calibrating the WUR? - Page 4

morriss · 05-06-2010, 05:53 AM

Quote:

Originally Posted by DPW928

No vacuum during tests.

Have you checked the relief valve to make sure it isn't leaking and causing your control pressure to drop?

You are referring to the relief valve on the gauge set, right? It was not leaking.

Dano- Thanks for the readings. I have those in the 2 write-ups I'm using, but I can't really use them until I get a gauge set that works properly. I'm still waiting to hear back from the on-line company I ordered the supposedly CIS - specific kit from. If I end up returning it and getting a refund I will contact Roger about the one he sells.
I know my system pressure is in range, but that's all I am sure of at this point. I can't really do anything else until I get a gauge set that works and has the proper fittings.

DPW928 · DPW928's Garage

Quote:

Originally Posted by morriss

You are referring to the relief valve on the gauge set, right? It was not leaking

Nope. Referring to the relief valve on the fuel distributor that controls return of fuel to the tank and sets system pressure.

morriss · 05-06-2010, 05:30 PM

Quote:

Originally Posted by DPW928

Nope. Referring to the relief valve on the fuel distributor that controls return of fuel to the tank and sets system pressure.

No, I have not. I do not even know where to look on the fuel distributor for it. Please share.
My system pressure is 71 (at 80*F), which is in range.

DPW928 · DPW928's Garage

It's on the rear drivers (oops) side of the fuel distributor. Look for a brass hex head and carefully remove it. Look for a small o ring on the end. If it is damaged, nicked, split, missing etc it can allow pressure to bleed off the WUR. BTW don't mess with the washer type spacers on the relief valve as they are what sets the system pressure, which is in spec.

Another possibility is that you are connecting the test gauge to the wrong port on the WUR. Carefully track the lines and make sure you are connecting to the line that goes to the top center of the fuel distributor. This would also explain why the fittings aren't appropriate.

rjm65 · 05-06-2010, 07:14 PM

It's #8.

morriss · 05-07-2010, 05:56 AM

Quote:

Originally Posted by DPW928

It's on the rear drivers (oops) side of the fuel distributor. Look for a brass hex head and carefully remove it. Look for a small o ring on the end. If it is damaged, nicked, split, missing etc it can allow pressure to bleed off the WUR. BTW don't mess with the washer type spacers on the relief valve as they are what sets the system pressure, which is in spec.

Another possibility is that you are connecting the test gauge to the wrong port on the WUR. Carefully track the lines and make sure you are connecting to the line that goes to the top center of the fuel distributor. This would also explain why the fittings aren't appropriate.

I'm pretty sure the gauge set is hooked up correctly. See http://forums.pelicanparts.com/porsche-928-technical-forum/536203-calibrating-wur-2.html
(page 2 of this thread) for pics of how I have it connected.

Fabio421 · 05-07-2010, 06:02 AM

The test hose will go to the WUR port that is closest to the rear of the car not the one towards the front of the car.

The common knowledge about how to position the shut off valve is wrong in my experience. The shutoff valve needs to be on the hose closest to the WUR side not the distributor side as I've seen reported in many places.

MPDano · MPDano's Garage

I'm pretty sure we pulled vacuum on the vacuum port. I don't remember how much but just enough to open the valve in the WUR. Could this be why you can't run the engine while the Gauge is hooked up? Can't hurt to try.

RJM65 pretty much did mine and I watched, but I got short term memory as I get older.

MPDano · MPDano's Garage

Also, hook up looks correct to me.

MPDano · MPDano's Garage

Here is the WUR Diagram. Looks like no valve under vacuum port but uses manifold vacuum. Either way, pull vacuum and see if it holds, then if it does, start the car.

DPW928 · DPW928's Garage

Quote:

Originally Posted by MPDano

Here is the WUR Diagram. Looks like no valve under vacuum port but uses manifold vacuum. Either way, pull vacuum and see if it holds, then if it does, start the car.

