Occasional CIS problem

[Porchdog]

I finally got around to the pressure test.

System and control pressures are both 4.6 Bar - No change with time.

They go to 2.0 Bar with pump off and very slow fall-off - like 1.6 Bar after 1/2 hour.

The WUR resistance measured 40 Ohm before starting (88°F ambient).

So - Fuel pressure regulator?

Thanks!

[wgirardot]

Sound like maybe someone messed with the WUR and opened it up. And when closing the WUR back up didn’t get the pin that controls pressure properly seated in the diaphragm.

Bill

[pmax]

Originally Posted by Porchdog

I finally got around to the pressure test.

System and control pressures are both 4.6 Bar - No change with time.
...

Read dhanl82's post, check the return.

If the return's OK and the problem turns out to be the WUR, please report back the findings for future reference. Too many of these CIS threads end up with no resolution or if there was a resolution, it is hidden in private exchanges never to see light of day.

Thanks

[boyt911sc]

9

Originally Posted by Porchdog

I finally got around to the pressure test.

System and control pressures are both 4.6 Bar - No change with time.

They go to 2.0 Bar with pump off and very slow fall-off - like 1.6 Bar after 1/2 hour.

The WUR resistance measured 40 Ohm before starting (88°F ambient).

So - Fuel pressure regulator?

Thanks!

Mike,

For control pressure to equalize the system pressure you have a flow restriction at or after the WUR. Closing the valve for the CIS pressure gauge kit mimics a clogged WUR or the return line immediately after the WUR. If the flow restriction occurs before the gas tank, the pressure reading would be greater than the system pressure.

A good way to test this problem is opening or breaking the fitting of the return line under pressure. But I am afraid you don’t have the correct set up to do this test in situ. Drop the WUR and I will do the test while you wait.

BTW, I will be leaving on July 24 for London & Paris with the whole family including my grandchildren for 3 weeks. Give me a call. PM sent.

Tony

[Porchdog]

So - no flow through the return line from the WUR - either compressed air or vacuum.

I will try the return line from the fuel distributor to the tank.

[Bob Kontak]

Originally Posted by boyt911sc

BTW, I will be leaving on July 24 for London & Paris with the whole family including my grandchildren for 3 weeks. Give me a call. PM sent.

I could be considered family, kind of, in a Porsche way. I can babysit.

Just saying.....

My passport is current.

I don't eat much.

Originally Posted by Porchdog

I will try the return line from the fuel distributor to the tank.

FWIW, I have just one factoid to pass on. A dude here in Atlanta many years ago on hot days would develop horrid running of his Lambda SC for short passages.

Turned out it was the rear wall 12 pin connector that was a little skunky as to connection to the frequency valve. The symptoms were the same as a dead O2 relay or pulling the Oxy fuse. Only in killer ambient heat did it surface when the connection was lost.

Here is a vid I made of pulling the O2 relay which would replicate the symptoms.

[boyt911sc]

Originally Posted by Bob Kontak

I could be considered family, kind of, in a Porsche way. I can babysit.

Just saying.....

My passport is current.

I don't eat much.

Dear Bob,

But you take lot of seat space. That means we have to rent another mini-van. And I could not sleep in a bedroom with somebody snoring. Getting another room for you is not an option. I noticed lately that you have been in good behavior. Take care.

Tony

[mike sampsel]

Originally Posted by boyt911sc

Dear Bob,

But you take lot of seat space. That means we have to rent another mini-van. And I could not sleep in a bedroom with somebody snoring. Getting another room for you is not an option. I noticed lately that you have been in good behavior. Take care.

Tony

Well if Bob’s out of the running ... I’ll assume I’ve no shot. Tony, fabulous you can go to London and Paris and take the grandkids too. Have the best of trips.

[Porchdog]

The restriction is somewhere in the distributor - the return line line from the firewall to the tank is open.

[dhanl82]

As I mentioned earlier, I had the same problem. I will list the steps that I took to isolate and solve it.

1. I disconnected wur return line and connected another line from the wur return port to a container for the fuel - ran fuel pump and had correct control pressure, this ruled out a bad wur.

2. I then disconnected the wur return line at the fuel dist. attached a rubber hose at the wur end and blew through the hose - this determined that there was no blockage between wur and fuel dist.

3. Keeping in mind that I would not be able to blow through the wur return line and through the fuel dist. to the tank due to the "push valve" being closed as it is designed to be when fuel pump is off, I removed the pressure valve from the distributor. I then attempted to blow air through the return line and fuel dist. by placing my finger over the fuel dist. open pressure regulator orifice where I had removed the pressure regulator assembly from. At first I was unable to blow through it but suddenly something broke loose and the air went through the wur return line through the fuel dist. and I could heat it bubbling in the fuel tank.

4. I put the fuel pressure regulator assembly back into the fuel dist. reconnected all line, ran the fuel pump and saw that system and control pressure correct - problem solved.

