First off, if I read this chart right, you should have an 036 WUR:

928 06.77 - 07.82
[ S1 ] V8 4.5L
K-Jetronic
Injector Valve 0 437 502 012
Fuel Pump 0 580 254 984 > 6/80
0 580 254 053 7/80 >
Air Flow/Mass Sensor 0 438 120 049 > 7/81
0 438 120 142 8/81 >
Fuel Filter F0179
Thermo-Time Switch 0 280 130 214
Fuel Distributor 0 438 100 027
Cold Start Valve 0 280 170 409
Fuel Accumulator 0 438 170 013 > 3/78
0 438 170 023 4/78-8/78
0 438 170 026 9/78 >
Warm Up Regulator 0 438 140 036 > 6/80
..........................0 438 140 087 7/80 >

Maybe I'm reading things wrong. I can't find any WUR that ends in 031.

Next up you know that CIS is all about the pressures. Some folks aren't aware that lower control pressure means more fuel. They often think it's the other way around but actually the control pressure that is applied to the top of the main fuel pintle shaft is lowered to counter the pressure of the air passing the air metering plate(that big round thing that moves up and down). You can verify this by watching the fuel pressure in your CIS gauge as the car is started and moves from a cold(rich) low pressure to a warm(lean) higher pressure.

Always, always work in well ventilated area, and have an extinguisher nearby. No smoking, no open flame.

First, you need to set your system pressure, and insure it's stable. If it is too high, you will also have too high control pressures when warm, and the mixture will be too lean and that's bad. First thing; remove the supply line to the WUR, and look down in the well of the WUR. You will see a screen in there. It is most likely plugged with gunk. Clean it carefully, and put the hose back on, or the test jig to the CIS pressure tester.

Then, I would locate the return line from the FD and chase it all the way back to the tank. Remove the fuel filler cap, and run the fuel pump with the WUR electrical connector off so that the WUR is not warming. You can often hear fuel being returned to the tank in many cars, but I don't know about the 928. If you don't hear fuel returning, then find the last connector before the tank return, and take that off. Route that line into a suitable container and run the system pressure test again. The system pressure must be stable for several minutes or you have a blockage. If the system pressure will fill the container for a few minutes and the system pressure is good, look at the return line that you just removed, and see if it's blocked back into the fuel tank. I've used a piece of coat hanger wire before on Merc and a Ferrari to clean a blocked return line.

If the container fills slow, and/or the system pressure keeps rising out of the specified range you have an issue in the regulator on the FD, or the return line to the tank. Most likely, it's the o-ring on the little plunger in the regulator. Locate the fuel regulator on the side of the FD, it is a brass nut with the slug and has a copper crush washer under it. http://ww2.justanswer.com/uploads/eu..._regulator.JPG

Inside of that thing is the piston with o-ring. http://forums.pelicanparts.com/uploa...1311043777.jpg

This o-ring or piston is usually what gets stuck. The fuel regulator comes out easy as it's spring loaded. Don't lose the o-ring or shim stack! Once that is out, jump the fuel pump for a second while holding your hand over that open port, and the piston should pop out. Sometimes you can get it out with a magnet.

The bore of the regulator housing and the piston is a tight fit. This combined with the spring and silver shims on the regulator set your system pressure. Clean the bore of the FD where the piston goes in, and clean the piston, then replace the o-ring at the end with one that is ok for Ethanol fuel. Put the piston with o-ring in, then put the regulator and shim stack back in with crush washer and test again. If it's still too high after 5 minutes, you can add one shim(thin washer) and test again. The system pressure has to be right, for the control pressures to be right through the range of operation.

Control pressures are all from the WUR. Low control pressure means high fuel flow, or rich setting. Higher pressure means leaner condition. Once you have your system pressure set, check your control pressures by attaching the electrical connector to the WUR. Over the span of about 2 minutes, the pressure should rise linearly to the specs in the CIS book for the 928. If it doesn't, or if it is too slow, you will need a rebuilt WUR.

