How to adjust ignition against timing marks on a Mazda 626?

[Ferret626]

Long story for a hopefully easy problem but here we go... I have recently performed a major overhaul of my Mazda 626 2.0L 1992 as the engine exhausted too much HC (=all gasoline not combusted in the cylinders). This is my first major car engine work - I have just replaced oil, spark plugs and similar before. Purchased a Haynes repair manual and used a lot of time & photos to document the procedure - especially when removing the camshafts. I disassembled the engine cylinder head - it proved to be a broken exhaust valve on cylinder #2. Cylinder head was cleaned and valve replaced by professionals. Replaced the gaskets and the timing belt together with the other drive belts. Now with everyting back in place the engine won't start properly (surprise surprise...). All electrical components seems to be OK. After the ignition key has been turned on and then released 1, 2 or sometimes up to 4 "puffs" could be heard when the fuel ignites - but it won't repeat the cycle. Looking down the spark plug holes one can see and smell that the cylinders have a lot of fuel and spark plugs are soaked (too much fuel injected, or maybe the result from trying too many times?). Spark plugs and battery are in good condition. The distributor cap had some oxide which I removed. My guess is that the timing is off (might have budged the position of the distributor during removal as I did not realize at that time how crucial it was to mark the position). How to use a stroboscope lamp to adjust the timing? I know one connects the tool to the battery and one of the spark plugs (number #1?), but I do not know how to adjust this to the timing marks. I have found the timing mark above the main sprocket, there are two marks "10" (towards the back of the car) and "T" (towards the front). In between there are smaller marks without a number. A small notch is visible on the main sprocket at TDC (cylinder #1 and #4 are in top position), probably the mark should be adjusted against the scale in some way...

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[Ferret626]

..and well yes - it would be interesting to know another thing too (maybe easier to answer?). Just to be sure that the distributor is not off by cycles:
- when the engine is at TDC (Cylinder #1 & #4 at top position, #2 and #3 at their lowest point), which spark plug should fire an ignition?

Right now the distributor rotor is aiming at spark plug #2. If the distributor is off a lot I will disconnect it and try to rotate it before installing again.

[Gimme3Doors]

You can't adjust the timing with a timing light until you have the engine running. The Mazda shop manual recommends that after replacing the timing belt, with the spark plugs removed and timing belt cover still off, rotate the crankshaft at least 3 times with a ratchet wrench (on the crankshaft bolt, transmission in park or neutral) in the direction of rotation. Then observe the timing marks for both the crankshaft and camshaft gears. They should all be lined up perfectly.

If you can't see where the distributor was positioned before the head was worked on, just guess mid-range. The firing order is 1 3 4 2. Make sure you have the spark plug wires connected correctly. Timing is based on cylinder 1 so the rotor should be sending the spark to cylinder 1 at TDC.

You need to disable the computer and vacuum advance if applicable from the distributor when setting the mechanical timing. But don't worry about that for now. Just try to get the engine running. With the engine running, aim the timing light at the timing mark. The label under the hood should say what the timing should be. With the bolts to the distributor loosened, rotate the distributor until the timing mark is where the label says it should be. After you have the timing set correctly, tighten the distributor bolts, and check the timing again.

[Ferret626]

Originally Posted by Gimme3Doors

You can't adjust the timing with a timing light until you have the engine running.

Okay, the rough adjustment then needs to be done first!

Originally Posted by Gimme3Doors

The Mazda shop manual recommends that after replacing the timing belt, with the spark plugs removed and timing belt cover still off, rotate the crankshaft at least 3 times with a ratchet wrench (on the crankshaft bolt, transmission in park or neutral) in the direction of rotation. Then observe the timing marks for both the crankshaft and camshaft gears. They should all be lined up perfectly.

Yep that part should be OK. During assembly I had misaligned one camshaft at first (there are two alignment notches on the camshaft wheels!). Saved by the photo I took before removing it!
Got it right on the 4:th or 5:th attempt...

Originally Posted by Gimme3Doors

If you can't see where the distributor was positioned before the head was worked on, just guess mid-range. The firing order is 1 3 4 2. Make sure you have the spark plug wires connected correctly. Timing is based on cylinder 1 so the rotor should be sending the spark to cylinder 1 at TDC.

There are number markings 1-4 on the distributor where to connect the spark plugs and it matches the firing order if the distributor rotor rotates counter-clockwise. The cables are connected according to the markings.
At TDC it points very wrong at spark plug #2, the firing order from TDC is 2 3 4 1 in my case. I have to disconnect the distributor at TDC then and rotate it correctly (by 90 degrees to the right).
Or hmm.. Wait!
If I switch the spark plug connections #1 and #2, then the firing order will be correct without removing the distributor, although cables will be wrong according to the markings! Non-academic but working solution (until next guy disassembles the motor!)?
If I get the motor running then I will rotate the distributer to avoid future trouble...

Originally Posted by Gimme3Doors

You need to disable the computer and vacuum advance if applicable from the distributor when setting the mechanical timing. But don't worry about that for now. Just try to get the engine running. With the engine running, aim the timing light at the timing mark. The label under the hood should say what the timing should be. With the bolts to the distributor loosened, rotate the distributor until the timing mark is where the label says it should be. After you have the timing set correctly, tighten the distributor bolts, and check the timing again.

Yep, the latter part should be possible to fix as long as I get it to run (and could find that label!)

Thank you for an awesome answer. Will test this tomorrow. Paarty!

[Ferret626]

I got the engine running after placing the engine at TDC, removing the distributor and turning it 90 degrees to the right (pointing at spark plug #1). Started instantly!
Switching the spark plug cables would have worked as well but it felt like an ugly solution...
Tightened the generator belt - it was shrieking (btw, I never managed to loosen the rusty bolt to the generator completely, had to use minor violence to put the new belt in place...)

The idle speed is too high at the moment (a bit over 2000 RPM, should be around 1000 RPM as I remember from before disassembling the motor). Will study Haynes manual about this issue, I think it needs to be adjusted before checking timing marks. Hopefully described well - at times there is very little information (or placed in a totally different chapter).

[Ferret626]

Originally Posted by Ferret626

The idle speed is too high at the moment (a bit over 2000 RPM, should be around 1000 RPM as I remember from before disassembling the motor).

I borrowed an ignition timing lamp and it was a very straightforward thing to adjust the timing (10 minutes?). It is now 12 degrees (+- 1 degree) when running on idle speed.
Idle speed is now lower - around 900-1000 RPM (approx. the speed before disassembling the engine). According to the label attached on the inside of the hood the speed should be 700 RPM +-50? Before disassembling the engine it never went that low...
Is this something to worry about (might be corrected if driving some 100 miles?)?

[Ferret626]

Originally Posted by Ferret626

Idle speed is now lower - around 900-1000 RPM (approx. the speed before disassembling the engine). According to the label attached on the inside of the hood the speed should be 700 RPM +-50? Before disassembling the engine it never went that low...
Is this something to worry about (might be corrected if driving some 100 miles?)?

Actually the idle speed is now "correct". The dial has four markings (0 RPM, 1000 RPM and two markings in-between). When engine is warm it is now on the first mark "below" 1000 RPM. Correct idle speed - I guess. Never been this low. The 25:th of October it is the time for "the goverment" to judge if the car is trustworthy on the streets - my hope is that the exhaust values and brakes will be OK! Case closed - thanks for your input!

[Gimme3Doors]

I'm glad you got it all running right. If you think the brakes need replacement just go ahead and do that. Replacing disc pads are really easy.