I have done engine overhall for my mazda 6 2003.i want to know how set timing and the timing marks?

First, DO NOT start the engine if the mechanical timing is wrong! My next obvious suggestion is to get it to a good mechanic and get them to sort it out for you.
I'm assuming your refering to the Mechanical Timing? Mazda use an 'Interference' engine so read this all the way through BEFORE doing any work. An interference engine means the valves will hit the piston face if the mechanical timing is even slightly out. That is why you don't start your engine with the timing set wrong. It's a VERY expensive repair.
Start from scratch. Remove the chain from the CAMs and cable tie it to something on the top of the engine to stop it disappearing out of sight.
Turn the Crank to about 10 to 15 degrees past Top Dead Centre (TDC). This is to move the pistons away from the valves so you can set the Cam timing marks. Set the Cam marks first then turn the Crank BACK to TDC. As long as the chain marker on the crank sprocket is lined up correctly the Cam chain markers should be correct.
Once you have timed everything into place use a socket and ratchet to turn the Crank pulley bolt Clockwise 2 full rotations. The timing marks should return to the correct positions.

how do you know that ?
what have you done to the engine?
has the belt/ chain broken?
statements do not get answer only more questions
post again as the posts are not linked

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• ADJUSTMENTS

1. Check engine condition (spark plugs, leaks in hoses, etc.).



2. Turn all electrical loads OFF.



3. Warm up engine and run for three minutes at 2500 - 3000 rpm.

Test Connector For Tachometer
Test Connector

1. Connect tachometer and timing light to engine (white check connector).



2. Ground test connector (green: 1-pin) with a jumper wire.



3. Check that idle speed is within specification.

M/T: 750 ±20 rpm in neutral

A/T: 770 ±20 rpm in park

Timing Mark

1. Check that timing mark (YELLOW) on crankshaft pulley and the mark on timing belt cover are aligned.

5°±1°BTDC

1. If timing is not within specification, loosen lock bolt and rotate distributor housing to adjust.



2. Tighten lock bolt to 14 - 19 ftlb (19 - 25 Nm).



3. After adjustment, disconnect jumper wire from test connector.
   

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Bummer, well it takes spark at the right time, compression and fuel to have the engine work.....Most likely there is a timing based issue, investigate ignition and valve timing.

Hi,
Looks like vacuum leaks and some sensors are not connected.
Re check everything again and tell us what happen, so that we could guide you better.
Thanks for using Fixya!

its not just the camshaft timing marks you set up, you also have to have the crankshaft timing mark set right to or you may damage your engine
check the internet for the right timing procedure for you model car ok

you should have timing marks that are lined up on your engine. You have your crank to line up at a certain point as well as the two cams. I don't know off the top of my head where these might be for this car but you can find it in a Haynes or Chilton manual if you so desire to also learn more about your overall car and take care of this or i can find these specs and send them your way. Up to you?

Hicksashley,

When you look at the engine on the pulley end you must find a triangular pointer on the main pulley and then look at the two or four cam pulleys for a dot like dent on the fin of the pulley. These are marks for timing, firstly you set the main pulley with the timing mark on the pulley to the triangular mark on the engine just above the pulley to the right or to the left, then you put both cam mark facing each other on the insides level with the top of the block. that it you should be able to start her up if your plug timing is in order,