Need Help CIS Problem

2.7S · 01-15-2006, 06:37 AM

Here’s the story:

She’s a 1976 911S with CIS, last time out she ran great. A few days later I tried to start her and….

She ran for a few seconds and gave off two very light pops from the Pop Off Valve followed by a clear crisp pop. With that the engine shut down without another sound. I opened the hood (the one in back, ha, ha) and checked around and didn’t see anything out of place. So, I tried to start her a few more times with just the starter coming to life.

Notes: On some occasions where she has been setting for a few days, or its below 60 deg., I have to tap the throttle to kick her up to just over 1,000 rpm to get her to iidle smoothly. This was one of those occasions.

The next day I decided to push up on the Air Flow Sensor Plate and the one under the Fuel Regulator. I did this to each a few times to insure free movement. The Air Flow Sensor Plate moved freely up and down, while the one under the Fuel Regulator was stiff on the first try, but seamed to loosen up with the second and third try. I was then able to start her and take her for a short test drive. Two blocks from the house she backfired and died leaving only the red generator and ERG lights on.

Tried the ignition key and only got the starter to co-operate. I waited a few minutes and pushed up on the two plates again and then attempted to start her. Same thing, only the starter came to life. Ended up pushing her home (all down hill). Once there, I gave it another try and to my surprise she fired right up. With that, I immediately put her to bed and closed the door.

After doing some homework, I preformed the following checks:

1. The air box has no cracks, its solidly mounted, and none of its mounting screws are loose.
2. Looked for loose hoses and lines - need to recheck.
3. Removed the air box cover and air filter.
4. Turned the ignition key on and:
· Heard a high pitch screech (I believe this is from WUR).
· Lifted the Air Flow Sensor Plate via its lever arm that is connected to the Fuel Distributor and got sound from the Fuel Distributor and then the Fuel Injectors. However, I didn’t getting any down pressure on the Air Flow Sensor Plate Arm once the fuel was flowing. At least its pumping fuel, just don’t know how much.
· Then tried to start and only got the starter again.
5. Tested the Fuel Pump Relay by swapping it with the other relay in the fuse plan, and again nothing but the starter.

Could not getting any downward pressure on the Air Flow Sensor Plate/Arm from the Fuel Distributor be the cause for it not to start? If so, what would typical cause this problem?

CIS problems are new to me, so I’m guessing loose or leaky vacuum lines from the Throttle Housing to the Auxiliary Air Regulator and/or the Auxiliary Air Valve? Or could it be the plunger in Fuel Distributor, or something else in the linkage between the Fuel Distributor and the Air Flow Sensor Plate that isn’t moving freely.

Please advise…

k9handler · 01-15-2006, 06:42 AM

Try the fuel filter and accumulator, if clogged up the car will not run well once gunk is sucked up into the fuel line. I had these problems a few years back and once I repaired the fuel tank and replaced the pump, accumulator and filter the car worked great.

2.7S · 01-15-2006, 04:19 PM

K9handler and Jim Sims,

Your quick responses to my S.O.S. are greatly appreciated. As soon as I posted it, I jumped on my wife’s honey-do-list, as she comes first. Once that was handled it was back to diagnosing the problem with the Pcar. Sorry for the slow reply/follow up. Hope I get a pass on this as its Sunday and the games are on to.

With further diagnoses, I believe I found the source of the problem, a cracked line that comes off the front side of the Fuel Regulator. It looks something like this (see drawing, not sure were its going to attach:

This line must have been damaged when the car made the clear crisp pop. Note, the line feels like a vacuum hose. Where the crack is, the line feels dry and rotted. However, an inch past the crack the line feels fine. Would this explain the lack of any down pressure on the Air Flow Sensor Plate Arm with the key on and fuel flowing through the Fuel Regulator and the Fuel Injectors?

I traced the subject line’s path the best I could with my hand and a mirror. Lost it along the front side of the housing for the Air Flow Sensor. Not sure where it went from there, but I think it leads to the Auxiliary Air Regulator and possibly to the Auxiliary Air Valve.

Any ideas on how should I proceed from here?

P.S. I know I need to get a digital camera and start my own reference library.

soon to be

2.7S · 01-15-2006, 04:42 PM

Sorry, still learning, had to convert my drawing to a JPEG Mage. Here ya go:

bigchillcar · bigchillcar's Garage

points, points, points..point made.

ryan

2.7S · 01-15-2006, 06:20 PM

Jim Sims,

Thank you,

I have reviewed the figure and rechecked the car and yes, front does mean towards front of car.

I hand to get down on my knees, reach way in behind the top end of the engine, and give it a big hug to come up with the correct answer. I was wrong, there are two cracked lines coming of the front side of Fuel Regulator (FR), Items 72 and 73 in figure (1976 911CIS). Note, Item 72 has an inch long crack in it starting from where it leaves the FD.

Questions:
1. Does the two rendering of Item 73 in the figure refer to a single line?
2. Item 73 connects to Item 42 (Cold Start Valve), yes?
3. Item 72 connects to the top of Item 65 (not sure what it is, please identify), yes?

To investigate further would require removal of parts.

Please advise.

And thanks again...

Larry

2.7S · 01-16-2006, 10:07 PM

Jim,

I take your comments to heart about not starting my engine until there fixed. I saw another P-car on another thread that wasn’t so lucky. Now that I’ve seen pictures of the front side of my engine, I’m glade these lines failed at start up and not while the engine was hot and a 100 miles from home. See pics. below.

Just a thought, I wonder if taking pictures prior to them blowing would have revealed the need for replacement? From one of the pictures you will see what appears to be a crack developing in one of the lines. Besides age, I wonder how much of a roll MTB had in this???

