2.7 Rough cold/no warm start, stall, CIS troubleshooting and some testing results

[rxtrom]

I know there are countless CIS threads and terrific resources which I have consulted. I am sure I have a few different issues based on the symptoms.

Car: 1971 911T with a 1975 911S engine.

Symptoms:
1. Slow to start Cold, with hand throttle all the way up gas pedal needs to be pressed once engine starts to keep engine from stalling. After about 5-10 seconds the car will stay at 3k RPM.

2. After leaving a destination once the car is warm, it starts much better almost instantly but needs gas pedal pressed a little to keep from stalling, again hand throttle is up to also help from stalling.

3. Sometimes the car will surge while driving.


Tests:
Fuel pressure test done with the Harbor freight kit, all shrader valves have been removed based on other pelican threads.

Cold control pressure 1.5-1.7 bar my very first test it reached 2 bar but the majority are in the former range

System pressure: 5 bar consistently

Warm pressure: unchanged from cold pressure. Since my engine is a 75' i ran this test with the car running. In another thread it was mentioned that the WUR is powered by the alternator.
I tested the WUR plug and it is 5.2-5.8 MV the WUR itself read I think 23/24 OHMs

The garage was about 70 degrees, and I THINK my WUR # ends in 045


From my research everything seems to be in spec with the exception of the warm pressure test, and I do not have a resource to check the volts of the WUR plug to see if it is getting appropriate power.

Any other thoughts or ideas would be much appreciated.

Rob

[SalParadise]

Rob, it looks to me like you have serious air leaks. When was the last time the CIS o-rings and tubes were done inside the manifolds? If they were never done they need it, but they will all have to be taken off, old ones removed, new ones in and then peened on the edge.

You probably have myriad other air leaks from the rubber pieces at the box (6) to hoses. You need to replace all this stuff with new.

CIS is tolerant of air leakage to a point in my experience. But if you have everything leaking it cannot meter worth a damn.

[rxtrom]

Thank you for the comment.

I did spray soapy water on the intake with the engine running and saw quite a few bubbles between the intake and head, Also from under the shroud. I assume this is not normal?

[SalParadise]

Rob, You need to get in there and replace:

1) Remove all the alloy intake pipes (6). Grind off all the peens (usually 3) per pipe, remove the red clay colored plastic injector sleeves and o-rings - clean the alloy intake pipe and replace with new sleeves and o-rings. This will make a huge difference.

2) While you are there, replace all intake gaskets of course.

3) Remove and replace the 6 rubber sleeves from the airbox to the alloy intake pipes.

4) Inspect the airbox for leakage or breaks.

I have a '75 S with a 2.7 so I know what you are going through. You have an air leak, probably several.

From experience, as I have been there, it is much easier to drop the engine to do the CIS. I have done the cheater of a partial drop to pull it all off and put it back on, but it's a headache and the access is tight to say the least. I would drop it in a weekend, clean it up, then during the week do the orings, sleeves and seals, then put it back in the next weekend. If the engine does not leak substantial oil I would shy away from removing anything else and stick to the CIS cleanup. You want a car to drive for the summer and you don't want to go down the slippery slope.

Did you buy the car in Connecticut?

[ossiblue]

Likely you have several issues as you suspect. My advice is to address each one separately, resolve it, and move on. Which to deal with first is your choice.

Agree with SalParadise about air leaks and those need to be take care of. He provides a good path to follow.

Your fuel pressures need to be addressed as well. The system and cold control appear to be in spec, but your warm control is really unknown until you can confirm the WUR is functioning. Get the WUR to heat and recheck the warm control pressure.

Something not yet mentioned but it jumped out at me as soon as I read your car/engine configuration. A CIS engine uses a high pressure/volume fuel pump and unused fuel is recycled back into the fuel tank which is specially designed to receive the returning fuel. These tanks have a "swirl pot" which prevents the return flow from creating air bubbles or currents which disrupts fuel flow to the tank outlet. A tank on a 71 does not have this design. Now, this may or may not create a problem for you, but it is something the be aware of if, down the road (pardon the pun), you get all other issues worked out and still have a running problem. Porsche thought enough about it to design a new tank for the CIS and later engines.

[rxtrom]

Thank you both for your detailed info. I am going to attempt a engine drop this weekend and will keep you posted. I will also need to research the parts mentioned above and get pictures (i am more visual) of these peens,

[SalParadise]

Originally Posted by rxtrom

Thank you both for your detailed info. I am going to attempt a engine drop this weekend and will keep you posted. I will also need to research the parts mentioned above and get pictures (i am more visual) of these peens,

I was using peen as a verb - you need to grind off the small dents on the sides of the manifold holding these red plastic sleeves in.





Then you're going to peen them back in with a small chisel or punch on the sides...

[T77911S]

Originally Posted by rxtrom

Warm pressure: unchanged from cold pressure.
Rob

not sure how you guys came up with air leaks when he said THIS.

the WUR needs 12v to heat up. chances are the AAR is not getting power either.

fix this FIRST.

[SalParadise]

Originally Posted by T77911S

not sure how you guys came up with air leaks when he said THIS.

the WUR needs 12v to heat up. chances are the AAR is not getting power either.

fix this FIRST.

A stock '75 S does not have an AAR. These were not until mid-1976. Mine does not have an AAR.

[rxtrom]

Not sure that I did this correctly but here is what I am going by that I have air leak at the intake and head.

https://youtu.be/0FsM05SASZg


https://youtu.be/fCRWwwu5KKg

[rxtrom]

A knowledgable friend told me the WUR ending in 045 is not correct for my motor, which is a 911/44 and should have a WUR ending in 009.

I'd likely get the correct WUR but it would take 2-3 weeks. So I am debating, based on the videos, tear down the CIS and replace the seals and gaskets or just wait. If I drop the motor I am going to end up doing a full rebuild, it needs it, but would like to use it for the season first or rebuild it in the peak of summer due to no AC.

I need a WUR Bosch part 0438 140 009 if anyone has one

[pmax]

Originally Posted by rxtrom

I tested the WUR plug and it is 5.2-5.8 MV the WUR itself read I think 23/24 OHMs

The garage was about 70 degrees, and I THINK my WUR # ends in 045


From my research everything seems to be in spec with the exception of the warm pressure test, and I do not have a resource to check the volts of the WUR plug to see if it is getting appropriate power.

Puzzled why you can't measure voltages when you got the resistance numbers.

[rxtrom]

Originally Posted by pmax

Puzzled why you can't measure voltages when you got the resistance numbers.

I tested the power at the plug to 5.2-5.8mv but my statement after that was that I didn’t have a resource to check to see if those were in spec

[proporsche]

rxtrom..here is basic-table to start with....you can learn a lot form this....

Ivan

[pmax]

Originally Posted by rxtrom

I tested the power at the plug to 5.2-5.8mv but my statement after that was that I didn’t have a resource to check to see if those were in spec

With engine on, there's power to the WUR. If you are measuring mV, something's broken in that connection somewhere.

[T77911S]

fix your power problem first.

[pmax]

Originally Posted by T77911S

fix your power problem first.

He's replacing the harness.

Should I replace this wiring behind the alternator, pics inside