Can someone explain how a timing light works?

[daveymark]

I need to advance the timing on the miata. I have no idea what that means. I've read multiple explanations, but still am having trouble comprehending it. where exactly do you shine the timing light? what are you looking for? am I looking for marks, that I can only see with the timing light? why can't I just rotate the CAS without the timing light?

 

[CalvinHobbes]

From about.com:

If you're doing a thorough tune-up, you'll want to check the engine timing. A timing light does this by shooting a strobe light aimed at your car's specific timing marks. The strobe flashes at the same time your #1 cylinder fires, which should mean that the timing mark (usually a line or notch on the flywheel) is lined up perfectly. If everything is timed correctly, you'll see a flashing notch down there. If not, you can adjust the timing until you do.

Fancy timing lights will allow you to set the timing a little ahead or a little behind the mark by exact increments. When it's dead on, the timing is referred to as TDC (Top Dead Center). If you want the timing a little ahead, you will "advance" the timing by a specific number of degrees, which is adjustable on the top of the light. If you want it a little behind, it's called "retarding" the timing. Some cars specify a number of degrees of advance.

 

[herm0016]

on many cars the mark is on the harmonic balancer or pully that is attached to the end of the crankshaft. many older cars have a stamped metal gauge that is bolted to the block near the balancer that will tell you what the timing is set at when using the light.

 

[daveymark]

so the pulley spins around, and the mark with it? does that mean I have to watch the little mark go in circles, and hope that the timing light flashes in time with the mark reaching a full revolution?

 

[franksta]

Typically the timing light is triggered by the firing of the #1 cylinder. You don't have to hope for anything (maybe just a proper functioning light). Is your car fired by a distributor for you to adjust the timing? If it has an electronic ignition you'll need a programmer and if that's the case you don't really need the timing light and more than likely your car doesn't even have timing marks.


EDIT: The timing light is a bright strobe light that only flashes when your spark plug ignites. All of the cars I've ever worked on I used the #1 spark plug. The marks on your pulley coincide with the position of the crankshaft. Using the timing light will tell you where your spark plug ignites in relation to crank position and thus timing.

Good luck, I hope my edit is helpful.

 

[Demon-Xanth]

To advance/retard the ignition on a distributor based car, you loosen a clamp holding the distributor down and rotate it until the mark on the harmonic balancer that is visible by the strobe's being triggered on the cylinder lines up with the proper mark on a reference plate that is usually attached to the block.

...and if there's any grammar nazis having a heart attack at my almost complete lack of punctuation I consider my life fulfilled.

 

[nakedfrog]

There's nothing STOPPING you from adjusting timing without a timing light. But it sure is going to be tougher to get your timing spot-on, if not well nigh impossible. It would be about as difficult as playing "Pin the tail on the donkey" while on a boat, drunk.
You say you need to advance it--do you know why, or by how much?

 

[Pacfanweb]

Originally posted by: daveymark
so the pulley spins around, and the mark with it? does that mean I have to watch the little mark go in circles, and hope that the timing light flashes in time with the mark reaching a full revolution?

The light will flash every time the mark comes around, so it'll appear to be basically motionless, sort of like it's hovering there.
The light flashes every other time the mark comes around, but you won't notice that.

There is typically some graduated marks on a tab next to or above the balancer where the timing mark is.
When that timing mark is at "0" on the timing tab, the #1 piston is at Top Dead Center.

To see this mark better, take some bright touch-up paint and wipe it in the mark.

Don't know what you want to set your timing to, but most cars have theirs somewhere Before Top Dead Center, or advanced.


I usually just set mine with the engine off, then all I have to do is verify that it's okay when I start it. But that's a different explanation there.

 

[alpineranger]

The better lights come with an adjustment to change the phase of the strobe. This way, you only need one mark on the crank pulley for #1 top dead center, which every engine has. Work the adjustment until the mark lines up, then read the advance. To set some specific advance, adjust the timing light accordingly and then turn the distributor. You can try adjusting the distributor by ear (listening to the sound of the engine), but this won't be accurate and at worst, you'll be way off. A friend of mine tried this once and had to replace his head gasket a week later as a result.

 

[LTC8K6]

Ever see a strobe light firing at a running fan? When you get the phase right, the fan blades appear to be standing still. This is what is going on with the strobe light and the timing mark on the pulley or balancer. That's why the mark on the moving pulley will appear stationary under the strobe light, allowing you to adjust the timing.

 

[exdeath]

Not sure if it's clear to you yet, but when you change ignition timing you also change when the light flashes since it uses the spark plug wire as a trigger. It will also flash in the same spot every time making the crank appear to stand still. When you adjust timing, you are changing the part of the crank that is captured on the strobe by making the light flash early or late.

