Looks like you have an obstruction in the return line. Your cold control is way too high and the warm controlled pressure is, effectively, unchanged from the cold. Your heating element may also be faulty as there is not change in pressure but that can be accounted for by a restricted return line. Your system pressure also appears to be too high, indicating the restriction may be in the main return line from all your devices--FD, wur, and throttle valve.

I actually just realized why there is no variance with the different time periods for the Warm Control Pressure -- my WUR only gets power from the alternator, so even with the key on, with no alternator spinning it gets no power.

Based on my research, there was a very small percentage of 74s that were wired this way, just about everything else is wired with a switched relay into the rear fuse panel.

I'm thinking I'll go ahead and replace all the return lines... they were tested with low pressure air but there is no way of telling that way if the line is partially blocked. They all look old anyway. I'll do that and retest afterwards.

Okay, that explains some things. You can connect a hot lead to the wur to get it to warm up and affect the heating element.

Pressure build up..........
 

Steve,

If you happened to read the post about the fuel pressure setting I posted today, I deleted it. For the simple reason that it would give your troubleshooting work a lot of distraction. So I deleted it because it would need a separate post to settle a few questions.

The control fuel pressure is reading too high due to FLOW restriction!!!!! The only way you could get the control pressure to equalize or come close to system fuel pressure is blockage or flow restriction somewhere in the system. It could be the WUR (before or after). You could pin point where this is happening by isolating section by section of the fuel return line system. There are several posts I already made in this forum about the subject.

The system fuel pressure is on the high side and this could be a false reading. At this point, you are not sure if you have a flow restriction that could affect the system pressure. What your data shows is the sign or presence of flow restriction in the system. The question is where. Test and confirm.

If I could remember correctly, there was another member (Schmicat) that I assisted to locate flow restriction recently. Either search his post or PM him. He will be a good guide for you. I tend to over simply things about CIS troubleshooting and forgetting not everyone are aware or had the experience about doing these simple tasks. But the simple fact is that CIS troubleshooting is really simple and fun.

Tony

Hi, did you say the car sat for two years? Did it have fuel in it? Have you checked the injectors to see if they work OK? Fuel does turn to an icky shellac-like substance after a period of time, and clogs everything, such as injectors, screens in the fuel head. You may have some issues in addition to control pressure.

Tony, I bet you're getting a lot of eye-rolling from behind the computer screens with that comment!:rolleyes:

Hi Pat,
Yes, it did sit for 2 years but the FD was broken loose with B12 by the PO before I got the car. I've cleaned the screen in the WUR and checked the other screens and they are clean -- the injectors are all flowing well (I've got one that is leaking and am planning on rebuilding or replacing but haven't gotten that far yet).

The car does run when you manipulate the flap in the airbox to give it fuel.

Tony and Larry, I'm going to start with replacing all the soft return lines and re-testing. If the Cold Control pressure is lower, I will run a 12v line to the WUR for the warm test as well. Probably will not be until tuesday night before I can get back over there to work on it, but I will update as I have information!

As always, thank you for all your help!
Steve

Hi Tony,
I just went back and reviewed the thread by Schumicat (I had read it during my research before I posted my original thread hence the thread title :) ). Am I correct in assuming the return line he is talking about in his final post here is the line that runs from the FD to the WUR? If so, that line is brand new as the original was leaking the first time i pressurized the system after I got it home.

Thanks!

Just for fun.........
 

Larry and et all,

Just for fun let me know a CIS problem that is difficult to diagnose that a DIY'er like you or me could not analyze or test? There is probably a few that I do not know but a solution is available to us. I've been looking since I got involved in CIS troubleshooting for a particular problem that 'we' could not diagnose correctly. And I'm still searching and looking. Thanks.

Tony

Steve,

The return line begins at the FD, runs along the firewall where there is a T connection for the line from the wur. From there, it continues through the frame, under the rear seat, into the tunnel, and into the tank. Your 74 does not have a line from the fuel accumulator into the return, if it is stock. If your new line does not cover the entire length of the return circuit, you still may have a blockage at the T, from the wur to the T, or down stream from the T to the tank.

