930 WUR - Pressure Test Complete (Pix), Perplexing Results

[Paulporsche]

Thanks, ianc. edited to AAR, and 7 injectors.

[oneblueyedog]

when I went through my cis on my SC, I took the unit off of the airbox to replace the foam cushion perimeter gasket. I cleaned off the varnish from the sensor plate and even removed the peg from the fuel distributor ( the thing you're not supposed to drop ). I noticed that the peg was machined on most of its perimeter but it also had some mirror polished wear marks in a certain orientation. I reassembled it not paying attention to the wear marks. When I started it back up it idled horribly and I spent a couple of nights checking pressures and such. I then remembered the polished peg. I checked the sensor plate and found it did not fall back easily after lifting it. I then rotated the peg with my fingetips until it rebounded back with ease. It started right up and has worked fine ever since.

THe peg must lap into the fuel distributor or wear in after 25+ years. I have no idea if this could be a similar problem in your 930 but I though I might share it with you. I imagine when you buy a rebuilt fuel distributor this is an important part they remanufacture.

If I ever have to get a fuel dist. It's Megasquirt time insread.

[RarlyL8]

Paul -
1) Gunson Gas Tester checks out OK. Steady baseline of 2.0% until you stick it up the pipe. Divebombs to 0.0%. A/F meter verifies.
2) I have fine-tuned the mixture to a point where it no longer occillates. It does respond well within that range.
3) Sensor plate was taken apart and cleaned when the engine was rebuilt. It still looks good today. No issues I can see.
4) The decel valve was left in place to ease transition of off-throttle events. I have no idea if it is worth keeping or if it in fact works at all.
5) I see no need to check the ignition. The car runs perfectly once started. It has a lean mixture off-boost. All symptoms tell me this is an air/fuel issue.
6) The idle has increased 300rpm. That is consistant with your lean mixture characteristic.
7) The mixture cannot be adjusted warm because it begins to occillate before the desired settings are met. So it probably can be set but it will occillate from 600-1600rpms if you attempt it.
8) You are correct in the functions of the AAV and AAR, however I have none of these devices on my engine.
9) I measured the CCP @ 65F.
10) I believe 100% that the bi-metal strip has failed. What puzzles me are the Pressure readings. They are not significantly out of spec. Could it be that the A/F ratio tells more to this story than the fuel pressure?
I don't beleive my WUR has an adjustment screw on the bottom, only the top (and it is not responding very well).
11) The inside of the tailpipe is black from the soot of fire.

Ianc-
1) You are correct in the function of the AA devices but again, they don't exist on my engine.
2) The cold start valve was my first guess a few months ago when the first symptoms occured. I have eliminated that as a possibility because of the lean condition that persists during off-boost driving. As you know the cold start valve has no function after the engine starts. The hard starts don't bother me, they are only an anoyance. The lean condition does bother me.
3) There were 2 thermo time devices on the original 930/63 engine. They no longer exist.
4) The car should not start at all if the Cold Start Valve has failed. If I artificially alter the control pressure with the adjustment screw on the WUR the car will fire up in just a few seconds. This leads me to beleive that the CSV is fine. Unfortunately there is not enough adjustment to eleviate the lean running condition.

I get the feeling that some folks either don't understand or cannot beleive that you can run and drive a CIS car every day with only a fuel distributor, WUR, and Cold Start Injector. These components truely are all you need, no, they are the only components you MUST HAVE. That is not to say that an AAV might not make life easier if you live in Canada but you get the idea.

Thank you both for your questions. I've had to re-visit all of my notes made when I first put this beast together. I remember thinking to myself back then "wonder how long this old fuel injection junk will last?" Guess I got my answer.

[Paulporsche]

RarlyL8,

It sure sounds like you have gone through a very thorough exam!

Your CCP is low. I think it should be about 1.9 to about 2.4 bar @ 65F. You said you were 1.5 bar. I think this could account for some of the issues. That's about 6 to 13 psi too low on a range of about 28 to 36 psi.

I don't know if you sent your existing WUR off to be rebuilt yet, but if not, look @ the underside. Often there is a brass plug there. It can be removed and a screw found within can be adjusted. This changes the relationship between the cold and warm CP. Even if the plug isn't there you could still open the unit up and make the adjustment, or perhaps drill it out to access it. If you search, I think I remember a thread or at least a response from JW on this procedure.

Regarding the decel valve: usually the older style fails, allowing a vac leak to occur. Often people bypass the problem by plugging the top line. I honestly don't know if this is appropriate for your style.

Also, have you measured the resistance on the bimetallic strip? There was a recent thread on WUR adjustment where the resistance was given. Was it 18 - 22 ohms?

