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Warren Hall Student
 
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WUR malfunction repair?

Hi guys,

I've got a WUR problem that I could use some help with and the advice of the gurus would be greatly appreciated.

My control pressure is off when the engine (77' 2.7S CIS) is cold. Basically the control pressure is the same when the engine is cold or hot. 2.9 bar to be exact. So basically it seems like my WUR is stuck in warm mode.

Here's the stats on the fuel pressures:

system pressure / 5.1 bar "good"
cold control pressure / 2.9 bar @ 12deg. centigrade "bad" should read 1.5
warm control pressure / 2.9 "good"

I started testing with the WUR 12v disconnected, and the engine cold. Then I turned on the fuel pump with the valve closed going to the WUR and got 5.1 bar system pressure.

Next I opened the valve to the WUR and got a cold control reading of 2.9 @ 12 deg. centigrade which is high.

I then proceeded to apply 12v to the WUR to see if the control pressure changed and there was no change after 15 or 20 min.

I confirmed 12v to the WUR with my multimeter. Next I confirmed continuity and impedance for the bi-metal strip. Impedance is 28 ohms. Close enough.

So I decided to remove the WUR and open it up.

Inspection revealed no blockage or any other obvious problem with the WUR. The diaphragms look good with no dimples. No obstructions in the passages.

So here's my question. Is my problem most likely the bi-metal strip? Is it tired and not holding back the spring pressure? What are the best routes to remedy this.

Maybe I'm a candidate for the adjustable WUR mod?

TIA
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Old 11-30-2006, 08:53 PM
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I would say tap the pin in a little and see, you can always tap it back out. I just did this on mine and it worked out. You can tap on the pin while your hooked up to the gauges to see the pressure come down.
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Old 11-30-2006, 09:03 PM
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Great idea. Thanks for the tip.
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Old 11-30-2006, 10:19 PM
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Bobby,
You may also want to consider a digital WUR. It is a direct bolt in replacement for the factory part and is fully adjustable. Tuning of
your A/F numbers is done with a Palm Pilot, which plugs into the
digiWUR. Incredible tunability and A/F numbers as installed on my
3 ltr. turbo. The price will surprise you as well, Contact Chris Carroll at TurboKraft for more info- 602-481-0264 or info@turbokraft.com.
Tell him Bryan with the '74 turbo sent you. No affiliation, just a very
satisfied customer. Good Luck
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Old 12-01-2006, 12:17 AM
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Hi Bryan,

Didn't even know there was such a thing. Sounds like a great alternative for the tired old WURs out there. Specially considering that replacement ones are $300 to $700 from Porsche. Wayne should look into carrying these digital new replacements.

I think I'll try Donnies' suggestion first since this motor is just a spare. My 3.2 EFI is on the engine stand at the moment but will be going back in the car in a month or two.
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Old 12-01-2006, 01:15 AM
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there was no blockage at screen on top of the WUR? there may be a blockage somewhere else.
personally, i wouldnt "tap" that pin in, that will put a dent in that thin metal diaphram. if u must, there is an allen screw on the bottom of the other diaphram that will change the tension on the spring.
sounds like someone may have already gotten in there and adjusted it so it runs right when hot, trying to cover up something else wrong. i wonder if u adjust it far enough, will the bi-metal strip no longer have any effect on the pressure??
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Old 12-01-2006, 04:33 AM
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Tapping the pin in will not dent the diaphram, Have you opened a wur to see how it works?

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Old 12-01-2006, 05:28 AM
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what do u mean by "tapping " the pin?
u are showing a pic of an earlier WUR! if he has a 77, he has the one with the vacuum enrichment which has a diaphragm with an allen screw on it to change the tension on the inner spring. no, i havent opened one of the NON-vacuum units but i have opened the later ones...have u?
i wouldnt go telling someone to modify or adjust their WUR until everthing else has been checked, u may be covering up another problem.
if his pressure is the same cold as it is hot, "tapping" the pin or even changing the pressure will only make it run correct for one running condition, hot or cold!! he either has a bad WUR or a restrition!
any idiot can take apart a WUR, but knowing its purpose takes little more inteligence!
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Old 12-01-2006, 05:51 AM
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bobboloo,
is your thermo time VALVE still installed? it is a small black "thing" connected to the vacuum line that comes off of the top of the WUR. the other side of the TTV is connected to the throttle body. the TTV also has a 2 wire connector going to it. if the vacuum line from the WUR is connected directly to the throttle body, it will make the control pressure high when cold.
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Old 12-01-2006, 06:01 AM
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Quote:
Originally posted by T77911S

any idiot can take apart a WUR, but knowing its purpose takes little more inteligence!
Well you sure told me! I will subscribe to the thread, and watch a real pro solve someone else's problem.

