New to me SC; couple running issues

[jburroughs12]

Hey guys,
I just picked up a new to me SC to partner the 964 and for more daily oriented duties (Since the 964 is very track focused and the SC is stock).
The car is in good condition, starts every time, burns effectively no oil, etc...
However, there are a few niggling issues that I need to address and I wanted to solicit some feedback here.

I have done research and have a game plan, but know there's a wealth of information here that could help. One of the issues with the internet is that there's everything and nothing on it all at the same time.
Surging idle (250-1300 RPM) on warm start-up, specifically after I start the car after it being off for 10-30 minutes.
Check for vacuum leak(s)
Removing oil filler cap whilst running DOES result in a slight idle drop (Need to verify if 50 or 250 RPM)
Adjust CIS fuel mixture
Warm up Regulator diagnosis
When idle settles down it's steady at 950 (hunts slightly but solely as a result of the inherent characteristics of the CIS system)
Sometimes struggles to start when cold
Idles great once started, but can take 5-10 seconds of cranking to start
Not sure of potential cause here other than fuel pressure bleeding down after sitting?
Feels down on power < 2,500 RPM
This could be a characteristic of the 3.0 engine, but I don't think so.
The best way to describe it would be like turbo lag; it's pretty flat and gutless, then > 2,500 RPM comes alive and is very sprightly
One thing of note is that sometimes the car stumbles slightly under light throttle load and lower RPM < 2,500, especially when cold
Could this be a timing issue? I just got the car over the weekend and haven't had a chance to throw a timing light on it, or check for vacuum leaks, etc.
It does have a new O2 sensor, as a side note.
The car drove reliably and cruised nicely at 80 MPH from San Diego to Houston, so it's definitely solid, just a few little issues I need to take a look at and was hoping you guys could help point me in the right direction if I've missed something.

Gratuitous pictures:
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[unclesol]

Congrats on the new addition!
I recently picked up an 84 Carrera that had a very similar idea surging issue. Long story short, my issue turned out to be a leaking left-side intake valve cover gasket, that was creating a major vacuum leak. Also didn't help that the PO had disconnected the O2 sensor, so the computer was not getting the necessary feedback.
All new valve cover gaskets, and a valve adjustment later, it runs like aSswiss watch now.
I hope this helps!

[High Life]

Sounds like a variety of issues..

I would start here:

CIS Troubleshooting for Dummies

This thread helped me a lot. I would also search the forum as many others have had similar issues. I have spent days reading and learning through other's misfortunes..

Next - buy a gauge set (you'll have a methodical approach to each of those nagging issues). You're just stabbing in the dark without pressure measurements.


Also - I have 2 books that have help me immensely in understanding my CIS w/Lambda system -A Bentley manual and How to tune and modify BOSCH Fuel Injection by Ben Watson..

There are others, but for the money - those 2 cover a lot of info - and are well written.

Read everything you can. I will tell its fairly common for an owner to feel like they are on an island with the CIS system - very few mechanics understand this system (the age of it makes it so). I'm sure there are good mechanics in Houston that can address CIS - but the pack is shrinking. IMHO - the best thing you can do is become the expert.

My surging idle was the relay ...

Strange Idle Issue - CIS problem?

[dhanl82]

Hello,
I purchases a 1982 sc 5 years ago and the fact that I knew nothing about cis injection was very concerning along with the fact that no one in this area seemed comfortable working on it. I decided that I had better learn all I could so I could do all my own work.
I found the following to be very educational:

I read all the prior threads on Pelican relating to it - a lot of very knowledgeable folks here!
Bentley service manual
"Bosch fuel injection & engine management" by Charles O. Probst
I also read everything I could find on the Internet.
It took me some time, but now I am totally comfortable maintaining it by myself and If I do need advice this forum is where I go. I would definitely recommend that you learn about it and do your own maintenance.
Hope this helps.
Dave

[TibetanT]

Hello There:

Welcome to Porsche 911SC ownership!!

