WUR / ohm reading is 0.00 ??

[alt77]

Bosch 0438.140.072 on a 3.0
Inside elec plug cable reads 11.1 DCV. The unit seems to not heat up as designed.
To my knowledge, the unit has never been opened or cleaned.
Can the electronic elements inside the unit be purchased separately? I have noticed that the repair kits do not supply or include the heating element in their kits.

All fuel pressures are normal and 700 amp cranking power.

Would appreciate any insights on how to get it working. Jump starting while rolling down the driveway sucks.

Will a rebuild kit fix my problem?

[AndrewCologne]

Can the electronic elements inside the unit be purchased separately?

One adress is here:
https://k-jet.biz/product-category/k-jet-parts/
Also kits are offered, ... and I guess in the US there do exist k-jet part dealers as well.
Just serach for "warm up regulator heating element" and check before which ohm value is the proper one for the heating element of your WUR model.

[Paulporsche]

Alt,

If all your fuel pressures are in fact normal, then the WUR should be operating correctly and if you have a starting problem, then its cause may be elsewhere.

How do you know your pressures are normal? Did you test them with a gauge?

[alt77]

No (paulporsche) I haven't tested the pressure as of yet. I can smell the gas without any throttle pedaling during starting the engine. Also, I hear and feel the gas in the feed lines to the throttle body and WUR. I let the fuel pump run for at least 30 seconds before starting. I'd admit, a pressure test is certainly forthcoming. I appreciate your insights.

[alt77]

Many thanks, (AndrewCologne) for the link. I believe this is in the right direction to solving my problem. I can now determine to do the fuel pressure test before taking the regulator apart and giving it a cleaning and replace the element.

Appreciate the 'Porschehood' of this forum.

[theiceman]

on a stock setup CIS car the pump should not even run until the engine is trying to start. You should actually smell no gas if it is working properly, i think you are WAY ahead of yourself if you think rebuilding the WUR will fix this without even any pressure tests.
You have all kinds of other things to look at first

[Walt Fricke]

Alt77 - you haven't said outright what operational issue caused you to check things.

A cold start issue? A failed heater element ought not to cause that. A hot start issue? A running too rich at operating temperature issue?

The usual checks on the WUR heating element are just its resistance, aren't they. Are you inferring resistance from the voltage drop? The easiest diagnostic is infinite resistance (aka a broken wire), which means no heat.

A failed resistor ought only to affect fuel mileage, shouldn't it? When cold, this system reduces control pressure, increasing fuel flow/richer mixture. As the WUR heats up, whether from engine heat or the resistance heater coil, the control pressure increases up to the warm control pressure. Beyond that point, the warm up part of this system can, mechanically, no longer affect control pressure. Engine heat is a kind of backup system, it just takes rather longer to heat the bimetalic strip to move from cold starting to regular running.

Maybe some shorts in the heater coils could cause things to heat up too fast?

[alt77]

Yes, it's a cold start issue. It's been this way for about 10years. I now have time to research and fix it. Thanks to all of those experienced with this problem.

Back to the issue; Beginning with starting the engine, it requires cranking for about 10 attempts in order to ignite the cylinders and begin to idle. I spend about 10mins pumping the pedal to keep it idling. During this time, it surges to 1500 RPMs once and back to 100 RPMs. Then repeats again to 1200 RPMs down to 100 and lastly begins to idle at 900 RPMs. I can then drive it like a real 911S Porsche.

Now to the WUR; I've checked the terminals on the unit (cold) and got an infinitely reading. 00.0? I plan to inspect the element inside for a (broken wire), but after reading some of the responses, I am confused by hearing that it may not be my problem. Walt , I have experienced the possibility of it running slightly rich. But feel confident that timing and fuel are in satisfactory adjustments. While driving, I can accelerate rapidly to 5000rpms very quickly with no noticeable power loss.

Anxious to keep this dialogue open...

[boyt911sc]

Originally Posted by alt77

Yes, it's a cold start issue. It's been this way for about 10years. I now have time to research and fix it. Thanks to all of those experienced with this problem.

