1970 911T will drive for 5 mins then stalls out

[GogglesPizano]

Hello everybody,

I am new to this forum, and new to Porsche. I recently picked up a 1970 Targa with a 2.2. The car had been in storage for the last 3 yrs (so i'm told). It will idle normally all day, but if I take it out on the road I can only drive for about 5mins then it will start to sputter and stall out. It will start back up pretty much right away but then i have to keep it running with the gas pedal. The throttle speed controller seems to have no effect on idle once it gets to this point. If I rev it the best way to describe the sound is as though it is missing or may be down a cylinder, yet when it is idling it sounds fine (to my untrained Porsche ears)

I appreciate any feedback.

Thanks

[Flieger]

Running for 5 minutes and dying sounds like the mesh screen filter in the fuel tank on the pickup tube has become clogged with rust, which is very likely for a car that has been sitting for long with a partial tank of (ethanol containing?) fuel in it.

Could also just be dirty carburetors.

[BoxsterGT]

+1 for Flieger.

Ck the fine mesh screen within the brass outlet fitting of the tank. Our host only shows the one from 74 on, not the earlier version that you have. Removing and cleaning it should work just fine.

Len

[whiterabbit]

Yes I also think the mesh screen. I had the same problem a few years back.

[GogglesPizano]

Thanks for your feedback! I'll look into it.

[rw7810]

Or the tank breather tube via the charcoal canister system is clogged and the tank is developing a vacuum

[Tom '74 911]

A new fuel filter couldn't hurt either. . .

[andrew15]

Check your idle jets as well - at lower speeds your carbs are still on the idle circuit and can get clogged with debris to produce similar symptoms to what you are describing.
AM

[911pcars]

Originally Posted by GogglesPizano

Hello everybody,

I am new to this forum, and new to Porsche. I recently picked up a 1970 Targa with a 2.2. The car had been in storage for the last 3 yrs (so i'm told). It will idle normally all day, but if I take it out on the road I can only drive for about 5mins then it will start to sputter and stall out. It will start back up pretty much right away but then i have to keep it running with the gas pedal. The throttle speed controller seems to have no effect on idle once it gets to this point. If I rev it the best way to describe the sound is as though it is missing or may be down a cylinder, yet when it is idling it sounds fine (to my untrained Porsche ears)

I appreciate any feedback.

Thanks

Could be a bad fuel pump, but test the old one before replacing it. Get a pressure tester, then test FP pressure and volume (about 1 qt./minute should do).

Sherwood

[RSBob]

Had something similar with my 73. When the car warmed up it ran like crap. Practically tore the fuel and ignition system apart. Turned out to be bad spark plug wires. Replaced the wires and no more issues.

[daniel911T]

Change out the old filter. Add new ones.

On my car I now have 3 filters before each carb. There is one just coming out of the tank, one in the engine bay before the pressure regulator, and one before each carb.

The carbs were thoroughly rebuilt less than 200 miles ago. I just had the tops off of the carbs today.... there was rust in the bottoms of the bowls, even through all those filters.

My solution: find a friend with a tank that's already been cleaned, coated, and pressure tested, and buy it for nearly free. I just installed the clean and coated tank today, and I've never seen gas so clean.

(The whole time I've owned the car I thought gas was orange!)

To make the point a bit clearer.... rust is a serious issue with that era of car, including the gas tank. There are also a few steel parts in the carb bowls that have been rusted out on all 6 Zenith carbs I've disassembled. Rust can really muck up your sensitive carbs.

My method for the quick and dirty rebuild is to pull out all the brass parts, drain the carb bowls, and spray about a can of carb cleaner in every orifice of each carb. Be sure to save some to spray through the main and idle jets.

One last thing to consider... check out the ignition system. The CDI box may be dying, and after about 5 mins of running, it is failing. Let it cool a few moments, and it's back in action. It could also cause your trouble.

Feel free to contact me if you need any help. I'm working with the exact same motor, and I know every piece of it way better than I ever wanted to. I've also fought the tuning wars to the point of near madness, but I've come out the other side with a car that runs pretty well.

-Dan

[GogglesPizano]

Thanks again everybody. My car is being shipped across the country, as I have recently moved. As soon as I get my hands on it I will try these helpful suggestions and let you know how it goes.

[sixbanger]

I'd take the tank out and clean it out. You will also be able to replace the old hoses at the same time. You don't want a fire.

[T77911S]

as everyone is aiming for, fuel starvation. dont forget it the needle seats for the floats.

check fuel flow, pressure and volume

[Joe Bob]

Screen and/or filter....would be a good idea to put a fuel pressure gauge to see how it's doing.....