Tune-up Procedures

Written for Dave's 1973 VW Super Beetle, but will apply to any aircooled Volkswagen

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The following tune-up steps are covered in this article -

Compression Test
Inspect, Adjust and Install Spark Plugs
Distributor (Cap, Rotor, Points, Condenser
Check the Condenser
Adjust the Idle
Set the Timing

Finding Top Dead Center
Timing With Stroboscopic Timing Light
Checking the Spark Advance
Static Timing

Check the Coil

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Step 1. Compression Test

Start the engine and warm it up for about 10 minutes.

Pull the spark plug connectors off all four plugs (careful--the engine is hot!)

Inspect the wires and the rubber seals on the ends. If worn or defective, replace them.

Stow the wires so you'll know what goes where.

Note: A handy trick is to wrap thin strands of copper wire around both ends of the spark plug wires--one loop for Cylinder #1, two loops for Cylinder #2, and so on. This way there is no question about which wire goes where. Refer to the diagram at the beginning of the Valve Adjustment procedure to see which cylinder is which and where the firing point for each is on the distributor.

With the spark plug socket on the ratchet, loosen all four plugs until they're hand tight. Use the extension and socket to screw out the last few threads by hand.

Lay the spark plugs out in a pattern to match the way they came out of the engine. You will carefully inspect and gap the plugs in the next step.

Check the compression with the compression tester:

Hold the rubber end of the tester in the spark plug hole, tightly.

Have a buddy turn the engine over six times and record the data.

The test results should be over 100 pounds and within about five pounds of each other.

Low readings indicate need for an engine overhaul.

Since you have the spark plugs out, proceed to Step #2, "Inspect, Adjust and Install Spark Plugs."

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Step 2. Inspect, Adjust and Install Spark Plugs

Note: See Rob's excellent article on Reading Spark Plugs, which includes a link to some excellent spark plug pictures).

Pull the spark plug connectors off all four spark plugs.

Inspect the wires and the rubber seals on the ends. If worn or defective, replace them. The large rubber seals around the spark plug leads are important - they seal the cooling air in around the heads, and MUST be replaced if they won't stay snuggly against the hole in the tinware.

Stow the wires so you'll know what goes where.

With the spark plug socket on the 3/8" drive ratchet, loosen all four plugs until they're hand tight. Use the extension and socket to screw out the last few threads by hand.

Note: It's best to wait until the engine is cold before removing the spark plugs. If you try to remove them from a hot engine, you run the risk of galling the threads. Bob Hoover has strong feelings about this -- "This is the standard rule for aluminum heads, and has been since the 1920's. The world is filled with engines having aluminum heads, but about the only folks who seem to have trouble with stripped spark plug holes are kids with Volkswagens. I wonder why that is..."

Lay the spark plugs out in a pattern to match the way they came out of the engine.

If you are going to reuse the plugs, inspect them carefully, comparing them to the pictures in the Bentley manual. If necessary, clean the plugs or install new ones.

Set the gap between the bottom bent electrode and the center straight electrode to 0.028" using the feeler gauge on the gapping tool. The bent electrode can be carefully bent in and out with the gapping tool to make the adjustment.

Note: If you have a capacitive discharge ignition (CDI) system installed in your car, the spark plugs should be gapped to 0.040".

Make sure there is a gasket on each plug, then put the plug in the spark plug socket.

Note: If the plug is very tight in the socket, you will have a very difficult time getting the socket off of the plug once the plug is installed. To prevent lots of frustration, apply some silicone grease to the plug before putting it in the socket; this will make removal of the socket much easier. Be sure to wipe the grease off the end of the plug before installing the spark plug wire.

Put the plug in the cylinder that it came from and hand tighten with the extension (do all four). Put on the ratchet and tighten them all--fairly tight but don't overdo it (snug and a tug). The cylinder heads are soft aluminum, so be careful you don't cross thread the plugs - they should start in the holes and turn fairly easily just using your hand. Torque the plugs to 22 ft-lb with the engine no more than warm.

Note: Very pertinent advice from our friend Bob Hoover: "Be damn sure to use a dab of anti-sieze on the threads of the plugs and that the compression washer is in place. Install the plugs BY HAND until the thread is full depth. Don't put a wrench on the plugs until they are fully threaded into their bores. And if you can't thread them in by hand, you've got galled threads and need to do something about it -- it ain't gonna heal itself."

