Try Daves test of ignition on. pump running, wur plugged in.
Record initial engine temperature and cold pressure when cold and see what it will rise to.
Should only take about 5-10 minutes to get to max deflection if the resistor is warming the bimetallic strip properly. If it won't go past 2 bar, the wur is out of calibration.
Do you have a 045 or 069 wur?

Right. If it fails the test, though, most likely it's more than a simple calibration problem.
Or as Tim said, then maybe it was re-assembled incorrectly. It should have never
been opened. The initial 1.5 bar after the OP's "tap" was close enough to spec for the
time being.

Many seem to forget this post over a month ago, i.e. before some started taking
the OP in multiple directions (throwing darts at the CIS component list).

"Dave",

I'm just curious, are you naturally a **** or do you have to work at it?

So far, the OP has found several issues that needed to be addressed - failed CDI, worn dizzy bushings, vac leaks, fuel pressures out of spec, to name a few. Addressing those things has not been wasted effort in my book. You may disagree, in which case you and I can simply agree to disagree.

I'm just trying to help a fellow Pelican out. I don't see why you feel the need to be derisive about it.

P.S. - I noticed something really strange. There used to be another user on here that went by the name of Lorenfb. He seemed pretty knowledgeable but he came across as a real douche nozzle sometimes. Such a shame, really. Life is too short, you know? Anywho, he had this really interesting thing about his posts. See, he didn't understand that typing on a computer isn't like typing on a typewriter -- you don't have to hit RETURN at the end of every line. I noticed this because it made his posts look funny with awkward line breaks, which is the same way you type your posts. That guy had a real sore spot for CDI issues too. I just thought those data points were interesting. Kinda weird how you both share so many similarities, right?

So what is your point? Is the plan here to tease the OP that you have it all figured out so that he can guess until he gets it right?

mysocal911,
Can you share your thoughts abou performance chips. Maybe the OP needs to install one just in case? I heard they double the HP and thus overcome the trouble of a stalling engine.....

OK guys. Please stop fighting. I feel like I am invested in this story and am dying to know the final solution.

Years ago I spent a lot of time figuring out the operation of the WUR in my 75 911 and I learned that the WUR has 2 separate critical calibration adjustments done at the factory. They are:

1 - The plug that the bi-metal arm is anchored on. This is the one most folks try and adjust by pressing it further in or out. But this one mainly effects only cold pressure.

2 - The other adjustment that is not often adjusted is the warm pressure adjustment and this is done by pressing in or out the entire fuel cylinder. This is the larger metal barrel that has the fuel hoses attached to it. This barrel is also pressed into the housing to a very particular location so that warm pressure can be calibrated.

My basic understanding is that adjustment 1 (the plug) only moves the cold start bi-metal arm up or down but once that arm gets fully warm it moves away and no longer has any effect on pressure. After the arm fully warms pressure is then controller by the location of the large barrel.

IMHO - it's beyond the average garage mechanic to properly adjust these WURs. You can easily wind up with strange conditions, like mixtures that tend to get richer and richer as load (air flow) increases or the inverse is also possible where they get leaner and leaner. It's not enough to simply check things at idle. If however you have a decent Wideband O2 AFR gauge you may be able to fully calibrate the WUR for all conditions (idle -> WOT).

The WUR is alot like the more modern AFM meter in the 84-89 cars and you can't simply muck with a few adjustments and assume it's correct for all air flow conditions.

Let me give a sample scenario for he WUR to help illustrate the problem. Let's say warm pressure is speced at 3.0 bar but for some reason you are not at 3.0bar but slightly less at 2.8bar you can easily compensate for this by simply adjusting the mixture screw to lean the mixture and you'll be at correct mixture for idle fully warm. BUT here's the problem the actual pressure that fights the air plate from rising is still to low by 0.2bar so now as air flow increases it allows the plate to move upwards at a much more rapid rate that it would if the control pressure was at 3.0bar. You need to think about this relationship of the control pressure and how it acts upon the air plate as air flow increases. Simply setting things up at idle is not enough if the WUR is out of calibration.

My thoughts on what's wrong with this particular motor. I'm betting that multiple things are causing the poor running condition and it's not just one single bad/marginal component. These cars are 30-40 years old and every car I've helped with over the years has had some sort of marginal issue that goes unnoticed. Allow a few marginal issues to exists and then have one critical component failure and it becomes very difficult to diagnose. You need a systematic approach to diagnosing the issues. If I was working on this motor and it had some miles on it I'd start with basics:

Start with mechanical FIRST! You can not fix a mechanical issue by looking at fuel or ignition.
- Comp and leak down tests
- Cam timing? has this been altered? or is it unknown?
- Exhaust? Are you sure you don't have a restriction?
Fuel system.
- Fuel system check and pump pressure and delivery rates
- Injector spray patterns
- Sweep the air plate through it's range of motion looking for sticky spots while watching injector spray patterns.
- WUR pressures
Ignition system
- Dizzy, cap rotor
- wires
- plugs
- coil
- cdi

Tackle one system at a time. If you have spark start with fuel system then double back and question marginal ignition.

