CIS pressure testing

[Mysterytrain]

wow this thread makes my head hurt...Adam go here:
http://members.rennlist.com/jimwms/CIS/CIShome.html

Thermal valve:
Holds off vacuum from the warm-up regulator when engine is started cold ('77 - '79 engines). Power is applied to the thermal valve when engine is started, and approximately 30 seconds later, the valve opens. When the valve is open, vacuum to the WUR is then determined by the intake manifold. --The vacuum holdoff results in a mixture richening at warmup. The inner hose connects to the intake vacuum source and the outer hose to the WUR.

Safety switch on air flow sensor:
This switch prevents fuel pump from running when ignition key is on and the engine is not running.

Operation of the '76 and later relay:

The relay has two sets of contacts - Normally Open (NO) and Normally Closed (NC). In electrical lingo, "Normal" infers no power on the relay coil. On the basic Porsche round relay, pin 87 is NO, pin 87a is NC and pin 30 is the "arm" of the contact that switches between the two.

Relay Connections:
The fuel pump is connected to pin 30 of the relay socket. (Note that you can't jumper power to the fuel pump by jumpering +12 Volts to a fuse on the fuse panel. The fuse which protects the fuel pump is in the wiring that goes from the NC contact to the ignition switch). +12 Volts from the starter terminal of the ignition switch goes to the NO contact and +12 volts from the "Run" terminal goes to the "hot" end of the relay coil (pin 86) and to the NC contact. The "cold" end of the relay coil (pin 85) goes to the Safety Switch on the air flow sensor housing, and the other contact of the Safety Switch goes to ground. The switch is closed when the airflow sensor plate is at rest (engine not running).

Operational Sequence:
Ignition switch turned to "Run" (Not Start) - Relay energized. Relay contact pulled to the NO position.

Ignition switch turned to "Start" - Starter voltage goes to fuel pump through the NO contact. Fuel pump runs while engine is cranked.

Engine starts and ignition switch released from "Start" position - The Safety Switch opens as the air flow sensor plate rises off its stop. This de-energizes the relay coil, and the relay arm flips back to NC, sending voltage from the "Run" terminal of the ignition switch though the fuse and through the NC contact to the fuel pump. Engine is running, fuel pump is running.

Engine dies due to accident or other malfunction - Airflow sensor plate goes to its stop, closing the Safety Switch, and energizing the fuel pump relay (remember the ignition is still on). Relay pulls the contact back to the NO position. But since there is no voltage on this contact from the starter, fuel pump is disabled.

Control pressure regulator (also called Warm Up Regulator):
Drops control pressure when engine is cold, resulting in a richer mixture during warm up. . The term warm-up regulator is a bit of a misnomer in that this component actually regulates control pressure the entire time the engine is running. It changes the pressure during the warm-up period. Power is applied to bimetal strip in the regulator when fuel pump is on. As the internal resistor heats up the strip, the control pressure supplied to the fuel distributor increases, leaning the fuel mixture. On cars with vacuum control, the WUR enriches mixture under load determined by lower intake manifold vacuum. Some versions also modify pressure with altitude. Lambda sensor systems don't use the vacuum chamber because of this adjustment being automatically accomplished by the lambda system electronics box. '81 saw a change in the internal resistor configuration for the WUR. A second resistor was added to heat the bimetallic spring, controlled by a bimetallic switch. This allows the mixture to lean out more quickly after start-up,about 2 minutes compared to the former 3 minutes.

[Gunter]

Good stuff, Ron.
Exactly as you describe.

Just came back from Seattle with my 915. JW applied his magic and did some surgery on it.
Winter project is to mate the "new" 915 to the SS 3.2 I built and swap it for my current 3.0. For the SS 3.2, you may remember that I use the CIS from a '78 on top of an '82 bottom with 98mm P/C's, 964-cams, SSI's.................
I plan to just run it briefly and wait for Spring to run it hard to seat the rings. I'll keep the 3.0 for a while but may sell it at some point.
Of course, no TTV on my set-up, just the correct WUR.
Did you keep the TTV on yours?

