Ign.DIst.Vacum Advance & Retard

vizail · 03-05-2006, 03:44 AM

I have been using my 911 with the advance Vacum line disconected and pluged. Still work's ok since apparenty the Centrifugal advance is Working.
If I connect back the line I start getting some backfires from the engine .
With a two way Vacum meter "Gage & Pump" I check how much Vacum the lines where producing, I check the advance and Retard sides and they are Ok.
I suspected that the Vacum Diaphram was broke. but tested it and did hold Vacum ,no apparent fracture in the rubber.
If I run the engine Advance Vacum Disconected it Works Ok + or - ,But when I connect the Advance Vac line it does't work well. I took a small brush with Lubriplate grease and lubricate the area (Weights and springs"remove the extra grease" and no luck .It Coughs and kick. Same as before

All the Help will be Apresiated

Vic

stlrj · 03-05-2006, 01:16 PM

Do you know which vacuum line goes where or are you guessing?

Joe

Early_S_Man · 03-05-2006, 01:32 PM

Vic,

Is this an SC engine with two vacuum ports on the distributor?

If so, the line to disconnect is the retard port, not the advance! You need both advance systems working properly. The retard mechanism is only active near idle ... has no effect on the working rpm range of the engine!

I suggest plotting your centrifugal advance curve ... to see if any further remedial action is needed.

vizail · 03-05-2006, 03:17 PM

Joe
I know were the Advance and retard lines go. I'm following the Vacum line Charts. The advance line is connected in a Port right of the Frequency Valve In The Trottle assembly.

Early _S Man . That is a good Suggestion to disconect the retard line and then connect the Advance . I'll do That.
Can you tell me more about the Plotting of the Curve?

Vic

stlrj · 04:23 PM

The retard line will have vacuum at idle and will cause your engine to slow down as soon as you connect it to the retard side of the vacuum unit and it will speed up your engine if you connect to the advance side.

Quote:

The retard mechanism is only active near idle ... has no effect on the working rpm range of the engine!

Well, not exactly. The retard works whenever you release your throttle anytime you're coasting, at times of high vacuum, at all rpm's and works with the decell valve and helps prevent popping, backfiring by retarding timming while adding some extra 02 to the mix for more complete combustion.

The beauty behind the retard is that it also gives you an instant 10-15 degrees advance at any rpm the moment you get back on the throttle for enhanced throttle response which is a very good thing for performance.

Cheers,

Joe

vizail · 03-05-2006, 04:02 PM

Joe and Early_S_Man
Can You be more specific. Or Have Charts for this explanation?

Vic

stlrj · 03-05-2006, 04:10 PM

Pick up a spec book for the charts.

Joe

vizail · 03-06-2006, 04:43 PM

Ok Now

How can one Plot a curve? With a DWEL CAM Angle gage(Unit). Those are colectors Items.

Vic

stlrj · 03-06-2006, 05:00 PM

All you need is an ol' fashioned 12V timing light with an inductive pickup.

vizail · 03-07-2006, 02:37 AM

Yes . I have tryed to time my 911 with an Old fachioned Inductive Timing light with not good results.. As we all Know the Static Timing is 5+- BTDC, I just set it there and work from then on.
I get very erratic readings when using a T Light . and the timing never gets right. hik-ups and backfire.

If I disconect the advance I can get better or acceptable performance. Do I will like to get it to work as it should be.

Vic

stlrj · 03-07-2006, 03:10 PM

Helps to know which engine we're dealing with.

Joe

vizail · 03-08-2006, 03:12 AM

3.0 1982/ SC Jetronics

Vic

stlrj · 03-08-2006, 04:19 AM

Has the distributor been out?

vizail · 05:25 AM

Out of what? . Do you mean out of the Engine? Yes about 2 years ago while restoring the engine. I Get the Car engine not running . I had to rebiult the engine since I wanted to Resto. The engine has been back in the car about 2 years adjusting here and there . Getting ready to complete the mechanical and then finnally get to the Paint.
The Only isues I have left with this car .
1. Fuel Injectors Inspecction
2.New Oil Lines
3.A/C
4.Transmission
5.Paint
And of course the tham Igntion. Dist

I've been practicing my DIY skills with this retirement Project and I'm slowly getting there

Vic

Gunter · Gunter's Garage

Can someone confirm that the vacuum ADVANCE line has to be connected ABOVE the throttle plate, and the RETARD is connected BELOW the TP?????
'82 SC's also have an Acceleration Enrichment Control Unit triggered by an additional Micro Switch on the TP-shaft.
I would try 7-8 deg. BTDC and make sure the Advance/Retard lines are connected in the right place on the throttle body.
Sometimes the timing light (Stroboscope) will not work right if the pick-up on the #1 cable is too close to another high tension cable especially when the cables are older and lose insulation capacity.

vizail · 08:56 AM

Gunter and Guys Thank you for coming aboard . Here I have a couple of Pix that include a testing of the Vacum Diapragm. Here it is.
The first pic is about the remote Vacum pump that I used to check the system

Here is the Test of the retad side( The apparent retard side)closest to the cooling Fan. It holds the Vacum meainning that the Diapram is good and actuates between 7psi(or Vacum) mooves to total position at 9psi

In this next Pic you see how much the plate travel apparently the plate travels more in the retard side?????

Now here is the Advance side( apparent advance side)

Now see this minimum travel of the plate at maximum PSI(or Vacum of 12psi)

The diaphramg sims to be ok since it hild the Vacum.
"HEY THE ROTOR IN MY 3.0 911 ROTATES COUNTERCLOCKWISE!
IS THAT OK "?
Ah!!! fortet to mention that I find the the retard Vacum line produce more vacum and only when decceleration

Vic

Gunter · Gunter's Garage

Yes, all SC 3.0 liter engine distributors rotate CCW (counter-clockwise).
The Bentley SC manual shows CW by mistake.
All other Porsche engines have the distributor run CW.
To test the diaphragm the old fashion way is to suck on the vacuum line while observing the plate movement.
The coil in the pix doesn't look like a black Bosch coil normally found in 3.0 liters.

stlrj · 03-08-2006, 02:47 PM

Since the distributor has been out of the engine, it's possible it was not reinstalled correctly.

See if the rotor lines up with the mark on the distributor rim with the engine at top dead center.

vizail · 03-08-2006, 03:19 PM

Gunter
Yes the Dist. Advance and retard plate moves a lot to the retard position but only a bit to the advance as you can see in the Pix. The Diaphramg is ok since I test it for leak and it hold the Vacum. The coil in the pix is the one that comes with the MSD. I had to install an MSD Unit since the CD unit died on me. I wonder if I can replace the Original One? Is shorter and will look better. Don't you Think?
The Ingnition plate is defective is my conclution It got to be.
As as being reinstalled incorectly as Joe sugested No.
I just put the pulley in the Z1 at Top dead center TDC. Of course it was not dead aligned since it was timed 5 deg. Or it has to alingned perfectly to the Dist. rim mark?

Vic

I'm getting very tired with this

stlrj · 10:44 PM

Quote:

Of course it was not dead aligned since it was timed 5 deg. Or it has to alingned perfectly to the Dist. rim mark?

We may have found your problem. It needs to be aligned dead on.

What happens is when you first line it up to insert it looks fine until you get it down, then the timing gear gives it a slight twist from the angle cut and then your off. Try again, this time compensate for the final twist so it lines up perfectly once you get it down.

Minor detail with huge consequences.

Joe