CIS troubles - two problems, related?

[mikesarge]

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!?

[AndrewCologne]

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=wapp
(Still in german and here google translator used. English translated version of this website is coming soon)

[mikesarge]

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

[AndrewCologne]

Originally Posted by mikesarge

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.

[mikesarge]

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!

[AndrewCologne]

Originally Posted by mikesarge

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?

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=wapp

[Paulporsche]

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.

[T77911S]

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.

[boyt911sc]

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.




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

[mikesarge]

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

[mikedsilva]

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

[mikesarge]

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

[Stephmk1]

Originally Posted by boyt911sc

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.




You will need a pressure 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

tanks i gone check mine!

[mikesarge]

Originally Posted by boyt911sc

Mike,



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

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

[Paulporsche]

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.

[boyt911sc]

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

[mikesarge]

Originally Posted by Paulporsche

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.

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!

[mikesarge]

Originally Posted by boyt911sc

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

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!

[Paulporsche]

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

[AndrewCologne]

Originally Posted by Paulporsche

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.

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.)



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




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