mark '87 930

This is an old thread.. but I thought I'd ask a silly question..

I am using the lead right at the distributor cap to hook up to #1, but the timing light isn't lighting up... My spark plug wires are braiding (not close to the distributor cap though), which is why I am so close to the distributor. Do the new timing lights require less energy from the spark plug wire to run that the olders ones (hence the reason for my timing light not working)?

Peter Zimmermann

Scott: All of Steve's info is correct, but I want to back up a step or two from your original question, and ask another. Why is the timing retarded? There are two answers that will take care of about 99% of this question: (1) Somebody set it wrong, or (2) Your dwell angle for the ignition points has changed. Let's address #1 first. If the timing was set wrong it was probably done to put a Band-Aid on a different problem - a fast idle, which most often occurs when the MFI throttle bodies are worn and taking in too much air. On to #2. Bosch points have a terrible tendency to close up during use, because of weakness in the rubbing block that runs against the distributor cam. As the block wears the contact points get closer (narrower gap) which translates to a higher dwell angle. Let's review what dwell angle is - it's the amount of rotation that the distributor turns between the time that the points close after firing a cylinder, and the time that the points re-open in order to fire the next cylinder. Something else essential to know; one degree of timing = one degree of dwell. Hmmmmm. So, over time, your points have closed up from the previously correct setting of 36 degrees (38 +/- 3 degrees is the spec for your car), to a vary narrow gap that translates to 45 degrees dwell. Hmmmmm. 9 degrees of dwell = 9 degrees of retarded timing. What do you get? A lousy starting, lifeless running car that is just about to leave you stranded. Always check dwell angle or replace the points before messing with the timing. Then time the car the way Steve told you.

Mark: Of course, your Turbo does not have points, and things are pretty congested near your distributor. First, be sure that you are using a known hot (12v) terminal for your timing light's red lead, and a known ground (the nut for the coil bracket works well) for the black lead. Here is where you will stray from the beaten path. Look forward of, and down into the dark, dingy confines of the engine compartment just forward of the A/C compressor. The rearmost cylinder is #4, and that is where you will hook your inductive pickup lead. Clip it onto the wire between the end of the braided section and the insulator boot on the plug connctor. You are now in business, just make sure that all of your leads, clothing, etc., can't get sucked into the belts/fan. The reason that this works is that 360 crankshaft degrees = 1/2 an engine revolution, and your timing reading for cylinder #4 will be the same as #1, if you could ever get your timing light lead hooked to that wire!

Pete

mark '87 930

Ironically, I actually did try that yesterday and no go, however, I didn't clamp it where you stated, I was on the braided part. The light works on my subaru, so I'll give it another go.
Thanks for the info Peter.

smshirk

I just did the very same thing, Thanks Steve

antar911

Now i have a 1979 3.0 and on the pulley @ TDC there is only a Z1 mark to the left and a 5 mark to the right about 3/8ths of an inch from the Z1 mark. Both inside (engine) and outside (rear of car) marks are on the pulley for each not just the Z1 location. There are 90 and 120 degree markings on the pulley as well both scribed inside and outside on pulley intended to aid when adjusting the valves.

Question: I assume the 5 on the pulley is referring to 5 degrees BTDC?

Steve Weiner indicated that there should be a mark on the pulley to the right of Z1 indicating a 35ish degree mark.
There is however, no 35 degree mark or any mark just before BTDC on my pulley other than the 5 mark just right of the A1 marking. My scenario is exactly as is shown in the Bentley repair manual (pp280-2). Bentley says: "to time 5 degrees BTDC @950 +/- 2 degrees with vacumn hose from advance connected and at 26 degree @6000 +/- 2 degrees w/hose disconnected. It does not explain or illustrate however anything about a marking on the pulley @26 degrees BTDC +/- 2 degrees."

