CIS troubles - two problems, related?
 

1. Year of engine: 1980
2. US or RoW (Rest of World): US, but 3.1 9.5:1 w/964 cams, supertech kit and backdated FD, no FV/Lambda (FD no. 010)
3. WUR model number: 072
4. Ambient temperature at time of test (in degrees C): ~10
5. WUR Resistance (in Ohms): D'oh! didn't measure. will update
6. System Pressure (in bars): 4.8
7. Cold Control Pressure (in bars): 0.6
8. Warm Control Pressure (in bars): 3.7
9. Time delta for Cold -> Warm Control Pressure (in minutes & seconds): ~7:45
10. Residual Pressure @ 5 min (in bars): 0
11. Residual Pressure @ 15 min (in bars): 0
12. Residual Pressure @ 30 min (in bars): 0
13. Residual Pressure @ 60 min (in bars): 0


1) So! I think one issue (hard hot start) is a fairly easy one- it's a check valve, probably at the fuel pump, right? I heard somewhere (???) that it could be the FD. It sputters and stumbles, and my AFR gauge shows lean for about 20-30 seconds on a hot start, then it comes back to being quite rich at idle, but drives great, just like normal.

It also looks like maybe the WUR is out of spec? or could a bad check valve (or FD) create artifically-low cold pressure reading?

2) The other issue, that's been a bit more annoying, may be a limitation due to my top end build and somewhat-mish-mash fuel system. it is rich as hell at idle. I can't reliably log this AEM AFR gauge (don't know how- have serial port hooked up, but no idea what program to log with, how to get RPM/load put into it, so usefulness seems limited). Anyway, it seems safe at WOT, pulls really nicely, and a peek at the AFR gauge shows a taper from super lean when I stomp on it (normal), then 14-ish down to 13-ish by redline.

Idle is always super rich, hot or cold, between 10-11.5

Is this just a limitation because I've got these cams, and this higher-comp setup? or do I need to lean it out? or will a pressure adjustment help me out?

Should I take it one step at a time, and rebuild the WUR? whats the next move!?

1. Your Residual Pressure is simply not present, means you defenitely need a new fuel accumulator, as actually this affects cold starts extremly

2. As you mention your engine is a 1980 US model, does it still come with a proper working lambda system? Does it work fawlessly?
https://nineelevenheaven-wordpress-com.translate.goog/der-911-us-sc-3-0-motor-mit-g-kat/?_x_tr_sl=auto&_x_tr_tl=en&_x_tr_hl=de&_x_tr_pto=w app
(Still in german and here google translator used. English translated version of this website is coming soon)

1) residual pressure bleeds down right at 5 minutes. Is this accumulator, or check valve?

2) no- the fuel system is backdated. No lambda. The FD is no. 010, so while the case is a US 1980, the fuel system is much closer to a ‘77 3.0

Means the FD has been backdated but other components like the WUR (072) is still at its original lambda ECU related state.

That means your Engine won't have an accelration fuel enrichment anymore! Beside power loss while accelerating your engine will run too lean at WOT which could result in overheating.
The WUR 072 only provides control pressure but NO fuel enrichment via vacuum loss when opening the throttle, like the older US WURs did. As those come with a manifold vacuum connection.
The connetced hose on your 072 WUR is only for venturi purposes and in your original CIS state the lambda ECU provides the fuel bump for enrichen the fuel mix while accelerating.

Thats the problem with manipulated CIS systems, if you just only replace a component with a one coming with a wrong part number, your system will get messed up.

That makes a lot of sense, the car was set up like this when I bought it, albeit on stock Ps and Cs. It’s always been super rich at idle, too.

It would seem that a matching, vacuum-ported WUR might help me run more reliably? Or am I just further opening cans of worms here? No great solution I can tell, aside from going EFI, or fully swapping to the C3 fuel system parts.

I’m going to put the fuel pressure tester between the pump and accumulator today, to see if I can narrow that issue down as well. Seems we’ve got the nightmare scenario of several problems combining together, so I don’t want to throw parts at it and start changing settings!

It's needed in deed. As said, your combustion will suffer from a too lean mixture and therefore power at acceleration and from also from a rise of heat at WOT with possible damage on longer WOT drives.

BUT! If you just swap to an earlier vacuum driven WUR, you need to plug it to the correct vacuum port! The "manifold" vacuum port on the front of your carburetor body is missing on your early US model. So you have to use the port on the very back of the carburetor body where also the vacuum line to the cruise control and also to the deacceleration valve (on the very right of the rear engine compartment) is present. As for this the vacuum hose already comes with a T-connection element at the rear of the carburetor body, you can simply deactivate the cruise control an use the hose part for the earlier vacuum based WUR.

