Help! Wont stay running 1982 911 sc

[flattie]

Hello
Im looking for some advice on a porsche 911 sc 1982 the car was just pulled out of storage has not been run in years. So far have drained the fuel tank, new fuel filter air filter, fuel pump, and injectors. The plugs look dark but could be from the multiple startings, Sometimes it will start up and idle just fine & stay running for several minutes, by the time you get in the car and put it in gear and ready to let the clutch out it dies, When you go to restart it, It will only fire and die right away. then it will continue to do that until you leave it sit for a few mins then you go back and try to start it sometimes it will start others it wont, The car is like mint only has 12,000 miles on it. Cap and rotor look real good along with the wires, Any ideas of what I should be looking for? Also when it is running if you rev the engine a little sometimes you will get a light pop NOT a back fire but more like out of the air box

[Gunter]

The fuel distributor may be clogged with gunk after sitting for many years; put some injector cleaner in the gas tank: 2 bottles of Techron per 80 liters.
Did you flush the gas lines from pump to accumulator?
You can check the flow pattern of the injectors by placing them in 6 glass bottles.
Fire extinguisher nearby.
Remove the airfilter, ignition ON, lift the air sensor plate inside the airbox briefly; you'll hear the injectors squeel, Stop.
Ignition OFF, check the bottles for even volume.
If the fuel distributor was gummed up, adding injection cleaner will help.
Popping could be lean mixture.
Does it have a pop-off valve in the airbox?

[flattie]

Well before I installed the new injectors I lifted up that actuator arm in the airbox and made sure I was getting fuel to all of the lines, And yes I was. Where would this pop off be? And yes I have already put injector cleaner in it. Problem is the car will not stay running & when it does how long is it safe to idle the car?

[Fast Corners]

There are a few different types of "pop off" valves. The most common is a black flapper valve that is installed on the left side of the airbox under the air filter. It looks like a tiny toilet seat. This valve protects the box from cracking when the engine backfires through the intake. If you do not have the valve check the box for cracks and if you have no cracks...install a pop off valve.

Do not let an air cooled motor idle for extended periods of time. I believe that the owners manual covers this issue. From the sounds of it I would believe that you have either a fuel delivery problem or you are drawing false air into the system. Check the rubber boots on the intake runners and you fuel delivery system.

[Gunter]

Pop-off valve looks like a little toilet seat.
It's spring-loaded and you'll find it in the airbox on the left side if it was installed.
It's an extra, do a search under pop-off valve.
Re idling:
Check the timing according to the specs: 5 deg BTDC at 950 RPM, vacuum disconnected.
Then set the correct mixture with the LONG 3 mm Allen. (I set mine by ear)
Sounds like it needs to be run hard after sitting for so long.

[flattie]

Well I dont see a pop off valve. I have good spark and fuel What else is there? Sometimes it will sit there and run real smooth for 3 minutes then it will spit and stumble and die then wont start again and stay running.... Im baffled

[Won]

Spit, stumble and intake backfire all sounds like a lean running condition. Improper mixture setting, unmetered air (vacuum leak), or out-of-adjustment WUR are a few things that might cause the condition. If it always runs well from dead cold then starts spitting after certain time, then the WUR is a likely suspect.

Try this:
take off the air filter cover and slightly lift up on the air meter arm that is connected to the metering plate (if not familiar with it, follow the path of air through filter and towards the rubber boot up top and you'll come across it) while having someone start the engine. That will temporarily richen the mixture; if the car was running lean, this will make it run better. If there is an improvement with richer mixture, then you need to figure out what's causing lean mixture and fix it. Be careful not to get caught by the fan while you're doing it, watch your fingers/necktie/shirts, etc.

[TibetanT]

Do all of the above as mentioned. Most importantly, put some new spark plugs in and make sure the valves are adjusted properly. Then, set the timing as Gunter mentioned.