Back to the issue; Beginning with starting the engine, it requires cranking for about 10 attempts in order to ignite the cylinders and begin to idle. I spend about 10mins pumping the pedal to keep it idling. During this time, it surges to 1500 RPMs once and back to 100 RPMs. Then repeats again to 1200 RPMs down to 100 and lastly begins to idle at 900 RPMs. I can then drive it like a real 911S Porsche.

Now to the WUR; I've checked the terminals on the unit (cold) and got an infinitely reading. 00.0? I plan to inspect the element inside for a (broken wire), but after reading some of the responses, I am confused by hearing that it may not be my problem. Walt , I have experienced the possibility of it running slightly rich. But feel confident that timing and fuel are in satisfactory adjustments. While driving, I can accelerate rapidly to 5000rpms very quickly with no noticeable power loss.

Anxious to keep this dialogue open...

Alt77,

If you know and understand how a CIS motor operates, you don’t need a WUR (0-438-140-xyz) to enjoy and drive the car. But you will need a pressure to do this. There is inherently wrong with your CIS if it takes 10 cranks to make it start and helped it run by assisting with the gas pedal. Could you make the motor start and run by just reaching through the window and turning the ignition switch?

One of my criteria for a good running CIS is to be able to start it at the first attempt. Maybe a second try if the motor has not been run for a while and stay outside the car. So my next question to you would be, what are your fuel pressures (CCP, WCP, SYSTEM, & residual)? Most likely you don’t know them and you are not alone. That’s OK for now.

I could lend you a newly rebuilt and calibrated WUR of your choice that you could try and install in your car. It is loaner and you could send it back to me later. There is no obligation to purchase. What I am offering you is an opportunity to test and try a properly tested and calibrated WUR without spending unnecessarily. If you could find anyone who has this program, go to them and I won’t be offended. I have provided hundreds of WUR’s to fellow Pelicanparts members without a single return until last week. The guy decided to go EFI and sent back the WUR. I knew one day that the streak would be broken and it finally came.

Tony

[alt77]

Tony and Walt, you both have enlightened my understanding of this WUR issue. I will be doing a pressure test in the coming week as both of you suggested.

In the meantime, the idea of preheating the WUR housing came to mind. My thinking was to use a heat gun set on low and preheat the housing for 30 seconds (could have done 15). BAM! It started up within 2 seconds and maintained a steady idle. The next phase will be to clean the filters and replace or repair any visual damage. Once repaired, I will post a final update on my experiences.

It's a privilege to have Porsche buddies like you guys !!

[Paulporsche]

See the chart at the bottom for correct fuel pressures for your WUR. When you do the cold control pressure test, make a note of the ambient temperature.

[ahh911]

Just checked wur couple of weeks ago.
Maybe of interest, this is what I did to record control pressure vs temperature. I've added the data in pencil to the image below, wur 090, 911sc 81, usa.

1. Removed the electrical connector from wur and inserted my own connector that I'd hook to an external battery.
2. Hooked up fuel pressure guage after testing that the connections held pressure and verified that reading was consistent with another pressure gauge (This is a new cheapo cisk fuel gauge kit so I tested against another gauge, they were within 0.15bar). Tested until no leaks.
3. Unbolted the wur keeping fuel connections in place, lifted it a little and slipped insulation under the bottom and sides to isolate the case of the wur from any surrounding heat sinks.
4. Put a temperature gauge (small dig meat probe) into the wur air vent and tried to keep it insulated.
5. recorded initial morning wur temperature and control pressure, no heating wur yet.
6. Using the external battery, heated up the wur till reading was about 48C.
7. Disconnected the external battery and let the wur cool down, took control pressure every 5degC drop roughly by Briefly running fuel pump, the fuel itself will cool it down a bit each time.
8. Recorded till nearly back to original room temperature and compared control pressure to other values I'd recorded the previous day at 15C to see if this method was valid, it lined up for that point.
9. This takes time to cool down, that's good as it stabilizes the internal to wur case temperature giving accurate representations of the inside temp.

Had the setup ready the day before so in the morning I could do a quick test followed by the rest of the above experiment.