First and foremost, did the car come with records ?
If it did, then my best advice is to read all the records to assess where/when the last complete service was done on the car.
Specifically, the engine compartment, when was the spark plugs changed (USE COPPER) when was the Air Filter, Oil Filter, Oil drained and replaced with new ?
Plug wires could be old and may cause issues. Fuel filter may be old and need changing, especially since you mentioned the "lag" when accelerating.


If none of the above have been done recently, start simple with new copper plugs Bosch 999-170-165-90-M14 Spark Plugs WR-5-DC+ <
You will need a timing light in order to complete the task.

Basically, set the valves per specifications, add the new copper plugs (if not new relatively new already), install new valve cover gaskets. Then, set the timing using the timing light...this requires adjusting the fuel intake in the process; 950 +-50 RPM.

I believe you may find there is nothing wrong. However, if you still have issues after what is said here AND by what is SAID ABOVE...post results again.

Most importantly, as mentioned read all of the documentation that came with the car so you know where you stand with your next service. Also, buy the Bentley for the 911SC it has been a wealth of knowledge for me to learn about this model.

Hope this helps and Good luck.

[jburroughs12]

Thank you guys very much for your help and direction. I bought a set of gauges to start my diagnosis, and have a Bentley manual.

One interesting thing is that when I hooked up the gauges there was 0 PSI reading, including after bleeding the gauge.

So I took a spare length of hose I had laying around and hooked it up directly to the FD line dumping into an empty bucket. The fuel is dribbling out, not consistent and strong like it should be. I don't want to start replacing things arbitrarily, but could this be a pump/filter issue, or even a FD issue?

I put the jumper switch on the fuel pump relay and it starts right up and sounds healthy.

I'll take a look at the filter in a bit here.

Here’s a quick video showing the fuel coming out of the FD line: https://youtu.be/JMnbHg2UDTc

[boyt911sc]

Originally Posted by jburroughs12

Thank you guys very much for your help and direction. I bought a set of gauges to start my diagnosis, and have a Bentley manual.

One interesting thing is that when I hooked up the gauges there was 0 PSI reading, including after bleeding the gauge.

So I took a spare length of hose I had laying around and hooked it up directly to the FD line dumping into an empty bucket. The fuel is dribbling out, not consistent and strong like it should be. I don't want to start replacing things arbitrarily, but could this be a pump/filter issue, or even a FD issue?

I put the jumper switch on the fuel pump relay and it starts right up and sounds healthy.

I'll take a look at the filter in a bit here.

Here’s a quick video showing the fuel coming out of the FD line: https://youtu.be/JMnbHg2UDTc

Test the fuel flow rate of the fuel pump after the fuel filter. You should get at least 1 liter per 30 sec.s or 2 liter per min. Do you have a picture of your new CIS gauge kit? Hope you do not have one from HF. What is your system pressure?

Tony

[jburroughs12]

Originally Posted by boyt911sc

Test the fuel flow rate of the fuel pump after the fuel filter. You should get at least 1 liter per 30 sec.s or 2 liter per min. Do you have a picture of your new CIS gauge kit? Hope you do not have one from HF. What is your system pressure?

Tony

Tony,
I pulled the fuel feed line to the accumulated per the Bentley manual and got ~.5 liters of fuel at 30 seconds. The tape line in the picture is marked at 1 L.

This leads me to believe the fuel pump is a) on its way out or b) there is some kind of blockage between it and the accumulator, which I think would be less likely.

My gauge is the HF one, but for the sake of these tests it’s been removed as a variable due to the perceived slow flow rate (confirmed by my above test).

My system pressure is so low as not to register at all, even after attempting to bleed the gauge. The 50% flow rate would cause that (in my little pea brain, that is).

Am I barking up the right three thinking it’s the fuel pump? I guess I could disconnect the output line AT the pump and test flow rate before buying a new one to confirm.

Thanks,
Joe

[jburroughs12]

Additionally, I went through the service records, the fuel pump in the car was installed in 1999 approximately 50K miles ago. I should get more mileage out of it, but 20 years is a fair amount of time for a $100 part.

