Engine Issues

[copper]

69 911T 2.0 Stock.

The car was running well earlier this summer. The points started going, and it was running rough as a result, missing due to horrible timing. (Dwell was really unstable)

Replaced the points and condenser and set the timing. Seemed to be running a little rich at the time. Lots of black carbon at the exhaust tip, but the plugs seemed decent when removed, just some black which cleaned up.

Anyhow, she's been running well until this week. On start up, she takes a little pumping to get going and coughs out a cloud. Then you have to tap the throttle to keep her from stalling, but as soon as she's out of the driveway and to the first corner, she stabilizes and I can shut down the idle control and she idles between 900 and 1200 RPM, depending on the day.

Once she's hot, she will give one backfire through the exhaust on decelleration from about 4000 or 5000 RPM. Also, once warmed up, if I stop somewhere and shut her down, she has a hard time starting, like she's flooded (no throttle and idle control closed) and I have to put the pedal to the floor to get her to catch. But only when warm.

The power is there, although it seems to have declined a tad. I don't hear or feel any distinct misses as when the points were way out.

I checked the exhaust system for leaks and found a leak between the muffler and heat exchanger and replaced the gasket.

Any thoughts on the cause of this problem?
It's been about 3 weeks since the new points. Should I adjust the dwell and timing again?

Is there a way to tell for sure if the mixture is rich or lean without a flowmeter?

Thanks
Jim

[k9handler]

fuel filter?

[copper]

Haven't checked it.

Is that a guess, or does this sound like it could be from experience? (No sarcasm intended.)

Jim

[k9handler]

I had issues in the past where the engine would run iratic and would lose power enough that I would have to pull over...shut it down and let it sit for a moment before I could start it up and continue on my way. Turn out that my fuel tank was rusting and the fuel filter was clogged with rust...I did the POR fuel tank treatment and replaced the fuel pump and filter and had no problems since. I looked at your post again and it seems your issue is fuel related but not similar to what I was dealing with...so just something to check.

[copper]

Thanks a bunch. I'll check that out.

I know on the MFI, you can clean the filter screen.
However, it appears that mine on the 69 is a sealed unit. Is this so? Or are they serviceable.

The car did sit for 10 years with a partial tank, so the possibility of rust is good.

Please tell me more about the tank treatment.

Jim

[copper]

Oh, and when changing the fuel filter, do I have to do anything special like bleeding the system, or depressurizing it first? I've changed the fuel filter on my motorcycles before, but I'm relatively new to the Pcar.

Jim

[Fishcop]

Sounds very similar to some of the problems I had with my 69. A Crane XR700 with optical ignition completely resolved the issues you are describing. Are you using a bosch or marelli distributor? And are you using an appropriate temperature sparkplug?

The above remedy cured all the fouling problems I was having and further cured hot/cold start issues.

Hope it helps

[copper]

I've got a Marelli. I could have bought an XR700 on eBay. It went for $10.50. But I could not find an optical sensor to fit in the Marelli and had heard about difficulties with fitting Pertronix or Crane systems into Marellis. So this meant I would have to change the Distributor. Needless to say, I let the next bidder take it for $10.50.

We figured the new points would correct the problem, as it was running well before and didn't have these problems. And I mean within the last couple of months before the point contacts failed. Now I'm wondering if the timing and dwell needs another adjustment since the points have been in for a few weeks and have had time to settle.

I will also replace the fuel filter as I'm not sure when it was last done.

Jim

[k9handler]

the fuel tank treatment is available from POR direct, and it's pretty simple as you just follow the instructions. The total project takes at least 72 hours (The tank treatment has a cure time) so it's not a simple two day job. The fuel filter is no big deal, unscrew it and put in a new one. My car was a CIS car at the time, so your MFI parts may be different. For example my car also had a small screen filter in the tank that was completely rotten with rust, you can buy a replacement part...but I just removed it as the fuel filter seems to be enough.

I would work on the spark/fuel issue first as that is more than likely the issue.

[RoninLB]

Originally posted by copper
Now I'm wondering if the timing and dwell needs another adjustment since the points have been in for a few weeks and have had time to settle.

I would reset new points after 500mi, then after 5k miles.

Why not check dizzy timing advance?

I don't know anything about MFI, but maybe it's rich enough that the engine needs 10mi to warm up?

[Fishcop]

I should have mentioned that I changed the Marelli for a Bosch. If you do a search you'll find an inexpensive resolution for a lot of us 69'ers is to use a later 2.7 distributor and have it machined down to Marelli specs. The advance is very similar (particularly for a T) and you now have a ready source of caps and rotors for which are no longer available to Marelli units. I believe someone has one on the buy/swap forum for under $100. It has been discussed a few times now how the original NLA Marelli is deteriorating after 35 years and with no back up or replacement parts a switch to a bosch is starting to become a necessity.

I haven't had trouble with my fuel tank (touch wood), so I can't comment on that aspect.

[copper]

I actually found the points for the Marelli, in stock, at Downtown Porsche in Toronto and had them that day. I was surprised. What surprised me further was that the points were only $11 Canadian. This, from a source that wants $2300 for a new heat exchanger...

I picked up a new fuel filter about 1/2 hr ago. I will get that in and see if that fixes some of the problems.

I do suspect that my fuel tank is rusted as when I removed my fuel sender to replace the gasket after 10 years of being stored, the lower 1/4 of the sender (not stored with a full tank) was discolored a reddish brown which I can only attribute to rust in the fuel. I'm not sure what the extent is, or how exactly to determine this, but any tips from anyone having a similar experience would be appreciated.

Thanks
Jim

[Fishcop]

Wait 'till you look for rotor buttons and caps for your Marelli