5. It appears that the return blockage was either at the orifice leading into the fuel dist. or the one exiting into the wur return line after the "push valve'

I hope this may be of some help. Please contact me if you have questions, as I may not have done a good job of describing my approach to problem.

Dave

[Porchdog]

Hi guys,

Tony is testing my WUR today.

After sleeping on it I understand Dave's approach. Assuming that we rule out the WUR, I will pull the pressure regulator and try to clear the lines.

Thanks Guys!

Mike

[boyt911sc]

Originally Posted by Porchdog

Hi guys,

Tony is testing my WUR today.

After sleeping on it I understand Dave's approach. Assuming that we rule out the WUR, I will pull the pressure regulator and try to clear the lines.

Thanks Guys!

Mike

Mike,

Since you have already removed the WUR from the car, inspecting the FD is a prudent course of action. I sent you a message last night about the PPV (primary pressure valve) inside the FD.

I will lend you some fittings and fuel lines to test fuel flow in situ. Like I mentioned earlier, the restriction based from your information is likely at or after the WUR. By the time you read this post, you would probably out of the house on your way to work.

Let me test the WUR first and I doubt it is the culprit. But we have to test and confirm before we could eliminate it as a culprit. Then locate and identify the location of the restriction point somewhere in your system. Point of interest is the cavity where the PPV is located. See you later today.

Tony

[dhanl82]

Mike,
I failed to mention something.
If you determine that all lines and orifices in and out of the fuel dist. are clear then it may be in the PPR assembly itself. There are, in the wide neck part, of the PPR assembly, 2 very tiny entry and exit orifices where the return fuel from the wur enters into the Push valve" chamber through one, goes past the push valve tiny green "O" and then exits into the PPR chamber and then out through the fuel dist. return line to tank when the fuel pump is running and the push valve is open.
If either of the orifices is clogged or if the interior push valve chamber is obstructed, there will be no return of fuel from wur allowed and thus the very high control pressure.

I disassembled my old PPR to see how the push valved worked - very interesting! There is a tiny "C" clip holding the assembly together, once removed, the shaft pulls out to reveal the push valve "O" ring etc.

I would be remiss if I did not mention that my back and forth communications with Tony were invaluable while I was attempting to solve this problem - he taught me a ton about the cis system during this process - thanks again Tony!

Dave

[Porchdog]

Dave,

I know Tony pretty well - he has been helping me for years and he is nearby.

Thanks for the clarification on the PPR.

I haven't been giving this the attention I should - My son's 944 is torn apart to get a clutch and torque tube, My daily driver dumped it's coolant on Tuesday, The other kids are home for the holiday, the house water heater died yesterday - I have just been crazy busy.

The car was running sweet after the WUR from Tony and a careful tune using the AFR Meter. The transient way this problem came on has been frustrating, I'm thinking I have a chance to get back to running happily again.

Thanks Guys!

[Porchdog]

I got to watch Tony do the magic today and the WUR is condemned.

I will report back after it is replaced.

Mike

[Porchdog]

The car is back together and running sweet.

Tony found that the WUR was plugged up. I left it with him. I think it took him a bit longer than usual to calibrate and there was a snafu with USPS, but I got it back today.

While the WUR was gone I changed the fuel filter and pulled and cleaned the pressure regulator. The filter had a bunch of fine, translucent particles in it - not plugged up, but floating in the fuel I recovered. The filter paper itself was clean and had no visible tears. It was a Mahle filter, less than a year and 1000 miles old.

Before I put the WUR back in I flushed the fuel. It came out very red at first - maybe from having the line open for a week? No particles though. Put everything back together, pressures looked good, No start.

I pulled the injectors and checked flow. Everything looked good - fuel was even a better color.




I started checking wiring - apparently I had pulled the power lead off my MSD unit while I did the filter. Plugged that back in.

Started it up and it ran rough, as you would expect badly flooded. It did smooth out. I let it sit an hour then started it and took it for a drive.

It's running very well. AFR looks good on my AEM gauge. Idle is a bit high fully warmed up - I will adjust tuning the next chance I get.

Thanks Tony!

[boyt911sc]

Mike,

Could I ask you a favor? Please post the heater resistance values (Ohms) that you obtained from your recent test. Thanks.

Tony

[Porchdog]

84° 25.8 Ohm

88° 25.7 Ohm

92° 25.4 Ohm

[Porchdog]

My problem is back.

I attempted to take the car to work this morning. Started right up but went crazy rich.

I thought it might clear up as it warmed up. It got worse.

I just got home and hooked up the pressure gauge.

4-1/2 Bar closed.
1/2 Bar open.
1-1/2 bar residual pressure.

Is it possible that the WUR failed in a couple days?

[tirwin]

1/2 bar open?

Not sure what you mean. 1/2 bar is after the car has been driven? Is that engine running? Can you explain how you tested?