Fuel return lines.......
 

Steve,

The fuel return line system for your car is well described by LJ. Include the fuel line return going inside the tunnel up to the gas tank. The blockage or restriction could be any where in the 'fuel return line'. So isolating section by section of the fuel return line system is necessary to locate or pinpoint which is the culprit.

Remember that the return line from FD to gas tank is comprised of several pieces of fuel lines joined together by connection or fitting like T-connection, compression fitting, etc.

For example:
If you break the connection of the return line at the fitting before it enters the tunnel, you have isolated fuel line from that fitting to the gas tank. So if the pressure test shows no change in the pressure reading (before versus after), the blockage is in the line between this 'fitting' and the FD. Keep isolating the rest of the fuel return lines as needed. Keep as posted.

Tony

Does anyone know the size and lengths I would need if I was going to replace all the return lines?
Thanks!

Tony,

I'm assuming you meant that in the event of a severe or totally blocked return fuel line the control pressure would be greater than the specified system pressure. The complete blockage of all the return flow back to the tank would certainly result in the measured system pressure being higher than the specified system pressure. (The measured control pressure can never be higher that the measured system pressure.)

In 2). Closing the valve to obtain system pressure is correct for engines with OR without the TPR, provided that the gauge and valve are correctly connected.

As far as pinching the TPR's return line, my problem with this is that the plastic line could very likely be too old (given that it's the original line) to recover from being pinched tight enough to stop the flow (either cracking the plastic line, or creating a permanent partial blockage of the return flow). This seems like a risky alternative to taking the time to make the proper hookup of the pressure gauge.

FWIW, here's my contribution to explaining how to hook up the pressure gauge -

Where to disconnect the WUR/TCPR lines from the Fuel Distributor:
http://forums.pelicanparts.com/uploa...1366678587.jpg

Where to reconnect the lines to the pressure gauge:
http://forums.pelicanparts.com/uploa...1366681071.jpg

Overall view of the connected gauge set-up:
http://forums.pelicanparts.com/uploa...1366681107.jpg
Black and White photos from the Porsche Workshop Manual.

I hope to get these posted in an upcoming revision to the CIS Primer, now still under construction, along with better info on the early ('73 - '74) CIS. Hope the photos help.

Under investigation........
 

Jim,

The procedure shown in WSM for measuring the control pressure for CIS with TPR is quite vague or unclear. The pictures you have attached show only one (1) pressure gauge while there are two (2) active fuel pressure regulators present.

Removing the banjo fitting and connecting it with the WUR in parallel connection would measure the total control fuel pressure produced by WUR & TPR as tandem effect. The TPR has 3 settings (cam settings) while the WUR has a variable setting. Unless you have two (2) gauges set, one in each branch (parallel) we could not tell the pressure contributed by the WUR from the TPR.

In short, an out of spec control pressure reading could be caused by WUR or TPR or both if you are using a single pressure gauge. Follow my logic? Unlike in the CIS without TPR, there is only one thing to consider which is the WUR.

While I have your attention, where does the banjo fitting connected in the picture you have attached? Upstream or downstream? I like to solicit some feedbacks from others about this set-up shown in the WSM photo and most specially from you. NOTE (edit)......saw the connection in the second picture. TD.

BTW, Jim Sims has mentioned pinching the return line from the TPR not the delivery line (hard plastic line) and with that, you could measure the system pressure. Any comment or suggestion is highly appreciated. Thanks.

Tony

Tony,

There is only one pressure gauge. The point made in the WSM is that the proper procedure is to measure the joint effect of the two pressure regulators in tandem. I don't see that as vague or unclear. That is what the specs in the spec book and in the WSM represent. That is the whole point of my comments. You are second guessing how the test is supposed to be performed. I have additional information taken from some Porsche microfiche dated in the mid-70s that backs up what they say in the WSM, but is more detailed so there is no doubt about what was intended. There is additional info in the microfiche that shows what the pressure numbers should be measuring the TCPR alone. I don't know why they didn't include this info in the WSM, perhaps they though it might be confusing. (I plan on posting some of this microfiche info on my Primer update.)