If you do have damaged threads, see Time-Sert Spark Plug Repair for a repair kit and excellent illustrated instructions.

Put the plug wires on the same way you took them off. Make sure the rubber seals are pushed down firmly on the spark plugs and that the rubber seal is seated properly in the hole in the tin.

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Step 3. Distributor (Cap, Rotor, Points, Condenser)

Open the rear boot. Get out the stool and sit down. Contemplate the air-cooled beauty before you.

Inspect the distributor/carburetor connections (if any).

Note: If the distributor on your car is a double-vacuum advance type, there should be two vacuum hoses from it to the carburetor. The advance vacuum hose comes from the left side of the carburetor right below the stepped cam. It connects to the rear (rear of the car) port on the silver vacuum chamber on the side of the distributor. The retard vacuum hose comes from the rear port on the carburetor, just to the right of the throttle lever. It connects to the port on the front and bottom of the vacuum chamber on the distributor. It is essential that these vacuum hoses be hooked up correctly; the car will run VERY poorly (if at all) if they are reversed. If you have a single-vacuum dual advance distributor (best match for the 34 PICT-3 carburetor), there will be only one vacuum hose connected to the port on the left side of the carburetor. The port on the rear of the carburetor MUST be plugged.

Pry the two spring clips off the distributor cap with the screwdriver. Inspect the cap for cracks and excessive pitting on the contacts. If defective, replace it. If OK, store it out of the way.

Note: Find the notch on the rim of the distributor body. It may be either at about 4 o'clock or 8 o'clock. When the rotor is at this position, the #1 spark plug fires. The rotor turns clockwise; the firing order is 1-4-3-2. It is a good idea to mark the ends of the spark plug wires in some way so you know which is which.

Pull off the rotor and inspect it. If the contacts are excessively pitted or worn, replace it.

Note: If you have an ohm meter, touch one lead to the center of the rotor and the other to the tip. Resistance should not exceed 10,000 ohms.

If the rotor is OK, store it away in a safe place.

To see how the points work, first make sure the transmission is in neutral. Then put the 19mm socket on the alternator nut and rotate the engine clockwise, the way it runs. Watch the points open and close as you turn the engine. The points are adjusted to 0.016" (50^o on the dwell meter) at the point where they are separated the widest.

Inspect the points. If they are excessively pitted, replace them. Always replace the condenser at the same time you replace the points.

Note: That's one school of thought. Another one says, "If it ain't broke, don't fix it!" In other words, if the condenser is working, leave it alone.

Note: If the points are only slightly burned/pitted, they can be touched up in the car using a small flat "points file", which is about the size of a fingernail file. The points themselves are very hard material, and will wear the file surface blunt, so the tip of the file can be broken off with pliers once it has been used, then next time you are using a new part of the file surface. If the points need filing, adjust the gap afterwards.

If the points are OK, check the gap.

If necessary, adjust the point gap by loosening the hold-down screw and moving the stationary point. (The hold-down screw must be loose enough to allow movement of the point but tight enough to hold the point in place when you change its position.)

Note: The adjustment device consists of (1) a notch and the end of the point assembly and (2) a little bump on the distributor plate.

Check the point setting with the dwell-tachometer as follows:

Replace the rotor and distributor cap.

Put a dob of grease between the distributor shaft and the nylon rider on the moveable point. Brighten up the sparking end of the rotor (if you're not replacing it) using emery paper - a file will remove too much material. Put the rotor back on the shaft. You can also brighten up the four contacts inside the distributor cap if they look a little burned. Replace the distributor cap, checking the spark plug and coil wires to make sure none of them have come loose.

Connect the green clip to Terminal No. 1 on the ignition coil terminal (the one to which the green wire from the distributor is attached--its on the left). Connect the black clip to ground (the bolt on the fuel pump is a good place, but make sure the wire doesn't become tangled with the fan belt!).

Start the engine and allow it to warm up. Turn the Function Selector on the dwell-tachometer to DWELL; observe the reading on the Dwell Scale (8 cylinder--multiply the reading x 2).

The correct reading is 50^o " 2^o (25^o " 1^o on the 8 cylinder scale). If too high, the point gap is too narrow. If too low, the point gap is too wide.

