CIS Pressure Test Quick Question

[Bill Jennings]

Im in the middle of testing the fuel pressure values on my 77 Carrera 3. I've done the three cold engine tests.
Ambient temp = 65 f
1. Cold engine, WUR unplugged, valve closed 4.8 bar, 70 psi
2. Cold engine valve open, WUR unplugged 1.1 bar, 16psi
3. Cold engine, valve open WUR plugged in 2.7 bar, 39 psi

I'm now ready to do the hot engIne tests.
Do I drive the car with the jumper test Rig still on the fuel pump relay socket or do I put the relay back in as normal?

It's probably a stupid question but I've not done this before.
I'm assuming I put the relay back in before doing this but wanted to check first.

Cheers

Bill

[Bill Jennings]

I decided to drive car with relay back in.
Hot engine results

Engine running at operating temp relay in test valve open 3.5 bar 50 psi
Following results all with engine off and test valve open
10 sec 2.2 bar 32 psi
1 min 2 bar 30psi
4 min 1.8 bar 26 psi
8 min 1.7 bar 25 psi
10 min 1.65 bar 24 psi
15 min 1.6 bar 23 psi
20 min 1.5 bar 22 psi
30 min 1.4 bar 20 psi

The symptoms I'm addressing are slow idle (750 rpm) at cold start
Occasional non start when engine very hot.
Occasional idle stuck at (2000 rpm) when engine very hot.
I have the original 5 blade fan and the hot issues occur after being stuck in traffic on a hot day. My oil temp gauge does not work so I am unsure how hot this engine gets.

Cheers

Bill

[boyt911sc]

Originally Posted by Bill Jennings

Im in the middle of testing the fuel pressure values on my 77 Carrera 3. I've done the three cold engine tests.
Ambient temp = 65 f
1. Cold engine, WUR unplugged, valve closed 4.8 bar, 70 psi
2. Cold engine valve open, WUR unplugged 1.1 bar, 16psi
3. Cold engine, valve open WUR plugged in 2.7 bar, 39 psi

I'm now ready to do the hot engIne tests.
Do I drive the car with the jumper test Rig still on the fuel pump relay socket or do I put the relay back in as normal?

It's probably a stupid question but I've not done this before.
I'm assuming I put the relay back in before doing this but wanted to check first.

Cheers

Bill

Bill,

I've done driving the car several times with the CIS gauge attached and the FP relay in place. But I don't recommend it for safety reason. Just run the engine at idle for several minutes until the warm control stabilizes. What controls the WCP (warm control pressure) is the amount of force applied by the spring/s inside in the WUR to the diaphragm valve with bi-metallic metal fully deflected. The state where the WCP is maximum is attained well below the operating temperature of the engine which is primarily controlled by the deflection of the heated bi-metallic spring. Once the bi-metallic is fully deflected, the added engine heat contributes in subsequent increase in WCP. Between 5 - 10 mins. depending on ambient temperature, the WCP could be attained. These were based on several tests in the past.

Tony

[Bill Jennings]

Tony,
I read on Jim's CIS Primer that I should do these leak down tests with a hot engine if you have a hot start issue as the heat may show a quicker leak down and I am chasing a hot start issue as one of my symptoms.
I was careful to ensure everything was tight and cable tied down before going on a drive but must admit to being nervous about it and did have the fire extinguisher ready on the passenger seat!

Can anyone comment on the test results please.

Pressure after 60 min was 1 bar by the way!

Cheers

Bill

[boyt911sc]

Originally Posted by Bill Jennings

Im in the middle of testing the fuel pressure values on my 77 Carrera 3. I've done the three cold engine tests.
Ambient temp = 65 f
1. Cold engine, WUR unplugged, valve closed 4.8 bar, 70 psi
2. Cold engine valve open, WUR unplugged 1.1 bar, 16psi
3. Cold engine, valve open WUR plugged in 2.7 bar, 39 psi

I'm now ready to do the hot engIne tests.
Do I drive the car with the jumper test Rig still on the fuel pump relay socket or do I put the relay back in as normal?