Heres a google translated vacuum connection overview of the newer US SC models:
https://nineelevenheaven-wordpress-com.translate.goog/unterdruckanschlusse-an-der-k-jetronic-fur-den-us-sc/?_x_tr_sl=de&_x_tr_tl=en&_x_tr_hl=de&_x_tr_pto=wap p

My 1980 engine has no lambda control. I use a 045 WUR with a vac line attached from the lower front of the throttle body to the lower chamber of the WUR. The top connection of the WUR is open to atmosphere. It is basically the 1978/79 setup.

good job AC.

the vacuum needs to to a port that is BELOW the throttle plate.
you can just look inside the TB and find one that is below it.

Mike,

Your residual pressure loss could be due to:

• Defective fuel accumulator.
• Defective fuel pump check valve.

You could test the fuel accumulator by blowing air through and observe any bubbles coming from the bottom. If you have a two-port fuel accumulator, remove the screw during the test.
http://forums.pelicanparts.com/uploa...1646856757.jpg

http://forums.pelicanparts.com/uploa...1646856757.jpg

You will need a pressure gauge installed between the fuel pump and the fuel accumulator to test for the FP check valve. Replace parts only after verifying that they are defective. Do not replace CIS components unless tested and verified to be defective.

Lastly, your WUR-072 is not a vacuum assisted unit and will not work without OXS and ECU. You can use any of these WUR’s for your set-up plus a thermotime valve:

• WUR-033
• WUR-045.
• WUR-069.
• WUR-089.

Tony

Great- thanks all! Will run some more tests, and track down an appropriate WUR

That cold pressure sounds quite low... that would account for the very rich running when started.

and just like that- with very low pressure from a small hand pump, i'm getting bubbles out of the bottom of my accumulator

Between that, and tracking down/properly installing an appropriate WUR, i'm hopeful i'll be in good shape here shortly. will update when parts arrive.

thanks all

tanks i gone check mine!

Hi Tony-

I bought a used WUR (045) from a member just now. That’ll have a vac port on the side, and one on the top, is that right? I thought I read some posts where folks just vented the top, but I’m not sure that’s right, if you’re mentioning this other valve that I may need to find and install.

I googled thermotime valve, and I mostly got thermotime switch and cold start valve results. I have both of those parts already installed, so I want to be sure I understand and will have all pieces necessary to make this system work right. Is the valve you’re describing a separate piece? Can you send me a link to what it looks like, and/or how to set it up?

EDIT: i found this post of yours, describing and showing the TTV: https://forums.pelicanparts.com/porsche-911-technical-forum/775313-ttv-test-results.html

Any tips on wiring this? I’ll keep searching I guess!

EDIT 2: a-ha! That extra 2-pin plug kicking around the engine bay is for the TTV-great! Let’s hope it works!

Now to find a TTV

Thanks
Mike

Depending on the ambient temps in which you use your car you may not need the thermovalve. Mine fell apart recently and I was unable to fix it. In fact, it may have been inoperative for some time. My engine (as described above) starts @ temps down to just above freezing without the thermovalve. BTW the function of this valve is to limit vacuum to that lower chamber of the WUR for about 30 seconds in order to provide further enrichment @ startup.

WUR configuration.........
 

Mike,

For the following WUR’s:

• WUR-033*
• WUR-045
• WUR-069
• WUR-089

*Note:
Except for WUR-033, the vacuum port is at the side for these WUR’s. There are two (2) hoses connected to these WUR’s, one is for vent and the other one is for vacuum.

Tony

That’s helpful- the results I was finding were unclear on the duration of its function. I almost never drive the car in temps below 40F, so maybe I can just vent it, and go without. That saves me a couple hundred $$.

Thanks!

Got it- will forgo the TTV. If this used 045 WUR is out of spec, I’ll be reaching out for cleaning/refurb. Thank you for all of your help!

See p 66 of this PET. It shows the correct vacuum routing for 1978/79 w/o lambda. The thermovalve is 17A. As you can see it is between the lower chamber of the WUR and the lower port on the throttle body. Since I don't have one I rely on a slightly lowered cold control pressure, which it looks like you had on your previous WUR.

https://www.porsche.com/all/media/pdf/originalparts/en/E_911_83_KATALOG.pdf

The lower vac. port of the throttle body of a 1980-1983 US model engine should give you only vac at idle, you should check that, as its the common port for the distributor retard at idle in case your engine is a 930.16/07 one.