I am leaning to either the wrong relationship between the CCP and WCP, or the strip.

If you do not want to tackle either of these procedures, then sending it to an expert is obviously best. If that's what you finally do, please let us know what they did and what it cost you.

BTW I am not one of those who feels you must have an AAR and/or AAV, especially in AL. I was just addressing some questions/ comments raised by others regarding those items. Do you start the car w/ the accelerator pressed down? If so, how far? And for warmup, do you do the same?

And, regarding service life of these components: 27 yr or so ain't too bad!

[RarlyL8]

After re-reading my old notes and these new posts I decided to test the WUR again this morning. The pressure tests came out identical. I then concentrated on the bi-metalic strip. Nowhere in my factory manuals or CIS manuals could I find where it states how long it should take for the pressure to raise once the ignition is cranking. I timed this event 3 times with extremely consistant results. The bi-metal strip is working. It takes 3 minutes to acheive and hold peak pressure. Is this 3 minutes correct?
All the data on the WUR tells me it is indeed working. Not perfect but probably not off-spec enough to cause the issues at hand.

SO it is time to look at other things. I'm not going to ignore the WUR but other things need checked. As you guys have pointed out, the only other system that could cause a lean condition and hard start is a massive vacuum leak. I have very few vacuum lines on this engine so they shouldn't be hard to check. The Fuel Distributor is next if I find no leaks.

Paul - I've feilded many e-mails questioning me on minimalistic CIS. This system was stripped when I lived in Illinois, very cold place in the winter. The only component I used in IL that I removed in AL is the AAV. I used it as a convenience item in IL, it became a PITA in AL by revving too high for my taste on initial start up in warm weather.
The method I use to start the car, even in the winter, is to get in and crank the ignition with NO throttle until the engine starts. Once the engine starts I give it throttle to 2000rpm and hold it for 30 seconds. That's it. If it's really cold you feather the throttle at stoplights until she warms up.

About the Fuel Head. I restored that unit whith the rest of the CIS stuff shortly after I purchased the engine. It was siezed up. The motor was a theft recovery with no history. Don't know how long it had been sitting with bad gas in it. Anyway, I took the fuel head apart and saoked the fuel cylinder with carb cleaner for about 2 weeks until the piston fell out on its own. I then carefully cleaned everything and put it back together. You're right about the extreme tolerances. These items are a machine matched set. Drop the piston you might as well throw the hole thing away.

Stay tuned for an update on Sunday. I plan to rip off the rest of the CIS system and check each vacuum hose thoroughly. I did that 3 years ago when I restored the CIS system but many original hoses still remain. They're rugged looking units! And yes, you can't really complain much about 27 year old system having a bad day.

[RarlyL8]

The problem has been eleminated. Litterally.

It was not the WUR. The two P-mechanics that diagnosed the WUR was the culprit are gonna have a crow sandwich. What was the problem? Well a couple of you hit the nail right on the head. You saved me some valuable time and money thrown at parts replacement.

I stripped off the CIS this morning to check all the vacuum hoses. It didn't take me long to find the culprit. The only peice of non-essential CIS equipment left on the system bit me. The throttle cable had been rubbing up against one of the vacuum hoses on the Decel Valve. It finally rubbed through.

Here is a picture of the culprit:



I removed this defective valve and plugged the holes.




The car started immediately. I put the adjustment screw on the WUR back to where it was originally and set the Fuel Head mixture by ear. After the car warmed up I checked the CO%, it was at 1.7%. I left it alone for now.

I've got to say a few words about the importance of the testing equipment used.
The CIS Pressure Tester told me that the WUR was functioning but a bit weak. That is why I started this thread. Mechanics were telling me the WUR was bad while the Pressure Tester told me otherwise.
The A/F Ratio Meter spotted this problem months ago. It is a narrow band unit. I have been told many times that a narrow band meter is not accurate. Well it was accurate enough to tell me I was lean without any other symptoms.
The Gunson Gas Tester always verifies the mixture. This is a very accurate machine if you allow it to warm up past the point of baseline drift. That is about 30 minutes.

We can now add this mistery solved to out growing archive of CIS tidbits. As these systems age they get more quirky and difficult to diagnose. Thank you all very much for taking the time to help me with this.

The car is now happily boosting once again!!

[Stephen B]

Can one of you guys tell me what purpose the deceleration valve serves?

Never mind!! Answered my own question by doing a search.

[cowtown]

Rarly, like you, I'm not running any of those non-essential parts on my 930 engine. I also don't have the decel valve - just the FD and WUR with a hand-throttle for cold starts. It runs fine. One more thing you can leave in the closet.

