1980 SC Newbie - Help Needed!

[tirwin]

Originally Posted by Ryoder

Yea its steady at 900-950 at idle, it isnt much higher while warming up though. I would have to see the idle process of one thats really dialed in to see how far off mine is from normal..

To answer your question about what is normal idle process, think of it this way. Any engine goes through several states. Cranking. Cold start. Warm start. Idle. Cruise. Wide open throttle.

When you're troubleshooting CIS, think about what state you're having the problem in. What is supposed to be happening in that state? If you understand that, the reason for the tests in the Bentley and the CIS thread make a lot more sense.

On a cold start, the WUR and the AAR add more air and fuel because you need a richer mixture for a cold engine. The two components together act like a choke. What that means for us is that once you start the car, rpms should rise to ~1200-1400. As the engine temp increases, the rpms will gradually come back down to normal idle at +/- 950 rpm. It usually takes 2-4 minutes and depends on the outside ambient air temp.

Once the engine is warmed up, the WUR and the AAR have done their cold start job and the AFR is leaned out to normal.

[boyt911sc]

Originally Posted by Ryoder

Hello everyone, after a long time lurking I finally took the air cooled plunge and purchased a 1980 911 SC Targa with roughly 121k miles. Would love your expertise in diagnosing some problems with the car. I took delivery of the car yesterday and these are the problems I am already having..

Problem #1. Car starts right up when cold and idles for about 3-4 min then dies. I can start it back up then it dies again in about 15-30 seconds. I can keep it running after this by giving it a little gas and keeping the rpms up.

Problem# 2. After the car has started to warm up while driving it will die when when I come to a stop or the car is in neutral for more than a couple seconds. Starts right up and I can continue on my way.

Problem #3. I drove car yesterday around the neighborhood for about 7 min then let it idle in front of my house for another 5 min. Shut it off and came back out 15 min later and the car would not start. Also seemed like it was cranking a little slow.

I pushed the car in the garage, put it on a trickle charge for an hour, let the engine cool down then it started again but problem #1 surfaced again..

Here is what I tested:
It seemed odd the engine was turning slowly during problem #3 because the battery is only 3 days old so I tested to see if it could be the alternator. Battery was at 12.7v with key off and 12.7v with car running. Could this be attributed to an alternator? I also have a suspicion a Fuel Accumulator could be to blame but that just from reading on here.


Other items to note:
The car got out of the shop 5 days ago from the Previous Owner and this is what was done..
1. Battery and ground cable
2. New distributor cap, rotor, spark plugs and ignition wires
3. Replace belts
4. Replace broken vacuum line @ throttle body
4. Shop set enrichment and idle @ shop (idles at 900 rpm)


**Finally if any of you are from the St Pete, Fl area I would love to meet you and learn all I can about these cars. Free beer is always available to anyone that wants to swing by and check it out.

Ryoder,

Welcome to the CIS club. Since you already bought the car and own it now, the previous owner has been relieved of his responsibility to this car. Have you tried to contact the PO? Even if you did, I doubt things will change. The car has some minor problems and could be fixed by any DIYer like you or me. And if you enjoy working on your car and like to learn about CIS troubleshooting, this the right forum to start. Or would you rather send it to a shop and just pay them for their services?

On the brighter side, you own a very nice looking red car and I bet you have been staring at this car with a big grin on your face. This is like the feeling you had when you first met your partner. Love at first sight.

Let’s get back to business. If I were in your shoes, I will have the fuel pressures tested and check for unmetered air. If you don’t know where to begin and get started, you are not alone. We all started like you and with the help from the other members, you will find your way home.

Tony

[spuggy]

Cool, I had a 944 that color - quintessential 80's Porsche

Originally Posted by Ryoder

starts right up when cold and idles for about 3-4 min then dies. I can start it back up then it dies again in about 15-30 seconds. I can keep it running after this by giving it a little gas and keeping the rpms up.

Don't start the car until you're ready to drive it, then drive away - keep motor spinning comfortably (light load) and RPMs reasonable until the oil is up to temp (or at least has some heat in it). Says that in the owner's handbook.