Question: I suspect since this is the norm as referred to in the Bentley manual, an adjustable advance timing light would have to be used on my type pulley in order to performance time at 6000 rpm for 26 degrees BTDC as spec'd or where ever the advance stops spinning out say somewhere between 4000 -6000 rpm. Would anyone care to comment or explain to me how I should time my car using this 26 to 36 degree advance approach with out either a marking on the pulley or an adjustable timing light for advance? ... or am i reading this all wrong.

thanks
antar911

Peter Zimmermann

antar: Is your car a USA, RoW, or California/Japan model?

Pete

Houpty GT

Let me jump in on this since this is my first post on my first Porsche.

I have a 1981 911 SC and have set the timing but am baffled by a particular problem. The Bentley states that the timing for the 1980-1983 timing should be 5 deg. BTDC with vacuum disconnected and blocked off. I do this and the car idles great and I believe pulls 17 inches of vacuum. I reconnect the vacuum line and the timing retards to 5 deg. ATDC. That is a 10 degree change. The idle stinks and I believe the car pulls 9 inches of vacuum.

I understand Steve stating the importance of the timing being correct operating speed but nobody wants to operate a good looking car that sounds broken at idle. I already had an Audi with Motronic CIS that did that (probally a valve stem seal problem).

The Bentley also says to check the idle at high speeds with the vacuum line disconnected. It states somewhere in the Bentley that this is to check the condition of the centripetal advance mechanism. Maybe this can be adjusted or repaired for those that have a problems with it.

My car is USA spec and has a cat-bypass pipe.

How much retard at idle do the other later year SC owners experience?

Peter Zimmermann

Your '81 SC should have two vacuum lines at the distributor. The car should be warm and idling at 900 +/- 50 rpm. When you remove the two vacuum lines, don't bother to plug them, your idle will speed up to approximately 1300-1400 rpm. Using the idle speed screw on the left side of the throttle body slow the idle to 900. At this point you can set the timing at 5 degrees BTDC. Lock down the distributor, replace the vacuum lines, and use the speed screw to bring the idle up to 900 +/- 50. If this does not work then you have any number of a variety of problems that can be anything from tune-related to compression.
Pete

Edgy01

...and as all early 911 owners should know, the firing order makes a good safe combination:

1-6-2-4-3-5...

antar911

Zim:
my car is a US 1979 3.0

antar911

antar911

Oh and by the way, does anyone know about my crank shaft pulley markings as I explained above?

thanks in advance.

antar911

psalt

Houpty GT,

Your engine sound about normal. The vacuum retard was a crude attempt to meet the curb idle HC emission test, serves no other purpose, and causes several bad side effects, one of which you have noticed. Two others are an initial stumble and stall on a true cold start (below 30F) and a measurable increase in engine and oil temperature at hot idle. Try disconnecting and plugging the retard hose (gray at the back) and resetting the idle to 950 rpm. The ignition timing on your USA car was retarded to run on the Porsche specified 87 CLC fuel, if you are running better fuel, you can advance the timing slightly. If you have an analog dwell meter, hook it up to the test connector under the left side engine cover (green white wire). Adjust the mixture screw so the FV dwell reads 30-40 dwell hot in closed loop. You will be surprise how well CIS can work.

Peter Zimmermann

The timing spec for a '79 USA 930 is:

10 degrees +/- 2 degrees ATDC @ 1,000 rpm +/- 50 w/vacuum attached.

You need an adjustable light to do the other setting, which is:

26 degrees +/- 4 degrees BTDC @ 4,000 rpm w/vacuum detached.

The pulley mark near Z1 is probably your 10 degree mark.
Pete

theiceman

All this sounds just too cool to ignore .. I think I i'll gets me a timing ligt and play with it .... It runs and sounds great right now ..... look out for the " i screwed up my timing " thread.

ice

dsmith

i may beat you to it, cuz i was reading this and thought, "i don't remember setting the idle to 900 AFTER pulling the vacuum lines." i checked it last night, and, sure enough, when i set the idle after pulling the lines, it looked like i had 15-20 deg BTDC, instead of 5deg. Now i just hope the pinging i've had at WOT hasn't killed anything! also, my car won't go over 5k rpms in any gear, so i need to check the throttle linkage. i'll do a wellness check after i'm done with taxes. might do a top end rebuild a couple years earlier than planned...