Also, double check charging system and battery condition.

Well, yes, the main thing here is that OsoMoore gets back on the road. I am happy to be wrong if the end result is he gets his issue fixed. It has never been my intention to give him a bum steer, but the fact is that several issues have been found and fixed. The end result is that the OP's car will drive great once again once this issue is licked.

We now return to your regular programming...

Sal,

thanks for bringing some level-headed sanity back here. I agree 100% and I believe the only way to get this resolved is to meticulously work through the published test procedures.

One comment about the WUR adjustments. I agree that adjustment (1, moving the light grey pin) should only affect cold CP. Once the arm moves up it's only the bottom spring affecting the CP and you have a normal pressure regulator configuration. The spring rate and the absolute position of the bottom cap (not shown in the diagram) affect the CP.

However, as the light grey plug is moved extensively I can see where even with the bi-metal strip being fully warmed up it remains in contact with the hat. I bet that is why some observe that the plug adjustment impact CP even when the engine is warmed up (b).

http://forums.pelicanparts.com/uploa...1436451078.jpg

The bottom line: I would like to see a measurement of the CP after the heating element in the WUR has been powered directly from B+ for say 10 minutes with the fuel pump running. If the CP reading is anything less than the required 3.5 bar then that's a red flag and needs to be corrected.

Ingo

Sal,

Those are very wise words indeed!

I think it's a bit too easy for "Dave" to Monday morning quarterback. As I recall, the OP originally started with arcing at the coil. In retrospect, any of us might have suggested a different path once all of the data has unfolded, but we didn't have all the data at the time. And if any of us was standing right there next to the OP, we might've taken different approaches or checked different things. That's the nature of troubleshooting over the Internet.

OsoMoore,

Hang in there!

Could you reply to my question about the injector volume? If you let them spray long enough and you saw relatively equal amounts of fuel, then that's the answer and we move on.

I think you need to heed Sal's advice. Try to get in touch with Tony. If he's not available (I think he's been vacationing lately), then you may have to send your WUR out in the worst case scenario. Brian Bodart (Rarlyl8) rebuilds them I think. You previously had warm CP around 3.0. If you can't get back to those numbers, then something is wrong. You've already disassembled it, so not much harm in fiddling with it a bit more now if you're comfortable with attempting to make the adjustments.

My point in my posts last night is that it isn't making sense that the engine is stalling if we assume that your fuel pressures are close enough to run (ok maybe not run well, but it should run), that you have found/fixed all vac leaks and that your electrical gremlins are gone. Your call on whether you want to re-plow those fields.

If we assume that something is bogging down the engine, what could that be? My thinking is that it could be that you don't have a closed cylinder at TDC (valve open) and could be cam related (as Sal notes). Compression test should rule that out. I'm not trying to create more work for you though.

The other possibility is that you have an issue with the fan/alternator. Is the fan shimmed correctly? Are the bearings in the alternator causing some resistance? Is there a downside to trying to run the motor with the alternator belt removed to see if the engine still bogs down?

Ingo,

Nice pictures they show clearly that messing with the plug only effects cold pressure. I agree with your test, heat the element and see what happens to pressure as it heats. I'd even bench test the WUR to be sure that arm moves totally away once the arm is warm, can we bench test the WUR with it opened up to see how the arm moves, is this even possible?

After reviewing these pics I'd say you really need to set warm pressure first and be sure the arm is fully moved away while doing this. Then after you setup warm pressure you proceed to setup the cold pressure. You really should not muck with cold pressure adjustment till you first verify and setup the warm pressure.

Wow, so many posts in one night!

Me too, me too. I appreciate the passion and wisdom you all bring. I'll try to keep the experiments in order continue in an organized path through diagnosing the issue.

Hello Sal! Some quick notes regarding your possible issues list:
- Compression was tested when I bought the car three years ago. All cylinders tested at 8% or less loss.
- Cam timing has not been altered since the engine rebuild about 60K miles back. Engine was running and then suddenly stalled at a light. The engine/cams have not been opened in that interim. Maybe I should check the dizzy advance now that the air leak is fixed.
- Nothing seems to be blocking my exhaust as far as I can tell. Could a blockage let it start cold but die when warming?
- We're checking pressures, see the last couple of pages. Cold pressures (system and control) seem in-line now. I can do the recently recommended test to run the injectors for a couple minutes and compare total output volumes.
- Injector spray seems fine to my un-expert visual examination.
- Regarding ignition system, it has new cap, rotor, wires, plugs, and coil. I disassembled and cleaned and replaced some parts on the dizzy, possibly correcting an early spark plug wire spark issue. CDI is fresh from a rebuild. Old CDI wouldn't run the engine at all. The "new" CDI allowed engine to start immediately, leading to our current cold start problem.
- Starter cranks strong, battery seems fine. I've been putting it on the tender from time to time as it gets low from extended sessions of cranking.


Regarding Tim's comment on the fan - it is shimmed properly. Internally it is fine as well, the shop replaced the brushes and declined to do the bearings because they seemed fine.