Idling from cold; when the oil is at its thickest - giving the lowest amount of oil flow. Factory explicitly says not to do that.

Prolonged hot idle isn't ideal either; air flow from the fan is directly related to RPM.

Originally Posted by Ryoder

Problem# 2. After the car has started to warm up while driving it will die when when I come to a stop or the car is in neutral for more than a couple seconds. Starts right up and I can continue on my way.

Listen to those who know CIS and work through it methodically; it'll work out..

Idle speed shouldn't have been set with the motor cold, but you never know... Once you get charging sorted out, I'd raise the idle so it at least keeps running while you figure things out.

Originally Posted by Ryoder

Battery was at 12.7v with key off and 12.7v with car running.

Should get right around 14V at the battery with motor running, just like any other 12V vehicle. Sounds like alternator or voltage regulator not working, or something disturbed and not (re-)connected that should be. Possibly when the shop was working on it.

Does the alternator warning light (in the oil temp/pressure combo gauge) come on when you turn the key to Run, before you hit start?

Is it a bulb - e.g. hasn't been replaced with an LED?

That bulb - and the resistance it provides, in both directions - is part of the alternator exciter circuit; if that bulb blows/replaced with an LED/not connected, there will be no output from the alternator.

If the warning light does come on, it should go out immediately the motor starts. If it doesn't, not charging.

Fan belt was replaced? Check the tension and/or the # of shims fitted; if the belt is slipping, no charge & insufficient airflow from the fan....

Not charging/low voltage won't help anything; CDI box needs good voltage, and many of the CIS doo-dads have heating coils too...

Originally Posted by Ryoder

Fuel Accumulator

Fuel accumulator keeps pressure up in the injector lines after the motor & pump stops running; to prevent the fuel boiling from heat soak after stopping.

The usual symptom of that being defective (unless it's leaking everywhere) is that hot re-starts - e.g. drive for an hour, leave car for 20 minutes, go to leave again - are problematic. It takes at least 15 minutes of driving the car to get the motor up to temperature, BTW.

It's fairly unusual for these to fail. Most often if they do, they simply don't hold pressure, or it bleeds off too fast. Can't check residual system pressure without a set of CIS gauges though...

Originally Posted by Ryoder

4. Shop set enrichment and idle @ shop (idles at 900 rpm)

Cold idle should be higher, then drop as it warms up and whatever air valves are fitted do whatever they do.



If it were me, I'd probably sort the charging out, tweak up the cold idle 200- RPM and take it for a drive to see what it does when its up to temperature with the correct voltage...

Good luck!

[911obgyn]

If it is actually a bad alternator it can be rebuilt locally by an auto, Marine electrical shop, they can test it on the bench rebuild it and you know it will fit.

[woland]

Hi!
I got my 1980 Targa from a private dealer too in 2006.
It sounds me curious to read that a shop has "set enrichment and idle": In twelve years I never set anyting in my K-Jetronic, nor in the four Audi 5 cyllinders equipped with the same ignition. I turn the key on and it fires.
I would check fuel filter + accumulator and the fuel pump relay (in the fuse box) looking for bad contacts. Tirvin gave you a good suggestion on removing the oil cap to see if the idle changes.
No changes means vacuum leaks



Gently enlarge the fins with a blade and spray deoxy to have a good contact in all five pins

[boyt911sc]

Originally Posted by spuggy

Cool, I had a 944 that color - quintessential 80's Porsche ..............

Fuel accumulator keeps pressure up in the injector lines after the motor & pump stops running; to prevent the fuel boiling from heat soak after stopping.

The usual symptom of that being defective (unless it's leaking everywhere) is that hot re-starts - e.g. drive for an hour, leave car for 20 minutes, go to leave again - are problematic. It takes at least 15 minutes of driving the car to get the motor up to temperature, BTW.

It's fairly unusual for these to fail. Most often if they do, they simply don't hold pressure, or it bleeds off too fast. Can't check residual system pressure without a set of CIS gauges though...

Good luck!

