1972 911 t mfi

[1972 T]

I recently acquired my uncle's 911T. It had been sitting with bad fuel for 10 years in his garage. Since he passed away I have not been able to ask him any of the questions.

The engine seems to run very rough and actually shake at mid to high range on the rpm. It idles very smooth. Here is a list of things I have already completed

I followed the manual with the check/ measure/ adjust theory.

cleaned out the fuel tank and hard lines, replaced all rubber fuel lines, new fuel filter, new plugs, cap, rotor, points, adjusted valves, checked fuel pump volume and pressure everything to that point is correct. I am beginning to suspect the injector pump but also wondering about the injectors themselves. Any thoughts? Any trustworthy MFI mechanics in Central California?

[Zeke]

You might be surprised to find that is a symptom of old plug wires. At that age, I'd invest in some new ones regardless. Worked for me.

[1972 T]

Thanks. Yeah forgot to mention that is one of the things I just replaced.

I did just run some 3M fuel injection cleaner through and ran it for about 5 min seemed to clear up and run better than before.

[tharbert]

You will find a few contacts here. I guess San Fran would be "central."

+1 on what Milt said. Sounds electrical to me. In fact, the MFI troubleshooting chart suggests electrical first.

May I suggest you post the results of each of the CMA steps. It gives the MFI enlightened something to get their teeth into. Thia may even turn into the next best MFI thread. Or maybe you can read this one.

Another cool collection of stuff.

By the way, where's the obligatory picture? Some folks get real interested when pictures are involved.

[Lukesportsman]

Way off topic in a way, but don't know your exposure to early 911's. IF you would have to tear off the pump, then seriously think about upgrading to E spec's on cam and pump. It will really wake up the little engine.

[BK911]

Since you changed the points, definitely verify the dwell and timing. Then pull an injector and look at it. Find somebody with an ultrasonic cleaner and let them soak overnight.

Post pictures!

[Rusty 356]

I've been working on my 72 as well. One thing you can do and is fairly cheap. Remove the injectors and take them to your local Bosch Diesel fuel shop. They can spray check the injectors and check popping pressures. If you stay with the tech, he will most likely continue to spray until the spray pattern looks like it should. I did this with my 2002 tii and it has been running great for 4 years. Haven't had to do that to my 72 Porsche yet.
good luck with the car. Drive it and it will just keep getting better.
Happy Holidays,
Rusty

[Zeke]

OK, let's assume the ignition is spot on. How about the MFI pump belt timing? Also, there is a tiny, fine screen mesh filter inside each injector. Soaking and blowing out in reverse helped me. I soaked them in Berryman's, an Early_S_Man favorite.

[RideShoot&Drink]

Needless to say, this thread is worthless without the pics...

[1972 T]

Thanks for all of the help!

I have the dwell spot on, timing spot on, injection pump timing is also spot on and I even removed the coil and bench tested it. The electrical system seems to be running flawlessly. I found a local who will test the injectors. I think this will be my next step, as the fuel I removed from the car looked and smelled strongly of varnish. This is what leads me to believe it is fuel related.

I will get pics up soon.

As far as the "E" spec upgrade, I have no clue what my uncle had done, but how would I know if the upgrade had already been done?

[tharbert]

I had a thought... Slap your timing light on it. Does your timing light seem to jump around a bit or intermittantly flash when you increase your RPMs to where it misfires? Could be a worn distributor, impinged vacuum advance or something of that nature.

[Rusty 356]

As I mentioned in a previous post, when he checks the pop off pressure and spray pattern, if he continues to spray them the atomization will improve. Or it should.
The other thing I did to my little bmw tii was to remove the delivery valves from the injection pump and clean them. If nothing else things will be a little cleaner.
Good luck,

Rusty

[1972 T]

It seems that I may have found the issue. When I had the engine resealed, the person who did the work took it upon himself to clean the injectors. As the vehicle ran with the clean injectors it was running too rich. So I thought to lean out the injector pump and it is running much better. Thanks for all your thoughts.

[BK911]

Looks like a pretty clean car. I would put a gunson on the exhaust to verify you aren't running too lean.

[911st]

Nice car.

Is the fuel pressure to the pump ok. I second taking the injectors to diesel shop for cleaning and matching.

It might be worth sending the MFI pump in to have it serviced and calibrated to Gus and Pacific Fuel Injection in the bay area.

They tend to get out of spec and everyone that I have heard from that has had this done was very pleased.

I played with my pumps a lot. You might take the pump off and soak it in cleaner and make sure the rack is moving wheel.

The correct way to adjust the pump in the car is on a dyno or on the road with a wide band O2. Setting the A/F at idle like on an SC is not likely going to do it.

Check your throttle plate shafts for leaks. If they feel loose or the RPM changes when you spray carb cleaner on them with the motor running they may need service.

I had a 72T. It is a nice car. I added a rotor with higher rpm from an E. A sport muffler can add hp. If you do this, let Gus know and he will set the pump to work with it. Adding Carrera chain tensioner's is a good investment. I lost a 930 motor to such a failure.

Enjoy.

[tharbert]

I think the car has carrera tensioners. I can see the oil lines in the engine compartment pic....

Nice car!

[Rusty 356]

Definitely a lot sweeter than my almost rat 72 T. But it runs well. Now if I can just get the front end welded in.

Happy New Year to All,

Rusty
(too many Porsches, too little time)

[mjshira]

very nice car. welcome on board.

[RWebb]

welcome!

here are some fun things to keep you busy:
http://forums.pelicanparts.com/porsche-911-technical-forum/189572-long-term-commonly-neglected-maintenance-post2955054.html#post2955054

[zotman72]

Check the screen at the gas tank outlet line. On my '72 T when I got running after it had sat for 10 years, there was all sorts of metal tank material clogging the screen. I had to pull the tank and get it sealed up. I had the same symptoms as yours, which I attribute to the high suction from the electric pump collecting the crap in the tank and clogging itself. Hope this helps. YMMV.