[Porsche_monkey]

For anyone with CIS trouble a vacuum leak test with an unlit propane torch would have found that problem quickly. It takes about two minutes to check all the lines.

[Paulporsche]

PBH,
Absolutely. One of the first things RarlyL8 mentioned was that all his vacuum lines "appear(ed)" sound. Literally. By eye.

RarlyL8,
Glad to see you are back in business. BTW, car looks nice...not the car of a crotchety old bastard!

[SpeedracerIndy]

Originally posted by Stephen B
Can one of you guys tell me what purpose the deceleration valve serves?

Never mind!! Answered my own question by doing a search.

The decel valve allows extra air to pass the throttle plate when you let off the throttle. It is essentially an emmission component and prevents backfire from a rich condition after the throttle is abruptly closed. If it's not there, the engine revs will simply fall faster after you let off the gas. It can be the culprit of a high idle after warm up when it wears out.

oops, just noticed you found the answer, nevermind...

[Stephen B]

Thanks for the reply Speed. I have an intermittent high idle after warm start... the d valve checked out last time the I/C was removed, but I didn't check the hoses closely - just valve function / diaphragm integrity. From my searches it sounds like the valve can be removed without any problems.

[Paulporsche]

Some actually prefer the valve removed. Besides one less component or hose to fail, the absence of the valve allows to revs to fall quicker when off the gas.

[hobieboy]

I have been following this very closely with great interest as I also have some CIS issues - the car starts well cold & hot, but when cold, mixture simply richens but the RPM does not rise (so it idles @ ~600rpm). When warm, idles goes up to 1100.

Sounds like my decel valve might be one of the culprit for high warm idle? And I plan to take a look at my AAV as well.

[RarlyL8]

I actually left the valve on intentionally to KEEP THE REVS UP between shifts. On a turbo this is a GOOD thing. What I did not realize at the time was this valve was not working. It never did work. Only by removing it did I find this out. All that time I thought the light weight fly wheel was causing the tach to drop like a rock between shifts. I was manually matching revs like I did in my old '73T.

How does this propane deal work for checking vacuum leaks? Never heard of that before.

Anybody need a rebuilt WUR for a 930? Don't think I'll have use for that now.

[Paulporsche]

Hobieboy,
Check your AAR. That's what keeps your revs up during warmup idling. The AAV only comes into play during startup. Also check your Cold Control Pressure. Quite often the mix is too lean @ the warmup phase but OK when warm. This is controlled by the WUR. And don't forget those vacuum leaks.

[Porsche_monkey]

Propane will be sucked in through a vacuum leak and you will here the idle speed raise from the added fuel. Quick-start (ether) also works. I just use actylene from my cutting torch.

Just hold it in front of your cold air intake to see (hear) the effect.

[SpeedracerIndy]

Originally posted by Stephen B
Thanks for the reply Speed. I have an intermittent high idle after warm start... the d valve checked out last time the I/C was removed, but I didn't check the hoses closely - just valve function / diaphragm integrity. From my searches it sounds like the valve can be removed without any problems.

The decel valve is also adjustable. That makes it easier to troubleshoot (as long as your lines aren't leaking). I had a high idle when warm problem that I cured by adjusting the decel valve. There is a nut with a stud through it on the top of the valve that you can turn to adjust how long it holds the revs up after releasing the throttle. i can't remember off the top of my head which way to turn it though. There are also two types of decel valves. One (like mine) is a smaller bell shaped object that sits up high behind the throttle body, the other type looks like the aav, and sits on the passengers side of the engine.

[Stephen B]

My decel valve is mounted to the turbo bypass valve assembly. Gold colored can above the coil in the attached picture.

[RarlyL8]

OK, got the propane deal. You use propane the way I use ether. The small red tube attached to the spray nozzle really helps direct the spray to exactly where you want it.
This time I didn't need to use a chemical sniffer, the damage to the hose was obvious. These hoses have 3 layers. It takes quite a bit for one to leak. The real stresser for them is 2 decades sitting on top a hot engine.
Steve, the valve you show pictured is the one I removed. Is your engine a Euro? Some of the induction components are a different configuration that stock US. What is that clear fiter for?
Hobieboy, I agree with Paul. A non functioning (or in my case absent) AAV will cause exactly the symptoms you describe. There are many components in the stock CIS system that kick up the idle when cold. It is unusual that none of them are working.
When you say high warm idle is your 1100rpm idle speed at the end of adjusment with the idle screw? If so then yes the decel could be the culprit. That is exactly where my warm idle was with all the adjustment used up at the idle screw. With the decel valve removed and capped off the warm idle has dropped to ~950rpm. Remeber tough that there is a 3-way going on between idle set screw, ignition timing, and fuel head mixture. All affect idle speed.