The manifold vacuum given at all revs is the correct one you need for the WUR vac. mechanism. Its the lower port behind the throttle body (green hose). (The upper (blue hose) one is for the distributor advance.)

http://forums.pelicanparts.com/uploa...1646928240.jpg

Below you can see where normally those manifold vac. hoses (green) lead to:

http://forums.pelicanparts.com/uploa...1646928370.jpg


As of your signature :-) I guess you dont need the deacc. valve and the cruise control, right?
If not already done just unplug the hose leading to the T-Part from the port of the throttle body and use a new hose leading to the WUR.
Cause by this as a needed side effect the vac. connection to the deacc. valve is removed an when deaccelerating from high revs the deacc. valve wont open and so the vac wont fall that low that the WUR will enrichen the mixture :-)

This is also very important for you mikesarge if your engine comes with a deacc. valve

I want to make sure I understand:

I have a deaccel valve- should I take the hose off of that, and decomission that valve when I install the new WUR? or are you saying that the deaccel valve is a necessary component to keep with the vac-controlled WUR?

Thanks!
mike

mike,

Andrew's diagram shows a 1980-83 setup with lambda. Notice no lower chamber on the WUR because the lambda control performs that function.

Compare it with the link I posted for you. You will see the vac connections for a 045 and similar WUR, which need that lower chamber vacuum.

You can use the decel valve or not. It is up to you. Its fn was to keep revs up slightly between shifts and when slowing. Some drivers like it, many don't.

Got it, I think I understand that- I'm going to tap in to the cruise control line with a T, as it's the closest place to the WUR with manifold vacuum. that I know of.

What I'm wondering about is specific to Andrew's comment regarding the Decel valve- I'm not sure if he's saying I need to decomission my decel valve, or if he was saying the decel valve needs to be preserved. it was unclear because of what I'm assuming is a translation issue.

You make the final decision........
 

Mike,

This is your car and nobody could stop you from deciding which direction to go. People eliminate the decel valve primarily due to lack of understanding. Same with the thermotime valve. A good decel valve will not cause the WUR to malfunction as claimed by someone.

Unfortunately, I re-read Andrew’s comment several times and could not understand what he was trying to say about the WUR’s unwanted enrichment. If you eliminate the thermotime valve, you will have a higher cold control pressure at START. Good luck.

Tony

A video of the TTV at work during cold start. See the pressure jump when it opens toward the end of the video. Allows a richer AFR at start as stated by others.

https://youtube.com/shorts/x3HXhqlwFMM?feature=share

Got it.

If I come across a TTV for not a ton of money, I’ll be right on it. I know the injection system isn’t going to be *perfect* on this car, but I’d like to make it as close to right as possible.

Thanks again

@ Paul
His Engine came with a removed ECU system and just changed to a non frequency vaklve driven Fuel Dizzy, means before 1980.

@Mike
Unplug the vacuum hose at the back of the throttle body, the hose which leads to the T-connector.
By this the vacuum for the cruise control and the deaccel. valve will be disconnect, but no problem if no cruise control is needed.

To that port (green hose in the pic above) you connect the vacuum hose to the WUR.
This port provides the permanent "throttle angle position independant" available manifold vacuum.
All other vacuum ports provide ported vacuums, means at idle only (dizzy retard vacuum) or just at cruising (dizzy advance vacuum) etc.

But this is only senseful in your specific case with removed Lambda-ECU where actually a vacuum driven WUR is needed for mixture enrichment while accelerating.

With a lambda CIS in a OEM factory state all parts work perfectly and NO power loss will be given if all parts have been set up/adjusted as they should.

There's a myth about the retard vacuum hose at the dizzy where many people do recommend to just unplug that one which is ... nonsense. Because: Beside less HC emissions for making passing the emission control/test it also makes the combustion at idle resulting hotter which on the other hand makes the OX-Sensor much hotter and by this making teh sensor working/reacting optimal at idle!
When hitting the throttle and leaving idle state the retard vacuum -->"directly"<-- will be superseded by the advance vacuum which makes driving/crusing at low load more efficient due to more ignition advance and therefore more torque. Means ... keeping the retard vacuum hose being connected at the dizzy will not result in any power loss.