The vacuum port (not shown on the diagram) is used to lean the mixture on deceleration. i.e. it should not affect the readings unless the engine is at high rpm and the throttle plate is closed. It does this by pulling down on the diaphram and increasing (not reducing) control pressure.

Fabio421 · 05-07-2010, 07:02 AM

You can disconnect the vacuum lines during test but it's not necessary to get it to run. If it won't start, it has nothing to do with vacuum lines.

rjm65 · 05-07-2010, 09:27 AM

Remove the lever inside the WUR (the one with the heating element), put the WUR back together and see if that makes a difference. Hook the gauge up, fire up the fuel pump, and if your cp reads within warm range now, then your cold CP is way out of wack and it's time to tap the post upwards. By doing this you're simulating a warm engine, and this will confirm what your warm control pressure currently set to.

I would double check the size of the O-ring that was replaced, if it's thicker than the original, it could also cause a drop in control pressure as described.

So if after you do the above the cp is still at 0, try adjusting the allen screw (the one shown in post #3). If that allows you to get the warm cp within range, then reinstall the lever with the heating element and now adjust the cold control pressure. If the cold cp is still reading 0, then take the WUR back apart and tap the post upward.

The warm cp and cold cp adjustments are tied together to a certain extent. You can never adjust your cold cp to read lower than your warm cp.

MPDano · MPDano's Garage

Yeah, I was also thinking of the same thing when I first read your topic about changing the WUR o-ring. These things are real finicky. I always like to get things running as/is then start changing stuff around.

morriss · 05-10-2010, 06:37 PM

Most of the tests I have tried to run so far were done WITH THE HEATING ELEMENT REMOVED.
I am mainly using the write-up at

Warm up regulator (WUR) Calibration - Benzworld.org - Mercedes-Benz Discussion Forum

It seems to be more detailed than than the "Playing with your K-Jetronic Warm Up Regulator, or WUR" write-up.

I only eyed the o-ring to find a replacement; the one I found that fit seemed to be about the right size. I could not tell 100% from the old one because it was semi-flattened.

I have contacted Roger and he is sending me one of his CIS kits later this week. Hopefully it will be exactly what I need. I have done anything since last week because the one I currently have leaks all over the place.

morriss · 05-25-2010, 06:40 PM

Got the gauge set on Sat. and have been fooling with the WUR since then. After much trial and error I discovered that the replacement o-ring I put in was ever-so-slightly too big in diameter. I put a smaller one in and things began to look up. With just the top half of the WUR in place the car would start and run. With engine off and fuel pump relay bridged, it read .5 bar, just like the write-up says it should with just the top half connected.
Next, I re-assembled the WUR, but left the heating element out; just the springs and little pin were put inside. With the fp jumpered I was able to set the control pressure at 3.5 bar (it was about 85* outside). However, it would not start with this set-up. I then fully assembled the WUR and tried to start the car (vacuum lines and elec. connector in place, gauge set removed) and it still would not start. Took the WUR apart, just used the top half again, and it cranks right up.
So, it will start with no pressure on the internal disk (p-spot to be exact), but won't start once there is pressure on it.
At this point I am almost ready to give in and pay the $280 for a rebuilt WUR from Porsche Parts-Special T auto.com,Porsche CIS fuel injection parts, fuel distributors, warm up regulators- . That's a lot of cash, but I have spent 6 weeks farting with this thing and have gotten no-where.

MPDano · MPDano's Garage

Yeah, seems like you tried your best to save this poor WUR. That was the same place I was about to get me a rebuilt one. Make sure you get an exact one, there are similar ones but he is the pro. To be sure you didn't get a frankenstein WUR, make sure he knows what year and US/Euro your specific car is.

rjm65 · 05-26-2010, 10:02 AM

Quote:

Originally Posted by morriss

With just the top half of the WUR in place the car would start and run. With engine off and fuel pump relay bridged, it read .5 bar, just like the write-up says it should with just the top half connected.
Next, I re-assembled the WUR, but left the heating element out; just the springs and little pin were put inside. With the fp jumpered I was able to set the control pressure at 3.5 bar (it was about 85* outside). However, it would not start with this set-up.

