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 Timing 101 FAQ

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PostSubject: Timing 101 FAQ   2010-11-29, 6:48 pm

Basic steps:

1: fully warm up the engine. Then shut it off

2: if you live at high altitude (anything above 2500 feet or so, if in doubt, do the following step): Look at the wire bundle between the air filter canister and fender; there are two "dead end" connectors hanging there (or taped to the harness bundle) with protective caps on them. Find the one with more than one wire; that's the ignition timing terminal. One is a black wire and the other will be red+yellow. Jumper them together; this forces the car into "low altitude" mode.

3: connect the large alligator clips of the timing light (TL) to the car's battery, black to "-" post (or to a good/solid ground on the chassis or engine) and red to the "+" battery post.

4: Locate the cylinder #1 spark plug wire (the #1 cyl is closest to front of car) and follow it towards the distributor. Find some place where the wire is fairly easy to access. I usually collect the slack in the wire to make a "U" loop right in front of the valve cover. Clamp the TL's probe around this wire. Most TL clamps have an arrow printed/molded into the case, the arrowhead should point towards the spark plug.

5: Take a rag, and maybe some spray carb or brake cleaner, some Simple Green, Purple Power, whatever cleaner you like/have, and clean off the timing marks on the front of the engine, just above the crankshaft pulley. Clean it so you can see the "T" mark and the various tick marks & numbers on either side of the "T"

6: Look at the crankshaft pulley... it'll have 3 different V-belt grooves. The rear-most lip, right against the front of the engine, will have a "V" shaped notched filed into it. You may have to manually turn the engine to see it... use a big socket wrench, breaker bar, whatever, on the bolt inside the crankshaft pulley. Turn this bolt CLOCKWISE ONLY as you face the engine; i.e. in the bolt tightening direction. NEVER turn this bolt counter-clockwise unless you have the engine crankshaft locked in position somehow... turning this bolt/pulley backwards, and thus turning the engine backwards, screws up the timing chain. Turn the pulley clockwise until you can see that "V" notch. The first time you look for it it's quite easy to miss, especially if the pulley is greasy or otherwise dirty. If you can't find it, try this technique:

6a: remove the #1 cylinder spark plug
6b: fit a cork into the opening, or have a helper hold their thumb over the plug hole... or stuff a wadded up paper towel into the hole. Just "plug" the hole, don't stuff anything inside the cylinder.

6c: Now turn the crankshaft pulley/bolt again until you feel pressure building up or the rag/cork pop out. That's the #1 piston on its compression stroke. The "V" notch will be somewhere between 9 o'clock and 12 o'clock when this happens.
6d: SLOWLY turn the crank pulley at this point until you spot the "V" notch.
6e: Using White-out, bright silver or white paint, even the wife's nail polish, highlight the "V" notch.
6f: Put the spark plug and spark plug wire back.

7: Look at the distributor. See how it has a mounting ear sticking towards the front of the car with a banana shaped slot in it? That's the adjustment slot. Loosen the nut over that slot just enough that you can move the distributor but not so loose that the distributor flops around under its own weight.

8: Start the engine and let it idle for a minute to stabilize. Leave it running for the next steps.

9: Aim your timing light at the crankshaft pulley near "T" mark on the front of the engine, pull the trigger, and see where the "V" notch is. The timing light should "freeze" the "V" notch against the tick marks on the engine face.

10: Slowly rotate the distributor body (be careful not to grip the wires, it's possible to get a jolt) until your highlighted "V" notch is opposite the "10" mark to the left (exhaust side) of the "T"

11: Tighten the distributor nut. Verify the "V" notch is still lined up with the "10" mark after the nut is tight.

12: If you installed that "low altitude" mode jumper in step 2, remove it. Use the timing light to check the timing "V" notch again; if it now reads around 15 deg BTDC your ECU thinks the car really is at high altitude. Do NOT re-adjust the distributor to get this back to 10 deg; 15 deg BTDC is correct for high-altitude cars.

While you've got the timing light connected, do a few quick tests of the ignition timing system. Engine should still be idling.

13: On the distributor you'll see a flying saucer shaped part - the distributor "vacuum advance mechanism" - with a single vacuum hose going to it. Pull the trigger on the timing light and check the timing... then disconnect this vacuum hose and hold your finger over the end of the hose. Did the ignition timing change at all? It should be 10 (or 15) deg BTDC still. If it moved, your vacuum hoses are not connected properly.

14: While that hose is still unplugged and capped, rev the engine. You can either reach around to the firewall side of the injection mixer (aka throttle body) assembly to reach the throttle cable & sector, or just have a helper slowly push and release the gas pedal over and over. Use the timing light to watch the ignition timing. As the engine RPMs increase, the timing mark will begin to move even more advanced (it'll move counter-clockwise away from the "T" mark). Make sure this motion is consistent with RPM and that the movement is nice and smooth. Any hesitation or jerkiness means the centrifugal advance mechanism inside the distributor is gunked up and needs to be cleaned & re-greased. Or that your helper has a crappy right foot.

15: Get a fresh vacuum hose that fits tightly over the vacuum nipple on the distributor advance mechanism. Let the engine idle. While watching the timing (it should be 10 or 15 right now...) apply vacuum to this hose. Either use a hand-held vacuum generator (i.e. a MitiVac tool) or just suck on the stupid hose. The ignition timing should again smoothly advance away from the "T" in sync with the vacuum. Repeat the test multiple times.

16: Now have your helper rev the engine to 2000 RPMs and hold it constant. If you're by yourself, get a straight-blade screwdriver and walk to the passenger side fender. Eyeball the injection mixer... roughly straight down from where the main air hose & pipe (the over-the-valve-cover pipe) you'll see a screw sticking up at an angle. Turn that screw until the RPMs build up to 2000... but count EXACTLY how much you turn it: 2 turns, 2.5 turns, etc. Remember that for later.

17: While the engine revs at 2000 RPM, check the ignition timing; it should be well above 10 (or 15) deg BTDC thanks to the centrifugal advance mechanism again (step 14 again). Actually, it should be 10 degrees larger: either 20 (low altitude) or 25 (high alt). If you didn't get a 10 degree timing change, somebody has installed incorrect weights or springs inside the distributor. Now reconnect the car's vacuum hose to the distributor. The timing should instantly jump quite a bit, you probably won't even be able to see the "V" mark easily. If so, congratulations: your ignition timing stuff appears to be functioning properly.

18: If you used that injection mixer screw to dial the timing to 2000 RPM, back it out exactly the same number of turns you cranked it in step 16. The RPMs will drop as you back out the screw. The engine should be at normal idle RPMs roughly 1 full turn before you finish backing out the screw if was adjusted correctly prior to step 16.

It probably took me longer to type this up, and longer for you to read this text, than it'll take to actually do the tests on your car.
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