Regarding the deaccel. valve.: If you use the retard vacuum at the dizzy but let the deaccel. valve vacuum hose disconnected then when deaccelerating from higher revs you will suffer from hughe pops and bubblering at the exhaust. Because when closing the throttle at high revs the combustion directly will lean out due to a huge vacuum rise in the manifold system, now in addition with a retarded ignition (as the throttle at idle now provides the retard vacuum to the dizzy) the party in the exhaust system with arbitary self ignited remaining fuel begins – !BANG!.
If you let the vacuum hose connected at the deacc. valve, then at a sudden throttle closing at high rpms this prevents a hughe vacuum rise in the manifold system as it bypasses metered air to the system (air sensor plate, throttle biody, manifold), which by this aviods .... pops and bubble sounds at the exhaust.

Cheers

What didn't you understand specifically? As Im not a native english speaker :-)


- On a lambda based CIS engine, as you know the orig WUR doesnt come with a vacuum driven control pressure, means enrichment at acceleration.
- If the ECU gets amputated from a lambda based CIS gengine then beside other problems like cold start, there will be no enrichment at acceleration/WOT anymore with beside power loss the risk of overheating
- So ... you need an older no frequency valve driven Fuel Distributor (mike in this case has one)
- and ... a WUR which comes with a vacuum connection for control pressure based enrichment at acceleration/WOT
- This vacuum provided to the WUR needs to be a permanent present, throttle angle independand manifold vacuum, not a ported vacuum like for the dizzy
- This needed manifold vacuum at originally lambda based engines is present at the lower vacuum port at the back of the throttle body (green hose in the pics), not at the front or the upper back vaccuum port.
- This means from this port you disconnect the hose which leads to the T-connector (crusie control and deacc. valve) and instead of that you connect the hose which leads to the WURs vacuum port (not the vent port!)
- So ... by this the cruise control and the deacc. valve won't get any manifold vaccuum anymore. And in mikes case this would mean he also must unplug the vacuum to the dizzys retard port ... to avoid popping sounds when deaccelerating. (As dizzy with retard vacuum connetced always must be used in combination with a working vacuum driven deaccel. valve – see explanation further above).

I hope I could clearfiy, if not just ask.


If all parts are origianl in factory state – yes.

But in case of mike as he uses an older WUR this one needs manifold vacuum.
An older engine model WUR in combination with a newer (lambda based) engine model deaccel. valve is a tricky solution as ... when deaccelerating the deaccel. valve opens, therefore the manfold vacuum drops and the risk is ... that then the vacum results that low in the manifold that the WUR -thinks- "oh, Mikes accelerating" and ... drops the control pressure and by this ... enrichens the mixture .... but here actually when deaccelerating. Uops.
This is theory ... and practically depends on actually how much the deacc. valve lowers the manifold vacuumto a point which lets the WUR enrichen.

My plan is to *not* disconnect deaccel valve, cruise control, dizzy, or anything else. I’m just going to add a T in the cruise vac line and run it to the port on the WUR.

I am trying to figure out if this is the optimal setup, or if some other combination of CIS gadgets should be added or removed.

I understand the TTV will optimize ~30 seconds on the first start, on the coldest days only, so because I do not already have one, and they look to cost over $100 used, I am willing to compromise there and go without.

If I will further do better by removing some other component, I am trying to figure that out.

Post #21.......Highlighted portion.
 

Andrew,

There is nothing wrong with your English. English is my second language too. I was referring to the bold and highlighted section in post #21.

Tony

ah ok .... this was explained in my answer above ...

Andrew,

You are very knowledgeable and very impressed with your CIS information. Unfortunately, your understanding with the deceleration valve/s is flawed. If the deceleration valve is defective (out-of-spec or leaking), it should not be used. So we are discussing a DV in good working condition.

The opening and closing of the DV will not affect the operation of the WUR unless you have a defective DV. I agree with your theory if you have a defective or out of spec deceleration valve.

The key to this discussion is how to identify a good or bad a decel valve. I spent a great deal of time learning, testing, evaluating, and understanding between a good working unit from a defective one using multiple samples.

http://forums.pelicanparts.com/uploa...1647006870.jpg

Tony

As we know both engines models, means pre 1980 and from 1980 leave the factory with deacc. valves. The one with the valve behin the throttle body and the newer models with the deacc. valve on the rear right of the negine
But ... here it depends at what vacuum state the deaccel. valve from 1980-83 opens and how much the vacuum loss in the manifold will be. As a significant manfold vacuum loss does affect the WUR enrichment, thats how it works.
As told its theory but at least mikesarge should check the AFR when deacceleating as Im only refering to/talking here about an engine model which has been modified in a significant way with parts out of specs as it is the particular case here :-) I do not refer to engine models where all parts are in spec. and no part mixing was done.