More pictures to follow, having a hard time uploading.

How hard of a job is it to replace these bad line. What do I need to be aware off.

Thanks.

Jim Sims · 01-16-2006, 11:54 PM

Per the photograph supplied the cracks are merely in the protective rubber sheath over the actual nylon fuel line which is likely still fine. Just patch the sheath; there are self-fusing silicone tapes (called "rubber amalgamating tape") available at places like Autozone that are handy for these repairs.

Having seen this, leaking fuel lines are not the source of the problem. I again suggest you check the timing and ignition next.

By the way, I too have a 1976 911S. Cheers, Jim

2.7S · 01-19-2006, 10:42 PM

Jim,

Per your suggestion, check timing and ignition:

Started by removing the rotator cap and preceded to check to the points. No way, only 8,000 miles on points and they’re cooked, closed, well worn, flash spotted with rust, and ready to be replaced. Installed new points and tried to start, no go? Next checked for spark, none.

Then proceeded to check the CDI unit and the coil. The CDI was receiving current and sending it out, but it wasn’t reaching the coil? Checked my book and it said to check the connections and the wires from the CDI unit to the coil. I did, and connections and wires looked fine. No signs of damage to the wires and the connections were clean and tight.

Hum, let me see. Getting juice out of the CDI, but its not reaching the coil. What could be breaking the electrical path from the CDI to the coil? Can you say car alarm? Pulled the fuse to the darn thing, turned the key over, and she fired right up. It seamed like a great weight had been taken off her. It sounds like she’s make a lot more power???? Could an old and failing car alarm rob a P-car of power?

Apparently the electrical path from the CDI to the coil goes through the car alarm. Could a car alarm failing during startup cause the points to close and during the process break the electrical path from the CDI to the coil? This would explain why she wouldn’t start after just replacing the points. Or would it be the other way around, points close causing an electrical surge on the car alarm, damaging it to the point of permanently breaking the electrical circuit. Does this make any sense; it’s way past my bedtime.

I will be checking the timing tomorrow. Is there anything else that needs checking before taking a road test?

Thanks,

P.S. Mine’s silver/black leather with blue carpet.

bigchillcar · bigchillcar's Garage

are you certain that you got the points gap correct? it's an extremely sensitive setting on these cars..off just a hair and it won't start. i'd check it with a dwell meter..my bet is that the timing is okay..maybe your points didn't have the grease on the shaft and wore out fast. just a hunch.
ryan

Jim Sims · 01-20-2006, 06:49 AM

I agree with Big Chill; use a dwell meter to get the point gap set properly. If the dwell (point gap) is off, the car will still run but not optimally and you may be burning the points. Dwell meters are small and inexpensive. Also, check the timing and then recheck the point dwell. It would improve your car's dependability to clean the electrical connections related to the ignition and reassemble them using silicone dielectric grease (not silicone rubber). Further, I would remove the alarm system; it just adds more failure points and IMO adds little to the security of the car.

Below is an image of my blue 1976S along side my son's 1973T; with considerable help from our Porsche buddies we repainted them both.

Jim

jstobo · 01-20-2006, 07:18 AM

8,000 miles on points I think are good. I would always change mine at 6,000 when I changed plugs and adjusted the valves. Of coure mine was a 69 and revved a little higher. I have now installed the pertronix. No more points for me.

al lkosmal · 01-20-2006, 07:21 AM

Double check your pop-off valve. The bonder/glue may have failed causing a leak. I have had this happen after a backfire thru the pop-off. Looked ok, but after screwing aroung with everything else for a day or two, I realized that it was sitting a little high and loose. Still appeared to be bonded, but not.....

Based on your symtoms, I'd keep checking for that vacuum leak.

2.7S · 01-25-2006, 11:02 PM

Jim,

Per your and Big Chill’s suggestion,

Last Friday, I used a dwell meter to insure that the points were correctly gapped, got a reading of 58.5. Then checked the timing, it was advanced one or two degrees max. So, I put things back together and took her for a test drive. Like I said earlier, it seams like a great burden has been taken off her. She ran smoother and there was a significant improvement in her acceleration. She pulled a lot harder in and through all gears, even 5th. Way more power…..

After the test drive, I noticed that I had left the smog pump belt off. Oops… Besides changing the points out, how much of an improvement would one see when leaving the smog pump belt off? Does leaving the belt off cause any problems? I do realize that the belt would have to go back on should the car ever needed to be smogged.

Couldn’t resist driving her to work today (50 miles round trip) with the smog pump off. She ran flawlessly. I can’t believe the improvement in her acceleration with the points replaced, the car alarm unplugged, and the smog pump belt off. I can hardly wait to take her out on another canyon or up the coast run (Hwy 1).

She goes to the alarm shop tomorrow to resolve the alarm problem. The alarm it is still on warranty, so I’ll let you know what happens.

As you suggested, I will be cleaning the electrical connections before I take her out for another run. I will also be rechecking for a vacuum leak (s) as “al lkosmal” suggested, starting with the pop-off valve, even though it looks fine.

Jstobo – I to some day may be able to say, “Installed the pertronix. No more points for me”.

All of your helpful suggestions are greatly appreciated.

P.S. Jim, thanks for sharing the great picture of your blue 1976S and you son's 1973T, they’re very nice indeed.

It’s late, good night…

Paulporsche · 01-26-2006, 05:50 AM

2.7,

I'm glad to hear your car is running better. I'm concerned about your point gap. Your dwell angle should be between 35 and 41 degrees. How did you get 58.5? Was your meter set to 6 cylinder?

I usually set new ones @ 36. Then, as the rub block wears down, closing the gap , the angle gradually rises to 40 when it's time for a change.