At this point, without the heating element installed in the WUR, you should have adjusted the control pressure to between 2.8 and 3.2 bar (with no vacuum applied to the WUR). Without the heating element installed you can only adjust the WARM CONTROL PRESSURE, so outside temp is not relevant for it.

Once you get the warm control pressure back to specs, go ahead and reinstall the heating element, then adjust your cold cp as per the temp cross reference chart in the manual.

My guess is the car would start when you had the .5 CP reading because that was allowing for a richer mixture on a cold engine. Once you put the WUR back together without the heating element, your fuel injection system was behaving as if the engine was warm, plus the you set the CP to 3.5 (even higher than spec) which created for an even leaner mixture.

That 3.5 reading is within spec if vacuum was applied to the WUR, but you didn't mention doing that.

Before you give up, without the heating element installed and no vacuum applied, get the WARM CP between 2.8 and 3.2 bar, THEN reinstall the heating element and adjust the COLD CP (by tapping the post up or down) so that your gauge reads what the temp chart says it should.

NOTE: The cross ref chart in the manual for adjusting the cold CP readings are for having vacuum applied. So if you adjust the cold CP per the chart but without vacuum applied to the WUR, it will be off.

morriss · 05-26-2010, 03:30 PM

Quote:

Originally Posted by rjm65

At this point, without the heating element installed in the WUR, you should have adjusted the control pressure to between 2.8 and 3.2 bar (with no vacuum applied to the WUR). Without the heating element installed you can only adjust the WARM CONTROL PRESSURE, so outside temp is not relevant for it.

Once you get the warm control pressure back to specs, go ahead and reinstall the heating element, then adjust your cold cp as per the temp cross reference chart in the manual.

My guess is the car would start when you had the .5 CP reading because that was allowing for a richer mixture on a cold engine. Once you put the WUR back together without the heating element, your fuel injection system was behaving as if the engine was warm, plus the you set the CP to 3.5 (even higher than spec) which created for an even leaner mixture.

That 3.5 reading is within spec if vacuum was applied to the WUR, but you didn't mention doing that.

Before you give up, without the heating element installed and no vacuum applied, get the WARM CP between 2.8 and 3.2 bar, THEN reinstall the heating element and adjust the COLD CP (by tapping the post up or down) so that your gauge reads what the temp chart says it should.

NOTE: The cross ref chart in the manual for adjusting the cold CP readings are for having vacuum applied. So if you adjust the cold CP per the chart but without vacuum applied to the WUR, it will be off.

Thanks, I will try your suggestions right now. I did not read anywhere that the settings were WITH vacuum, so I think you might be right that I am off.
I hope this solves the problem because I called "John" at Special T (the link above) and he was not very friendly. Basically told me to "shove off if you are not going to buy a WUR from me."

morriss · 05-26-2010, 06:58 PM

Okay, pulled the heating element out, left the springs and tiny pin in, car off, fuel pump bridged, set pressure to 3.0 bar.
Next, fully assembled WUR, mightyvac connected to bottom side vacuum port of WUR, pulled 15 in.Hg on the vac, car off, fuel pump bridged, set pressure to 2.1 (outside temp 87*).
Unhooked mightyvac and connected engine vacuum hoses, plugged in fuel pump relay, tried to start car and no dice.
Realized I had not reconnected the 2 fuel injector lines on the top of the fuel dist. I had to undo them to hook the gauge set to the fuel dist.
Connected the two fuel lines.
Tried to start car again, and it backfired out the top of the engine.
Waited a couple of minutes and tried again - nothing. Still won't start.

Question: To set the cold control pressure, the WSM gives mightyvac readings as "340-420 mbar / 350-450mmHg). However, my mightyvac has "in.Hg" and "kpa." I figured mmHg stood for millimeters and "in.hg" stood for inches, so I did the conversion and it came out to 13.4 - 16.5 inches. I pulled 15 in.Hg on the mightyvac when setting the cold pressure on the WUR.
Am I right in assuming mmHg = millimeters and in.Hg = inches?