Next, I believe the 928 has two vacuum ports. The control pressures are influenced by the vacuum port as well. I would let the WUR cool back down, pull a vac of about 15"HG(~7PSIA) on the small port and test the WUR again. This will also tell you if the diaphragm in the WUR is perforated which is another common failure. I don't know what the lower port does, but on the Ferrari it senses the air between the large metering plate and the throttle plate. So, this is an intermediate pressure in the intake system, and I'm not familiar with the vacuum numbers there. But it should be checked that it's not perforated as well by pulling a vacuum on that port and see if the vacuum stays for a while. If not, the membrane inside the WUR is toast and you are in big trouble, cause it's NLA as far as I know.

<edited to correct error in WUR part>

 

Update:

Previous issue With low cold pressure car starts fine then stalls as it warms up.
I received this 78 after it was worked on to correct a 4k Rpm red line and running rich. The FD was taken apart along with the Wur nothing internal was replaced but adjusted to try to get it to run. So I do not have a good base line.

At this point I got the Wur set correctly based on the pressures listed. This is all done with a cold car using the battery To energize the heating element and watching it.
25 cold start
30
39
44 lbs when warm a few minutes
54 lbs With lower vacuum applied
Fuel pressure 72
All looks to specs

I adjusted the air flow plate based on manual recommendations now car hardly starts back fires and will not keep running. I am assuming this is a lean issue but now that the Wur is set the FD is out of whack. Can this be when the Wur was off with it running real rich it compensated for a FD issue? This is the first time the Wur acted like it was suppose to and the car is getting worse.

 

I may have said this before - my car runs system of 75psi, and HOT control of 45psi (vacuum connected) - provides all the power I can use. Not sure what cold control is (gets down to < 10C here), but it starts well cold, drives away without hesitation. Gets 11L/100km on a cruise. I suspect your 54psi warm is a bit high - have you checked what it is after a run around the block? Its not unusual for people to adjust the main mixture to compensate for a problem elsewhere - look up the process (elsewhere on rennlist) for resetting base adjustment of the FD mixture adjuster.
jp 83 Euro S AT 55k

 

Found a chart for 78 Euro Wur chart and you are correct the pressure is a lot lower than Row. Will try to adjust for a lower pressure and see if things improve.

 

thought an update is in order
Seems like with numinous adjustments the car is starting and staying running. Looks like some progress is being made next is the timing and looking at the non charging alternator.

 

Found the drivers side cam off by 2 degrees, temp gauge goes to hot when at idle after a while, alternator not charging, drivers cam seal leaking.

 

Just to throw it out there....the fuel distributor has a lot of parts in it, washers, springs, caps, orings.....I lost a few washers cleaning mine and did not even notice. I cut a few orings putting it together as well. I did not line up the inner slits with the fuel holes correctly.....

I tried to be meticulous in the assembly, and still ended up doing it 5 times before I got it right! What I am tryin to say, is that it is easy to make a mistake, and knowing what I know now, I would be concerned if I heard someone had opened the fuel distributor for adjusting, especially if I did not know how good they are with them.....might need to open her up....

 

Perhaps a stupid question but could a bad working pressure regulator valve in the FD cause a too low fuel flow although rest pressure ( when engine is shut) is OK ?
I have an issue for which my system pressure is between 4.5 - 5 bar, while it should be 5.2 - 5.8bar. Shimming the pressure regulator valve does not raise my system pressure .
Testing the flow via WSM gives about 800cc/30sec while it should be 1120/30sec. Pump, filter,accumulator were renewed 2years ago and there is no clogging in the lines/filters from tank to FD.
Could it be that the O-ring on the pressure regulator valve is sticking preventing the little plunger to move backward for letting a part of fuel flow back to the tank within the 30secs specs ?
I know that it needs to seal when fuel pump doesn't run for a good warm start, but could it be sealing too tight ?