frequency valve

[delkins]

i had a issue a few months ago with my 82sc, with hot starting and such, i replaced the accumulator and fuel filter, i guess i have some issues with my frequency valve also my mech said to just disconnect it which has been done the car seems to run ok but does not start on first crank always starts on second crank no problem i get a puff of white smoke on start up and it smells like its rich on start up smoke goes away after a min or so, guess what i'm asking does the frequency valve need to be hooked up to run correctly mech said its just a safety item if your in a crash to shut fuel off?

[Bob Kontak]

It needs to be functioning along with the O2 sensor.

You will lose wide open throttle enrichment, for starters. All the good stuff it does for fuel economy (with O2 sensor) is over-ridden when you drop the pedal so why turn your back on it?

Others will have more to say regarding your mechanic's comments.

[boyt911sc]

Originally Posted by delkins

i had a issue a few months ago with my 82sc, with hot starting and such, i replaced the accumulator and fuel filter, i guess i have some issues with my frequency valve also my mech said to just disconnect it which has been done the car seems to run ok but does not start on first crank always starts on second crank no problem i get a puff of white smoke on start up and it smells like its rich on start up smoke goes away after a min or so, guess what i'm asking does the frequency valve need to be hooked up to run correctly mech said its just a safety item if your in a crash to shut fuel off?

delkins,

It is obvious your current mechanic knows very little about CIS or you misunderstood what he was talking about. Find a mechanic who knows the system well. Not all good mechanics know about this antiquated fuel injection system. The safety device that your mechanic mentioned was the AFS (air flow switch) that shuts down the FP when the engine stopped running. A severe frontal crash could still keep the engine running. The '82 SC is built and designed to run with the lambda system (OXS) and FV. Is your engine still using the ECU and OXS? Keep us posted.

Tony

[delkins]

as far as i know it is just disconnected a quick disconnect plug on the back side of throttle plate it falls off sometimes on its own is this the airflow switch?, i know nothing about the system, everything else is hooked up

[boyt911sc]

Originally Posted by delkins

as far as i know it is just disconnected a quick disconnect plug on the back side of throttle plate it falls off sometimes on its own is this the airflow switch?, i know nothing about the system, everything else is hooked up

delkins,

If you want the lambda system to work on your CIS, find someone who could fix it. It could also run without the lambda but the fuel efficient would be down. If I were you, I'll try to get the ECU/OXS, & FV to work and have a more efficient engine. Last resort, is to have it running less the lambda system. Both doable by DIY'ers. Keep us posted.

Tony

[T77911S]

turn the key on. if you hear the fuel pump running, you disconnected the safety switch. only remove that for testing purposes.

your starting issues could be a lot of things, first of all air leaks.
try to find a mechanic that knows CIS and get things working as they should.

[Bob Kontak]

The airflow switch is on the back of the sensor plate unit. It is not a quick disconnect. Yours comes loose because the plastic on the wire side connector is broken or the metal clip is missing. The side that connects to the air sensor is pretty solid.

[Gunter]

Originally Posted by delkins

i had a issue a few months ago with my 82sc, with hot starting and such, i replaced the accumulator and fuel filter, i guess i have some issues with my frequency valve also my mech said to just disconnect it which has been done the car seems to run ok but does not start on first crank always starts on second crank no problem i get a puff of white smoke on start up and it smells like its rich on start up smoke goes away after a min or so, guess what i'm asking does the frequency valve need to be hooked up to run correctly mech said its just a safety item if your in a crash to shut fuel off?

Reconnect the Airflow Switch (careful with the wire clip!) and solve the hot-start issue which is usually the check valve outside or inside the fuel pump or the accumulator and in rare cases the check valve in the FD.

The Lambda CIS works best with ALL components connected like Tony says. Paul (psalt) recommends disconnecting and plugging the vacuum retard line on the ignition distributor for better performance.

Find a different mechanic/shop that really understands the Bosch K-Jetronic CIS. Disconnecting the safety switch should have no effect on performance other than having the pump run steady with ignition ON prior to start.

[Peter Zimmermann]

delkins, here is what you can do, without your mechanic.

1. Raise engine lid,
2. Loosen two rubber straps for the air filter cover, and lift off the filter,
3. Turn on ignition, do not crank/start engine,
4. Reach into the open air box, locate the bend of the sensor plate arm (a curved metal piece that is the only obvious, easy to see, component inside the plastic air box). Lift that arm, gently, about an 1/8" to a 1/4", and then quickly release it (its possible to flood the engine doing this so be quick!). While the arm was raised did you hear the FV buzz?

...yes. The freq valve system is functional.
...no. The freq valve system must be diagnosed.

Post what you find. BTW; the symptom for a faulty/not functional freq valve is hard cold starting, and very bad running for the first five or six minutes following a cold start - unless someone has tried to put a bandage on cancer and set up the fuel mixture to work without the valve (very bad technique).

[boyt911sc]

Originally Posted by Peter Zimmermann

delkins, here is what you can do, without your mechanic.

1. Raise engine lid,
2. Loosen two rubber straps for the air filter cover, and lift off the filter,
3. Turn on ignition, do not crank engine,
4. Do you hear a prominent buzzing noise to the left of the throttle body?