So, here are the new ideas I've gleaned since last afternoon.
1) Do the "warm not-started WUR test". Ignition on, pump running, WUR plugged in. Record cold pressure, then watch it for about 10 minutes. Then apply the hair dryer for another 5 minutes. I don't have a good temperature gauge other than checking the weather in my zip code. Is it sufficient to record that as the starting temperature? I don't mind buying more tools, but I've been spending a lot recently.
2) Check my WUR model by looking on the side to see if I have a 045 or 069.
3) Test the fuel distributor's injector equality by turning on the pump and ignition, and raising the sensor plate until the baby bottles are about half full. Ensure there are no significant differences in fill height. Remove the nipples entirely to avoid pressure buildup in the bottles.
4) Once things cool down again, use my nifty phone to take a video of the engine start and run (until it dies).

I am leaving for vacation next week, and have an appointment to drop the car off at the local Porsche experts (recommended by reliable local friends) if it is not fixed by Sunday night. I was scheduled to drop it off this past Monday, but waited to get pressure gauges and one last week of testing. My wife is quite sick of running on just our main car, when we are used to have two throughout the spring and summer. She loves riding in it as much as I do driving it, and it has been a source of stress for both of us.

So, the real first failure was a CDI box fail. If this is the case have you suspected a possible bad coil?

Before this CDI total failure was the engine running properly? And how long did the car sit before it was running again after the CDI box failed?

The other tool that would be very helpful is a Wideband O2 gauge so we know exactly what's going on with the mixture. These are not super cheap, a permanent install gauge is about $160 these days and is an excellent addition to any of our air cooled cars.

Here's one I highly recommend:
Aem 30 4110 Wideband O2 Uego Controller Air Fuel Ratio Gauge Kit Bosch 4 9 LSU | eBay
Very accurate with no free air calibration required.
Every air cooled car should have one of these in the cockpit. This single gauge tells you a lot about the health of the motor.

The "episode 1" issue was arcing in the engine bay. After a few weeks of trying 1 thing at a time (cap, rotor, wires, plugs), I cleaned the dizzy, got a new coil, and replaced the green signal wire all at once. After those changes it ran fine for about 200 miles (although the woo-woo noise persisted.)
Episode 1 began on 3/20 and was concluded on 4/26. Engine ran fine and all was right in the world. See http://forums.pelicanparts.com/porsche-911-technical-forum/856863-bouncing-tach-when-cold-zap-noises.html

In the current "episode 2", at first it wouldn't run at all. The big triumph in episode 2 was replacing the CDI box. That got it starting, although it won't run when hot.
Episode 2 began on 5/6. CDI was replaced on 6/1.

The car hasn't had much rest in these months. I've been cleaning things, fixing things, and testing them just about every day.

Sal, he has replaced the coil. Could the replacement coil be bad? Sure, and in fact there have been some threads in the last year or so where that very thing has happened. But if I remember correctly, those were all no-start situations. He is at least getting the car to run (for a while).

I completely agree! I bought one myself and as you say it is a fantastic tool. It sure takes the guesswork out. In fact, I used it recently to help a local Pelican tune their car. But OsoMoore has spent a bunch of money lately. Maybe he can put that on his Christmas list. ;)

Yes, do that test, as it's very simple and will eliminate a potential problem source.

When warm the car stalls do you have any idea if it's possibly stalling because of lean condition? It would be very helpful to know if it's simply stalling because mixture is lean. If it's a rich mixture stall at idle you'd smell the fuel. Usually to stall under rich conditions you'd need to be extremely rich like below 11.0AFR and you'd see signs of darker exhaust smoke and smell the extra unburned fuel. If you do not see any of these signs I'm betting you are stalling because it's lean. Another simple test is to get the car warm and have it idling and try pushing up slightly on the air plate to richen the mixture, if pushing up on the plate helps it idle better you know it's lean. You can also have the mixture allen key in place and try pushing the plate down slightly if that helps then you are to rich. Simply try forcing the air plate slightly up or down and see if it helps the warm idle condition.

OP, I am really curious about a couple of questions lingering in my mind. Maybe you can re-confirm some observations:

Does the stall during warm-up only happen when you let the engine sit at idle (not helping it with the throttle) or does it happen no matter what at some point into the run?

If the former is true a wide-band would really help to see which if the mixture is walking away and if so in what direction. What if for example the closing auxiliary air valve causes this because the idle screw isn't set right?

When the engine is finally stalled out, can you re-start it somehow by introducing extra fuel (say a hit with carb cleaner into the intake). That would confirm a lack of fuel. Or can you get it started by introducing extra air (open throttle or introduce another air leak)

Further, can you monitor both system and control pressure during the warm-up cycle to better understand if one or the other is doing something "unwanted"?

By the end of the day the engine needs air & fuel in the right ratio, and spark at the right time to run. Idling is a special case because there is almost no load. Thus the intake charge (amount of carbureted air) into the engine needs to be very small. That's why idling tricky

Also, timing could be getting away as the engine warms up but I don't have a good explanation for how that would happen. After all we don't have the Motronic that changes timing based on IAT.

Ingo