[Gunter]

If there is no pop-off valve in your airbox, it is possible that a back-fire in the past created a vacuum leak that needs to be traced; search PP under Vacuum Leak on how to check.
There is also the possibility of problems with system pressure and/or control pressure checked with a special gauge designed for CIS.
I suggest that you get the Bentley SC Repair Manual and read up on the CIS.
There is a lot to understand about the system and may be too much for a novice.
Maybe a knowledgeable Pelicanite nearby can come and have a look?
Other than that, a shop with experience on these engines might be able to narrow down the problem.
Wild guessing and/or replacing parts is not the answer.

Look at the write-up and pictures here:

Air Box Pop-Off Valve:

Sometimes the CIS fuel system is prone to backfires. This can cause a small explosion within the CIS airbox. Without some type of pressure relief valve, this explosion can blow apart the entire airbox. Replacement airboxes are several hundreds of dollars. The work-around is to install a pop-off pressure relief valve in your CIS box. The process is quite easy, and it's very cheap insurance against costly backfires. Be sure to check out our Pelican Technical Article on Installing a Pop-Off Valve.


10-0843-000-M253 911 CIS Air Box Pop-Off Valve, 911 (1974-83)
Brand: APA [Photo] [Photo]

$47.50

[flattie]

Thanks for all the info. I took the fuel filter back off. I had the car idleing for about 4 mins everything was fine I was going to back it out of the garage and it died. So I pulled and injector and liffted up on that arm and it only sprayed for a few seconds then it was all over. Im thinking its starving from gas that would be the stumble. So tonight Im going to hook a hose up to the fuel pump and pump all the fuel out of the tank again into some plastic jugs to see what the fresh gas I put in it looks like. Maybe the tank has some crud in it???? When I took the filter off It appeard to have a dark color of fuel coming out of it. What is in line right next to the fuel filter???? Is that a water seperator? I blew in to the fuel filter and there is alot of resistance there compared to when it was new

[Gunter]

Dirty fuel would clog up the filter.
DO NOT use the new pump to get the fuel out of the tank, the pump is very sensitive to dirt.
Use gravity to empty the tank.
If the new pump has an external check valve, unscrew and clean.
To make sure that the tank is clean, empty the tank and open the cover on top that holds the fuel level sender and use a flash light to look at the bottom.
Careful! Have a fire extinguisher nearby.
Fuel delivery components:
Pump delivers to Accumulator which is next to the filter, then into the filter, then into the fuel distributor.
Flush out the lines from the pump to the Accumulator, disconnect and empty out the Accumulator, disconnect and clean all fuel lines.
There is a tiny screen in the line on top of the WUR, open the line and check/clean.
The injectors also have a tiny screen inside.
Consider disconnecting the injector lines for cleaning, then soak the injectors overnight fully submerged in injector cleaner, blow out with air.

It's a lot of work but needs to be done.
Get a new fuel filter.
I still recommend the Bentley, lots of good info you'll need.

[JK-81SC]

I went through a similar problem with my '81 a few years ago. It sat idle for a few years while I was in the middle of several projects. You have replaced several of the components that are prone to getting clogged, which is a good start.

My car had a sticking metering piston in the fuel distributor. It had a ring of varnish that had to be removed. The piston is machined to very tight tolerances, and the slightest bit of gunk will keep it from moving. If you decide to take the distributor off, be very careful with the piston. If you drop it or nick the piston it may be damaged, and new fuel distributors are crazy expensive. Here's a diagram that I copied from some else. It labeled as control plunger in this picture.

[flattie]

Ok I will do those things What is the WUR???

[JK-81SC]

The WUR is the control pressure regulator, or warm up regulator. Once you get your car running on a regular basis, it is worth your time to check the fuel pressure. Once you have correct fuel pressure vs. temperature, the car will start easy and run great. Here's another pic from Pelican, it's the part in red. There are many, many hours of reading about the WUR.

[Gunter]

Warm Up Regulator, also called Control Pressure Regulator.
Situated between #1 and #2 intake runners.

Buy the Bentley and you'll learn all about Accumulator, CSV, ASS, TTS, WUR, AAR, AAV, Deceleration Valve, Frequency Valve, OX Sensor, Lambda and the many components that make your '82 run.

You'll love it.

[flattie]

Thanks for all the info. I got it up and running now the gas tank had some crust inside it I had it boiled out and changed the filters again and bam its up and running good now