2.7 will not run well after CIS rebuild

[Ginger77]

Yes. I read all of the links. In the end I found the same user stating elsewhere that the vibrating persisted and he found his ignition box was the culprit. However, there was another person that blamed the gauge. I'll go back to my larger pressure test kit.

Is there any way I can test the thermovalve or would you suggest me to reroute the vacuum lines and take the thermovalve out of the equation for now?

I suppose I'll install the new TTS too. Assuming it works in spec despite me not getting any resistance values with my multimeter.

[pmax]

If you’re asking what I would do if this were my car, I would remove the darn thing, set the CCP/WCP per no/vacuum spec respectively and see how it idles cold and warm but not suggesting you do the same lest angering the Porsche gods, it’s up to you.

[boyt911sc]

Originally Posted by pmax

...........(edited)...........

So, I would consider eliminating it from the puzzle by taking it out, just for testing purposes, although many do it permanently since it is apparently for emissions and can hang up your throttle on lifting. Porsche got rid of #4 in later versions of the CIS.

Good luck !

That is not correct. The thermovalves were still used to the last ‘83 SC’s using vacuum assisted WUR’s (-069/-089) and and the SC’s with lambda system switched to non-vacuum assisted WUR’s (-072/-090). Thermovalves are used with vacuum assisted WUR’s.

The decel valves that are out of spec or defective cause premature valve opening during heavy deceleration. The solution is to fix and recalibrate the decel valve instead of removing them. The lack of understanding how the decel valves operate and how to correct the problem resulted to their elimination or removal from the system.

This is like having a patient coming to your clinic limping with a bad or swollen foot, instead of diagnosing the problem you decided to amputate the bad foot to eliminate the problem. Now, you made a bad situation worse.

Tony

[pmax]

Originally Posted by boyt911sc

That is not correct. The thermovalves were still used to the last ‘83 SC’s using vacuum assisted WUR’s (-069/-089) and and the SC’s with lambda system switched to non-vacuum assisted WUR’s (-072/-090). Thermovalves are used with vacuum assisted WUR’s.

Unless there's a thermo valve in my 80, it's absolutely correct.

The decel valves that are out of spec or defective cause premature valve opening during heavy deceleration. The solution is to fix and recalibrate the decel valve instead of removing them. The lack of understanding how the decel valves operate and how to correct the problem resulted to their elimination or removal from the system.

This is like having a patient coming to your clinic limping with a bad or swollen foot, instead of diagnosing the problem you decided to amputate the bad foot to eliminate the problem. Now, you made a bad situation worse.

Tony

Decel valves function during deceleration and are supposed to get out of the way, doing nothing otherwise. The failure of the latter non-function is where it matters to me.

[Ginger77]

So, I spent some time after work and dinner taking items off and inspecting. First up was the FD and I soon discovered the plunger was not sticking. It felt well lubricated so it can't have been the culprit. I took out the fuel pressure regulator and that felt fine too. I took out the assembly, inspected, assorted the shims and put it all back together. For reference, there's 4 shims in there that measure 3mm in total. I put in 2 more during the rebuild to see if I could get the pressure near to 5 bar but it remains in the 4.5-4.7 bar region. That was the case with the old Bosch pump and filter as well as with the current Pierburg pump and new Mahle KL-25 filter.

I also checked the metering plate height. However, after rereading the Robert Bosch manual it states the metering plate height should be measured in the presence of control pressure. I thought I had found a low metering plate but I'm afraid it will rise when the FD receives pressure and is probably in spec. Correct? I need to check when the FD is back on.



Lastly, I took out the little pressure gauge. Tomorrow I intend to put stuff back together and test pressure with the larger pressure gauge from my kit. However, by now I have tried and tweaked all the settings of CIS. That also goes for the throttle body. Is there a base setting for the throttle plate stop screw and the idle screw?



I'm noticing 3 visible threads on the stop screw and now that I took the rubber top piece off I can look into the TB. How far should the idle screw reach? This might be an irrelevant question with regards to my issues but there's nothing wrong with trying to get a good starting position



All in all, I can't pinpoint the issue. I would very much appreciate any thoughts and input.

