YACTT (Yet Another CIS Troubleshooting Thread)...

[m1sandman]

Howdy,
I recently acquired a 74 that had been sitting for roughly two years. The PO said the Fuel Distributor was stuck and he used B12 to get it moving again and the flapper moves well when you move it manually. He said that the WUR was rebuilt but I don't know how long ago that was. It took a week or two but we were finally able to get spark (should have started with the points instead of ending with them, but lesson learned).

I've read a bunch of threads on the pressures and found reference to the 74 having a system pressure of 70psi and a control pressure ~50psi. I've been able to test system pressure and it is 70psi, but the gauge that came with the car had very old lines on it and they blew shortly after. I've borrowed another gauge from a friend but its will take some fiddling to get it in line the correct direction to get the Control pressure.

In the meantime, I pulled the WUR and checked the screen and it had some nastiness about it, so its been cleaned with carb cleaner and reinstalled. I have run low pressure air through the fuel return lines and they appear to be flowing properly. The car will start with the throttle lever in the up position, but then dies immediately, then will normally backfire the next time I try to start it (luckily it came with a stainless airbox with pop-off valve). We can get the car to run by starting then immediately manipulating the flapper in the airbox to allow more fuel, and as long as that is happening, the car will run.

Obviously without a control pressure its very hard to tell, but based on the other threads I've read and consulting with my local Porsche CIS guru my initial thought is the WUR needs to be rebuilt. Have I missed any other tests that might point us in a different direction?

Thanks!
Steve
Tampa, FL

[boyt911sc]

Steve,

May I ask you this question before you decide to have the WUR rebuild? What made you think the WUR needs a rebuild? What's the number (ID) on the WUR? Have you tested the WUR?

A fuel pressure gauge kit is mandatory for fuel injection system troubleshooting. Without one, you'll be doing a lot of guess-work and could be a very expensive way to fix a simple problem.

I'm no expert by any means, but I have not encountered a CIS problem that could not be diagnosed correctly by a DIY'er like you or me. There are simple tests and procedures that you could do to verify and confirm the condition of almost every individual CIS components in your car using ordinary tools excluding CDI and exhaust composition analysis.
Keep us posted.

Tony

[allaircooled]

Check this site out if you haven't already.

Welcome to the forum by the way. Nice to see someone local to me.

[m1sandman]

Chris, Thank you for the welcome! I'm glad to be here... My brother and father both have 911's and I finally was able to join them. I've been all over that site you linked me to -- it is a great resource and helped me determine the flow so I could identify the return lines!

Tony, I've read lots of the posts that you have contributed to for CIS troubleshooting, which is why I know the importance of pressure testing, etc, and I'm glad you have entered the thread as I respect your help a lot. I have to swap around some fittings on the loaner gauge that I have now before I can test the control pressure, but will be able to do that tomorrow at the earliest but more likely one evening this week. To answer your questions:

1. "What made you think the WUR needs a rebuild?" At this point its been a process of elimination -- I know the system pressure is within spec (measured at 70psi). I know the cold start valve is working, I know I'm getting fuel to the injectors if I lift the flapper manually, I know that the return lines are not clogged (I found that in several of the threads you had commented on), and I now know the screen in the WUR is not clogged. I'm sure there are other things I should be testing and don't have the knowledge of yet, but thats why I'm posting.

2. "What's the number (ID) on the WUR?" I will have to pull it again and look -- i had it out today and should have written in down but didn't, and now I don't remember off the top of my head.

3. "Have you tested the WUR?" I have not and would appreciate any advice on properly testing the WUR.

Thanks for the replies Gents! I'm looking forward to getting this one back on the road...

[manbridge 74]

Another 74. Willkommen.

Post a pic of your sweet ride tout sweet if at all possible.

I would be curious as to your WUR number as well.

Along with fuel pressures, has everything else involved with a basic tuneup been checked/completed?

[allaircooled]

Can't believe I forgot to ask you to post pictures! Most important! Heck I am flying home on Wednesday for a couple of weeks, maybe you would like to show me your new ride in person.

[m1sandman]

Hi Manbridge,
We've got fresh gasoline, the leaking fuel lines replaced, fresh oil and we're running with the airbox open for now. Outside of that, been pretty focused on 1) getting spark and 2) now getting fuel

Chris, would love to get together... PM me and we'll swap contact info!

Here are a few pics since you guys requested them...


Ready for the trip home...