Readjust the point gap as necessary.

Note: Changing the point gap changes the timing. If you change the gap, be sure to check the timing per Step 5 below.

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Step 4. Check the Condenser

Remove distributor cap.

Turn crankshaft until the points are fully open (any cylinder).

Disconnect the LT (green) wire from the coil.

Connect a test lamp wire to the ignition coil terminal and the other lead to the distributor wire.

Switch on the ignition. If the lamp lights, the condenser is grounded internally and must be replaced.

Now reconnect the distributor wire to the coil.

Pull the main high tension wire from the coil, and with the ignition on, turn the engine over. The spark should jump a 1/4 inch gap to earth. If it won't jump this distance, replace the condensor.

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Step 5. Adjust Idle

Note: These instructions are for the 34 PICT/3 Carburetor.

The idle adjustment must be made when the engine is warm, the points are properly adjusted, and the engine is timed.

Set the parking brake firmly and block the wheels. Put the transmission in neutral.

The idle is set with a "volume control" screw and a "bypass" screw of the left side of the carburetor. The volume control screw is on the bottom and is the smaller of the two. Both are recessed into the carburetor and must be accessed from the side.

Set the switch on the dwell-tachmeter to RPM and attach it to the engine. Connect the green clip to the left-hand terminal on the coil (the one to which the green wire from the distributor is attached).

Note: If you have a Capacitive Discharge Ignition (CDI) system installed on your car, hopefully you provided a test lead to which the dwell-tachometer can be attached. See the CDI wiring diagram.

Connect the black clip to ground (the bolt on the fuel pump is a good place -- just make absolutely sure the wire doesn't get tangled in the drive belt, which is very close by!).

Start the engine and run it for at least five minutes to warm it up.

Allow the engine to idle. Make sure that the automatic choke is fully open (it's the butterfly valve in the top of the carburetor - with the engine warm the valve should be standing straight up) and the stepped throttle (fast idle) cam on the left side of the carburetor is all the way up so that the screw on the throttle arm is resting on the lowest point on the cam.

Note the rpm on the tachometer; you will adjust it to 900 rpm (the specification given in the book) or your preference, as follows:

Adjust the screw on the throttle arm so that it just touches the fast idle cam. Then turn it in 1/4 turn.

Note: This step is very important. It opens the throttle butterfly in the carburetor 0.004" so that the idle jet will work properly.

Turn off the engine momentarily.

Slowly turn in the volume control screw (the smaller bottom one) until it bottoms lightly. Then back it out 2-1/2 to 3 turns.

Restart the engine and adjust the bypass screw (the larger one on top) until you obtain the desired idle speed as indicated on the dwell-tachometer (850 - 900 rpm). Turning the bypass screw in increases the rpm; turning it out decreases the rpm.

Note: Dave's experience is opposite - he found that turning the bypass screw OUT increases the rpm; turning it IN decreases the rpm.

Turn the volume control screw one way or the other to obtain the highest idle speed, then turn the screw clockwise (in) until the engine speed drops by about 25.

Note: This step is a little tough--it's hard to see a 25 rpm difference on the tach, expecially if you're using a tach designed for an 8-cylinder car. Do the best you can.

Reset the idle to desired idle speed using the bypass screw (850 - 900 rpm).

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Step 6. Set the Timing

See our Timing Discussion.

Note: This procedure will give the timing specifications for both the vacuum advance (single and dual) and centrifugal advance (009) distributors, as all three are used with the 34 PICT/3 carburetor. The timing is correct (at idle) when the spark leaves the distributor exactly when the correct timing mark on the crankshaft pulley lines up with the crack in the crankcase.

Note: First make sure the valves, the point gap and the idle are properly set. Changes in point gap and idle speed change the timing.