If you just strobe the crank pulley you will see a static line landing at some spot on the stationary indicator tab. But if you were to adjust timing while firing the strobe you would actually see that stationary line move up and down the scale on the tab in proportion to your timing adjustments.

Say you want 15 deg BTDC and wanted to confirm, you would note if the crank mark is at the 15 deg mark on the tab. If it was 12 deg instead, you'd adjust the distributor (or knob or whatever means the ignition system allows) to advance more, and you'd see the stationary line move under the strobe and you'd dial it in until it showed 15.

All it's doing is showing you a freeze frame of crank position in degrees BTDC at the time the spark occurs, the definition of ignition timing.

Some don't have scales on the tab, they just have a single mark. These require a timing light that has a degree dial. You always time the mark on zero on the tab, so if you want 18 deg advance, you set your ignition to 18 degrees advance (which would show the mark 18 degrees ahead of zero with a regular light) program the gun with 18 degrees of delay (ie: make the strobe 18 degrees behind or out of phase with the actual spark) so that you are still timing to the same 0 mark instead of a scale. Almost a must when you are timing at high RPM for top end, as the tab isn't wide enough or the pulley/hub/balancer isn't degree'ed that far to show dynamic timing advance at wide open.

What makes it tricky with mechanical ignition (distributor) is adjusting timing over the whole range, not just idle. It's kind of like convergence on a CRT, you get one edge perfect, and the other edge is too red, make that edge perfect and the other edge that used to be perfect is now too blue.

 

[daveymark]

thanks, that helps to clear it up. The reason I am considering advancing the timing 14 degrees is because I'm getting hesitation during acceleration. Like I push the pedal all the way to the floor, it hesitates before it revs. if I slowly press the gas pedal, there is no hesitation.

 

[Pacfanweb]

Originally posted by: exdeath
Not sure if it's clear to you yet, but when you change ignition timing you also change when the light flashes since it uses the spark plug wire as a trigger. It will also flash in the same spot every time making the crank appear to stand still. When you adjust timing, you are changing the part of the crank that is captured on the strobe by making the light flash early or late.

Technically speaking, the light flashes at the exact same time regardless of what the timing is.
That is, when the #1 plug fires.

But yeah, you are changing WHEN the #1 plug fires in relation to the piston by adjusting the timing. And that'll make the TDC mark appear to move, as you mentioned.


Here's the easiest way to set timing without the engine running:

First, you have to know how much advance (centrifugal or vacuum) your distributor has.
A typical performance or OEM dist. has 20 degrees of advance.

So you're going to set the intial, or base, timing.

Decide what you want your timing to be, in this case, let's say you want a total of 36 degrees.
You know you have 20 in the distributor, so you'll need 16 degree initial.

Bump, use a socket, or otherwise set the timing mark on the crank to 16 degrees on the timing tab. Needs to be on the compression stroke.

Loosen your distributor. Use a spark tester or even a spark plug that is grounded...put the #1 plug wire on it. Turn the key on. (run position, engine off)

Now, slowly rotate the distributor until the plug fires. I suppose you could use a timing light and watch when the strobe flashes.
Stop the distributor where the plug fires/light flashes, and lock it down.

Timing is set if you didn't move the distributor when you locked it down. You can check it running at that point if you want, but it'll be at least within 1 degree at worst.

 

[Pacfanweb]

Originally posted by: daveymark
thanks, that helps to clear it up. The reason I am considering advancing the timing 14 degrees is because I'm getting hesitation during acceleration. Like I push the pedal all the way to the floor, it hesitates before it revs. if I slowly press the gas pedal, there is no hesitation.

14 DEGREES?? How can it be THAT far off? Does this car have a timing belt, and if so, you sure it didn't slip a tooth?

No way a dist. can be that far off without something being wrong.

And I don't know of a car that can stand a 14 degree advance from stock. You'd need racing gas and one hell of a battery and starter to fire that thing up once it got warmed up.

 

[daveymark]

miata.net explains that it is a common procedure to advance timing to 14 degrees. perhaps I read it the wrong way?

Text

edit: I will be advancing it TO 14 degrees, not 14 degrees. it is already at 10 degrees.

 

[boomerang]

Advance the timing to 14 degrees BTDC. OK, that makes sense. Myself and everyone here thought you wanted to advance the timing an additional 14 degrees.
Edit: I was typing while you were editing. That's quite the in-depth article. In the old days, we'd advance it incrementally, driving in betwen until we got spark knock. Then retard it a few degrees for insurance. Sounds like they've done all the research for you.