So, what would be the proper troubleshooting precedure for this gentleman to follow, it would be much faster for all involved if you would just outline the exact steps to troubleshoot the CIS.
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Old 12-01-2006, 07:39 AM
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thanks, read my post above
Old 12-01-2006, 09:50 AM
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Question

Do we have an ego-trip here?
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Old 12-01-2006, 10:19 AM
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Quote:
Originally posted by T77911S
what do u mean by "tapping " the pin?
u are showing a pic of an earlier WUR! if he has a 77, he has the one with the vacuum enrichment which has a diaphragm with an allen screw on it to change the tension on the inner spring. no, i havent opened one of the NON-vacuum units but i have opened the later ones...have u?
i wouldnt go telling someone to modify or adjust their WUR until everthing else has been checked, u may be covering up another problem.
if his pressure is the same cold as it is hot, "tapping" the pin or even changing the pressure will only make it run correct for one running condition, hot or cold!! he either has a bad WUR or a restrition!
any idiot can take apart a WUR, but knowing its purpose takes little more inteligence!
The pin he refers to is the post that the bi-metal strip is attached to. Tapping the post (pin) in moves the strip away from the diaphragm so no damage would inccur. Maybe you thought Donnie was refering to the pin that pushes on the diaphragm. If you look at the picture Donnie posted of a modified "adjustable" WUR tapping the post in would move the strip downward away from the diaphragm toward lower control pressure. I believe this was probably the way the manufacturer probably made micro adjustments to set the cold spec when necessary. Ideally you would think that they would be assembled and no adjustment would be necessary but if one was out of spec they could have adjusted it this way. The thing that leads me to think this is that if this "feature" wasn't meant to be then Bosch would have made the post for the strip as part of the casting (cheaper). At least that's my story and I'm sticking to it.

It's not unlikely that my bi-metal strip has "relaxed" over the years from constant pressure from the internal springs that fight the battle for "warm running". As matter of fact it has no discernable bend in it like the one in the picture has.

As for the TTV mine is connected and functioning properly (I tested it) but vacumm is irrelevant in this case since my tests were with no load and the engine not running. If I encounter a problem underload in the future I'll investigate vacuum.

I have confirmed that the other components all work properly. AAR, AAV, decel, and TTV. Even the cold start setup is fine.

My problem however is with cold control pressure being out of spec and the test I performed is done without load and doesn't involve any of the vacuum components.

P.S. I believe Donnies' advise is good.
Anyway, I'll try adjusting the strip and report back.
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Old 12-01-2006, 10:41 AM
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One more thing before this gets out of hand.

This BBS has the potential to teach us more than just about Porsches. It can also teach us about diplomacy, patience, and our own short comings. I've discovered a few of my own here. Even butting heads with someone else has the potential to teach you something if you let it.
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Old 12-01-2006, 10:57 AM
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i did think he was refering to the one on the diaphragm.
edit---( but again, donnie was talking about a 74 WUR, i was refering to a 77 WUR. i did not know how the 74 was adjusted, so ive learned something.)
sorry donnie.
but once again, u have a vacuum controlled WUR, his pic is one of a non-vacuum model. i just went and "whacked" on my spare WUR, that "pin" he refers to will not move, and mine does not have a nut on top. you have to turn the allen on the bottom of the vavuum diaphragm to change the pressure.
i assumed the hot readings were being done with the engine running.
maybe the nut came lose that holds the bi-meatal strip inside the WUR?
u may have been PO'd, PO may have adjusted WUR to run correct when hot

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Old 12-01-2006, 11:10 AM
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When I adjusted the WUR on my 77, (at least the two WUR's that I worked on for my old 77), I did it with the allen, not by tapping on a pin.

Donnie, Make sure you are talking about a WUR for a 77, as there are different configurations for different years. Your diagram does not apply to the WUR's that I have seen for the 1977 model year, which I believe, is what this thread is discussing.
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Old 12-01-2006, 11:26 AM
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Guys, the nice diagram Dweymer posted looks like it came from a Pano article, reproduced in one of the Upfixins, on how to modify a WUR so you can adjust it without having to take it apart if you need to move the pin up rather than down.