I thought posting the pictures would indicate pretty plainly how the factory says to run the tests. I don't intend to try and justify why they stated to do the tests this way. The control pressure spec numbers are based on the (single) gauge being connected to the WUR and TCPR in tandem per the WSM.

I understand what Jim Sims said about pinching off the return line. The effect would be the same regardless of which side of the TCPR is closed off, however. Either way the fuel flow is stopped from it's return path back to the tank. I think you may be correct that most of the return lines are cloth braided soft rubber. My bad, perhaps, but the lines are still old.

Control fuel test........
 

Jim,

Thanks for the explanation. I read the WSM several times and it never mentioned how to test the WUR or TPR using this set-up. My question is how do you differentiate if the culprit is the WUR or TPR using a single gauge? If the measured control pressure is off the chart as an example, using a single gauge does not tell you which is the culprit. There should be a specific test method for identifying the root cause of the problem. This is what I'm trying to find out and you are the best person to ask. Maybe there are documentation of the tests some where. I appreciate your feedback.

Tony

Has a link to this thread been posted yet?

http://forums.pelicanparts.com/porsche-911-technical-forum/539988-1974-911s-cis-problems-questions.html

Answers a lot of questions CIS in 74s'.

Return flow restriction........
 

Jeff,

Thanks for bringing this up. It was explained in post #45.

Tony

Tony,

I agree that the WSM doesn't address how to perform individual tests on the WUR and TCPR. I had the same question and after several years, realized the answer was not going to be found by re-reading the WSM. Or anything else I seemed to be able to lay my hands on.
My intent in posting the photos on this thread was to clear up what seemed to be murky water on how to connect the gauge (according to the Factory that built the CIS). Since the two regulators were apparently designed to work in tandem, the tandem outcome from the two regulators is the spec to test the pressures against. These are the numbers provided in the WSM and the little spec book. There are no separate numbers for each regulator. I think the WSM says something to the effect of "if you don't get these numbers, replace the TCPR". Not the kind of answer an inquiring mind wants to hear. So even if you find a way to measure the control pressures individually you don't know what are good numbers to check against.

Only recently did I come across some obscure Factory information (the microfiche I mentioned in a previous post) that addressed separate pressure readings for the TCPR. However, nothing in that document addressed how the typical shop (or for that matter, any shop) was perform the test. Here are the numbers:

Idle position: 2.9 Bar
Mid-throttle: 4.1 Bar
WO throttle: 2.8 Bar

No separate numbers were provided for the WUR alone.

To add further insight, here is what a friend and respected rebuilder of FDs and WURs recommends for those with a problem with the TCPR: Replace the dual regulator set-up with the vacuum operated WUR for the' 75 US models - 0438 140 129. The TCPR is not rebuildable.

To sum it up, the WSM is perfectly clear on how to run the test. What is not perfectly clear is why they didn't add separate tests for the WUR and TCPR. And what's further frustrating is that there is no one around now in the Porsche factory design group who can answer the question.

Let's think if there's really a need for the factory to post separate pressure numbers for the WUR and TPR.

You can check that the WUR is operating (as in progressively increasing pressure) by starting from dead cold with the TPR unplugged. Applying 12V to the WUR should make the control presure rise. Ok, the numbers won't match the factory because the TPR is unplugged.

Next, get the TPR back in line. By moving the throttle, you should see pressure moving by about 1bar up and down. If there's no variation, then the TPR it's bad.

If you see variation, then you can try to bring it to spec by adjusting the 5mm allen on the WUR bottom. With a WUR completely warmed up, this should affect the warm control pressure.

My point is, you dont need separate pressure readings from WUR and TPR to make an educated guess about which one is failing, and since neither is rebuildable, it's enough. Separate tests would add complexity to the procedure and need more fittings.