 

[exdeath]

Originally posted by: Pacfanweb

Originally posted by: exdeath
Not sure if it's clear to you yet, but when you change ignition timing you also change when the light flashes since it uses the spark plug wire as a trigger. It will also flash in the same spot every time making the crank appear to stand still. When you adjust timing, you are changing the part of the crank that is captured on the strobe by making the light flash early or late.

Technically speaking, the light flashes at the exact same time regardless of what the timing is.
That is, when the #1 plug fires.

Well yeah, I was just trying to describe it simply from the perspective of just using a timing light. By changing when the #1 plug fires, you change the time that the light flashes with respect to the crank indicator

 

[boomerang]

Originally posted by: daveymark
thanks, that helps to clear it up. The reason I am considering advancing the timing 14 degrees is because I'm getting hesitation during acceleration. Like I push the pedal all the way to the floor, it hesitates before it revs. if I slowly press the gas pedal, there is no hesitation.

You can certainly try advancing the timing, but I think you have another problem.

I'm not at all familiar with Mazda's, but if you tell everyone what year the car is, someone may be able to help you.

 

[nakedfrog]

Originally posted by: boomerang

Originally posted by: daveymark
thanks, that helps to clear it up. The reason I am considering advancing the timing 14 degrees is because I'm getting hesitation during acceleration. Like I push the pedal all the way to the floor, it hesitates before it revs. if I slowly press the gas pedal, there is no hesitation.

You can certainly try advancing the timing, but I think you have another problem.

I'm not at all familiar with Mazda's, but if you tell everyone what year the car is, someone may be able to help you.

I'd try watching the timing mark as the engine is revved.

 

[daveymark]

The timing is something I'll be looking at after I replace the plugs, wires and o2 sensor. hopefully one of those takes care of the issue. timing was the only thing out of all those things that I couldn't wrap my mind around.

 

[EricMartello]

Originally posted by: daveymark
thanks, that helps to clear it up. The reason I am considering advancing the timing 14 degrees is because I'm getting hesitation during acceleration. Like I push the pedal all the way to the floor, it hesitates before it revs. if I slowly press the gas pedal, there is no hesitation.

Hesitation is usually caused by a less than optimal A/F ratio. You should check and replace your fuel filter (some cars have two; one in the tank and one up front). You should also make sure that your fuel pressure is constant. If it is dipping or erratic, that most likely means your fuel pump is about to die.

Other possibilities include a dirty air filter, bad compression, vacuum leak (this is also common on older cars), fouled spark plugs, deteriorated spark plug wires, bad ignition coil, fouled distributor. Most of those things are items you'd check and/or replace during a tune-up...and none of those things are remedied by a timing advance.

 

[tweekah]

Use the timing gun, make sure you don't get pings after advancing.

Tutorial - http://www.miata.net/garage/ignition.html#timing

Where to point the gun - http://www.miata.net/garage/timingmarks_closeup.jpg

The engraved TDC mark will reflect the flash of the gun in a specific knotch on the scale when the #1 plug fires.

 

[Pacfanweb]

Originally posted by: exdeath

Originally posted by: Pacfanweb

Originally posted by: exdeath
Not sure if it's clear to you yet, but when you change ignition timing you also change when the light flashes since it uses the spark plug wire as a trigger. It will also flash in the same spot every time making the crank appear to stand still. When you adjust timing, you are changing the part of the crank that is captured on the strobe by making the light flash early or late.

Technically speaking, the light flashes at the exact same time regardless of what the timing is.
That is, when the #1 plug fires.

Well yeah, I was just trying to describe it simply from the perspective of just using a timing light. By changing when the #1 plug fires, you change the time that the light flashes with respect to the crank indicator

I know, hence the

 

[Pacfanweb]

One other thing you might need to look at is this: 14 degrees is an initial, or base, setting. Do you have to disconnect a plug, or ground a wire to remove the advance so you can set the base timing?

I know on some cars there was a "spout" plug, that you had to remove to stop the computerized advance and revert to the base timing.
Otherwise, you'll end up with severely retarded timing.

I haven't read that link, but I assume it covers this?

 

[tweekah]

Originally posted by: Pacfanweb
One other thing you might need to look at is this: 14 degrees is an initial, or base, setting. Do you have to disconnect a plug, or ground a wire to remove the advance so you can set the base timing?

I know on some cars there was a "spout" plug, that you had to remove to stop the computerized advance and revert to the base timing.
Otherwise, you'll end up with severely retarded timing.

I haven't read that link, but I assume it covers this?

Yes, mcguyver a paperclip to put the car into "diagnostic mode". If this is a 89-91 model make sure you don't have the dreaded crankshaft issue which can seriously affect the timing of the car.

As others suggested the problem may be something else. Maybe check the slack on the throttle cable and idle speed.