Finally in its new home (thats my brothers 73 targa behind)...

[allaircooled]

Wow is that the original color? I'm liking it.

[m1sandman]

Yep, original color tho its much patchier than it appears in the pictures. I'm the third owner... the gentleman I purchased it from bought it in 1980 and it was a well maintained and well loved vehicle. Its got basically no rust (just a little at the base of the A pillars that has been touched up) and all the reliability upgrades had been done on the engine.

Was just surfing the Rat Rod thread and think it would definitely fit nicely in that category.

[theFONZ]

Vacuum leaks will wreak havoc on a CIS system. You need to make sure you don't have any before swapping parts and adjusting stuff. Do a search for vacuum leak tester, and there are a few threads of homemade setups.

And definately get a proper CIS fuel tester.

[boyt911sc]

Steve,

Find the correct fuel pressure gauge kit. The 'kit' is installed between FD (fuel distributor) and WUR. Break the connection at the WUR side. Some illustrations from manuals show the installation at the FD. I strongly suggest to do it @ WUR. You could try the installation at either sides and you'll experience why.

Your '74 should have a running FP when the ignition is @ ON/RUN (not start). No need to run the engine to test your WUR. With the fuel pressure gauge properly connected between the WUR & FD, you are ready for the test.

1). Disconnect the electrical plug to the WUR for cold control fuel pressure check. Turn ignition SW @ ON position. Record reading.

2). Next, connect the electrical plug (WUR) and observe the control pressure rise over time. Record the pressure reading versus time. Example: 30, 60, 90, 120 sec......and so on until the control fuel pressure stabilizes probably around 4 mins. or so. Keep reading until the pressure stopped going up and record the time in minutes. These numbers I coined it as your WUR profile (baseline data).

Before doing the test, measure the resistance in your WUR by using a multi-tester set @ resistance (Ohms). The WUR's for the early CIS ('73.5 -'74) are getting harder to find these days. Keep us posted.

Tony

[m1sandman]

Fonz, thanks for the suggestions on the vacuum leak. I did purchase new injector seals and haven't installed those yet, so i'll move towards the top of the list. That search was a good one, after I do the CIS pressure tests I'll to the reverse vacuum cleaner with soapy water spray test.

Tony, thanks for the steps. I'll get the pressure tester setup with the valve on the correct side and test, then post the values and the part number for the WUR. As an aside, can you tell me which of the pins on the WUR is the 12v connection and which is ground? Is the pin closest to the inlet and outlet ports the power side?
Thanks to all for the help!

[ossiblue]

Originally Posted by m1sandman

Fonz, thanks for the suggestions on the vacuum leak. I did purchase new injector seals and haven't installed those yet, so i'll move towards the top of the list. That search was a good one, after I do the CIS pressure tests I'll to the reverse vacuum cleaner with soapy water spray test.

Tony, thanks for the steps. I'll get the pressure tester setup with the valve on the correct side and test, then post the values and the part number for the WUR. As an aside, can you tell me which of the pins on the WUR is the 12v connection and which is ground? Is the pin closest to the inlet and outlet ports the power side?
Thanks to all for the help!

One caution.

You have a 74. If the CIS is stock, you have a slightly different set up between the fuel distributor and the wur. The 74 uses a throttle positioner valve that is fed from a line coming from the fuel distributor. This line shares an outlet port with the line that goes to the wur. When you connect your test gauge between the fuel distributor and wur, the line that goes to the throttle valve must be on the wur side of the gauge. That will mean you will have to connect your gauge set directly to the FD after removing the banjo fitting that supplies the throttle valve, and reconnect the banjo fitting between the outlet of the gauge set hose and the line to the wur.

I defer to Tony on most things CIS as his expertise is proven. However, I do know that most of his work is done with later models and the throttle valve only was on 73.5 and 74 model CIS engines.

If you are not sure what I just described, take a look at your fuel distributor where the line to the wur emanates. Is there a banjo fitting on there with a line that runs back to the throttle body? Please let us know.

BTW, it doesn't matter which pin is hot and which is ground.

[m1sandman]

LJ, thanks for the tip -- I'm learning that my car is slightly different than most of the CIS cars I'm finding tips for (for instance, I don't have a relay and fuse in the rear panel for the WUR, but I did find reference on one of the forums to a 74 with the power for the WUR coming straight off the alternator (which is why I never get 12v when I test it). The factory shop manual that my brother has shows the relay and fuse in the current flow diagrams for the 73 911T and the 74, so I think mine must be an inbetweener.