It's probably a stupid question but I've not done this before.
I'm assuming I put the relay back in before doing this but wanted to check first.

Cheers

Bill

Bill,

Do you remember how long it took to get this control pressure (39 psi.) reading after plugging the electrical connection? Your residual fuel pressure seems odd because the pressure seems to stay 'forever' in the system specially the last 10 mins. Have you checked for air/vacuum leak? Keep us posted.

Tony

[Bill Jennings]

Tony,
I don't know specifically as that wasn't something I recorded but it was less than a minute. I think the pressure rose slowly at first, then sped up and finally levelled off.
I have not checked for vacumn leaks but will do so.
Thanks
Bill

[Bill Jennings]

Tony,
I've sprayed ether over anything I can see that is vacumn related without effect.
I note that the engine stalls if I spray ether into the intake and that the idle doubles from 1000 rpm to 2000 rpm when I pull the vacumn hose off of the distributer.
I also note that the idle does not change if I pull the fat vacumn hose off that goes from the WUR to the intake boot (at the intake boot)..

I've also just noticed a oily mist coming from the oil tank breather where it is connected to the airbox.

Cheers
Bill

[Vereeken]

Bill,

My residual pressure stays also long in the system (up to 3 hours). It does not give me any grief.

I do believe that you should look for a quick drop after shutdown and then you need to watch that it is at least 1 bar after 20 minutes.

I am suspecting you have a distributor with vacuum advance AND retard?

I assume the vacuum hose from WUR you are describing is the Vent to atmosphere?

Michel

[Bill Jennings]

Vereeken,

I believe I do have vacumn advance and retard on the distributer though I think the vacumn goes to the top of the throttle body, I apologise for the wrong terminology earlier.
I'm unable to post pics as Ive been unable to upgrade to the latest OS on my iPad and my wife drowned my laptop!

It was suggested to me that I should check the springs in my distributer but I havnt done that yet.

Thanks Bill

[wasserkuhl]

Originally Posted by Bill Jennings

Vereeken,

I believe I do have vacumn advance and retard on the distributer though I think the vacumn goes to the top of the throttle body, I apologise for the wrong terminology earlier.
I'm unable to post pics as Ive been unable to upgrade to the latest OS on my iPad and my wife drowned my laptop!

It was suggested to me that I should check the springs in my distributer but I havnt done that yet.

Thanks Bill

email the pics to me again Bill, I'll upload them.

[Vereeken]

[QUOTE=Bill Jennings;7068069It was suggested to me that I should check the springs in my distributer but I havnt done that yet.

Thanks Bill[/QUOTE]


I was going to suggest something similar but easier. Simply detach the vacuum retard from the distributor and plug that line with a golf T.
Start from cold and see what the revs say.

There is also a nice thread called "Distributor clean and lube real easy" you might want to follow up.

I think the high revs when hot are something unrelated to your WUR. It indicates an AAR that is stuck open (doubtfull as you do not have it all the time) or a decel valve of which the membrame is torn. But we need a picture to determine what kind of Decel valve you have.

I believe from what I can read that your cold and warm problems are unrelated.

This would be my list assuming you have ruled out vacuum leaks.

For cold problem
1. Disconnect and plug vacuum retard.
2. Remove AAR and check opening of slide door inside AAR. Also note outside temp. Do not start car with AAR removed.
3. take a picture of air throttle plate resting position (air filter removed) when NO pressure is in the system.
4. With zero system pressure move air plate up down. Do you feel resistance? Does the plunger follow the movements. Push it all the way up and let it drop. Does the fuel plunger drop right after (say 1 second after the plate).

For warm problem
1. Stop hot (20 miniutes driving) engine remove AAR and look to see if slide door is completely closed.
2. WIth AAR again installed. Rev engine and let fall to idle disconnect and plug vacuum hose to the decel valve. If rpms change diapraghm is kaput. On SCs i believe 1 out of 3 decel valves has issues. unsure about your model.

