Troubleshooting my '74s CIS system
 

Hi all,
First post for me since acquiring my first Porsche - a 1974 base model coupe. The car runs but doesn't run nearly as well as I think it should. Runs rough when cold and has an unsteady idle that is difficult to get under about 1300 rpm. If I try to turn down the idle below that, it gets pretty unsteady. Off-idle running is actually pretty decent, though I have no other 911 experience to go by. Anyway, I decided to go through the CIS system to make sure pressures are in-spec, everything tests out within normal ranges and there are no vacuum leaks. Here is what I found so far:

- System pressure is 4.2 Bar - below spec. I have not yet adjusted the pressure regulator with shims to raise it into spec.
-My WUR is not stock - see pics. It does function, meaning it warms up and control pressure changes, but since I don't know what the pressure over time chart should be, I have no idea if its in spec.
- Flow rates were inconsistent from injector to injector. I moved the injectors with lower flow to the FD ports that had higher flow. The problem did not move with the injectors, so the variation is within the FD. The difference between the higher and lower flow rates is about 6%.
- The control pressure regulator for throttle position is completely disconnected. The fuel line from the FD to the valve is disconnected. Kind of surprised the car drives as well as it does with the valve disconnected.

I have not tested for vacuum leaks with my smoke machine yet. That's next. Here are my questions:

1. Does anyone know what my WUR is from and do they have specs for it? There is no model number stamped into the WUR after the Bosch part number. It's blank.
2. Is the difference in FD port pressures significant enough to warrant having the FD sent in for servicing?
3. Does anyone know why my control pressure regulator for throttle position would be disconnected? I suspect it stopped working and was disconnected because they are NLA. Anyone else do this with their '74-75? If the car would run fine without it, should I be concerned?

Any help or insights would be appreciated.

Thanks,
Brian

http://forums.pelicanparts.com/uploa...1711213370.jpg
http://forums.pelicanparts.com/uploa...1711213370.jpg

CIS Troubleshooting…………
 

Brian,

Could you post another picture of the WUR showing the Bosch ID # (0 438 140 XYZ). The last 3 digits identify your WUR. The numbers are blocked by the wire in your picture. Thanks.

Tony

Hi Tony,
There are no numbers. It's blank. I know there is supposed to be a 3-digit model number after the Bosch part number but this WUR doesn't have one.

Brian

Brian - that label (top pic) is a part number.
what Tony is asking is the pic of your WUR, the three additions numbers are hand stamped and hidden under that green wire insulator. It might be faint or dirty but there’s 3 more numbers somewhere after the 438-140- _ _ _

Here’s an example of how the number it’s stamped ….


http://forums.pelicanparts.com/uploa...1711220757.jpg

The TPR has 3 positions. Idle setting, slightly lean at mid throttle position, and richer wide open throttle. No way to tell why the TPR is disconnected without connecting it and testing control pressures. They eliminated the TPR on later models and changed to a vacuum WUR.
System pressure is a bit low. Might need shimming, or could be a worn O-ring on the pressure regulating piston.
Yours looks like it could be an 0 438 140 129.
http://forums.pelicanparts.com/uploa...1711220674.jpg

If you have the original 0 438 100 004 fuel distributor, there is no way to adjust individual fuel flow. If flow difference doesn't follow when you moved injectors it is probably inside the fuel distributor.
Flow difference may be from a clogged tiny filter screen, the little red thing in the O ring to the left in the picture. They are at the outlet of the 6 fuel lines to the injectors.
http://forums.pelicanparts.com/uploa...1711222635.jpg
Before you spend the money to send it out for repair you could try and clean it yourself. There are a couple of companies for around $100 that make rebuild kits for the fuel distributors. They have the steel plate and O rings needed to refresh the internals. I found with a little care it is not too difficult to replace all the O rings. Mostly what I find inside is not rust, but the reddish residue from gas.
http://forums.pelicanparts.com/uploa...1711223547.jpg

I checked the WUR really closely with a flashlight, looking for a faint stamping on there. I know one SHOULD be there but I don't see one. I'll double-check in the morning to make sure I didn't miss it.