I don't think any WURs came with a nut on top. That is part of the home brew adjusting system which required drilling and tapping and so on. The problem addressed was that you can tap the pin down externally, but what if you tap it too far. Nice not to have to disassemble the WUR to get it back up again.

My knowledge of the innards of WURs is based mostly on diagrams (I've just been looking several of them in Probst's book), as I only opened one up once, and that a while ago. It looked enough like what I expected, but that's all the image I retain.

But I deduce two things here:

1) if you can adjust the (main) coil spring that controls what one might call the valve diaphragm (up on the top on diagrams, the one which controls fuel flow), it is going to affect control pressure across the board - all other things being equal, both cold and hot pressures will be higher or lower depending on what you did to it. That is going to affect the control pressure regulation part of the WUR's job. One doesn't hear about this much, but if there is an internal adjustment for it fine if your hot pressure is off. And since Bobboloo says his warm control pressure is within spec, he isn't interested in changing this.

2) The warm-up part of this (cold enrichment) is controlled by the the bimetallic long flat spring with the heater around it. If I read the diagrams right, this spring is a kind of one way deal: it can push down on the main coil spring (reducing the effective spring pressure and leading to enrichment), or it retracts (due to heat) and at some point has no effect at all on anything. I am thinking this may be the case because various of the diagrams show the working end of the bimetalic spring down on the cup on top of the coil spring, and others show it part way up the shaft that connects the spring assembly to the fuel pressure diaphragm up top. If a guy had one apart he could tell easily enough by looking at how the connection is made.

In short, it looks like it can push down but not pull up. In which case, in setting the cold control pressure you don't need to have power to the WUR/heater, and in fact you probably don't want it, because it won't stay cold otherwise for long as you are messing about measuring and whatnot.

With regular springs, my understanding is that their rate never changes, but that they can "sag" due to "creep." Up to some point, adjusting them will restore function. I don't know if this applies to bimetalic springs, or if some part can exceed its elastic limit but not be easily detected (like, for instance, the harp spring on the clutch, where part of it breaks but it looks at least superficially OK).

But I digress.

So I'm with B'loo: tap the external "pin" in a little and see if that will compensate for a spring which has yielded some over the years. It may not work, but doing this has been recommended (or suggested) for enough years that I am persuaded it can't hurt. And the alternative is what? Buy a new bimetalic spring at Home Depot? I guess some clever rebuilder has a source for these parts in the right shape and other characteristics, but I've not seen a source advertised.

Walt Fricke
Old 12-01-2006, 01:06 PM
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WUR Vacuum Question

Scroll down to my post (PBH) my info might help you adjust your WUR if it is an internal problem rather than a pin depth problem.
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Old 12-01-2006, 01:24 PM
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The will move. You need to 'adjust' with the pressure gauge in place so that you can see what you are doing. Its very primative tuning with a center punch and a hammer. The biggest problem is that it seems to move all at once and then you over shoot your mark. Making the plug adjustable really helps you zero in on the pressure you want because you over shoot on purpose and then use the screw to fine tune. Also, for the record, the plug we have been refering to is the one in the picture above to the left of the heating element.
If you have 12 volts at the connector and 28 ohms as the coil resistance you might want to make sure the connector pins on the WUR are not all funky. With it opened up you should be able to feel the element getting hot. There is also an allen screw 'adjustment' under the spring on some models. I think tampering with this will alter your warm pressures. If you are brave you might be able to adjust it from both areas to get you back into the cold / hot window.
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Old 12-01-2006, 01:27 PM
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[QUOTE]Originally posted by Walt Fricke
[
1) if you can adjust the (main) coil spring that controls what one might call the valve diaphragm (up on the top on diagrams, the one which controls fuel flow), it is going to affect control pressure across the board - all other things being equal, both cold and hot pressures will be higher or lower depending on what you did to it. That is going to affect the control pressure regulation part of the WUR's job.
]


walt, u said what i have been trying to convey. if the pressure is not changing between hot and cold, then u can only make the WUR work properly in one condition, either hot or either cold but not both.
the only things that will make the pressure too high all the time is a restriction or a very miss adjusted WUR with a bad heater.
Old 12-01-2006, 01:31 PM
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