Quite a few things can cause your 2.0L Mazda 626 (or MX6) to crank and not start, one of those things is a broken timing belt. So, if you've been wondering how to test for a broken timing belt, this tutorial will show you two simple tests.
These tests are pretty simple and can be done without expensive testing equipment.
Contents of this tutorial at a quick glance:
- Symptoms Of A Broken Timing Belt.
- TEST 1: Check Rotation Of Distributor Rotor.
- TEST 2: Removing The Valve Cover To Expose The Timing Belt.
- More 2.0L Mazda Tutorials.
NOTE: The 2.0L Mazda engine is an interference engine. In plain English, this means that when the timing belt breaks, the cylinder head valves will hit the pistons. This results in bent cylinder head valves. In some extreme cases, the valves will break the piston. If a broken timing belt is confirmed, this means that the cylinder head will need to be removed for further inspection.
Symptoms Of A Broken Timing Belt
As mentioned at the beginning of this tutorial, when the timing belt breaks, your 2.0L Mazda 626 isn't gonna' start. It'll crank, but no start. Here are some more specific things you'll see:
- A spark test reveals that none of the 4 spark plug wires are delivering spark. This is because the Ignition System won't create spark with a distributor rotor that does not turn.
- A Noid light test reveals that the fuel injection computer is not pulsing the 4 fuel injectors. Again, this is because the computer won't pulse the injectors with a distributor rotor that does not turn..
- If you were to do and engine compression test, none of the engine cylinders would produce a compression reading on the compression tester.
Let's jump into the first test in the next subheading:
TEST 1: Checking The Rotation Of The Distributor Rotor
If your Mazda 2.0L engine is equipped with a distributor, then this test applies to you. Only the 1993 through 1997 Mazda 626 and MX6 2.0L engines come equipped with a mechanical ignition distributor. If your Mazda 626 does not come equipped with a distributor, then skip this test and go to: TEST 2: Removing The Valve Cover To Expose The Timing Belt.
The purpose of this test is to see if the distributor rotor turns. In case you are wondering why, let me explain: The timing belt turns the distributor rotor via one of the 2 cylinder head camshafts. So if the timing belt is broken, the timing belt will not be able to turn the camshaft. The camshaft in turn, will not be able to turn the distributor rotor.
All we have to do is remove the distributor cap and see if the rotor turns when a helper cranks the engine.
OK, this is what you need to do:
Remove the distributor cap but do not remove the distributor's rotor.
NOTE: Do not remove the distributor from it's place on the cylinder head.
Disconnect the distributor's electrical connectors to disable the creation of spark.
NOTE: If the ignition coil is outside of the distributor, then you must disconnect its electrical connector too.
Now, when you're ready, have a helper crank the car while you observe the distributor's rotor.
If all is OK, you should see that:
1.) The distributor rotor will turn as the engine cranks in steady circular motion or...
2.) The distributor rotor will NOT turn as your helper cranks the engine.
Let's take a look at what your test results mean:
CASE 1: The distributor rotor turned. This is a clear indication that the timing belt on your 2.0L Mazda 626 (or 2.0L MX6) is not broken.
I recommend that you perform TEST 2, just to make sure that the timing belt hasn't skipped a few teeth on the cam gears. Go to: TEST 2: Removing The Valve Cover To Expose The Timing Belt.
CASE 2: If the distributor rotor DID NOT turn: This is bad news and confirms that the timing belt is behind your vehicle's no start condition.
Since the 2.0L Mazda engine is an interference engine, there's a strong likelihood that the valves have hit the pistons and are bent.