...yes. Frequency valve is functional.
...no. Reach into the open air box, locate the bend of the sensor plate arm (a curved metal piece that is the only obvious, easy to see, component inside the plastic air box). Lift that arm, gently, about an 1/8" to a 1/4", and then quickly release it (its possible to flood the engine doing this so be quick!). While the arm was raised did you hear the buzzing?

...yes. The freq valve system is functional.
...no. The freq valve system must be diagnosed.

Post what you find. BTW; the symptom for a faulty/not functional freq valve is hard cold starting, and very bad running for the first five or six minutes following a cold start - unless someone has tried to put a bandage on cancer and set up the fuel mixture to work without the valve (very bad technique).

Peter,

Why would the FV get energized when you turned the igntion switch @ ON position (not START)? I can't find in the wiring diagrams that could make the FV to run by just turning the IS @ ON. Would really appreciate your help to understand why the FV got energized. Thanks.

Tony

[Peter Zimmermann]

Originally Posted by boyt911sc

Peter,

Why would the FV get energized when you turned the igntion switch @ ON position (not START)? I can't find in the wiring diagrams that could make the FV to run by just turning the IS @ ON. Would really appreciate your help to understand why the FV got energized. Thanks.

Tony

Boy, did I ever screw that post up! I will edit it now, thanks for the heads-up!

To all who are interested, post #9, this thread, has been edited. Please do not read the quoted piece in post #10!

[Gunter]

Tony beat me to it.

delkins,

Under the passenger seat it the Lambda brain and there is an important relay and because of location, things get neglected and rust is the result.

When the relay fails, the FV stops working and the idle/running gets real bad. I recommend that you carefully pull off the relay, inspect the pins for rust, clean it, add some dielectric grease or Vaseline to the pins and re-insert. Your '82 also has an Accelleration Enrichment Control Unit as part of the ECU under the seat. Keep the area clean.

The fuse for the Lambda relay is #18 (Clock, Interior lights, etc.)

[Vincent Hill]

Also part of this is the throttle switch. the little one with the 2 wires and arm that is pushed up and closed when the throttle is closed. Porsche no longer makes / sells that switch but it is still available on line for an Audi and a few other cars. If you need one, I can look up the part number and where I bought my last one. This has a lot to do with starting and the power the engine makes while warming up. (I am sure I will be corrected if I missed anything on this ) Bob & Tony are pretty sharp and I also agree with everyone that you MUST find someone else that understands how this all works because I have NEVER heard anyone say disconnect the Frequency Valve which has a lot to do with performance other than WOT (Wide Open Throttle)

[Bob Kontak]

Here is a pic of my new relay Gunter speaks of. The factory one has a prong on it to fasten it to the Lambda box. It is right at the front of the passenger seat. Easy access.



Also, the frequency valve connection to the Lambda box runs through the pictured wire connector. I have read of one situation where the pin/socket connection was corroded and interrupted the signal. Just deep back-up if the basics have you stumped.

[Bob Kontak]

Originally Posted by Vincent Hill

I have NEVER heard anyone say disconnect the Frequency Valve

My two cents is that this is just a terminology miscommunication. Delkins did note the sensor switch falls off from time to time and the car would not run well at all if the freq valve was "dead".

Here is a link to a new standard connector that has the correct boot and retaining wire.

AMP Connectors and Terminals

Here is the thread it came from.

Where to buy an individual fuel injector electrical connector?

[Bob Kontak]

Originally Posted by Vincent Hill

Bob & Tony are pretty sharp

Thanks Vincent. My advice error frequency is too high. Tony's data is consistently correct - even when it does not solve a particular problem.

[boyt911sc]

Originally Posted by Peter Zimmermann

Boy, did I ever screw that post up! I will edit it now, thanks for the heads-up!

To all who are interested, post #9, this thread, has been edited. Please do not read the quoted piece in post #10!

Peter,

I like to do the test without dumping unnecessary amount of unburned fuel in the intake manifolds by running the FP (bridging terminals #87a & 30; Ign. SW @ ON). Would you agree or disagree that it is a more appropriate procedure than lifting the AFS (air flow sensor)? Please comment.

BTW, it was not easy for me to make a post contradicting a 'guru' that I have high regards. Every time I read your posts, I always learned something from it. Please continue to help us learn and continue our education. Thanks.

Tony

[Vincent Hill]

Originally Posted by Bob Kontak

Thanks Vincent. My advice error frequency is too high. Tony's data is consistently correct - even when it does not solve a particular problem.

I have seen and driven your car and know how well it runs. Notta with Tony's Also your car jinxed my car! In Columbus the drivers side window had a problem and when I got home It needed a new bottom lift rail. With everything installed the window came down OK but "Went up slowly"! Do you know anything about a passenger window going up slowly??

[Bob Kontak]

Originally Posted by Vincent Hill

Do you know anything about a passenger window going up slowly??

Chill, Vincent. Best you talk only when you have your facts straight.

Bob's Window.AVI - YouTube

Edit - crank up the volume!!!!

[delkins]

ok thanks for all responses i called the mechanic, yea its not the freq valve that disconnected, but the safety switch, he said car would not run with freq valve disconnected, the car takes like 2-3 times to start and yes runs a little herky jerky untill warmed