Distributor Issues

[Guest]

Hi.
Started car testerday, idled for about 20 seconds then cut out completely. Flattened battery after leaving 20 mins between attempts. Fuses ok, Fuel ok, put in new relay under pass.seat. Still no joy. On checking distributor rotor arm, the shaft it attaches to also came out and at the bottom of the casing there were two springs sitting unattached to anything. What do these attach to, there seems no obvious points. One is slightly larger than the other. Do I need a new distributer and any idea how much these cost. Any help greatly appreciated. First 911 and this is only day 5!!! Cheers

 

[bones]

Firstly unless you have already set your engine to TDC on cylinder 1 don't remove the distributor body or you will have to remove the engine to set the static timing. This fault you have sounds really odd, the springs you describe sound like the springs from the advance /retard weights. I can only assume that somehow your distributor has at some point been wrongly reassembled or has just unscrewed itself!? The top part of the dizzy shaft has it's own little assembly involving the bob weights and springs. I've recently had my dizzy rebuilt but out of the engine , I think it would be hard to work on in the car. Where do you live?

 

[Guest]

Hi,
Live in Edinburgh. I wont be removing the distributor body, i'll have it picked up and taken to the specialist next week. The springs are only about 1cm long with a ring on each end to attach to something. There is still a shaft sticking up about 3 inches beyond the advance/retard weights. This is very much in place and solid. There is a cover which slides down onto this that the rotor then fits onto. When the whole lot came out it was a T shape, the horizontal part of the T being the rotor itself. At the other end there is a small t shape bit with bits sticking out of each end, the bottom bits would seem to move the advance/ retard weights. Maybe the springs go onto those? The distributor casing is still bolted in and solid, with the shaft still very much attached into the engine casing. Its hard to describe all this. Sorry about that. Thanks for answering back.

 

[Guest]

Dude,
The 3.2 has no points, therefore no advance mech in the dizzy. The loose shaft is a problem. I checked my bentley - no drawing of internal dizzy? Look for a detailed drawing. try pelican?
The broken shaft would explain the no go? No rotor to fire the plugs.
There must be a key way or locating spline?
Keep us informed.
best of luck.

 

[bones]

Hi Peter there's no points on my SC but it has advance/retard weights and springs in the dizzy, I've seen them and I have spares. I didn't realise the advance/retard was purely electronic on the 3.2, how does that work then?

 

[Guest]

Peter,
The DME controls any advance required, via the crank sensors. Plus the air flow meter enters the equation.
From Pelican'; found this quote:
#
The DME system uses six primary sensors for input:

1. Air Flow sensor - Measures airflow, and air temperature
2. Reference sensor - determines where the engine is in the rotation - a single pin on the flywheel tells the computer that the engine is TDC for Cyl #1
3. Speed sensor: Determines how fast the engine is rotating
4. Head Temp Sensor: Measures engine temp, adjusts fuelair mixture accordingly
5. Oxygen sensor: Measures exhaust output and adjusts fuel

Later models also have a knock sensor: when detonation is detected, it retards timing in 3 degree increments until the knock is gone, then starts advancing the timing again.

Cam timing is set when the engine is built. It can be adjusted within a small window for low end or high end performance. Changing camshafts changes this timing window.

Ignition timing is controlled by the DME based upon input from the sensors, notice the end of the distributor rotor is more arc shaped rather than a small point. The arc allows the DME to advance or retard ignition timing anywhere within the arc of the rotor end - usually +/- 7.5 degrees.

In short, the inputs to the DME tell it what cylinder it needs to fire on, at what timing and how long to keep the injector open.

There are several aftermarket ignition systems out there that measure crank angle and use a series of capacitors to produce spark - I've installed them on CIS (early 911930) cars, but have not installed one on a DME 911.

The quickest and cheapest "oomph" for a Carrera that I've seen (without tearing the engine apart) is a mass flow sensor (with chip upgrade) and a set of SSI with a sport muffler.

AFJuvat


__________________
Es geht nicht darum wie schnell man faehrt, sondern wie gut man schnell fahren kann.

Ihr Brunnen der nutzlosen Porsche Information

I wonder if the springs are doing something else- like retaining the shaft? Wouldn't think so?

 

[Guest]

Hello all,
Thanks for all the comments. I'll talk to Porsche tomorrow and have the car taken over to the specialist midweek. I'll post a reply and let you all know the outcome, and perhaps shed some light on what seems to be a bit of a mystery with regards to the springs. I can't figure out how the rotor can turn if the part its connected to has no way I can see of engaging with the shaft it goes over, which comes up between the advance/retard swithches. I,m obviously missing something. Lets hope rebuilt or a new dizzy will get the car up and running!

 

[sep4]

Just to clear my mind, was a chrome 6-pointed star type rotor attached to the shaft immediately below the rotor arm?

 

[Guest]

Hi
Can't recall seeing anything like that. There was nothing attached to the shaft below the arm itself.

 

[bones]

Well that clears that up Peter. I'm thinking of fitting the CIS to EFI kit at some point but I would still have to retain my part mechanical distributor as the SC doesn't have all the necessary sensors etc.
Portway mention the pistons are not at TDC these things are easily overlooked.

 

[bones]

An interesting point I discovered today in the development of the Motronic engine management system which was first fully implemented on the 3.2 is the fact that although the advance curve is electronic the retard is mechanical and that explains the bob weight springs Derek found in his dizzy.

 

[Guest]

And finally!!!
Hi bones. You are correct. Springs control the tension on the advance retard switches. There are two and one is slightly longer than the other. What had happened is the part the spring attaches to on one of the switches had snapped, and the other was half way there too. Managed to source a used dizzy from porscheshop (Great guys) and fitted with engine set to TDC etc. New rotor and cap and the car fired up first time, much to my relief. By the way, a new dizzy from OPC showed none available worldwide!!! I still have the old one which i'm sure could be brought back to life if someone gets stuck. Back on the road and off to the north of Scotland on the first long run in the morning. Not the worlds most sensible everyday car, but why not eh! Fingers crossed no more issues, and thanks for all the comments and views from all.

 

[bones]

That's great to hear hang onto the dizzy I have half a spare as they are hard to come by new and expensive. I had my rebuilt at JZ while I waited for £20.00. It's only the retard that is affected by the bobweights. Your 911 is suited to practically any journey they are amazingly tough cars. Hope you find some cheap petrol !