BTW a nice test would be ... on a vacuum driven WUR engine put a manometer between the WUR and its vacuum hose. And then when from idle rising to 5.000 rpm and then suddenly closing the throttle this should open the deaccel. valve for a short moment cause of the huge rise of vacuum in the manifold. And at this moment watch the manometer at the WUR.

Yeah, this does complicate things! I’ll run a bunch of tests when I get back up and running, hopefully soon (though pelican says they may not ship my accumulator for like 2 weeks?)

And hopefully with a co-pilot and AFR/wideband I can triangulate the ideal setup for running this thing. Just the vac-assisted WUR should make a huge difference though I suspect!

Bought a new (used) 045 WUR, fuel filter, and accumulator

new test results here seem to point to a rectified residual fuel pressure, and a dead WUR fairly conclusively:

1. Year of engine: 1980
2. US or RoW (Rest of World): US, but 3.1 9.5:1 w/964 cams, supertech kit and backdated FD, no FV/Lambda (FD no. 010)
3. WUR model number: 045
4. Ambient temperature at time of test (in degrees C): ~11
5. WUR Resistance (in Ohms): 27
6. System Pressure (in bars): 4.7
7. Cold Control Pressure (in bars): 4.7
8. Warm Control Pressure (in bars): 4.7
9. Time delta for Cold -> Warm Control Pressure (in minutes & seconds): never moved @ 5 mins
10. Residual Pressure @ 5 min (in bars): 1.9
11. Residual Pressure @ 15 min (in bars): 1.6
12. Residual Pressure @ 30 min (in bars): 1.4
13. Residual Pressure @ 60 min (in bars): .3

So, given that, what's the move? how does one rebuild a WUR? I'm happy to support a forum member like boyt911SC, i'm also a fairly intrepid wrench, so I could face this down myself as long as it doesn't require any tools too far out of the ordinary.

thanks all for your help on this one!

Sems the valve area/plate of the WUR is flawed.
You can try and buy a repair KIT and do the rebuild on your own, or ask someone like ... Tony:-)


http://andrewcologne.bplaced.net/911/WUR_1.png

http://andrewcologne.bplaced.net/911/WUR_2.png

http://andrewcologne.bplaced.net/911/WUR_3.png

Alright, we are back in business. Consider this one “solved” with two fixes:
1) the new accumulator, as noted above; and,

2) a newly refurbished WUR from boyt911sc

Just installed the WUR this afternoon, and while I’m still figuring out the final mixture setting, it runs better than it ever has as long as I’ve owned it. I always wondered why the throttle pedal did not change the AFR as much as I thought it should on decel, and having a WUR with a vac. port designed for this system took care of that.

The car is much more well behaved off idle and in low-load low-rpm situations.

It’s also a great deal quicker on the top end.

Not scientific by any means, but here’s the afr breakdown:
Idle: 11.8 or so
Low-load acceleration: 14-16
Decel: 16-17
WOT: 15 at the stab, then down to 14 pretty quick, then 12 or so by redline.

Anyone have any thoughts on where I might do well to set my mixture from here? Don’t want to burn a valve, but it seems a little rich at idle and at redline. Likewise it seems a bit lean on decel, so I think I might be in the sweet spot.

Thanks to everyone who helped me with this so far!
Mike

Assuming your cold control pressures are within spec, you might consider using your AFR meter to set the AFR at idle with the adjustment screw, then adjust the idle speed with the big idle air bypass screw, iterating as needed. Then see what your on the road AFRs are.

You can always go back (easy adjustments) if you don't like what you see.

Maybe the lag from lean to rich (mid-12s to low 13s seem to be what racers aim for, since WOT is the only thing they tune much for) is why Bosch/Porsche introduced an acceleration enrichment loop as part of its FV/processor?

This was pretty much my strategy, idle is pretty much perfect at 950 rpm so now I’m just trying to figure out the best spot for me to set the mix given my FD (010) and engine (3.1, 9.5:1, 964 cams)

I think I’ll keep leaning it out a bit at a time until WOT approaches 13 at red line, as long as part-throttle behavior stays good. I’ll report back with results as I get them .

Seems your sensor plate setting needs to be checked and maybe needs a re adjust.