My control pressure map showed there were 3 slopes, one below 20C, one from around 20C to 35C then another from 35 to 40degC above that temperature the control pressure remained solid. All my control pressures were less than spec except the final +40degC control pressure which was in spec.
I thought it through and explained it as the angle of the bimetal strip to the control plunger had changed, if the strip has deformed upwards from years of sitting and then it's simply knocked down in the z axis (about 1.4mm for my wur) that won't fix the details and is probably what i'm seeing. The range of control pressure coverage is more than adequate so just planning on shimming the angle of the fixed portion of the bimetal strip or reading on how or if you can bend back the strip by the small amount calculated using high school geometry (1.4mm it's been hit down and the length of the strip) then knocking the pin back up till at 38DegC the control pressure reaches it's max. I think I understand, but won't prove it till the next time I poke around in the wur. It's mostly for fun, just passing along whatever comes up, doesn't mean it's 100% right and really don't expect most people to care much unless retired, or bored but it's data that could help youngsters who come to this board in the future from a universe where petrol and 911s are still allowed.
Phil

[alt77]

If our government prohibits combustion engines in the US...I'm moving my 911S into Canada!!

I appreciate and will follow the charts provided in this post. Very timely for my fuel and vacuum test this week. This is a critical test and it needs to be attended to with correct knowledge and information. (thanks to Paul and Phil)

Paul, the suggested chart of my engine (bottom chart) indicates an installed oxygen sensor. My setup is without the sensor....will my readings be considerably different? I'll no doubt be answering my own question by doing the test.

[Paulporsche]

The control pressures "go" with each particular WUR so your readings should match the chart. Think of CPs as a kind of back pressure working against the fuel pressure to ensure the correct mix at any given time.

Now, whether your engine runs at its best at those control pressures is yet to be seen.

Why don't you have an O2 sensor? Is this a track car? Has it been without the sensor for as long as you have owned it?

My engine is a 3.2 made from an 80 3.0 and, since it is emissions exempt here in Ontario, has no O2 sensor. I use a 045 WUR, which is for 79 cars.

BTW to partly answer your initial question, you can check the resistance against the number printed on the bimetal element. Usually they are somewhere around 26 ohms or so. Once you do your tests, you may find people on this forum, including Tony, who can help you with replacement WURs or elements. There are also people who can repair WURs, including someone I used near San Francisco.

[Walt Fricke]

AAH
Your warm up CPs look like they are rich until they reach the point where the warm up system no longer is part of the equation - where your measured line becomes horizontal. Assuming all these readings were taken at idle, on a stock 3.0 US 80-83 engine with the oxygen sensor mediated AFR control that system is inoperative. On a '78-9, or any Euro 3.0, there is none of this stuff, just the WUR and the system pressure regulator in the FD.

Interesting that you put a 3.2 crank in a 3.0 engine, but left the intake stock 80 3.0? US 80, or were the engines delivered to Canada Euro spec? Small US intake ports? No WUR would be "stock" for that. However, the CIS system can be modified. You'd expect to need more fuel, since you get more air in per RPM, which you can get in part just because up to a point more air means more fuel through the FD. If a lower hot control pressure is needed, you can open the WUR up, and tap the big slug where the fuel flows in and out up a bit. This lowers the spring pressure on the diaphragm which actually controls the pressure (sort of same thing the bimetalic spring does).
How did you hit on the '78 WUR?

Interesting modification. I suspect that no stock temp vs CP chart is going to be entirely correct for this engine. If it starts easily, idles well, and when warm has an AFR at a reasonable figure for cruise, maybe that is as good as it needs to be?

Innovate's AF meter can be purchased with a sensor you shove in the tail pipe, which works fine for testing in your garage or driveway. It is easy to weld a bung on the header wherever the factory put one, or in an otherwise suitable place. Same with other AFR gauge systems.

I refreshed my recollection on the issues: hard cold start, won't idle until warm/hot without some foot on the gas cycling, and surges at idle/low RPM. Look up "surges at idle." That may give you some clue as to weather that is a rich or a lean phenomenon - I can't remember which is which.

You can lean out the cold start (if that is indicated) mixture by tapping the smaller steel slug whose other end holds the bimetalic strip up a bit (requires disassembly of the WUR to tap from the inside). Or modify it so you can pull that slug up from the outside.