Spuggy,

I agree with most of the things you mentioned in your original post but disagree with this one. The vapor lock in a CIS is a myth that came about from carbureted systems that operate at very low system pressure (5 psi. or less). A typical normally aspirated CIS has a system pressure between 65~75 psi. and the 930/turbo has a system pressure between 95~105 psi. As you can see the disparity in the system pressures between a CIS and a carbureted system.

Secondly, gasoline is an incompressible fluid. No amount of vapor lock in the fuel line could prevent the “fluid” from being expelled at 70 psi. system pressure (turbo @ 100 psi.). Have you actually seen or witnessed a vapor lock in a CIS?

If vapor lock is actually occurring in a CIS, then why did the engineers switch from the plastic fuel lines to the metal fuel lines in later models? The metal fuel lines have a much greater heat transfer capacity than the plastic materials.

I did some testing and experiments applying heat to the metal fuel line in a CIS to create a “vapor lock” many years ago to investigate it. This was a very risky experiment that involved heating a combustible and flammable liquid like gasoline. My objective was to create a condition (vapor lock) that would prevent the liquid from being injected. At a much warmer conditions, heating the fuel line under test was able to deliver fuel once the FD plunger was raised or elevated from its rest point.

If someone could safely demonstrate a vapor lock exists in a CIS, I will be a convert. I will be forever grateful if someone could prove or demonstrate the existence of vapor lock in a CIS. This is a technical discussion in the Technical Forum and nothing personal. Thanks.

Tony

[Coastr]

I don't agree the seller has any responsibility here - we are talking about a nearly 40 year old car, not a CPO camry. The most I would ask from the seller is to give me any information on what recent changes/behaviour they had seen. You're wasting mental energy trying to get anything from a previous owner except advice and information. Better to suck it up and put the energy and time into making it right. Chances are the PO sold it because they couldn't fix it. CIS cars need special care if they aren't running right and not many shops or owners have the knowledge or patience to do it.

Have you done the 'oil cap off at idle' check? This is a very simple test for gross vacuum leaks. If it doesn't drop at idle then you have a big vacuum leak.

Having said that, I seem to recall every person that has problems with hot starting or difficulties transitioning from cold run to warm run need to pay attention to the WUR. But you can also unplug/replug the AAV and AAR and see if that makes a difference. Best thing to do is start reading because you need to start developing knowledge on CIS or a check writing habit.

[Ryoder]

So this weekend I was able to get the car warmed up to the point it would drive. The cold start issue is still the main problem. I also took off the oil cap and the car died immediately which I guess means there are no significant vacuum leaks.

Here is a video of the car about 1 min after starting. It stalled shortly after I ended the video.

https://youtu.be/bi39NC6KCTI

[boyt911sc]

Ryoder,

Buy or borrow a CIS pressure gauge kit and check your cold, warm, residual, and system fuel pressures. This is a mandatory tool for any fuel injection system troubleshooting. Without one, you are wasting your time and effort trying to fix your problem/s.

Test for sources of unmetered air. Until you have confirmed and verified the absence of unmetered air, I will bet my money that you have vacuum leaks. A smoke test will take a few mins. to evaluate the integrity of your vacuum system. Keep us posted.

Tony

[woland]

Your engine sounds like something... messy.
A 911 cold engine has to fire without touching the throttle

I read the list of the works done by the PO

1. Battery and ground cable
2. New distributor cap, rotor, spark plugs and ignition wires
3. Replace belts
4. Replace broken vacuum line @ throttle body
4. Shop set enrichment and idle @ shop (idles at 900 rpm)

I wondered why those particular jobs were made at the time of selling the vehicle. I'd never done this, unless the car was unused for a long time even in the wet. This is not something to do to a KJetronic.

Consider the possibility of injectors stall. Removing it is very simple and washing it wit ultrasounds can tell you a lot on their condition.

https://get.google.com/albumarchive/106799704896439228817/album/AF1QipOyu_dfGEAlFMuaRFxLR3YeUClly-suFD-vppzG

Have a look too to airbox straps: A slack airbox changes the balance air/fuel

[Ryoder]

Thanks for all your suggestions so far.. I love the car but it is quite frustrating to have it stall every time the car is in neutral the first 10 min of driving..

