No Start 1: Checking For Spark
The starting point, for any Cranks but Does Not Start condition should be testing the ignition system first. Specifically, making sure that all of the 4 cylinders are getting spark.
Your 1.8L Nissan will either have a distributor-type ignition system or the more modern COP ignition coil system. Either way, the first thing you and I need to do, to find the root cause of the no start condition, is to make sure all four spark plug wires or all four COP ignition coils are sparking.
If the ignition system is the cause of the No Start, you're not gonna' see spark at any of the 4 spark plug wires. If there is spark being fed to all 4 cylinders, then we can correctly deduce that the ignition system is not behind the No Start condition and can move on to other tests (like testing fuel pressure).
Remember, the idea behind checking for spark is to see if all of the 4 engine cylinders are getting spark. Here are the most common causes of a no-spark result:
CASE 1: Spark was present in all 4 cylinders. This result tells you three very important things: 1.) the crank sensor is functioning correctly, 2.) the ignition control module (also known as the igniter or power transistor) is OK -this applies to distributor-type systems, and 3.) the ignition coil is good. You don't have to spend any time testing them or any money replacing them.
Your next step is to verify fuel pressure. Go to: No Start 2: Checking Fuel.
CASE 2: Spark was NOT present in all of the cylinders (DISTRIBUTOR TYPE): This test result tells you without a doubt that the no-start condition of your 1.8L Nissan Sentra is due to a malfunction in the ignition system.
Now, with no spark in any of the engine cylinders, this what I would suggest:
- Check for spark directly on the ignition coil tower using a spark tester.
- This is the best way to test the distributor cap. The distributor cap and rotor are infamous for causing no-spark no-start conditions.
- If you do get spark coming out of the ignition coil tower, you now know beyond a shadow of a doubt the distributor cap and rotor must be replaced.
- Test the ignition coil and ignition control module (also known as the: igniter or power transistor).
- If no spark is firing from the ignition coil, then the next step is to verify that the ignition control (igniter) is activating it. This is a pretty simple test.
CASE 3: Spark was NOT present in all of the cylinders (COP IGNITION COIL TYPE) This test result tells you without a doubt that the no-start condition of your 1.8L Nissan is due to a malfunction in the ignition system.
It's almost impossible for all 4 COP ignition coils to fail at the exact same time. So the most likely cause for this No Spark condition is a bad crankshaft position sensor.
No Start 2: Checking For Fuel
Checking that the fuel pump is delivering fuel to the fuel injectors is not that hard on your 1.8L Nissan Sentra (since you're able to tap into the rubber fuel pressure hose that connects to the fuel injector rail with a fuel pressure gauge and its appropriate adapter).
A bad fuel pump will cause your 1.8L Nissan Sentra to Crank but Not Start since the fuel pump is the one responsible for supplying fuel to the fuel injectors.
The absolute best way to test the fuel pump is with a fuel pressure gauge, using any other method is not as accurate. Still, the other method that I've used to test for a lack of fuel is spraying starting fluid into the throttle body and then having a helper crank the engine. If the engine starts, then I now know that I need to take a closer look at the fuel pump to see if it's fried or not.
When testing the fuel pump (with a fuel pressure gauge), you'll usually see one of two results:
CASE 1: Fuel pressure is at specification. Not only does this result tell you that the fuel pump is OK but that the following components, that supply the fuel pump with power, are OK too:
- Fuel pump fuse.
- Fuel pump relay (which is known as the Main Relay).
And so, there's no need to spend time testing them or money replacing them.
CASE 2: Fuel pressure is not present. This usually means that the pump has failed, but not always. I would recommend testing/checking the following before condemning the fuel pump:
- After verifying that no fuel pressure exists, check that the fuel pump is getting power by tapping into the power circuit that feeds the pump with 12 Volts with a multimeter.
- Once you're tapped in, have a helper crank the engine while you observe your multimeter in Volts DC mode. If voltage is present (12 Volts), then you have confirmed that the fuel pump fuse and fuel pump relay are working perfectly.
- Confirming power to the fuel pump (with a multimeter) also verifies that the fuel pump has failed and needs to be replaced.
- If no voltage is present, as your helper cranks the engine, then the cause of no-fuel condition is due to either a bad fuse, fuel pump relay (known as the Main Relay).