So I'm guessing a 6% difference in fuel flow is significant enough to warrant taking the FD apart and cleaning it? Also, does anyone have a pic of the fuel fittings on the top of the FD where the WUR fuel line and the fuel line for the TPR get their fuel from? I think the fitting on there is not original so I need to know what goes there before I can re-attach the TPR to test control pressure at idle, part-throttle and full throttle.

thanks,
Brian

This was in bad shape when I bought it for spare parts. Unfortunately the throttle body was shot but I got the rest back into shape with quite a bit of cleaning.
On the left you can see the TPR connection is first on the top of the fuel distributor, then the stem that connects to the WUR.
You can get a pack of copper sealing washers and remove the bolts on the fuel distributor injector lines and see what shape the small red filters are in. I find it interesting that the filters are not mentioned in the parts catalog or service manual. You can also try testing the fuel flow with the injectors removed to see if fuel flow evens out.
Here is a good thread on cleaning fuel distributors.
http://forums.pelicanparts.com/porsche-911-technical-forum/272657-cis-fuel-distributer-cleanout-w-pics.html

http://forums.pelicanparts.com/uploa...1711283701.jpg

This is the definitive thread on early CIS, best on the Web

https://www.ddk-online.com/phpBB2/viewtopic.php?t=51455&start=390

Of course the entire thread is great too!

Here's a link to testing the K Jetronic. Pages 23-25 show testing injectors.
https://members.rennlist.com/vilhuer/K%20Jetronic%20Workshop%20Manual.pdf

Here is a clearer pic of my WUR. There is NO model number after the Bosch part number. Now what?

A couple more questions - if I want to replace my fuel line from the FD to the throttle valve regulator, how do you get these polyamide lines off and back on again at the throttle valve side? There is no fitting or clamp. Are these lines supposed to be heated to get them off or on? I'm not used to working with lines like these.

Does anyone know where I can get that banjo fitting on the top of the FD that supplies fuel to both the WUR and the throttle valve regulator? I'll need that to reconnect mine.

Thanks,
Brian

http://forums.pelicanparts.com/uploa...1711327172.jpg

Hi Brian, Others know more than me on the other issues.

Why do you need to remove the line? It is best to leave them alone unless truly necessary. There is no way to remove the polyamid line other than damaging it at the fitting with a soldering iron and pulling it off. You can then trim it to an undamaged spot for reinstallation if it is still long enough. These lines are difficult to install without a proper tool to hold the line while you press the fitting onto it. There are some threads here on methods.

Len Cummings (BoxsterGT here) here may have replacement line material, if you need it. These guys may also be helpful: https://www.dssales.net/CIS.htm

For CIS Systems the best advice is to be sure everything outside of the CIS System is spot on before messing with the CIS parts. This means a complete tune-up (points, rotor, cap, air filter, fuel filter, dwell, timing, and valve adjustment). CIS is very robust once it is right.

Hi Harry,
For some reason, the throttle valve regulator is disconnected at the FD. The line is just hanging there. I assumed a bunch of dirt got in the fuel line as a result so I was thinking of changing the line. I suppose I could just clean the fitting at the banjo bolt end and test it out though. Any dirt in the line would be cycled back to the fuel tank anyway rather than the FD.

Brian

Preliminary Investigation………
 

Brian,

There could be several reasons why the TPR was removed. It could be defective and not repairable. Same also with the OEM WUR-001. Why do you need a TPR? Deleting the TPR from your CIS and installing a good working WUR would be an upgrade.

First, you need to test and evaluate the TPR. Do not remove the polyamide fuel line from the TPR unless you have experience working with this type of fuel lines. If the line is not leaking, leave it alone. These are some of the “control TPR” I use for my tests.

http://forums.pelicanparts.com/uploa...1711373967.jpg

Second, test and evaluate the control fuel pressures (cold and warm) for your mysterious WUR. Check the heater resistance (Ohms). Keep us posted.

Tony

Thanks Tony. I did test the WUR already, but my system pressure was low (4.2 Bar) so I'm not sure the readings are relevant. I need to shim the FD to get system pressure in spec and then re-check the WUR. The one thing I can tell you is that the heating element is working and control pressure changes over time when the element has 12V applied to it. The problem is, without knowing the model number of the WUR, I don't know what "in spec" control pressure is for this WUR over say, a 10 minute test period. Without that, it's hard to say if its working properly or not.

Brian

Tony, to answer your question about why I need a TPR - I just assumed that if Bosch/Porsche designed it as part of the CIS system, it was needed. From what I understand, it leans the mixture at part-throttle and richens it at full-throttle by modifying control pressure. So, if it isn't working, doesn't that mean I'm running too rich at part-throttle and too lean at full throttle? I just know these CIS parts are designed to work as a unit, so I wanted to get everything connected properly and then get pressures (system and control) in spec to see how the engine runs at that point. I still have to do a smoke test for vacuum leaks as well. That's on the to-do list.

Brian

Knowledgeable People……….
 