I'm 100% agree with your statement........
 

Jim,

We have nothing to disagree!!!! I was hoping you have some test under your sleeves that we don't know. Those numbers are available in the shop manual. I was not questioning or doubting the procedure. What I was looking was a simple test procedure to test or evaluate either the WUR or TPR. Thanks.

Tony

I sort of follow along the lines of above. I disconnect the banjo fitting that goes to TPR and proceed with pressure tests like every other 911 with non-vacuum controlled WUR. If TPR rubber diaphragm was ruptured you would see fuel coming out of disconnected fitting. This rupturing would also give you false FP reading as some fuel would bypass back to tank via return line if you didn't check for rupture.

Also, as an old carb guy I can see that the TPR functions like an accelerator pump and can be adjusted as such by feel or better yet a mobile CO tester to check for proper A/F ratio under quick engine load transitions. My first 74 had "S" cams but FD was from a base model. Flooring the throttle, from say, 2500 rpms in 2nd would cause a bog that had to be remedied by swinging TPR all the way to the rich side (forward toward front of car, IIRC).

Flipping over the spare WUR I have shows stake marks in the aluminum similar to injector bosses, so I imagine it could be rebuilt at least once if a guy had a dremel.

Ok, I wanted to report and update from work completed tonight.
I have replaced all the return lines in the engine bay save the one from the TPR to the 4-line junction. With my brothers help, we blew high pressure air through the return line that goes back to the tank and I feel confident that we do not have blockage there.

After all of these replacements, I did a cold control pressure test again with the same results as previous - 72psi. I did try one other thing that I didn't try the other day, and that was lifting the throttle lever which produced a reading of 78psi. I did not take any further readings for system pressure.

So where do we go from here? The only other thing I can think of that I didn't do tonight would be to take the line off the 4 way junction that returns to the tank and run it into a container instead.
S>

Go back and read post #52.........
 

Steve,

The blockage is still there and probably around the FD. Don't keep changing fuel lines to locate the culprit. You need a systematic approach to finding this nagging problem. Isolate and pin point where the restriction is occurring. Read post #52. Have you contacted Andy (Schumicat)?

Tony

Hi Tony,
I've read #52. I have not contacted Schumicat, but I've read his thread multiple times (my return line from the FD was just a standard hose and clamp, it didn't have a screw on fitting like the one he's olding in his last post... is this just a difference between his SC and my 74?). I understand that there must still be a blockage, and I will pull the main line that goes back to the tank from the 4-way to see if I get any difference and let you all know what happens.

While replacing the lines last night, I pulled the 4-way junction and confirmed that it was clear. What else around the FD are you thinking might be causing the blockage? Is there something outside of a return line that could be causing it?

When you blew through the lines with air, were the lines connected all the way to the tank?

(apologies for the ASCII diagram)

| |
v v
3 4
1<-- ====== __|__|__ ====== <--- 2

Hey,
Ok, so in my world there are 4 return lines that all attach to the 4-way T:
(1) Return line to the tank --> T
(2) Return line from the FD --> T
(3) Return line from the WUR --> T
(4) Return line from the TPR --> T

I broke #1 loose at the T and blew high-pressure air through all the way to the tank. I got good flow results there. There was a short rubber line going from the T to the hard return line that exits the engine bay for the tank return, which I replaced with new hose.

I replaced #2 with new hose.

I replaced #3 with new hose.

I did not replace #4 because I could not easily reach where it connects to the TPR to remove it. I will try that at some point in the near future.

I blew high pressure air through all 4 of the ports on the T and there is no restriction there.

I'm planning on pulling #1 off and dumping that from the T to a container and testing to confirm the tank return is in fact not restricted. Outside of that, I don't know what to do next.

Just out of curiosity what are you replacing these lines with, the proper coline lines on barbed fittings I hope? I say this as I made the mistake of replacing one with FLAPS available 1/4" rubber line when I first got my car and got a schooling on just how bad an idea that was.

been watching your thread about to go back and try and tackle continuing idle issues in my '75.

