Another WUR issue
 

Car: 1980 930 euro. Fresh rebuild on basket case engine. 0 438 140 112 wur

Symptoms: car has very little power below 3k and does not run smooth (feels lean).

System pressure: 6.2

Cold control pressure: 1.7 at 70 degrees

Warm control pressure: 2.7

Leak down: 1.8 /10 min - 1.6 /20 min

Both the control pressures look out of spec to me but I want to make sure I'm checking it correctly before jumping to conclusions. vacuum port on bottom is hooked up, but the top (air filter) in open. Does this look like a bad WUR to you?

also: if a put a vacuum to the top port I can get the warm pressure up to about 3.5.

No , It sounds like mine and it works great 490 ftq at 4200 rpms and 423 Fwhp, I have the same low numbers on my 112 ,the system pressure should be at 7+ bar at that low Warm cp, so add some shims the your regulator , and readjust your CO ,

does your car start good when cold and when hot? forget what the spec's say try what I said first , Do you know what your boost control pressure is ? and do you have a wide band AFR gauge ?

Not my car. Hot or cold the car fires right and idles smoothly. I'm out f time this week but I'll jack with the FP next week when I'm back in town. Have no idea what the boost control pressure is. But that brings me to another point: in messing around with the blow-off valve I noticed that the piston does not seal real well. Putting a vacuum on the real port does not move the piston, and if you pressurize the the main housing you can hear air bleeding out the other side. Everything see,s to fit ok, but is it really suppose to leak that much?

Warm control pressure for the -112 should be 3.63-3.67 bar, system pressure 6.2-6.4 bar.
Your cold pressure is about right, my guess is the WUR is not receiving electricity or the bimetalic strip is shot. I'd check the plug and see if it's getting good power. We handle rebuilds if you need one.

+1

Thanks. I knew the specs so I know they are out of wack. I thought the bi-metalic strip was only an aid for warm up and and heat transfer would eventually take care of it anyway. I've taken apart WUR in the past where it was just the BMS that was out or adjustment, but sill working. If the WUR wasn't getting power wouldn't the fuel pressure always stay low? In any even i will probably check it out anyway. How much for a rebuild, and turn around time?

Why would an '80 model have a -112 wur, and does it really make a difference?

Also: while I was testing i noticed that I could control the control pressure with the switch on the fuel pressure gauge. Do you suppose it would be OK to to use the gauge to adjust it to spec and do a test drive to see if it solves the problem?

The BMS gets lazy with age. Old and/or damaged wires can reduce the voltage to the plug as well.
The -112 is an early Euro unit so consistant with a 1980 year 930. The -054 has similar specs and should work as well. I keep cores in stock to rebuild and swap out or you can send me yours. Takes a couple weeks to turn one around. Price isn't a bank breaker, I'll send you some info.
I'm not really following how the fuel pressure gage can adjust the pressure, it is only supposed to read it.

Just a little off topic, but for what it's worth I'm running with a 054 (listed as for '78-79) on my '87 only because I had the opportunity from a Pelicanite to purchase a newly modified BL WUR. It works fine doing what it's supposed to do.
I do not know what the differences are, but it may have something to do with the BM strip or the heating elemement resistance. When I swapped my stock 153 out for the 054, I seem to have just a little bit shorter warm up period before the control pressures go from cold to warm levels. I don't know - just guessing here - but if anyone knows the differences then please share. If I were industrious I'd throw an ohm meter across both and see if there's a difference with the heating coil.

James, I too am confused on your comment about controlling pressure with some "switch" on the pressure gauge. Ellaborate a bit, if you would?

I have what I thought was a problem , Had her on the dyno, she ran great but to lean on top , at the same time i was have an issue with my fuel pump getting low voltage, 10.3 volts w/car running , At the time I did not have CIS test gauges or a wide band AFR, I do now, I sent out my WUR to get tested and re calibrated to spec, while that was being do I rewired my fuel pump with a 40 amp relay and thicker wires , Now I have 13.5 volts to the 044 fuel pump,You should look into that also.

The person who tested my WUR told that my old sets was to low

CCP 1.0 bar 23 deg C
WCP 2.3 bar
BCP 1.8 bar

It was suggested to set it back to spec, and it was done and had it back inside of a week,
Now i got my new AFR gauge and the CIS tester, ready to get work, My system pressure was at 7.2 it should be at 6.0 to 6.5 bar , I install the Newly re calibrated 112 WUR , she was not Happy at all , even after I lowered the SP , So long story short sent back the WUR had it set BACK the the lower specs and it works great , Idel at 14 afr cruse at 14.7 afr, initial boost drops to 10.1 then quickly raises to 12.2 and stays,

I have even tested my 112 on a friends 81 930, stock except for a K27, I raised the SP to 7.0bar, re adjusted the CO, the has never ran so good, My friend was impressed , His 112 ,CCP 2.2 bar at 10 deg C , WCP 3.6 bar , his CCP is way off , I re installed his WUR and left it unplugged so that ran off the CCP , readjusted the CO, and it ran great,

So some times stock setting does not work for every one,

Maybe Bob can chime in on this

Stock settings are not optimal on a heavily modified engine or with modified system pressure or increased fuel head output. It is a balanced system where the system pressure and flow rate affect WUR pressure outputs.

The difference between specs on the -054, -112, and -153 have to do with ROW, US/CAL, and European climates. They overlap so can typically mix and match.

Just to put closure to the question I posed this morning, I did get off my lazy rear and nabbed the VOM to test the resistance on the two WUR's I have: BL modified 054, currently in my car, resistance value of 23 ohms------vs. my stock WUR number 153, resistance value of 39 ohms. Appears to affect the time to warmup characteristics, for what it's worth.
Another piece of trivia to file away....

As you know the CIS pressure gauge has a switch (valve) on it so you can switch from system pressure to control pressure. By partially opening the valve you can regulate control pressure.

I adjusted the FP with the switch, Set the Afr, and adjusted the timing. It runs tons better. Now I still have to fix the WUR.