Brian,

You don’t need to know the spec of this mysterious WUR. I will tell you why later. First, set the system pressure to 70~72 psi. You will need an assortment of shims to get your target system pressure. After you successfully set the SP to 70~72 psi., time to test the control pressures (cold and warm).

After you have set the SP (system pressure) of your FD, then time to test your WUR. The control pressure is a function of temperature so you need to know the approximate ambient temperature in the garage or work area.

Test run the FP (fuel pump) with the gauge hook up. To measure the CCP (cold control pressure), disconnect the electrical connections to the WUR before you run the FP. This is very important. The pressure reading on the gauge (power to WUR disconnected) is CCP.

To measure the WCP, you need to connect the power to WUR. You also need to install the correct plug to the WUR. There is a transition time between CCP to WCP base from the heater resistance and calibration. So work experience would be very helpful if you have done this type of work in the past.

This is how you measure the WCP:
1). Disconnect power to WUR.
2). Engine cold, test run FP. The initial reading is CCP.
3). Using a timer, measure at 1 minute intervals after connecting power to WUR.
EXAMPLE:
0…………..CCP
1 min.
2 min.
3 min.
Etc…………WCP (pressure reading max. out and steady)
Note:
Measure the heater resistance (Ohms) when engine/WUR is @ RT.

If you have any question, just ask. It might look complicated but it is easy and simple. Keep us posted. Thanks.

Tony

Tony, you commented "There could be several reasons why the TPR was removed. It could be defective and not repairable. Same also with the OEM WUR-001. Why do you need a TPR? Deleting the TPR from your CIS and installing a good working WUR would be an upgrade."
Now, if your suggesting changing to a later vacuum WUR, would a later throttle body from a '76-77 be needed for the additional vacuum port?

Brian,
To give you an idea of what to expect. The O ring you should replace along with the shims are shown in my photo.

http://forums.pelicanparts.com/uploa...1711385072.jpg

http://forums.pelicanparts.com/uploa...1711384541.jpg

Ed,

If you are into concourse restoration, keep everything as original. The problem with the early CIS (73.5~ ‘74) with TPR and FD-004, they are not users friendly. The polyamide fuel lines do not use fuel like fittings unlike the later CIS. The TPR’s and WUR-001/-008 are all practically not rebuildable items. And the factory later replaced them with better designed components.

The ‘76-‘77 CIS are much better and improved than the early CIS. And the SC’s are much better than the mid-year CIS. The different CIS components are inter-changeable if you know how re-calibrate them.

Tony

Hi Tony,
I already did the CCP and warm CP tests on the WUR. However, with base system pressure out-of-spec, I kind of figured the numbers were invalid. I'm going to do as you suggest and get SP within spec (aiming for 4.8 BAR), then re-run the CCP and warm control pressure over time tests.

One thing I CAN confirm is that the WUR heating element works, since I saw variation in control pressure over time when it was plugged in.

Brian

Brian, also measure and post the resistance value (ohms) of the WUR heating element. That may help narrow down what you have.

The resistance value of my WUR is 49 ohms.

Brian

The ones I've seen on Porsche CIS are in the 20-ohm range, or in the 30 ohm range. 50 ohms would result in a slower warmup. Interesting data point. Thanks.

Tony has a lot of experience and would have a better knowledge of the correct resistance value range than me. I have 3 WURS. The 001 at 18 ohms, an 008 at 54 ohms, and the one that Brian's resembles, a 129 at 45 ohms.

Anyone have a clue about where my particular WUR came from and what the proper control pressure graph to use would be? Once I shim my FD and get system pressure corrected, I will re-test my WUR, but without a graph to go by, I won't have any idea if it's functioning within spec or not.

Brian

Early CIS Warm-up Regulators………..
 

Ed,

The early CIS warm-up regulators like -001/-008/-129 would have mid 50’s Ohms resistance. So Brian’s mysterious WUR would work plus a good working TPR.

Tony

Hey that's good news Tony. I'm going to adjust system pressure into spec tomorrow and then run the cold and warm CP tests. I'll post the results.

Brian

Brian,

If you need some help testing and evaluating your TPR, I could do that for you for FREE. It would take me only a few mins. to do the test in my CIS Bench Tester. Send it to me with a RSL (Return Shipping Label) preferably UPS or your favorite carrier. I will be leaving this weekend for Amsterdam and be back in 2 weeks.

BTW, you will need a good TPR with your non-vacuum assisted WUR for enrichment in your engine to run well. Keep us posted.

Tony

Thanks for the offer Tony. I may take you up on that.