[boyt911sc]

Originally posted by Gunter
Walt: Here is how it works: When you turn the key to start, the yellow wire from the ignition lock wired to the Solenoid, energizes the Solenoid; engine cranks. At the same time, the second yellow wire on the Solenoid is wired to the TTS, energizes the TTS and for a few seconds the TTS sends 12V to the Cold Start Valve (CSV)
Meaning: At the moment of start/cranking, there is a continuous current from ignition lock to Solenoid-TTS-CSV.

My humble apologies to Adam. I should have recognized from his replies that we are dealing with genius, a real wizzard.

Dr. Gunter,
I spent an hour analyzing and reviewing the electrical diagram ('78SC-US model) regarding your information as stated above.

My observation is that the thermo-time switch (TTS) does not energize the cold start valve (CSV) or sends 12 volts power to it. Rather acts as a timer-switch device. Meaning that the bimetal- heater limits the duration of the valve operation (time) or on-off switch to ground the circuit (thermo).

The TTS and the CSV are connected in parralel thus get energized simultaneously by the yellow wire during start-up. My CIS experience is limited and would like to know more. Thanks.

Tony

[Gunter]

Sounds good.
I think Porsche intended that the CSV would only activate during cold-start. That's why the TTS is mounted on the chain cover to sense the engine temp. When hot, the timer is out of the loop, I think.

[T77911S]

the TTS is in series with the CSV. it acts like a light switch in your house except it is controlled by temp.

[adamb113]

O.k. Back from Vaca. Turns out my home town of Danvers, MA blew up while I was gone. Chemical factory exploded. Equivalent of 2000 ton bomb. Key word so far being that I was "GONE" ( as in not around, not my fault). My house was 2.5 mles from ground zero. Just a little cracked plaster, no broken windows.
Here are the figures on the car
Cold Sys pressure 4.8 bar. Spec is 4.5 - 5.2 So OK there
Cold Control press is 1.2 bar. Spec is 1.6 - 2.9 So a little low
Hooked warm up connector back up to CPR
2.8 bar after 6 minutes. spec is 3.4 - 3.8 So very low
Checked supply voltage at connector and it's 11.4 volts. o.k.
So only other thing that could cause this condition other than bad CPR is restriction in return line. I imagine the only way to check this is to disconnect it at the tank and measure the flow. Looks like it should be about 750cc in 30 sec. Seems unlikely.Worth doing? Ever heard of that happening? Just replace CPR?
Ideas or input?
Thaks,
Adam

[T77911S]

a restriction would cause a HIGH pressure.
connect a vacuum pump to the WUR and pull a vacuum with the car warm. pressure should go up. if u dont have one, go to advance or auto zone, it is worth the money.

[dweymer]

Restriction in a return line, or blockage in the WUR would cause high pressure, I just went through that.

What are the abient(sp?) temps, but it seems you just need to pull the plug out of the WUR a bit due to cold AND warm being low.

[KFJ_SC]

From my (albeit limited) knowledge the plug only affects the cold control pressure. There is a thread about an adjustment screw that affects warm control pressure.

[Gunter]

Carefully check/clean the screen in the line to the WUR. Any dirt?

[Ferrariguyma]

Adam is helping me with my CIS unfortunately he is home sick today. We spoke breifly on the phone and he mentioned I might want to price a CPR for my SC. I searched the parts section on Pelican and found no such thing. Is the CPR the same as the WUR? If not anyone know where I can buy a CPR?

Thanks to all who have offered us help and advice! I hope to be driving the car soon!

Andrew

[JohnKo]

Andrew,
CPR is Control Pressure Regulator which, I believe, is Bosch-speak for what many people call warm-up regulator of "WUR."

Good luck!

[Gunter]

Originally posted by JohnKo
Andrew,
CPR is Control Pressure Regulator which, I believe, is Bosch-speak for what many people call warm-up regulator of "WUR."