Finding Top Dead Center -

If you are uncertain as to which mark is which on the crankshaft pulley, determine TDC as follows:
1. Remove the No. 1 spark plug.
2. Remove the distributor cap and find the notch on the rim of the distribtor that marks the position of the No. 1 spark plug wire.
3. Rotate the engine (19mm socket on the alternator nut) until the rotor is approaching the No. 1 spark plug position.
4. Insert a pencil (eraser end first) into the No. 1 spark plug hole until it rests on the top of the piston.
5. Move the crankshaft back and forth with the 19-mm wrench on the alternator nut until the point at which the piston is highest in the cylinder is found (i.e., the pencil is at its furthest point out of the spark plug hole). This is Top Dead Center; mark it clearly on the crankshaft pulley with white paint.
6. From the TDC mark, measure on the rim of the pulley 7.6 mm to the left from the TDC notch and mark with white paint; this is 5^oATDC, the point at which the dual vacuum advance distributor is timed.
7. Also measure on the rim of the pulley 11.5 mm to the right of the TDC notch on the rim of the crankshaft pulley. This is 7.5^oBTDC; mark this point also with white paint. This is the point at which the centrifugal advance (009) and single-vacuum dual-advance (SVDA) distributors are timed.
8. From the TDC mark, measure on the rim of the pulley 45.8 mm to the right on the rim of the crankshaft pulley. This is 30^o BTDC; mark this point also with white paint. This is the maximum advance point at 3500 rpm.

Timing With Stroboscopic Timing Light:

Note: The strobe light emits an extremely bright light, which is flashed from a pistol-like instrument. See also the instructions that come with the strobe light.

Make sure that the timing mark appropriate to your distributor (see above) is clearly visible on the crankshaft pulley (i.e., marked with white paint).

Attach the inductive pick-up clip on the timing light around the No. 1 spark plug wire, away from the other spark plug wires to avoid interference. Observe the arrow on the clip pointing to the spark plug (if there is such an arrow).

Power to the strobe light is provided through the red clip. Attach it to the terminal on the right side of the coil (the one with the wires to the automatic choke and idle solenoid -- terminal #15).

Note: If your car is equipped with a Capacitive Discharge Ignition system, power to the coil is provided indirectly through the CDI unit. In this case, just attach the red clip on the strobe light to any convenient 12-volt power source. We use the wire to the automatic choke.

Attach the black clip to ground (the bolt on the fuel pump is a good place, but again make sure the wire doesn't become tangled with the fan belt!).

Attach the dwell-tachometer in accordance with the idle procedure above.

Note: If your car is equipped with a double vacuum advance distributor, the vacuum lines must remain attached to both the carburetor and the distributor during this test. If you have a SINGLE vacuum distributor, the vacuum hose must be removed from the distributor and plugged so that air will not be sucked into the carburetor.

Start the engine and allow it to idle at about 900 rpm (if the idle speed is other than this, adjust the idle in accordance with the idle adjustment procedure).

Point the timing light at the split in the crankcase and pull the trigger on the timing light. When the trigger on the strobe light is pulled, with the engine running, the strobe produces a very bright light which flashes every time the No. 1 spark plug fires. This bright light is used to observe the relationship between the timing mark on the crankshaft pulley and the split in the crankcase.

On cars with the double vacuum advance distributor (two vacuum hoses), the throttle valve must close adequately for accurate timing adjustments. To check, disconnect the vacuum retard hose (attached to the front of the vacuum chamber and rear of the carburetor) with the engine idling. The timing mark should move 15-18mm to the left. If not, the carburetor needs to be adjusted.

Turn off the engine and loosen the distributor clamp nut (10mm) enough so the distributor requires a strong twist to be moved but will stay where it is moved to.

Restart the car and aim the timing light at the crankcase pulley at the point where it passes the split in the crankcase. Move the distributor one way or the other until the proper timing mark on the pulley (as seen in the strobe light) lines up with the crack in the crankcase.

The correct timing setting for the vacuum advance distributor (two hoses) is 5^o After Top Dead Center (ATDC). This means that as you view the 5^o mark at the crankcase split (with the strobe), the TDC mark on the pulley will be about 7.6mm to the RIGHT of the crankcase split.

The correct timing setting for the centrifugal advance distributor (009) AND the single-vacuum distributor (vacuum hose plugged) is 7.5^o Before Top Dead Center (BTDC). This means that as you view the 7.5^o mark at the crankcase split (with the strobe), the TDC mark on the pulley will be about 11.5mm to the LEFT of the crankcase split when the distributor is properly timed.

Shut off the engine, and while holding the distributor in the correct position, tighten the distributor clamp nut. Restart the engine and recheck the timing.