All that being said, there is a banjo fitting just inside the line that runs from the FD to the WUR, but I have not traced it yet. Safe to assume this is the one you are talking about? That also complicates my gauge setup, so it may take a little more time to get readings -- i'll take a look at the fittings today and see what all i need to swap out on the gauge.

[95avblm3]

Steve,

Slightly off-topic, but here is another thread to keep in your back pocket should other issues creep up down the road (which it will): 1976 911S – from garage find to on the road.

It's a fun read by a guy who has a car similar to you...

Welcome to the 911 club.

Jeremy

[Paulporsche]

Just wanted to add because I don't think I saw them mentioned:

When you construct the WUR Profile that Tony mentioned, make sure the engine is cold (hasn't been run in at least 4 hrs) and record the ambient temperature for the first cold control pressure test. The required CCP varies w/ the ambient temp.

If your resistance of the bimetal arm is within spec, you may find that the CCP just needs to be reset via the "knocking the plug" procedure, rather than rebuilding.

It's also important to know your CO% but for now the fuel pressures are more important.

Vacuum leaks can be located in some very hard places to find. I had a paper thin spot worn almost through the aluminum pipe that went to the AAR on my engine. 30+ years of rubbing against the engine oil cooler had produced a small spot in the wall that I was able to flex like a piece of tissue. I had 3 mechanics tell me I had no vacuum leaks, but if there wasn't one at the time, there was going to quickly be a massive one!

Through a lot of help and patience from Tony and others I was able to repair that area and reset the control pressures. The engine hasn't run so well in years!

Always make sure that all your ignition parts are operating within spec before you move on to CIS components.

[boyt911sc]

Originally Posted by ossiblue

One caution.

You have a 74. If the CIS is stock, you have a slightly different set up between the fuel distributor and the wur. The 74 uses a throttle positioner valve that is fed from a line coming from the fuel distributor. This line shares an outlet port with the line that goes to the wur. When you connect your test gauge between the fuel distributor and wur, the line that goes to the throttle valve must be on the wur side of the gauge. That will mean you will have to connect your gauge set directly to the FD after removing the banjo fitting that supplies the throttle valve, and reconnect the banjo fitting between the outlet of the gauge set hose and the line to the wur.

I defer to Tony on most things CIS as his expertise is proven. However, I do know that most of his work is done with later models and the throttle valve only was on 73.5 and 74 model CIS engines.

If you are not sure what I just described, take a look at your fuel distributor where the line to the wur emanates. Is there a banjo fitting on there with a line that runs back to the throttle body? Please let us know.

BTW, it doesn't matter which pin is hot and which is ground.

Larry,

You are correct. There is slight different in the set-up for the '73.5 - '74 CIS compared to the SC's. I have over-looked this difference. Thanks for catching it.

Tony

[manbridge 74]

Originally Posted by m1sandman

LJ, thanks for the tip -- I'm learning that my car is slightly different than most of the CIS cars I'm finding tips for (for instance, I don't have a relay and fuse in the rear panel for the WUR, but I did find reference on one of the forums to a 74 with the power for the WUR coming straight off the alternator (which is why I never get 12v when I test it). The factory shop manual that my brother has shows the relay and fuse in the current flow diagrams for the 73 911T and the 74, so I think mine must be an inbetweener.

All that being said, there is a banjo fitting just inside the line that runs from the FD to the WUR, but I have not traced it yet. Safe to assume this is the one you are talking about? That also complicates my gauge setup, so it may take a little more time to get readings -- i'll take a look at the fittings today and see what all i need to swap out on the gauge.

This is correct. 74 911s have no power to the WUR until engine is running. Also, they came with a one wire WUR so you need to post the number off of yours to determine if the one you have is the proper replacement.

[m1sandman]

Ok, I was able to get 2 pieces of information today on the WUR. The last 3 of the part number are 009 (see attached picture), and the resistance measured at 32.2 ohms.

Unfortunately I'm going to have to get some different adapters to be able to run a control pressure test because of the banjo fitting inside the fuel line between FD and WUR. Anyone know the specs on the threads I need to have to be able to screw into the FD and accept the fitting including the banjo on the other end of the gauge?

WUR:

[m1sandman]

BTW, those of you with 74's, you mind posting pictures? I'd love to see what colors, ride heights, and wheel configurations you all are running.
Thanks!