[47silver]

If gauge used nylon it may pulse. Need to use polymid

[Ginger77]

It's PA hose

[boyt911sc]

Originally Posted by Ginger77

So, I spent some time after work and dinner taking items off and inspecting. First up was the FD and I soon discovered the plunger was not sticking. It felt well lubricated so it can't have been the culprit. I took out the fuel pressure regulator and that felt fine too. I took out the assembly, inspected, assorted the shims and put it all back together. For reference, there's 4 shims in there that measure 3mm in total. I put in 2 more during the rebuild to see if I could get the pressure near to 5 bar but it remains in the 4.5-4.7 bar region. That was the case with the old Bosch pump and filter as well as with the current Pierburg pump and new Mahle KL-25 filter.

I also checked the metering plate height. However, after rereading the Robert Bosch manual it states the metering plate height should be measured in the presence of control pressure. I thought I had found a low metering plate but I'm afraid it will rise when the FD receives pressure and is probably in spec. Correct? I need to check when the FD is back on.

Diederick,

It would be the other way around. When the FD is under pressure, the plunger will have the control pressure pushing it downward not upward as you stated. The rest position of the sensor plate is determined by the “pin stop” located under the sensor plate.

Tony

[Ginger77]

Hi Tony, thanks for chiming in. You may have made a very good point. If the plate lowers even more then it's definitely out of spec. I will assess this later today.
Unfortunately I forgot to take a photo but I'm rather sure my sensor plate is adjusted with a screw from underneath. With that screw it seems I can push the plate up from the arm and then lock the screw again with a tiny nut.

[boyt911sc]

Originally Posted by Ginger77

Hi Tony, thanks for chiming in. You may have made a very good point. If the plate lowers even more then it's definitely out of spec. I will assess this later today.
Unfortunately I forgot to take a photo but I'm rather sure my sensor plate is adjusted with a screw from underneath. With that screw it seems I can push the plate up from the arm and then lock the screw again with a tiny nut.

Diederick,

Correct.

Tony

[pmax]

Originally Posted by boyt911sc

The decel valves that are out of spec or defective cause premature valve opening during heavy deceleration. The solution is to fix and recalibrate the decel valve instead of removing them. The lack of understanding how the decel valves operate and how to correct the problem resulted to their elimination or removal from the system.

This is like having a patient coming to your clinic limping with a bad or swollen foot, instead of diagnosing the problem you decided to amputate the bad foot to eliminate the problem. Now, you made a bad situation worse.

Tony

Spare me the haranguing. The decel valve delete predates you.

You know what the official fix for an errant decel valve is for the later CIS systems ... crush the pancake, yes, just crush it, just the pancake, not the nipple mind you, but crushing it nevertheless.



There's the precision recalibration for you as instructed by Porsche themselves.
More goodies here ... SC decel valve woes

Back to Ginger !

[Ginger77]

I had a bit of time this morning. I put the FD back on and adjusted the mixture with the other method of undoing one injection line, watching for fuel as you go clockwise and then back off a half turn.

This took me a little longer as for some reason I have a habit of mostly over tightening bolts with copper washers. After cleaning up some fuel spillage and renewing all of the copper washers I hit the Google and found that M8 likes a torque of 9Nm and M10 17Nm this did the trick and all was good.

I then raised the meeting plate. The thread is super fine so it may not look much but I gave it more than a full rotation. How does this look?

After this I checked the cold control pressure with the gauge from the kit and only got 0.5 bar instead of the 1 bar that the small gauge showed. I then ran out of time so I decided to check pressures tomorrow. I have two manometer gauges so I'm going to double check whatever reading I get.

[Paulporsche]

I tested my thermovalve by removing it from the car and applying a 12v dc power supply to it. When cold (ie no power) you shouldn't be able to blow through it. With power you will able to blow through it after about 25 seconds or so.

The thermovalve comes into play to prevent vacuum from pulling on the lower chamber of the WUR, thereby richening the mixture for a cold start.

[boyt911sc]

Originally Posted by Paulporsche

I tested my thermovalve by removing it from the car and applying a 12v dc power supply to it. When cold (ie no power) you shouldn't be able to blow through it. With power you will able to blow through it after about 25 seconds or so.

The thermovalve comes into play to prevent vacuum from pulling on the lower chamber of the WUR, thereby richening the mixture for a cold start.

Paul,

You can not use pressurized air to test a thermo-time valve and obtained a valid conclusion. I thought the same before I realized that the test was flawed. Instead you need to use vacuum. I had a post regarding this test.

