1980 911sc CIS rebuild question. Going through PPI process

[toddbelforte]

I’m in the process of checking out a car to purchase. It’s a low mileage car that has been mostly sitting for the last 3 to 4 years.

The owner couldn’t get the car started. Brought to reputable mechanic. They replaced the fuel pump and filter. It only had a little gas that they did not drain but added new fuel. The car is in Tennessee. My understanding is that the car is starting but still not running right. This was documented by the mechanic after the fuel pump and filter replacement …,

“Found vehicle to not have fuel throttle and buck under load”

If the CIS needs a tear down from the potentially bad/ old fuel, does anyone have an idea what that might cost or if this would likely be the route I’d have to go as the new owner ?

Maybe be the fuel pump wasn’t the correct pump? I’m working on getting information about the fuel pump itself.

It’s a really nice, one owner, fully documented since new car that I don’t want to walk away from, but I am cautious about inheriting major costs for repairs

Your thoughts welcome!

[Schulisco]

My personal opinion - and don't get me wrong: Almost every 911 with CIS for sale is light years away from running perfectly. If it does, the owner either won't sell or he suddenly died or the price has shot up so much that even a Carrera or a 964 becomes affordable... besides - every 911 with CIS will require more or less work. The effort, the pain and the money will not be invested by any seller or dealer, only the next owner... not to mention the lack of knowledge about the CIS.

I would assume that the car does not have just one problem, as most CIS cars do due to lack of maintenance and lack of knowledge about the CIS system. The big advantage and at the same time disadvantage is - you can "tune" the CIS to any state in which it either starts or somehow runs, but as I said, far from running perfectly in all conditions.

What a CIS absolutely cannot tolerate is long periods of standing. So under these circumstances the car is only affordable for someone who can tinker with it himself.

If the price is good enough and you still have the money to fix all the problems over time, go for it! Getting a low-mileage, fully documented, good-condition 911 SC is becoming increasingly difficult. On the other hand, if you have to have everything done in a garage - stay away!

Thomas

[jac1976]

Maybe be the fuel pump wasn’t the correct pump? I’m working on getting information about the fuel pump itself.

Brought to reputable mechanic. They replaced the fuel pump and filter.

Seems it’s one or the other.

[HarryD]

There is an old saying, there are three types of CIS owners:

1) The guys with working CIS systems are probably out driving their cars so they won't reply.
2) The guys that tinker with their CIS systems and have them royally screwed up will keep you running in circles with suggestions.
3) The guys that have spent a fortune on Webers or EFI will tell you they're great to justify their expenditure to themselves.

That said, before you tinker with the CIS components, make sure the car is in excellent tune.

Verify the points (if you have them), plugs, cap, rotor, wires, fuel filter are in tip top shape. Replace if there is doubt.

Drain any old fuel and refill with fresh (non ethanol if possible) fuel.

Do a valve adjust.

Set timing and dwell (if you have points) to spec.

Once this is done, and the car is still not running well, look for vacuum leaks and correct as needed.

Once these items are resolved, it is time to look at the CIS parts. Lots of threads on troubleshooting.

The good news is that once you have your CIS dialed in, it tends to stay that way.

[montauk]

There’s a cube relay under the passenger seat that controls the oxygen sensor stuff. After I went down a lot of rabbit holes with nothing curing the rough running, I replaced that $10.00 relay and the car ran perfectly. Maybe that’s the problem maybe not. If the price is right for the condition of the car, buy it. Everything on the CIS can be fixed. You might need refurbished used parts like a WUR but that’s not a problem.

[Mark Salvetti]

That sounds like a pretty unique car these days. Is it a special color too?

I would not let CIS issues alone deter you from this car. You can either do it yourself with help here, or find a shop that knows CIS. The risk is a shop that doesn't know CIS - to me that is when the cost can get out of control if they just burn hours and throw parts at it.

If leak-down is good and there are no broken head studs, I think you should be OK. There is always going to be a risk of major repairs on a 45 year old car, even if it is running great today.

Mark

[HarryD]

toddbelforte

Please add your location to the information on the left of the posts or in your signature line. It may help us lead you to some local CIS expertise.

[john walker's workshop]

If it's nice otherwise and the price is right, just buy the damn thing and deal with the rest. Hard to find a deal these days.

[PeteKz]

Ditto all the comments above, especially Schulisco and HarryD.

Are you a DIY car guy? If so, and the price is good considering it isn't running right (at least $5000 below the market), then go for it. At least it's running, which is a good place to start. The shop that replaced the filter and pump probably were just throwing parts at the problem. Sure, change the filter because it's cheap, but the pump was probably fine. Get the old one with the car, and you will have a good spare.

