|Installing Distributor Body and Setting Static Ignition Timing|
If the distributor body has been removed, without proper marking (oops), it must be aligned to the crankshaft with cylinder #1 at TDC (top-dead-center), while the ingnition rotor points to the spark plug wire for cylinder #1. This ensures that the cylinder is at the top of its stroke when the plug fires.
There are three timing marks (notches) on the crankshaft pulley, these indicate the TDC points for the three pairs of cylinders. There is also a notch on the fan assembly, this is the alignment point for the timing notches on the crankshaft pulley. There should be a "Z1" mark next to notch that is for TDC of cylinders #1 and #4. On my car (87 carrera), I couldnt see the "Z" markings on the pulley, but there is another way to tell which of the three markings is the Z1 point: there is another notch about five degrees before the Z1 notch.
The objective is to turn the crankshaft so that cylinder #1 is at TDC (the Z1 mark aligns with the notch on the fan assembly), then install the distributor so the rotor points to ignition wire #1. The Z1 mark on the crankshaft pully represents the TDC point for BOTH cylinders #1 and #4, so you need to make sure it points to cylinder #1. There are a few different ways to tell whether its pointing to cylinder #1 or #4.
- Trial and error. You can align it to Z1 and try starting it, if it doesnt go then turn the crankshaft 360 degrees (clockwise) and try again (after aligning the rotor to wire #1). This will rotate it from #4 TDC to #1 TDC. This is the method I used. On my first attempt it was pointing to #4 (no fire), so I turned the crankshaft 360 degrees, adjusted the distributor so the rotor pointed to cylinder #1, and it fired fine.
- Feel for air pressure. If you remove spark plug #1 and put your hand over the hole, youll feel pressure when the crankshaft turns to the compression cycle for cylinder #1.
- Use a pointer as a flag. If you remove spark plug #1 and stick something (like a screwdriver or pencil) in the hole, it will push out when cylinder #1 reaches TDC. But be sure there is room for the screwdriver or pencil to move freely!
Note: If youre unsure of the cylinder numbering, youll find it on the labels in the engine tin. They are numbered as follows:
front 3 6 2 5 1 4 rear
[Also see the cylinder layout diagram elsewhere on this site]
Youll also find the firing order listed on the lables in the engine compartment, but just in case its 1, 6, 2, 4, 3, 5.
Okay, now there are several different ways to turn the crankshaft to align it to the Z1 point.
- Socket wrench on crankshaft pulley nut. If you can get a socket on the crankshaft pulley, you can turn it (clockwise) with a socket wrench. If its difficult to turn, you can loosen all of the spark plugs to lower compression.
- Spacer tool on fan pulley. There is a tool in the porsche toolkit for turning the fan. You can crank the engine this way (clockwise), but you may need to put pressure on the fan belt so it doesnt slip. Once again, its easier to turn if you loosen all of the spark plugs.
- Rocking the car. With the car in fifth gear, you can rock it until the pulley aligns to the Z1 point.
- Turning over the ignition. You can turn the ignition (with key) in short bursts until you get it close to the mark, then rock the car in fifth gear to get it exact. This is the method I used and it worked fine, even with just one person, as long as you have patience ;-)
Once you have the crankshaft sitting at TDC for cylinder #1, you need to install the distributor body so the rotor points to the ignition wire for spark plug #1. Youll notice a small notch on the distributor that aligns to the ignition point for spark plug #1. Put the rotor on the distributor shaft and turn the shaft so the rotor points to (just before) the notch on the distributor body. You will probably have to try it a few times until you get the gears to match up properly. Now install the distributor cap and you should be up and running. If it doesnt fire, you may be aligned to TDC for #4 instead of #1. If so, try rotating the crankshaft 360 degrees, then readjust the distributor rotor to point to the notch for cylinder #1.
On the DME-based cars (1984-1989 carreras) there is no dynamic adjustment of the timing (ie with a timing light) required because its done automatically by the DME computer. On earlier cars, you have to adjust the dynamic timing with a timing light after setting the static timing.
Happy igniting! These procedures were brought to you from the various helpful people on this list who walked me through the procedure a while ago. There are too many names to list, but special thanks to Hamid, Andy, and Fred, who really helped me to understand how the ignition system works.