Further testing
 

(Process of elimination will get you there...)

Further suggestion -

Remove the TCPR from the hookup temporarily.

Hook up the gauge set to the FD at the WUR connection.

Disconnect anything from the other end (the end that would normally go the WUR).

Put the open end of the gauge set into a container to catch fuel, preferably a graduated container.

Make sure the gauge valve is closed, and have a timer ready.

Turn on the fuel pump, and verify you have 72 psi or so at the gauge.

Fully open the valve and start the timer, letting it run for 30 seconds and close the valve.

Measure the amount of fuel and report.

No fuel = blockage in the FD.

160 to 240 ml/min flow rate = no problem here. Need to look somewhere else.

Had a very few minutes today to run some further tests:

Jim, flow rate out of the FD was measured thusly:

~115ml --> 30 sec = 230ml/min (which is within the 160 - 240ml you mentioned)

Fuel pressure with primary return line pulled off the return to the tank into a can:
72psi
Fuel flow out of return line is good

Fuel pressure with WUR return pulled off the t-block into a can:
72psi
Fuel flow out of return line is non-existent

So based on these observations, this is what I'm thinking:
Return lines are clear and unobstructed
WUR is either obstructed or out of adjustment and has the return closed completely off.

Next steps? Pull the WUR apart and look inside? send the WUR out to be rebuilt? If so, who should I send it to for the rebuild?

sobamaflyer, I used hose that came with the car that appear to not be cohline (there are no cohline markings on them). School me on the cohline, please... To be clear, these are just for the return lines in the engine bay.

Thanks for all the help!
Steve

Test.......
 

Steve,

If there was no fuel coming out from the WUR outlet, that's the obstruction in the fuel flow return. Were both pressure readings of 72 psi. taken with the valve open? There should be continuous flow of fuel via the WUR and TPR when the FP is running.

I had a chance to look at the fuel system for '74 CIS. So what is your system fuel pressure now? You have to run your test with theFD's, WUR's & TPR's return lines open to atmosphere and collect them in a suitable container. All three (3) fuel return lines should have fuel coming out while the FP is running. The TPR could be also contributing to the problem (?), we don't know until it is tested. Why? Assuming the the WUR's return line is 100% blocked, the TPR is always open (theoretically) and would result into slight reduction in the pressure reading for the control fuel pressure. If I understood correctly your data, they are both control fuel pressure readings (?).

So what is your system fuel pressure reading (valve closed)? Keep us posted.

Tony

Tony,
Both pressure readings of 72 psi were taken with the valve open (cold control pressure). There was a continuous flow of fuel out of the TPR return but not out of the WUR return.

I have not taken another system pressure reading, but as none of the other pressures have changed with any of the changes that I've made, I would expect them to be the same as before. I don't understand how if the WUR and the TPR are not included in the system pressure reading having them open to atmosphere would make any difference in a system pressure reading either.

I'm fairly confident that the WUR is the root of the control pressure issue at this point based on all the testing over the past 20 days and the results from today. Should I pull it apart myself and attempt to clean/unclog or can you please recommend someone that would be best to have it rebuilt? Once I've got a clean, well adjusted WUR with good return flow, if there are additional issues that need to be addressed, I will address them at that point.

Thanks,
Steve

Please update the status..........
 

Steve,

The last email I got from you stated that the refurbished WUR -009 did make the engine run for the first time after several futile attempts in so many years. It would help others if you update this post. Sharing your experience with us would benefit others that might encounter or have similar problem with their cars. Thanks.

Tony

Please update and share your results.........
 

Steve,

I know the engine started right always for the first time with the rebuilt WUR. So how's the car doing these days? Still running OK? Or PM me. Thanks.

Tony

Jim. You say in item no.60 that wur o438 140 129 is for '75 US models and vacuum operated. I have one with that no. with no vacuum fitting [not original to my car] Think I will have to start a story of my own. I'm having starting/running problems after a long sleep [the car!] + it appears to have an identity problem too.Regards,Michael.