In CIS, poor running almost certainly is poor fuel delivery. I find that just pouring Chevron Techron into the tank, then driving the piss out of it, will improve the running substantially. Then you can work on the finer points.

But if you are not a DIY car guy, I strongly advise you to keep looking, and if you have the cash, to go to a newer Carrera model, with the G50 transmission cars (1987-1989) being the best of the series. Of course if you can afford a 964 or 993, they are even better...

[Locker537]

Sounds like a good car to buy!

[toddbelforte]

Thanks for all the great info. I updated my location. Living in the San Francisco Bay area gives me a lot of local resources/ local tribal knowledge fortunately.

Agreed a later year 911s certainly have their benefits.

Pursuing this 1980 since it’s a Weissach model. Plat metallic

I am a do it yourselfer it’s just I don’t have experience with this fuel injection. I built a 914 six with a 3 L Euro Carrera engine/ PMOs. It’s finicky being carbureted, and I would like to put in the time into the CIS if it needs attention. Good advice to make sure all the electronics, timing, valves etc..,is correct and see if the CIS is the real issue or not. If the PPI works out and I buy the car the first thing I would do is drain the gas tank and inspect it. Go from there.

Really hoping this car works out as I love the unique model.

[nickelplated5s]

If it passes PPI for rust, leak down and head studs buy it. First thing is drain the tank and look for schlag. Sitting for a few years with non ethanol and low fuel you probably have it. New tank. Second is to buy a spool of weed eater line and run it through tunnel lines. It's barbed and will come back clean or not. Len here sells replacement sets. I'm stuck with MFI but everyone above can help you after that. To paraphrase "fuel baby." Those years are my second favorite but I'm biased with a 67...

[toddbelforte]

Thanks Nick for the fuel line advice. Are they stainless on SC’s? I only know about the jankie plastic ones on the 914. Replaced those with stainless.

Really crossing my fingers this works.

[Ian Comerford]

Agree with the above advice and would add once you have drained the old fuel and filled with fresh take it for a good drive and see how it runs at the end. As has already been said, they don’t like standing and often need a good clear out if they have.

[PeteKz]

Todd, if you can tune carbs, you can learn CIS. If it's a good price, and the head studs aren't broken, buy the damn thing. If the head studs are broken, negotiate a lower price, then buy the damn thing.

[boyt911sc]

Originally Posted by toddbelforte

Thanks for all the great info. I updated my location. Living in the San Francisco Bay area gives me a lot of local resources/ local tribal knowledge fortunately.

Agreed a later year 911s certainly have their benefits.

Pursuing this 1980 since it’s a Weissach model. Plat metallic

I am a do it yourselfer it’s just I don’t have experience with this fuel injection. I built a 914 six with a 3 L Euro Carrera engine/ PMOs. It’s finicky being carbureted, and I would like to put in the time into the CIS if it needs attention. Good advice to make sure all the electronics, timing, valves etc..,is correct and see if the CIS is the real issue or not. If the PPI works out and I buy the car the first thing I would do is drain the gas tank and inspect it. Go from there.

Really hoping this car works out as I love the unique model.

Todd,

Act quick if the price is RIGHT! Don’t wait too long or this car will be gone soon. You could easily fix any CIS problem known to men. There are numerous members in this community that could assist you. Good luck.

Tony

[Schulisco]

Ohh. A Weissach Edition changes completely the situation. Although it's not that valued and recognized outside of US and despite that the fact, that's "only" an interior and exterior special edition without any technical improvements than the common stock 911 SC from 1980 - it's a still a special edition. It will never climb in value as an 2.7 RS but this is also not the goal, right?

https://www.stuttcars.com/porsche-911-sc-weissach-edition-1980/
https://fineeleven-com.translate.goog/fahrberichte/porsche-911-sc-weissach-edition/?_x_tr_sl=de&_x_tr_tl=en&_x_tr_hl=de&_x_tr_pto=wapp

Get a good deal at an affordable price based on the issues being covered and get it. The Weissach Ed. justifies a slight premium... but not tens of thousands.

Thomas

[Showdown]

I'm with John Walker and Tony; Just buy it and start fixing it.

As long as you're up for the challenge and like complex problems, the car will be a wonderful experience.

CIS is just a system of components. There are plenty of resources, including from Porsche that provide abundant detail of how each part of the system works and if you go through it methodically, you'll get it working.

My CIS was a mess but I, without any prior wrenching experience was able to get it working just by being focused and iterative in the repair process.

[toddbelforte]

I always appreciate encouragement to buy stuff I want and the unbridled enthusiasm about my ability to learn new skills.

The owner seems pretty reasonable and the price seems right in comparison to other 911 SC models.
.
Agreed it doesn’t have performance upgrades, but it is such a unique model it would be fun the share with the Porsche community. And the interior… Either love it or hate it.

[toddbelforte]