Michel

[Bill Jennings]

Wasserkuhl,
Many thanks for the kind offer to post my pics again (I need to make a 50 km round trip to find some wifi to upgrade the iPad & iPhone OS). I'm working all weekend but hope to take these pics Sunday night.

vereeken,

Many thanks for the to do list!
However, I do not think I have a AAR as my car was supplied with a hand throttle but I will look for it. Wasserkuhl reminded me that I had one, I had forgotten as it has never worked since I bought the car. That's another for the to do list!

Cheers
Bill

[Vereeken]

I have no experience with hand throttles but if you have an electric AAR it should be on the right cilinder bank between 4 and 5.

[Bill Jennings]

Vereeken,
I have begun to realise how little I know about my CIS in fact I cannot even identify all of the components yet! I now believe I do have a AAR though. Its possible hand throttle is purely decorative.

Wasserkuhl has kindly offered to post some pictures for me which should identify most of my components.

I have done some but not all of the tasks you suggested so far!

My usual cold start RPM is 700-750 but is 1000 RPM with vacumn line plugged at distributer. That vacumn line needs replacing as it broke when I removed it.

Not read the distributer clean & lube etc thread yet...... But I will!

A pic of my decel valve will be posted soon.

Not checked AAR operation yet but now pretty sure I have one!

Air throttle plate moves freely with no resistance, not sure if the plunger is moving correctly or not.

I am currently wading my way around the various CIS threads Including Jims CIS Primer to get a better understanding and and grasp of the terminology.

Many thanks

Bill

[Vereeken]

Lets see some pictures first. Maybe you have a 77 with UK specs. Would make sense if it is in Australia.

If disconnecting your retard hose on your distributor gives you 250 rpms more it is time to revitalize your distributor or leave the retard hose disconnected. Many seem to do that as it was intended for emissions related stuff.

What is the ambient temp when you do those tests?

If you have an AAR and a hand throttle I suspect your hand throttle actually to be the heating levers not a hand throttle. And that would make sense given your location and year.

Michel

[Bill Jennings]

Michel,
Pics have been sent to Wasserkuhl to upload.
Yes it is a UK 77 I imported it!
I'll have a good look at the distributer after reading that clean and lube thread!
What will leaving the vacumn line plugged do to the rpm when hot?
Maybe a drive in the car will test that though!
I'll redo the tests and record the temp.
I have two hand levers one red handle and one black handle.
The owners manual says the red is heat the black is hand throttle.

Cheers

Bill

[Vereeken]

If you disconnect the retard vacuum from the distributor it will do nothing to performance when driving the car.

If you by chance disconnected the advance from the distributor it will give you a lethargic car in the low rpms but will not damage anything.

But given that you state that the rpms rise when disconnected I guess you have pulled the correct one.

[wasserkuhl]

Pictures as requested...

It seems to me that you car has had the later AAR added at some point, maybe even a full CIS System from a 78/79 911 SC?

Some very late 77 Build Carrera 3.0's had this system from factory, my fathers did when he owned it brand new in 1977.

As it has the Hand throttle between the seats it seems a mystery. Have you confirmed that its a matching #'s car, does it have the correct Crankcase numbers? email me the engine# along with the Case-halve #'s and I can tell you if its the original engine.

Here are the Photos
AAR

Air Throttle Plate

Air Throttle Plate 2

Decel Valve

Fuel Dist

Thermo Time Switch

WUR

[Vereeken]

Hmm, As Wasserkuhl says...

You have an AAR and a decel valve but a WUR without vacuum port on the left hand side.

So I am guessing this is a mix and match car. Nothing to worry about, just will take some time figuring out.

The test list above is still valid.

[wasserkuhl]

Originally Posted by Vereeken

Hmm, As Wasserkuhl says...

You have an AAR and a decel valve but a WUR without vacuum port on the left hand side.

So I am guessing this is a mix and match car. Nothing to worry about, just will take some time figuring out.

The test list above is still valid.

All Porsches from this era were mix and match......some variances evident everywhere.

just need to ascertain the engine# and case halves.

But we now know its a later AAR CIS system and can trace the problems to the broken vacum advance lines and possibly the WUR.

Should simple to rectify the problem now.