And, to start with, checking out that the cold start injector system works. I note that it only squirts when the starter is running, and then only as long as the thermo-time sensor sees that a) you haven't cranked too much, or b) the engine isn't warm. A bimetalic heater coil system in the sensor does this control. It is an on or off system, so is pretty easy to bench test the sensor with a 12V source or a propane torch or both and an ohmmeter or something to check to see if the contacts in the sensor are closed (cold) or open (hot/warm).

Interesting engine modification questions.

[ahh911]

[/QUOTE]


Truth is, the fuel pressure gauge just confirmed what I knew already with 95% certainty. Because the cold start map was already close enough I could understand before testing with a fuel pressure gauge that the setting was rich because it would always start when cold, idle low (1200rpm too rich) then idle high (1700rpm as the heating element leaned out the mixture faster than the engine "warmed" at idle) and from there the rpm would come down nicely. As a simple test I unplugged the heater to the wur and the rpm's never went high and simply continued lower and lower (1200rpm to 1000 ... 400rpm) till surging (rich then "richer" as the car warmed up and fuel condensed less), plugged in the wur and a little while later the rpm raised and stabilized.

Rain was local so I removed the wur and knocked from 1.375mm to 1.31 mm from the setting on the data above, to reduce richness. I should take data as before and addend the graph just for data information. After that I'll angle the bimetal strip up by a very small amount and see if it is truly a simple trigonometric response to the long term deflection of the bimetal strip. I'm thinking I won't bend it back over the curvature as from what I've read, this aging could be the result of annealing over a long period of time, but I'll think about it some more. For now my thinking will be to re-angle it at the mount post by simply filing down a small amount either on the bimetal strip itself, or maybe a tiny angle washer type shim set with a tab, but I'll figure out the details next time it's apart.

Phil

[ahh911]

As explained above, shifted wur pin back up ~.06mm to increase control pressure.

Looks to me like there are two counterbalanced non-linear effects affecting the control pressure. One is logarithmic and the other is exponential. When pin is too deep, like the first set of data the curve looks more exponential, when it's too high it looks logarithmic (second curve). I guess the angle of the bimetal strip having shifted up plays a secondary role for these results. Note, my system pressure is barely 4.5 bar, on the lowest limit of spec. Data taken at 5 degC intervals from 45C down to 15C.

Next time I open this thing up, I'll change the angle of the bimetal strip and push the pin even further back up to the sweet spot and see how the graph improves, but clearly no rush.

[ahh911]

FYI
Pressure vs temperature for WUR another data set:

Knocked wur up late last year by another .07mm to increase cold control pressure.
Measured the results earlier, 3rd data set, the current setting.
1st curve one setting. 2nd curve pin is knocked up .06mm, 3rd curve pin is knocked up again 0.07mm.

wur 090, 911sc 81, usa

At the least it's mildly interesting, gives a sense of what's happening as the pin holding the bimetal bar is shifted up and the distances required vs result.
Did not shift the angle of the bar, just it's vertical height.


Phil

[pmax]

And in that vein, in case readers get mixed up thinking the two were the same person, as I did, alt77 the OP was referring to the 072 while ahh911's the 090 WUR with a different chart.

[ahh911]

It is clearly written, 090. It's to give a sample of what happens across the temp range vs bi-metal strip vertical distance. Most likely applicable to all versions to some degree, I'd think.

Given my system and warm control pressure are at minimum, the last data set 3 was struck upwards more than I meant to, I wanted the cold control pressure slightly lower to track the other two variables as one would think they are related (i.e. low system pressure gives way to low warm control and therefore the cold control pressure should be set to minimums as well). Next time I'll do as Andrew I believe suggested in his excellent web page, use the vice to push the pin down in a controlled manner, or some derivative that has more sensitivity as I'll be looking for .02mm pin push down from where it is in set 3, the setting currently in the car.

https://nineelevenheaven-wordpress-com.translate.goog/abgasregelung-beim-sc/?_x_tr_sl=de&_x_tr_tl=en&_x_tr_hl=de&_x_tr_pto=wapp

Phil