Newbie towed home tonight

[72viper911t]

I've had my 72 911 (first Porsche) for a couple of days. This car has a 3.0 sc conversion with I believe (CIS). Today, I took it on a 200 mile drive. After a long run I parked and let it sit a few minutes. After start up, it ran rough, sputtered, and later died on freeway.
When I got home I started reading the threads. Spark was fine. I opened the air box to find the pop off valve completely dislodged from it's hole. Glue didn't hold. I stuck it back in and the car fired up. Does this air box need to be air tight for the car to run? Could this have left me roadside?

[Geronimo '74]

I doubt that that was the problem, But I'm not a CIS expert.
Not really sure what it could be though.

[80-911SC]

sounds like hot start, accumulator, fuel pump, hot fuel any number of issues .......

have you had any one other than your self(not implying any thing ) but did you have a PPI done ? do you have a local shop around ? or a lot of times if people post their location n here people are willing to help. St Paulie and Heineken are the more popular enticements although pizza works, and Butters owner just promised cookies by mail to someone on another post ......

You are also obligated to post pictures with your first posts so that we may praise your purchase and or ridicule the previous owners style/color choices .......

Best of , Post more info as you get it and DON'T FORGET THE PICTURES < WE LIKE PICTURES>

[Mitch Leland]

Viper,

You might start by using the "search" feature if you think your problem is centered around your air box:I put in - "airbox pop off" and came up with this...

EXPLOSIVE Airbox!!!

Actually there was a whole list of relative material on your airbox and engine starting failures.

Has Newbie posted pictures of his new 911, and you will get more help if you post your location.

[72viper911t]

Is this 72 911t a fair price?

PPI done by Auto Atlanta. No problems found with engine other than a couple of small oil leaks and the need for stainless fuel hoses.

[James Brown]

If the pop-off valve becomes disloged allowing air to get into where vacuum is, the car will sputter and stall and not run. A CIS system requires 0 vacuum leaks to work properly. Use a good epoxy to seal the pop-off valve in the hole. Did you hear a back-fire when you started it after the long run? There kinda muffeled (or very loud), that could have fired the pop-off valve out.
get a firm grip on how to troubleshoot the CIS system or find someone that does. it is the heart and soul of the engine and does work great but can get out of adjustment. search some threads on CIS adjustment.

[80-911SC]

oh crap, is this the car that was on here a month ago in the for sale that the poster mad the engine issues with , I dont remember the posts but i am hitting the search button right now , Mitch you posted on that didn't you or does any one else remember??????????????

Not trying to scare you but give them, us , just a minute ...I'll get right back.

got to go to bed but will check in am

[jwetering]

Originally Posted by James Brown

If the pop-off valve becomes disloged allowing air to get into where vacuum is, the car will sputter and stall and not run. A CIS system requires 0 vacuum leaks to work properly. Use a good epoxy to seal the pop-off valve in the hole. Did you hear a back-fire when you started it after the long run? There kinda muffeled (or very loud), that could have fired the pop-off valve out.
get a firm grip on how to troubleshoot the CIS system or find someone that does. it is the heart and soul of the engine and does work great but can get out of adjustment. search some threads on CIS adjustment.

No doubt... I don't know what the first few replies were thinking. They are just wrong (you see even on the internet!)

A dislodged pop off valve will absolutely cause sputtering and leave you stranded. Epoxy that thing in there righ now and get back on the road.

[80-911SC]

are you in GA?

[80-911SC]

Originally Posted by jwetering

No doubt... I don't know what the first few replies were thinking. They are just wrong (you see even on the internet!)

A dislodged pop off valve will absolutely cause sputtering and leave you stranded. Epoxy that thing in there righ now and get back on the road.

Damn i thought my suggestion of getting someone who know to look at it was right on but I guess you know better , by the way what are symtoms of a bad accumulator ??? hard start after sitting? stubleing ? doesn't sound that dumb to me ........ but Id get it to a shop before just epoxying and drive it . thats sound advice.

Especially if thats the car I think it might be .

I am still checking

[jwetering]

80 - the man asked this question here....

Originally Posted by 72viper911t

Does this air box need to be air tight for the car to run?

There's kind of only one answer to this question. (it's yes by the way)

[HarryD]

I had a similar problem with my car. I had a huge backfire and had the valve come out of the hole.

I chipped off the old glue around the hole and valve body. I then cleand the hole and valve with carb cleaner and isopropyl alcohol. Used some 400 emery cloth to rough up the valve body and the hole then used regular (not 5 minute) JB Weld to reglue the valve into place.

My mixture is fine after the fix. I figure the backfiring was from the slow failure of the pop off valve glue creating an air leak.

[James Brown]

Sometimes good, sound advice is just a bit off....The clue was the pop-off valve was sitting in the air box and when he put it back, the car ran. It could be a bad accumulator or 10,000 other things. firt things first.
80-911sc, you know this car first hand? was it yours or a friends? that could be some good advice. First-hand knowledge.

[HarryD]

Originally Posted by James Brown

Sometimes good, sound advice is just a bit off....The clue was the pop-off valve was sitting in the air box and when he put it back, the car ran. It could be a bad accumulator or 10,000 other things. firt things first.
80-911sc, you know this car first hand? was it yours or a friends? that could be some good advice. First-hand knowledge.

Jim,

Good advice. At this time I would reglue the valve and check for vacuum leaks. Assuming none are found, get the mixture checked on on a CO machine. The pops are typically a lean mixture with the most likely suspect unmetered air.

72viper911t,

How did the car run and was it easy to start before it died?

[don gilbert]

Ive been stranded a couple time from a pop valve that came loose. The best thing i have found to put it back in is the black urethane. (not silicon) Ive done about 5 with it and have not had a failure yet.

[al lkosmal]

+1 on the popoff valve. You were spot on in your troubleshooting. Popoff valve loose = massive vacuum leak =no go. Popoff valve tight = no vacuum leak = go. Been there, done that.

Regards,
al

[vash]

the airbox is the space below the airfilter. popoff valve being sealed is essential to your car running.

[w21055]

+1 on the airbox. If you are on the southside let me know and I would be willing to look at it with you. I pondered buying that same car.

[72viper911t]

Automotive Professionals in Atlanta installed the valve in September and have offered to correct (reglue) the valve free of charge, so I will take them up on that.
80sc, if you know of some issues let me know, but I don't think the seller posted on Pelican. Btw, I'm in Smyrna, northside of Atlanta.

[72viper911t]

Originally Posted by w21055

+1 on the airbox. If you are on the southside let me know and I would be willing to look at it with you. I pondered buying that same car.

It would be worth the drive just to check out your collection and see what that viper looks like.