Good luck!

Yeah, and very pricy. You want to be sure that you need a WUR by checking the Control Pressure first.

Is someone just guessing here?

[Ferrariguyma]

Adam, told me not to buy it. He knows I am trigger happy to buy new parts. He just suggested I price and locate one just in case. He is down for the count with a cold. When he gets back to my car he will let me know if I need a WUR after he runs more tests.


Hopefully I won't! Does anyone know of the best place to buy one in case I do need a WUR?

Thanks again

Andrew

[Ferrariguyma]

My car has a custom center fill tank I bought from TRE. Could this be causing some of the problems I am having? Is there such a thing as a CIS fuel tank? The center fill I bought from TRE does have a return tube and seems to have all of the same connections the original factory tank had. Just wondering if this could be part of my problem.

Thanks

Andrew

[adamb113]

Gunter,
Where is the screen located that you are suggesting I check?
Dweymer,
"but it seems you just need to pull the plug out of the WUR a bit due to cold AND warm being low."
What plug?
KFJ_SC,
A warm up adjustment screw? Where is this? Never heard of it.

My Bosch book was very quick to say to replace the WUR/CPR if the pressures were low and there was good fuel supply and voltage to the connector. Are there any other references that have more detail as to analyzing it in more detail cleaning it/adjustments. Is Bosch just trying to generate revenue or is it really not that repairable? I should probably look at some of the threads you guys have pointed out. Any one in particular that focuses on this issue past what we have discussed.

Gunter,others,
What is your recommened list of actions I should take on Sat to get a better diagnosis?

Thanks,
Adam

[Gunter]

Originally posted by adamb113
Gunter,
Where is the screen located that you are suggesting I check?

I BELIEVE THERE IS A SMALL SCREEN IN THE FUEL LINE ON THE WUR, OTHERS MAY CONFIRM.
Dweymer,
"but it seems you just need to pull the plug out of the WUR a bit due to cold AND warm being low."
What plug?
THEY ARE REFERRING TO AN ADJUSTABLE "PLUG" IN THE WUR. IT'S A MODIFICATION THAT REQUIRES DRILLING AND TAPPING.
DO A SEARCH.

WUR Adjustment Plug

Modified my WUR

KFJ_SC,
A warm up adjustment screw? Where is this? Never heard of it.
SAME THING AS ABOVE. PAY ATTENTION TO WHAT JW SAYS IN HIS REPLIES.

My Bosch book was very quick to say to replace the WUR/CPR if the pressures were low and there was good fuel supply and voltage to the connector. Are there any other references that have more detail as to analyzing it in more detail cleaning it/adjustments. Is Bosch just trying to generate revenue or is it really not that repairable? I should probably look at some of the threads you guys have pointed out. Any one in particular that focuses on this issue past what we have discussed.

THE BENTLEY MAY SERVE YOU BETTER IN THIS CASE.

Gunter,others,
What is your recommened list of actions I should take on Sat to get a better diagnosis?
MAKE SURE THE WUR GETS POWER. CLEAN THE SMALL SCREEN IN THE LINE TO THE WUR. USE THE PRESSURE TESTER TO DETERMINE COLD AND WARM PRESSURE.

Thanks,
Adam

[T77911S]

put a vacuum pump on the WUR. it should increase pressure with an increase in vacuum. that will also check that the diaphram is good. it should hold a vacuum.
my brother tried adjusting his WUR, finally just went and bought a new one and it fixed hard starting and overall running.

[dweymer]

Got my WUR adjusted!!!
System pressure-4.75bar
Cold control-2.25
Warm control-2.9

Thanks ALL.

Now on to the idle & mixture

[Gunter]

Originally posted by dweymer
Got my WUR adjusted!!!
System pressure-4.75bar
Cold control-2.25
Warm control-2.9

Thanks ALL.

Now on to the idle & mixture

Adjusted?
What exactly did you do?