The Previous Owner said he knew this was an issue but thought it was addressed. Oh well I am moving forward. I bought the car and will not continue to bug him..

I purchased a fuel pressure tester kit and once that arrives I plan on going through and checking everything. I think I am going to ask a local PP member to come over and assist since he said he has been through this before.

Another (probably dumb) question:
If the air box was cracked would the car always run rough like this or would the problem go away when warmed up like mine is?

[7783911]

Interesting thread

I take my 83 to a very good shop and i ve mentioned the possibility of vacuum leaks based on the oil cap test..but they poo poo d that notion? I ve happen to have the car at the shop now for valve work and will again repeat my request re vacuum leaks since the cis will be out and easy to test. My car runs and idles great (in high temp the idle may climb 100 rpm over time..but nothing like hunting..just gradual

When i had a charging issue..measured voltage at battery with and without engine running and i discovered that...

1 I need to be at 1500 RPM to get charger excited which produces 13.6 or so at the battery
2 The idiot light on the dial needs to be correct in order for the exciter to get the juice needed to be excited and start charging (replaced LED with standard bulb..all fixed)

Just my thoughts..any comments on the oil cap situation? The garage seemed to think this was not ALL years this would ocur...but i can go back and insist on full test for leaks and then have them pull cap to see after corrections are made?

[Bob Ashlock]

A few posts back "TIRWIN" raises the possibility that it might be the CDI box. Indeed, the start/die/restart is a common symptom of one that is just barely hanging on by the skin of its teeth. This is a typical situation when the discharge capacitor inside has degraded to the point of providing barely enough energy to make spark. At that point, everything comes into play. Battery voltage, heat, leaning fuel mixture, and run-time all can be factors. Normally, a good CDI box will tolerate low battery voltage (down to 8V or so) just fine, but not when they are degraded. 12.7V should be fine, however I'm surprised you measured that low with the engine running. Normally, revving up the engine to, say 2000rpm or so, should result in a charge voltage of around 13.5 - 14V. So the charging system may also be part of this problem.

Admittedly, I do have a dog in this hunt, since I routinely repair & service those boxes. But like TIRWIN said, rule out the other stuff first to see if the problem points in the ignition direction. If it turns out you suspect your CDI unit is flaky, I can lend you a temporary test unit to plug in so you can determine if that is the problem or not. At least that way you will have scratched another possible suspect off the list. And, if it turns out your box needs repair, Pelican offers my service.

[dcbullet]

Originally Posted by Ryoder

I also took off the oil cap and the car died immediately which I guess means there are no significant vacuum leaks.

Can't help you with your other issues but the car dying upon removing the oil cap typically means the oil tank breather hose restrictor is missing. You need to be able to take the oil cap off while at idle so you can check the oil level.

Here's a thread about it.

oil breather hose restrictor - idle issue update

[eatdog]

My first post! Congrats on the new car. I just picked up a 74 a couple weeks ago but it’s not nearly as nice as your car.
I have been playing with CIS for years on Rabbits. Here’s a couple links that I found helpful. You are in the right place I found this forum searching CIS issues and the knowledge here is incredible. Getting that pressure gauge is the first step.

https://youtu.be/a4fJAfXYxWk

The Bad Habit Rabbit - Volkswagen Rabbit Page - Fuel Pressure Gauge

[RDM]

Originally Posted by dcbullet

Can't help you with your other issues but the car dying upon removing the oil cap typically means the oil tank breather hose restrictor is missing. You need to be able to take the oil cap off while at idle so you can check the oil level.

Here's a thread about it.

oil breather hose restrictor - idle issue update

The 1980s didn't come with these.

[dcbullet]

Originally Posted by RDM

The 1980s didn't come with these.

Are you sure? The thread I linked was for an 81. I have an 82 and it required one. And the OP has an 80 that dies upon removal of the oil cap.

[pmax]

^^^ 80 has the "restrictor", a screen, on the angle connector at the back of the "pope's hat".

[RDM]

I know because I ordered one for my oil line and it doesn't fit....