I don't want to throw parts at the car, but this might be one of those "while I'm in there" items.

[boyt911sc]

Originally Posted by jburroughs12

Additionally, I went through the service records, the fuel pump in the car was installed in 1999 approximately 50K miles ago. I should get more mileage out of it, but 20 years is a fair amount of time for a $100 part.

I don't want to throw parts at the car, but this might be one of those "while I'm in there" items.

Your fuel pump is delivering insufficient amount of gasoline as per your test. One (1) liter per minute is not enough to get you the needed system pressure. Time to replace and install a good one.

Tony

[Bigtoe32067]

Don’t listen to the people telling you spark plugs and valve adjustment will fix your problem because they won’t affect an idle surge. Idle surge is vacuum leak or fuel delivery or possibly timing if someone changed it in the past.
Tony

[jburroughs12]

Originally Posted by Bigtoe32067

Don’t listen to the people telling you spark plugs and valve adjustment will fix your problem because they won’t affect an idle surge. Idle surge is vacuum leak or fuel delivery or possibly timing if someone changed it in the past.
Tony

Those are items I'll be taking a look at for general health of components, but my thoughts on the running/idle issues tied into vacuum/fuel.

I ordered up a fuel pump and will get it installed Wednesday. We'll see how it goes from there.

I put a timing light on the car and it's running ~5* at idle. I can't remember off the top of my head the 2,000 and 6,000 RPM numbers, but they fell within spec. I believe they were ~12* and ~29* respectively.

I'll report back once I put the new pump in and do my fuel pressure tests per the manual.

[jburroughs12]

Update: Got the new fuel pump in, volume looks good. Right at 2L/min. I put the gauge set on and still got 0 PSI. I pulled the gauge set and ran an open hose from the connection from the FD at the WUR and got a trickle.

I'm going to plumb the hose in AT the FD to see if there's a blockage in the line or if it's an actual FD issue. In which case, that'll be the next thing to come out and looked at.

[jburroughs12]

Here's a quick video of the "pressure" through the FD: https://youtu.be/LINOlb-RYEk

[boyt911sc]

Originally Posted by jburroughs12

Here's a quick video of the "pressure" through the FD: https://youtu.be/LINOlb-RYEk

There should be more fuel coming from the FD through the clear plastic line you installed. Something is not right. Why are you getting air bubbles in the clear tube? Have you inspected the PPR (primary pressure regulator)? Is the FP new or used? The noise I hear in your video does not tell me the FP is healthy by its sound.

Get a good set CIS pressure gauge. I buy tools from HF but not their CIS pressure gauge kit. Get a S&G tool. If you need some assistance in evaluating your fuel distributor, send it to me and I will test it for FREE. After I installed the FD on my tester, it would take me only a few seconds to verify your system pressure whether it is good or bad. And save you from lots of aggravation. PM me if you are interested.

Tony

[jburroughs12]

Originally Posted by boyt911sc

There should be more fuel coming from the FD through the clear plastic line you installed. Something is not right. Why are you getting air bubbles in the clear tube? Have you inspected the PPR (primary pressure regulator)? Is the FP new or used? The noise I hear in your video does not tell me the FP is healthy by its sound.

Get a good set CIS pressure gauge. I buy tools from HF but not their CIS pressure gauge kit. Get a S&G tool. If you need some assistance in evaluating your fuel distributor, send it to me and I will test it for FREE. After I installed the FD on my tester, it would take me only a few seconds to verify your system pressure whether it is good or bad. And save you from lots of aggravation. PM me if you are interested.

Tony

My thoughts exactly RE: something not right with the FD. The fuel pump is a new Dansk unit from Pelican Parts, and pushed out the appropriate volume when I ran the test from the accumulator line.

I have not inspected the PPR, figured that would be part of the FD diagnosis. The sound wasn't present at first, but came on during the video for some reason.

Thanks for the offer, PM coming your way.

[boyt911sc]

Joe,

The package containing your FD & WUR arrived this afternoon. I tested the FD and it has uniform flow rates and very consistent. System pressure was @ 73 psi. The WUR-090 failed the test. The CCP (cold control pressure) @ 67°F was @ 68 psi. The restriction is so severe that no fuel is passing through the WUR. You also need to get a good working CIS pressure gauge kit.

I will send back to you the FD and include a WUR loaner you could use to test in your car. PM me your shipping address. Thanks.

Tony

[dhanl82]

I thought I would mention that sometime back I I bought a HF fuel pressure gauge set and also got zero pressure readings so I exchanged that one for another one and still got zero pressure readings. I tried everything, some people said to remove the schrader valves - did that and still no success so I returned that one and purchased the model 33800 sold by S & G tool that Tony has recommended. I have had no issues with it - works flawlessly.

Please excuse me if I am confused, but it seems to me considering your tests results showing low fuel flow and bubbles in the fuel line going from the fuel distributor ( the circuit that exerts pressure on top of fuel distributor plunger) - to the wur that, if in fact it is below spec., would lead me to think that there could possibly be another problem in addition to the wur problem, since your video shows this issue prior to the wur. I do not know what the "normal" fuel volume should be at this point in the circuit so I am just raising the question.

Dave

[jburroughs12]

Originally Posted by dhanl82

I thought I would mention that sometime back I I bought a HF fuel pressure gauge set and also got zero pressure readings so I exchanged that one for another one and still got zero pressure readings. I tried everything, some people said to remove the schrader valves - did that and still no success so I returned that one and purchased the model 33800 sold by S & G tool that Tony has recommended. I have had no issues with it - works flawlessly.

Please excuse me if I am confused, but it seems to me considering your tests results showing low fuel flow and bubbles in the fuel line going from the fuel distributor ( the circuit that exerts pressure on top of fuel distributor plunger) - to the wur that, if in fact it is below spec., would lead me to think that there could possibly be another problem in addition to the wur problem, since your video shows this issue prior to the wur. I do not know what the "normal" fuel volume should be at this point in the circuit so I am just raising the question.

Dave

Duly noted on the gauge set. I'll order up a quality set this week. Thinking on the flow rate issue a bit more, I'm going to put the fuel filter from my 964 (less than 1,000 miles and 3 months on it) into the SC to see if that's the cause for the low flow rate at the FD.

I put a new fuel pump in, and direct from that the flow is right about where it needs to be, but as soon as I plumb the accumulator and filter back in and test AFTER them the rate drops significantly and I get the bubbles. The filter is an easy swap and can help to mitigate another variable in the system.

If that doesn't work/help I'll then inspect all of the fuel lines to ensure they're not kinked/bent inappropriately as well as make sure they're free from obstruction.

[boyt911sc]

Originally Posted by dhanl82

I thought I would mention that sometime back I I bought a HF fuel pressure gauge set and also got zero pressure readings so I exchanged that one for another one and still got zero pressure readings. I tried everything, some people said to remove the schrader valves - did that and still no success so I returned that one and purchased the model 33800 sold by S & G tool that Tony has recommended. I have had no issues with it - works flawlessly.

Please excuse me if I am confused, but it seems to me considering your tests results showing low fuel flow and bubbles in the fuel line going from the fuel distributor ( the circuit that exerts pressure on top of fuel distributor plunger) - to the wur that, if in fact it is below spec., would lead me to think that there could possibly be another problem in addition to the wur problem, since your video shows this issue prior to the wur. I do not know what the "normal" fuel volume should be at this point in the circuit so I am just raising the question.

Dave

Dave,

Your observation is correct. There is a likelihood that there could be another restriction point down stream. To confirm the the absence of flow restriction, the OP needs a good pressure gauge kit in the first place. The S&G 33800 gauge is a very reliable pressure gauge kit and I have 3 of them. It is imperative that Joe finds a good set of gauge to do the testing.

The good news is the the FD is in excellent condition with remarkable identical flow rates. I will send a WUR-090 loaner that he could try in his car as soon as I get them to pass the calibration tests. I am in contact with Joe and discussed the strategy. Thanks.

Tony