Try it with a good and bad TTV using pressurized air and you will be surprised with your test result because some of the good TTS would fail the positive pressure test but works well with vacuum. It has to do with the design of the disc valve.

Tony

[Paulporsche]

Good to know. Thanks Tony.

In my situation, I tried both sucking and blowing alternatively to test mine. Unfortunately, as I mentioned to you when we discussed this, I think I have lost my diaphragm, so the result was the same.

But, as you point out, since this is a vacuum limiting device, the test should be done using vacuum.

[Ginger77]

I'm not quite sure I understand the method. What is the procedure to test the TV? I can pull a vacuum with my available tools. I have reinstalled my old TTS and I will return the new item if all works well.

[Paulporsche]

Diederick,

If you attach a vac line to the front of the TV where the vac was originally applied you should find you will not feel the vac from the other nozzle when the engine is cold. If you energize the TV you will feel the vac pulling through after about half a minute as the unit warms from the elec current and opens up its diaphragm. I did mine off the car using a 12v source but I don't see why this couldn't be done in situ, since its operation occurs while starting. I think I would just feel for no vac then followed by vac at the line that attaches to the WUR as the engine turns over/starts.

Tony,

I know you test all these components extensively. If you have a different or better procedure, please let us know.

EDIT: I see from 47Silver's PET diagram that the line from the TV goes to the top of the WUR on a 77. On my car, which has an 80 engine set up like a 78/79 with a different WUR, the line goes to the side of the WUR.

[47silver]

this is from the pet.
are all connections properly done?

i mentioned earlier that I was able to adjust the throttle plate by laying in cigarette rolling paper around the inside of the throttle body and that set the plate tolerances properly. I wetted the paper a bit so it would stick.

[boyt911sc]

Originally Posted by Paulporsche

Diederick,

If you attach a vac line to the front of the TV where the vac was originally applied you should find you will not feel the vac from the other nozzle when the engine is cold. If you energize the TV you will feel the vac pulling through after about half a minute as the unit warms from the elec current and opens up its diaphragm. I did mine off the car using a 12v source but I don't see why this couldn't be done in situ, since its operation occurs while starting. I think I would just feel for no vac then followed by vac at the line that attaches to the WUR as the engine turns over/starts.

Tony,

I know you test all these components extensively. If you have a different or better procedure, please let us know.

EDIT: I see from 47Silver's PET diagram that the line from the TV goes to the top of the WUR on a 77. On my car, which has an 80 engine set up like a 78/79 with a different WUR, the line goes to the side of the WUR.

Paul,

This is how I bench test a TTV (thermo time valve). I call these thermo time valve because it operates under a certain period when energized. And the duration or time involved range from 20 sec. to 30 sec. based from my collected data over the years.

These are some of the thermo time valves in my collection that passed the tests. The bad ones were segregated and stored separately.


The first test is to hook up a hand held vacuum pump and determine if the TTV is good or bad. A 16” Hg is an arbitrary value that I use for vacuum testing WUR & TTV. Look at the gauge, the vacuum should hold or stay steady. And the vacuum test hose is connected to the middle nipple (see picture below).


If it could not hold the vacuum for several seconds, it is leaking and deemed defective. The second test is to apply 12 volts to the TTV and observe how long before the valve opens up. You could hear the valve pops open and watch the vacuum gauge reading drops to zero.

Tony

[Ginger77]

Thank you. I will apply a vacuum to the TTV with my hand pump and see if it holds. Then once the engine is running I'll check to see if it's pulling a vacuum from the WUR by taking the hose of the WUR and putting my finger on it. I doubt it's defective since it came in its original Porsche packaging, never opened, but there's no harm in checking.

And yes, I have used that exact same diagram as a guide for the routing of hoses.

Any opinions on the positioning of my metering plate? It's hard to measure 0-0.5mm into the bowl. Perhaps I can use a feeler gauge as there's not enough room to slide my callipers in. As far as the idle screw and TB stop screw go, I think I'm in the ballpark.

So the next job is to test the TTV. Recheck the plate heights. Swap out my manometer for the quality WIKA brand one, retest fuel pressures and adjust if necessary. Then start the engine and see where we're at. How do you feel about starting the engine when you've tested WCP? I feel it's kind of hard to start a cold engine when the fuel pressure is at warm state. The other day I did this and I had disconnected the AAR during fuel pressure testing. So, lean mixture and extra air did not make for a happy engine. Should I let the WUR cool down first?