You can't eel for air leaks, and there are a ton of places that can leak on a CIS motor. I disagree with the comment about the WUR not being a precision device. The adjustment for the bi-metalic strip is only a couple thousandths of an inch which means it can go out of adjustment pretty easily, and its hard to get it back right again. Your cold pressure seems a bt low, but that should cause a rich condition if anything. Buying the tester was the right thing to do and will save you time in the long run. I think you should disable the O2 sensor system so it doesn't interfere with all your other tests. Are you familiar with adjusting the mixture?

Thanks for the help, I will unplug the o2 sensor, and I agree that my cold pressure was a bit low, that was my initial thought when I was testing the thing int eh garage. I would like to carry through with that last fuel pressure test if it is a valid and useful one, but I am not sure what it is/ how to do it?

Thanks for the help
Scott

Residual pressure is simply how long the system maintains pressure once the fuel pump is switched off.

You have to do more than just unplug the sensor. You have to disable the whole system. Specifically, make sure the frequency valve is not bleeding air into the system.

Ok, thanks, is there a spot where I can cut the system off from the top?, and disable it, some connection somewhere?, or will just unplugging the two prong plug on the back of the frequency valve do it?

Thanks
Scott

pete, thanks for the help, thats a lot simpler than I thought it would be. so I should leave the fuel pressure gauge in the same location, and run it with the wur just like I did before, and unplug the wur and fuel fuel pump at the same time and see how long it takes to drop down to 0psi?

Im assuming this should take a while?

Thanks
Scott

You need to disconnect the hose and plug the line so no air leaks in.

if the frequency valve + 02 sensor could be the problem, it might be because a while back when i took the engine out of the car, the cover of the 6 pin connector by the rear drivers side shock tower came off, so on the motor side of the connection, i just had 6 gangling wires that I color matched to the other 6 when I put them back in, but it could be the case that I mixed up the two black wires with a red stripes, which are the two wires that go to the frequency valve.

Or maybe that has nothing to do with the problem, haha

-scott

There is no hose on the frequency valve. The frequency valve does not bleed air into the system.

bob, i was just about to say that, because I couldnt find one when I was feeling around back there,

thanks
scott

there are fuel lines though, and just fuel lines from what I can tell

The connector on the wall connects the frequency valve to the lambda box under the passenger seat.

Your symptoms are similar to a guy last year who had corrosion in that connector and his frequency valve would shut down. I can let you know how to test it. I have done this test.

If the O2 is unplugged the car will run. If the freq valve is disable the car will run horribly.

Do not touch the frequency valve.

I think 911brick is thinking of a different part. However, the fuel system does not really have many hoses. Just lines. The hoses are big and heavy duty given the pressure and heat cycling they have to endure.

I do think you need to test the freq valve. The test is relatively easy. Let me dig for the link.

I will pm you my phone is you want to call.

Here is the link. Look at my post number 32. The frequency valve relay is under the passenger seat and it is square. Hooked to the lambda box. You can jumper the relay male prongs but I would just use wire and connect the three sockets corresponding to the numbers in my post. I would be glad to set it up on mine and post pics before you try this.

The freq valve will run (and buzz) with nothing else running - and the key does not have to be on. I would also like to double check that your 80 is the same as my 81. They both had O2 but there are some differences. Give me an hour or so. Gotta pick kids up at football game.

http://forums.pelicanparts.com/porsche-911-technical-forum/559200-911-sc-running-flat-no-idle-2.html

Here is the diagram for 1980 from the Porsche Factory Manual. It is the same as the 81 but 81 has an accel enrichment.

EDIT - SCOTT - SEE POST 121 FOR A MUCH FASTER WAY TO CHECK THE FV

Fuse 18 is hot all the time and feeds terminal 30.

Connect 30 87 and 87b at the female ports without the key on and the freq valve should buzz. If it does not then we can move to the 6 pin connector. MAke sure your dome light / glove box light and or luggage trunk light works as this is the same circuit (fuse 18) and confirms you should have juice at port 30.

http://forums.pelicanparts.com/uploa...1314410600.jpg

And your point is?

My mistake, I misread your post.

Scott does not need to disable the O2 sensor right now. The car won't stay running for starters. He is not in a position to set CO.

He is currently testing fuel pressure. Earlier in the thread Ossiblu stressed the pressure test first then move on to vacuum leaks which I am confident he has. Essentially he is starting from the beginning.

Bringing up the freq valve was great because there is a chance that his freq valve is not working which will result in very poor running. If it buzzes with the relay test then he needs to leave the freq valve alone. If 12 v was manually put to the freq valve (which seldom fails) connection terminals and it buzzed it would not test the wiring and the relay. I think it can be a quick test and I do not think it is the problem as the car will run with the freq valve disconnected - just really badly.

The quick and dirty test is to pull the relay while the car is is running and if it loses throttle response and stumbles the freq valve is working (with relay plugged in). We don't have that ability.

Scott,

Couple of things...

Maybe I missed it but I don't see the results of the warm control pressure test. If you didn't figure it out already here's what you do. Set up your CIS test gear the night before and let the car sit overnight. In the morning, disconnect the electrical connector on the WUR, jumper the fuel pump relay to start the fuel pump and check your cold control pressure. Then plug in the electrical connector to the WUR. It should increase as the bimetallic strip heats up. Measure how long it takes to get to the peak number and note the peak. In my experience it was maybe 30-40 seconds and 4.7 bar on my car if I remember correctly. Report back on what you find.

As someone else mentioned, don't rule out vac leaks. Lots of places in these systems where you can have them. Search on the forum and you will find the carb cleaner method, the unlit propane torch method, the soapy bubble method and the take it to the shop with a smoke tester method.

Do the FV check as Bob suggested.

Good luck!

See post 80 for his pressure test.