I was going to follow the steps in the Porsche manual to test it. Basically measure control pressure at half-throttle and at full-throttle to see if they are in spec. Is there anything more to testing the TPR?

Thanks,
Brian

Brian,

Testing is easy. Knowing the values of the control pressure @ idle, mid-throttle, and WOT are critical. All three (3) control pressures should be with in specification. And you need the fuel line fitting to accommodate the WUR and TPR.

Tony

OK, so I spent the afternoon doing some testing and adjusting of the CIS system on my '74. First, I removed the pressure valve on the back of the FD to raise system pressure. It was initially 4.2 Bar. I disassembled it and found two factory shims in there. I cut up an aluminum pop can and made two more shims, which I sandwiched between the two factory shims. I thought that would land me right at 4.8 Bar which is middle of factory spec. I reassembled the pressure valve and tested system pressure, which is now 4.65 Bar. A bit lower than expected but in spec. Next, I checked cold control pressure on the WUR. Cold control pressure (no power to WUR) came in at 0.85 Bar @ 7.2 deg C. I don't have a graph for my WUR so no idea if that is OK or not. Next, I plugged in my WUR and measured control pressure over time. Here are the results:

Initial CP - 0.85 Bar
@1 min - 1.4 Bar
@2 min - 1.9 Bar
@3 min - 2.2 Bar
@4 min - 2.5 Bar
@5 min - 2.65 Bar
@6 min - 2.8 Bar
@7 min - 2.85 Bar
@8 min - 2.95 Bar
@9 min - 3.0 Bar

After 9 minutes, the WUR pretty well leveled out at 3 Bar. I also did a smoke test to check for vacuum leaks by sealing off the throttle to prevent air leaks, pulling off a vacuum hose and tapping the smoke tester in. The only real leak I could find was on the pop-off valve in the air box. If I pushed down on the flapper, the smoke stopped. I smeared vaseline on the o-ring to see if that would help. Maybe I need a new o-ring - I don't know. I know engine vacuum should pull down on the flap when running so maybe it's fine.

I'm going to put the bellows between the air flow meter and throttle back on tomorrow and run the engine with the adjusted system pressure to see how it runs. Control pressure seems a bit low (rich) to me. I'm considering throwing another shim in the pressure valve to raise system pressure to 4.9 - 5.0. That should lean out the control pressure a bit further at the same time. Thoughts?

Brian

Tony, just saw your response. I ordered that FD fitting to get the TPR plumbed back in on the same port as the WUR. I'm not 100% sure the place I ordered it from can source it though. If anyone has a good one off a junk FD I could sure use it. As soon as I can source one, I can check the TPR control pressures.

Brian

Brian, I would add another shim or two to the FD SP valve. That should put you pretty close to 5.0 bar.

I added a couple more shims to the FD SP valve. Pressure is now up to 4.8 Bar which is right in the middle of spec. I have to re-run my control pressure numbers later today. I took the car for a short drive yesterday and it ran pretty well. Beforehand, I could barely get it to idle under 1500 rpm. It now idles at about 1000 rpm, which I know is a bit high. The idle seems to drop down to an unsteady 600-700 rpm and wander for 15-20 seconds when I pull up to a light, then settles back in around 1k rpm. Not sure what that's about.

Brian

Hey Brian,
Did you get that 74 CIS issue solved?

I have a 74 too, and have my CIS out for a leaking fuel line (hose clamp?)
That is well documented on other posts.

I have a 017 FD and a 001 WUR, the car ran great.
I recently found out the 017 FD is not original (who knew? I got it that way in 1986)

This what I have for the WUR connection.
(sorry the pic is sideways, it looks OK on my computer)


http://forums.pelicanparts.com/uploa...1714106353.JPG''

The 73.5 and 74 CIS are unique, you know what they say "NEVER buy the first model year, they haven't worked out the bugs!"
That is true in this case, I just read that the 73.5 CIS was the first time it was ever used in a passenger vehicle. And I know they made NUMEROUS changes as they learned more (who is THEY? Porsche and Bosch...)

The experts here know a lot. Ask a question. Someone that has experience in that matter will answer. I have learned a lot here (much by just searching and reading)

It looks like Rube Goldberg owned that car before you. You will need to correct his "jury rigged" repairs. The car is worth it (finally).

Paul

Hey Pete,
I just checked my 50 y/o 001 it is 20.7 ohms
(thanks for the info. I "thought it worked" because the car started and ran great. And another "data point" for you)

I have bought 911 fuel fittings (and many other things) from
Belmetric
https://belmetric.com/fittings/banjo-fittings/

and Special T Auto
https://www.specialtauto.com/

Paul