First Post - Problems with 76 911S

[kbucknam]

Hello All:

This is my first Porsche and my first posting. Wanted a 911 all my life and finally purchased a 1976 911S Targa a few months back.

Been having problems with starts. Takes a few cranks to get it going and often times when it starts runs like it is running on only 3 cylinders (bucking and sputtering). When I press on the gas, I usually get slow RPM increase and then a backfire or two. Eventually the idle will get to a normal steady rate. When driving it sputters a little taking off from a stop. Once I get to higher gears it runs great. Took her into a local reputable Porsche mechanic last week. He replaced the fuel accumulator, cleaned out the WUR (it had some rust build up at the screen, and checked the wiring of the warm-up valve sensor. All his tests indicated it was not losing fuel pressure and it was starting up fine. Of course, after an invoice of $400, once I got it home the same old symptoms.

This weekend I filled up the tank with Regular (had been using premium) and put in some gas dry additive. Started all right this morning, but still sputtering a little.

Also - I've got a popping (not a backfire - I don't think) on deceleration. Is this a normal 76 porsche sound?


Any advice?

[MotoSook]

kbucknam, Like you I wanted a 911 for a long time. I finally bought one toward the end of college. As most of us know, in college you were poor, not poor or creatively poor. I was creatively poor and managed to get my first 911, a '76 911S (the creative part).

I did not know much about 911s and I got the 911 for a pretty low price. Had I know about some of the problems with that series 911, I would have waited until I could afford an SC.

I drove the car until I started to have problems with it and one shop told me it needed a motor rebuild or a swap. Well that was about the cost of one year's tuition so I stored the car.

Sorry for the long test above, but I understand your excitement in having your first 911 and the disappointment because your dream car is having problems. I'll try my best to help.

First, get a copy of Wayne's book, the 101 Projects book. Get all the manuals you can find. It will save you time and money.

Order a fuel pressure tester from JC Whitney. It's about 60 bucks. If you don't have a multimeter, got one so you can trouble shoot the electronic gremlins that will occur in our old cars.

Get a timing light. Sears has one with a dial to advance the strobe. I think I paid $50.

Finally, strap on some cajones and don't be afraid to work on your own car. The Pelican forum will be very helpful.

Now for your problem. Did the mechanic change you fuel filter when he changed your accumulator? Did he test the fuel pressures to determine that the accum was bad (not making an assumption that he did)?

Have you or your mechanic changed your spark plugs? Did he check timing? Is your vacuum retard working properly?

If your tech checked the fuel pressure, them you might have an ignition problem.

Hang in there and the forum will come to your rescue. There are some very knowledgeable guys here.

Welcome to the community.

Souk

[1980SC]

Sounds like your warm-up control pressure is too lean. Common problem. The WUR can be adjusted for this, but do buy that CIS fuel pressure tester that Souk mentioned. It's a very valuable tool if you want to get your fuel injection working properly. There is a tech article here on Pelican about adjusting the WUR.

Rob
1980SC

[Targa77]

On the top of your fuel distributor (top right of engine) there is an access hole on the left side where you can adjust the mixture by using a long 3mm allen wrench. This opening might have a plug inserted (thin steel shaft with a loop at the top). Insert the wrench and turn it one click clockwise to richen the mixture. If one isn't sufficient you can try two clicks. Now see if your car runs better. You will need a CO gauge to accurately adjust your mixture but this will at least give you a clue as to the problem being the mixture adjustment. I adjusted mine and it runs like a champ now. Like the others stated, I would also check the plugs, point gap, etc. Hope this helps.

[wckrause]

Before doing any of the previous items, get the Fuel Injection book by Probst, and learn how your CIS system works. Even if you don't end up doing the work yourself, you'll be able to ask enough intelligent questions to keep your mechanic honest.

Questions like:

Why did you replace the accumulator? How did you test it to know it was bad? What role does it play in cold starting (none).

Did you measure the system and control pressures? What were they when warm and cold? Are they within spec.


I had spent at least $1000 with two different mechanics trying to fix a cold start problem. Neither one could fix it, and blamed it all on "vacuum leaks". Using the Probst book, a CIS pressure tester, and help from this board (lots of help). I was able to fix it with a squirt of Gumout through the thermovalve, and a couple of taps on the WUR. Now it starts like a champ at -18F.


Get the Probst book!!!

[Rot 911]

In your posting you wrote: "This weekend I filled up the tank with Regular (had been using premium) and put in some gas dry additive. Started all right this morning, but still sputtering a little." Which makes me ask the question: How long was this car sitting around before you bought/drove it. Always start with the simple things. Is it possible you have bad gas or had some water in the gas? Both could give you the symptoms you describe.