the element is shot, warm up pressures will be noticed until the heat of the engine compartment warms the WUR.
_________________
White 87 924S "Ghost"
Silver 98 986 3.6l 320 HP "Frank N Stein"
White 01 986 "Christine"
Polar Silver 02 996TT. "Turbo"
Owned and repaired 924s since 1977
Porsche: It's not driving, it's therapy.

Rasta Monsta · Joined: 12 Jul 2006 Posts: 11733 Location: PacNW

Also check the WUR plug on the harness for +12v ignition switched.
_________________
Toofah King Bad

WeiBe (1987 924S 2.5t) - 931 S3

kcoyle · Joined: 15 Jan 2011 Posts: 712 Location: Long Island, NY

Thanks guys, makes sense.

I think it also explains something else I was meaning to look at. On cold startup the car comes to a nice high idle, about 1200 for a minute then drops to a rough 800 or so for another 3 or 4 minutes, them it smoothes out and is fine.
Maybe the bimetallic strip isn't getting voltage so it takes 3 or 4 minutes for the car to warm it up, so it's running rich for the first few minutes.
_________________
1982 931- Stock with MBC at 8psi

Relax, all right? My old man is a television repairman, he's got this ultimate set of tools. I can fix it.

Joes924Racer · Posted: Tue Mar 13, 2012 9:14 am Post subject:

Boy do I know this road well. What a road.
_________________
1979 porsche 924 Na
1980 porsche Turbo 931GT Replica
Have u ever driven a turbo.

staticsan · Joined: 19 Jan 2009 Posts: 450 Location: Sydney, Australia

The AAV also heats up with the same mechanism as the WUR; i.e. an internal heater plus heat from the manifold. That would also affect idle speed.

Wade.

kcoyle · Joined: 15 Jan 2011 Posts: 712 Location: Long Island, NY

Did some more testing.

WUR and AAV had 11.5 V with car off, pumps running. WUR bimetallic strip will heat up with car not running, it just takes a while. The pressure started rising after 3 minutes and topped out after 5min at 3.4 bar.

System pressure 5.8 bar -low end of spec
cold control 1.2 bar-way below spec
warm control-3.4 bar - bottom of spec

So, it appears I have to remove WUR and inspect, yes?
_________________
1982 931- Stock with MBC at 8psi

Relax, all right? My old man is a television repairman, he's got this ultimate set of tools. I can fix it.

Rasta Monsta · Joined: 12 Jul 2006 Posts: 11733 Location: PacNW

I'd shim the FPR and get your primary pressure up to spec, and retest. Volume test wouldn't hurt either.
_________________
Toofah King Bad

WeiBe (1987 924S 2.5t) - 931 S3

kcoyle · Joined: 15 Jan 2011 Posts: 712 Location: Long Island, NY

Damn, your fast.

I forgot to add that spray patterns looked ok, there were no leaky injectors, and all 4 injectors had the same amount in each bottle when done testing. I neglected to actually measure how much gas in how many seconds though.

I'll look up shimming the FPR.

Thanks.
_________________
1982 931- Stock with MBC at 8psi

Relax, all right? My old man is a television repairman, he's got this ultimate set of tools. I can fix it.

kcoyle · Joined: 15 Jan 2011 Posts: 712 Location: Long Island, NY

OK, found the spot to shim and shimmed with shim(washer)

System pressure is 6.1 now, up from 5.8.
Cold and warm control are still the same.

Volume test was good at return line.
I'm also going to check the voltage at pumps, the connections look like crap.

Now what to do about low control values?
_________________
1982 931- Stock with MBC at 8psi

Relax, all right? My old man is a television repairman, he's got this ultimate set of tools. I can fix it.

Rasta Monsta · Joined: 12 Jul 2006 Posts: 11733 Location: PacNW

Wish there was some such thing as a "known good WUR" to test with. . .but there is not.

My philosophy is, if there is any chance the WUR is factory installed and your pressures are off, I would assume the WUR is bad and refurbish it.
_________________
Toofah King Bad

WeiBe (1987 924S 2.5t) - 931 S3

ideola · Joined: 01 Oct 2004 Posts: 15550 Location: Spring Lake MI

Rasta Monsta · Joined: 12 Jul 2006 Posts: 11733 Location: PacNW

^Genius!

_________________
Toofah King Bad

WeiBe (1987 924S 2.5t) - 931 S3