Trying to diagnose and replace what's causing your 1.8L Nissan Sentra to crank but not start can leave you tearing your hair out.
Especially since so many things can cause an engine no-start problem like: a bad fuel pump, a bad crankshaft position (CKP) sensor, a blown head gasket and the list goes on
Well, there's 'light at the end of the tunnel' because with a solid diagnostic strategy, you can do it yourself and replace whatever the faulty part is (or have it done).
In this article, I'll show you the basics of how to test/troubleshoot such an issue.
Contents of this tutorial:
You can find this tutorial in Spanish here: Cómo Probar Un Arranca Pero No Prende (2000-2006 1.8L Nissan Sentra) (at: autotecnico-online.com).
APPLIES TO: This tutorial applies to the following vehicles:
- 1.8L Nissan Sentra: 2000, 2001, 2002, 2003, 2004, 2005, 2006.
NOTE: The following real life case study may be a handy read: No-Start Case Study 2002 1.8L Nissan Sentra.
Difference Between A No-Start And A No-Crank Condition
Before I go into the details of troubleshooting an engine no-start problem, let me tell you that a no-crank and a no-start condition are not the same thing.
Here is a brief description to help you take advantage of this tutorial:
Engine Cranks But Does Not Start: Means your 1.8L Nissan's starter motor will crank the engine but the engine won't start. This is usually due to a fault in the ignition system or fuel system, or a mechanical problem with the engine (like a thrown rod, etc.).
Engine Does Not Crank: Means the engine will not crank when you turn the key to start the engine. In other words, the engine doesn't turn over at all. This is usually due to a faulty starter motor, ignition switch, neutral-safety switch, or a locked-up engine.
If your Nissan's engine doesn't crank and you suspect the starter motor, here's a tutorial that'll help you test it:
Engine No-Start Condition Basics
The most basic and important thing you need to know to start troubleshooting the engine no-start condition is that your 1.8L Nissan Sentra's engine needs 3 things to start and run. These are:
When your 1.8L Nissan Sentra cranks but does not start, it's because one of these three things is missing in the mix.
So to fix the problem, you and I need to check for spark (with a spark tester), fuel pressure, and if necessary, the internal condition of the engine with a compression test.
I'll go into more specific details in the following headings:
1.) Ignition System
- The ignition system is responsible for generating and delivering spark. Without ignition spark, the engine will crank but not start.
- The ignition system of the 1.8L Nissan vehicles covered in this article uses a COP (Coil-On-Plug) ignition coil system. With a COP ignition coil system, each cylinder has its own ignition coil; thereby eliminating the distributor entirely.
- In my experience, the most common ignition system component failures that result in a no-start no-spark condition are:
- A bad ignition coil (if more than one fails).
- A bad crankshaft position (CKP) sensor.
- A bad camshaft position (CMP) sensor.
- All of the above components of the ignition system can be methodically tested to find out exactly what has failed (if indeed something has failed).
2.) Fuel System
- The fuel system is responsible for supplying the engine with fuel.
- The fuel system components that cause the most no-start, no-fuel problems are:
- The fuel pump relay.
- The fuel pump.
- The fuel pump can be tested with a fuel pressure gauge to determine if it has failed.
3.) Engine Mechanical System
- The engine pistons and cylinder head valves (and all other associated components such as: timing chain, etc.) are responsible for drawing in the fresh air that the engine needs for the combustion process.
- Although rare, mechanical problems inside the engine can and do cause starting problems.
- Possible internal engine problems are:
- A blown head gasket.
- A blown engine.
OK, the list of possible things that can go wrong looks pretty long, but it's rare that two different components of two separate systems fail at the same time.
The cool thing is that there's a diagnostic strategy you can use to pinpoint what's wrong with your particular engine no-start issue. Let's learn more about it in the next subheading.
No-Start 1: Checking For Spark
The starting point for diagnosing a cranks but does not start problem should be testing the ignition system first. In particular, making sure all four cylinders are getting spark.
Your 1.8L Nissan Sentra has either a distributor ignition system or the more modern COP ignition coil system.
In any case, the first thing you and I need to do is make sure all four spark plug wires or all four COP ignition coils are sparking to find the root cause of the engine no-start problem.
If the ignition system is the cause of the engine no-start issue, you'll not see a spark at any of the four spark plug wires or from all four COP ignition coils.
If spark is supplied to all four cylinders, we can correctly conclude that the ignition system is not behind the engine no-start issue and can proceed to other tests (like testing fuel pressure).
The following tutorial explains how to test the ignition coils for spark:
Remember, the idea behind the spark check is to see if all four engine cylinders are getting spark. Here are the most common causes of a no-spark test result:
CASE 1: Spark was present in all four cylinders. This result tells you three very important things:
- The camshaft position (CMP) sensor is working correctly.
- The crankshaft position (CKP) sensor is working correctly.
- All four ignition coils are OK.
No need to spend time testing any of the aforementioned ignition system components or money to replace them.
Your next step is to check fuel pressure. Go to: No-Start 2: Checking Fuel.
CASE 2: Spark was NOT present in all cylinders. This test result tells you without a doubt that your 1.8L Nissan Sentra will not start due to a malfunction in the ignition system.
It's almost impossible for all four COP coils to fail at the same time. So the most likely cause of this no-spark test result is a bad crankshaft or camshaft position sensor.
The following tutorials will help you test these sensors on the 2000-2002 1.8L Nissan Sentra: