Before I start Chasing CIS Gremlins...

[Showdown]

Before I get started I do want to preface that I've read Tim's excellent CIS posts, Jim's Basement Workshop front to back and spent way too much time (according to my wife) searching Pelican for answers about my CIS.

The long and short- my car has performance anxiety.

1977 S 54k miles, new to me as of last fall. In for lots of deferred maintenance this winter: carrera tensioners, 11-blade fan, SSIs, new muffler, new valve covers, valve adjustment, new airbox...and a lot of other stuff...

Cold starts are hit and miss. Warm starts are hit and miss. Once the idle settles in the car performs wonderfully, no bucking, no stuttering, it pulls hard and well throughout the whole range and is a pleasure to drive... until I have to turn it off and pray that it starts up.

In a pinch I can pop the filter cover and lift the air sensor plate to get the vacuum going and I'm good to go... It may feel cool to pop the engine lid outside of a restaurant, roll up shirtsleeves and get the car going but it most certainly doesn't look cool...ask my wife.

I have concluded that I need to pressure test and smoke test the CIS system so that I can ask the Pelican community for guidance. I don't want to pay my mechanic to do this.

In one of Tim's posts he mentions that an easy way to determine if you have a vacuum leak is to remove the oil cap and watch the RPMs. Change means no or insignificant leak, no change means leak. I have no change so I'm assuming I have a vacuum leak somewhere and that could align with the startup issue... maybe.

So before I dive into this I had a few questions:

1.) Can I do all of these tests (pressure, smoke) without an engine drop?
2.) Can I do all of these tests with the heater blower still installed (I haven't backdated yet because...Chicago.)
3.) Is there a definitive guide, write-up, slideshow, video that walks an idiot through this process, assuming that I'm said idiot.
4.) Is there anyone in Chicago I can bribe to help me with this? I'm really good at bribes, I live and own a business in Chicago after all.

Thanks in advance!

And obligatory photo because, Porsche.

[dfhtrhjn]

1) You're right to check for vacuum leaks.

2) When you start the car; if it fires up for a second and dies immediately (even after 5 tries) then your cold start value is working. It sprays gas on ignition to help you start. If you're cranking a bunch before start then this may be an issue.

3) When it's finally running; does it hesitate, buck, or have trouble reving before it's warmed up? If so, then it might be the Warm-Up Regulator (WUR). It's pretty easy to mod it and make it adjustable, and it happens to every WUR eventually.

[Paulporsche]

Showdown,

The first thing is to make sure all ignition components are up to spec and working correctly.

Then you can move on to vac and CIS tests. You need a pressure tester with CIS fuel line fittings to do the fuel and control pressures.

You should take note of the WUR and and publish the number stamped on it. We can then help you determine if you have the correct one, and check which graph you will want to use for pressure verification.

You can do pressure and vac leak tests with the engine in the car. Not all engines lose rpm when the oil cap is removed, so it is a good but not definitive test.

Check Youtube for videos of tests done by others.

Tim has great posts on this system. Another is Tony (boyt911sc). Check for his posts on this forum, and for Jim Williams' website on CIS.

Your symptoms are not unusual for cars of this vintage, so you'll find a ton of info here if you search.

I'm sure you will get this sorted. Don't be afraid to ask questions. There are many knowledgeable people here who are willing to help.

[Paulporsche]

Control Pressure Charts for 1975-1977 cars. Check which WUR number is yours. When my 77 had its original engine, I think the WUR was 033.

[Glenfield]

I have some CIS gauges if you want a lend. You can come grab them depending on where you are in Chicago. If you also have a fuel pump jumper rigged up, I can show you how to test the pressures. Been a while but i hear it’s like riding a bike. Feel free to PM me.

[Showdown]

Thanks fellas,

Gauge and smoke machine parts on order! Looks like next weekend I’ll be elbow deep in my engine bay.

For what it’s worth, here’s a video of what I would consider a good cold start; the car did start after all and I didn’t need to roll up my sleeves. Sometimes it just cranks and then I need to lift the air sensor arm.

https://youtu.be/lbuWbLmb3pA

[gomezoneill]

I have concluded that I need to pressure test and smoke test the CIS system so that I can ask the Pelican community for guidance. I don't want to pay my mechanic to do this.

If you don't know what your doing why would you think this way?

[Showdown]

Originally Posted by gomezoneill

If you don't know what your doing why would you think this way?

Gee, I guess I was unaware that I don’t know what I’m doing, thanks for that.

The car is having trouble with cold and sometimes warm starts. From why I’ve read here, on Rennlist, and Jim’s Basement Workshop I’ve concluded that it’s likely a CIS issue so testing the pressure to gather some data so I can narrow down the precise problem seems the be exactly the right thing to do; at least according to all the other folks who’ve said as much.

My mechanic already had a shot at fixing this and they didn’t, so rather than throwing more money at the problem without any guarantee, I want to give it a go myself. I’m hoping to learn more about the car and become more adept at working on it myself; just like everyone else here.

Do you have any constructive or helpful suggestions?

[boyt911sc]

Originally Posted by Showdown

Thanks fellas,

Gauge and smoke machine parts on order! Looks like next weekend I’ll be elbow deep in my engine bay.

For what it’s worth, here’s a video of what I would consider a good cold start; the car did start after all and I didn’t need to roll up my sleeves. Sometimes it just cranks and then I need to lift the air sensor arm.

https://youtu.be/lbuWbLmb3pA

Showdown,


Try to start the car without any assistance from your gas pedal. From watching the video, you seemed to be pressing the gas pedal during initial start. Put the car in neutral and parking brake on. Get out of the car and reach for the ignition switch to start the engine. If you could video it, the better. Determine how many attempts before you could make the engine to start and idle.

At this point you have no idea what are your fuel pressures. Bad way to start your troubleshooting. You need diagnostic tools to determine your problem/s. Pressure gauge kit is a mandatory tool for fuel injection troubleshooting. Another vital gadget you need is a smoke generator to help you locate those pesky and hard to locate vacuum leaks. Keep us posted.

Tony

[Showdown]

Thanks Tony,

I have a CIS gauge and smoke machine coming next week so I’ll be able to start gathering data.

Here’s another video with no gas pedal assistance. Once the car does start, it’s still a bit rough until I start driving it and then once warmed everything is fine.

Like I said, I’d consider this a great start up, it’s not uncommon for it to take much longer

https://youtu.be/gsCTbS0MZnE

[boyt911sc]

Originally Posted by Showdown

Thanks Tony,

I have a CIS gauge and smoke machine coming next week so I’ll be able to start gathering data.

Here’s another video with no gas pedal assistance. Once the car does start, it’s still a bit rough until I start driving it and then once warmed everything is fine.

Like I said, I’d consider this a great start up, it’s not uncommon for it to take much longer

https://youtu.be/gsCTbS0MZnE

From the video, the rpm several times spiked up. Were you stepping on the gas pedal? That’s the reason I wanted people to get out of the car and try it without any assistance. So what was causing the sudden spike in idle speed?

Sorry to question you but it is difficult to assess the problem if we are not in the same page. I could be wrong, but it seems that you were touching the gas pedal(?). If you were not sitting in the car, it would be obvious you were not pressing the gas pedal.

Next time you test it, do it on a cold motor. A morning start up would be ideal. I would bet on that most likely culprits are:

• WUR.
• Unmetered air.

Thanks.

Tony

[Showdown]

Hi Tony,

Thanks for the helpful responses, let me try to clarify the videos;

Video 1:
https://youtu.be/lbuWbLmb3pA
Shot yesterday afternoon after the car had been sitting for about 6 hours.
I didn't touch the gas until 54 seconds into the video and then I revved the engine a few times.


Video 2:
https://youtu.be/gsCTbS0MZnE
shot this morning with the car ice cold- last start was yesterday at about 3pm to shoot the first video
I didn't touch the gas pedal at all (I was sitting in the car so I could show the gauges better):


I'm planning on first doing a full CIS pressure test next weekend to collect all of the data on the system and then I'll do a smoke test to see if I have any leaks in the vacuum. I'm hoping that will pinpoint the exact source of the issue and then I can figure out how to correct it.

-Julian

[SkiVT]

As was mentioned, while waiting on the pressure gauge post your WUR part number and maybe a picture of the engine with vacuum lines visible. You will need to know the WUR number for the correct pressure charts anyway.

[Showdown]

My WUR is 0 438 140 033

I tried to take photos but until I remove the heater hoses it's impossible to see much. I did make sure that no hoses are loose or unattached...

[targa80]

While you are going to test your CIS pressures may I suggest you stop off at your local Walmart and buy six plastic baby bottles. The bottles are good for viewing the injectors for leaks, even spray pattern and equal fuel delivery by lifting throttle plate for a few seconds to allow the injectors to turn on. The accumulated fuel in each should all be the same. I used a scissor to cut the tips to fit the injectors into the nipples. Clear packing tape will hold the bottles together.

[Showdown]

Great tip, I knew I was saving my daughter’s bottles for something

Hoping the issue is within the CIS system and a simple one at that

[targa80]

For the smoke test you can do a partial drop so you can remove the peanut cover from the throttle body to add a rubber glove over the opening so you can pump smoke into the vacuum side of CIS.

[Paulporsche]

There is a Youtube video by a fellow named Ken in Hawaii who does a smoke test with a cigar on his 911SC with CIS.

[Paulporsche]

Obviously, testing will get you a long way towards getting this fixed correctly, but until then, if you feel like experimenting, you can try Souk's field test. Try lifting the arm and sensor plate in the fuel distributor ever so slightly while the car is running. If the revs rise then that means your mix is too lean. You can then richen it with a 3 mm Allen wrench in the hole between the plate and the fuel distributor.

You can reach into the opened airbox and access the arm from below it, as seen in Pat's photo.

This is not to take the place of testing but, until then, it may help get you up and running. To me, it sounds like you are running lean in your videos, but testing will help tell you if this is true and why.

[boyt911sc]

Originally Posted by Paulporsche

Obviously, testing will get you a long way towards getting this fixed correctly, but until then, if you feel like experimenting, you can try Souk's field test. Try lifting the arm and sensor plate in the fuel distributor ever so slightly while the car is running. If the revs rise then that means your mix is too lean. You can then richen it with a 3 mm Allen wrench in the hole between the plate and the fuel distributor.

You can reach into the opened airbox and access the arm from below it, as seen in Pat's photo.

This is not to take the place of testing but, until then, it may help get you up and running. To me, it sounds like you are running lean in your videos, but testing will help tell you if this is true and why.

Paul,

Souk’s procedure is good provided you don’t have unmetered air going into the system. I called his attention about it and he could not edit his posts because it had been old and no more access to old posts. Other than that, it is a remarkable technique.

So to set your mixture correctly you need to perform these basic tests first and foremost:

• Setting your control and system fuel pressures to specification.
• Verifying the absence of unmetered air going into the system.

Tony