Checking the Spark Advance:

Attach the dwell-tachometer per the "Adjust Idle" procedure and the stroboscopic timing light per the above.

Start the engine. Pull on the throttle lever to increase the engine rpm while you hold the strobe light on the crack in the crankcase and watch the marks on the crankshaft pulley in the strobe light. The TDC mark and idle marks should move to the left (advance) as the rpm's increase to about 3500 rpm. Maximum advance should be 28-32^o ATDC (you made a mark at 30^o) and then return as the rpm's return to idle speed.

Note: This advance timing is more important than the idle timing. Ideally it should be 30^o advanced at 3500 rpm and return to the specified timing at idle.

Static Timing:

Note 1: This procedure is for use on centrifugal advance (009) and single-vacuum/dual advance distributors with points ONLY. Dual vacuum distributors and distributors equipped with electronic ignition must be timed with a stroboscopic timing light.

Note 2: If you have a single vacuum distributor, there is no need to remove the vacuum line to static time the distributor. However, if you are going to use a stroboscopic timing light, the vacuum line must be removed and plugged so that air will not be sucked into the carburetor during the test.

Unfasten the clips that hold the distributor cap-- a medium-sized screwdriver works best for this.

Lift off the cap and find the notch on the rim of the distributor either by sight or run your fingernail around the rim under the Number 1 spark plug wire. The notch should be at about 5 o'clock on the 009 distributor.

Rotate the engine with the 19mm wrench on the generator pulley until the rotor is pointing directly at the notch in the distributor rim, then put the cap back on and clip it down.

Get out your static timing light (just a 12 volt bulb in a 18" long (or so) wire and an alligator clip on one end and any kind of a metal attachment--a pointy thing--on the other).

Clip the alligator clip to the connection on the coil where the thin wire (usually green) from the coil to the distributor is connected.

Turn on the ignition key (DO NOT START THE ENGINE!).

While holding the pointy end of the static timing light to ground (e.g., the engine case,) rotate the engine backwards (counterclockwise) a little, then slowly forward, watching the timing mark (7.5^oBTDC) and the light at the same time, so when the light comes on you are ready to stop turning.

If your engine is timed correctly, the light will go on when the 7.5^oBTDC timing mark is lined up exactly with the crack between the two halves of the crankcase.

It wasn't perfect? OK, so move the engine backwards a little to take the slack out of the distributor, then clockwise again until the timing mark on the pulley is exactly at the place it should be 7.5^oBTDC.

Now loosen the distributor clamp nut (10mm) and rotate the distributor clockwise until the test lamp turns off (points closed), then slowly counterclockwise until the breaker points open and the test lamp flashes on.

Tighten the clamp nut and check the timing per Steps #7 and 8 above. If it's right you're through--if not, loosen the nut, move the distributor, tighten the clamp nut, and try it--until it's right.

Switch off the ignition as soon as possible.

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Step 7. Check Coil

Pull the center wire out of the distributor. FIND SOMETHING WELL INSULATED TO HOLD IT!

Hold the end of the wire about 1/8" 1/4" from a bare metal surface and have your buddy turn the engine over with the key.

If you get a bright, hot blue-white spark, the coil is like new. If you get a good strong yellow spark, the coil is getting old but is still serviceable. If you get a weak, orange spark that will hardly jump the 1/4" gap, you need a new coil.

If you need to replace the coil:

Remove the old coil simply be removing the two 10mm bolts that hold it onto the fan housing. Install the new one by reversing the process.

The thin wire coming up from the distributor connects to Terminal No. 1 (-). The wire from the ignition switch connects to Terminal No. 15 (+), and the big center wire connects to the center of the distributor.

Try the check on the new coil to see what a good spark looks like.

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Disclaimer stuff: Rob and Dave have written these procedures from their own experiences. We have not assumed any specialised mechanical knowledge, but we DO assume that anyone using these procedures has at least some basic mechanical ability.

We hope you find the procedures useful, but we don't take any responsibility for anything which happens to you, other people, your VW or any other property or goods resulting from your use of these procedures.

Feel free to print off any procedures for your own use. If you intend to link them to another site, reprint them or in any other way redistribute them, please leave them complete, including this disclaimer section, and provide a link to this Web site.

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Have fun fixing your VW - just keep them fweeming, OK?

Last revised 28 May 2004.