There is a method to the madness of diagnosing a no start condition and in this article I'll explain what I did to diagnose a no-start condition on a 2002 1.8L Nissan Sentra that belongs to some friends of mine.
As you'll see, as I spin this yarn, the camshaft position sensor was the component that had failed and was keeping their 1.8L Nissan Sentra from starting.
Contents of this tutorial:
- The Complaint: Nissan Sentra Cranks But Does Not Start.
- STEP 1: Making Sure That The Fuel Pump Is Working.
- STEP 2: Checking All Ignition Coils For Spark.
- STEP 3: Checking That The Fuel Injectors Are Being Activated.
- STEP 4: Checking For Trouble Codes.
- STEP 5: Testing The Cam And Crank Position Sensors.
- More 1.8L Nissan Sentra Tutorials.
The Complaint: Nissan Sentra Cranks But Does Not Start
As I mentioned at the beginning, the 2002 Nissan Sentra cranked but did not start. My friends were under the impression that the fuel pump was bad and were getting ready to have it replaced when they called me to get my opinion.
Testing the fuel pump pressure with a fuel pressure gauge is a piece of cake on this Nissan Sentra, so I offered to go over and check it for them.
STEP 1: Making Sure That The Fuel Pump Is Working
Since the concern was that the fuel pump had failed, the first thing I checked was the fuel pressure with a fuel pressure test gauge.
On the 2002 Nissan Sentra, testing the fuel pump is easy since all you have to do (to test fuel pressure) is connect the fuel pressure test gauge in-line with the fuel hose that connects the fuel filter to the fuel injector rail.
If you take a look at the photo above, I disconnected the fuel hose at the point where it connects to the metal fuel line on top of the intake manifold plenum (the orange arrow points to this location) and installed the fuel pressure test gauge there.
Here's a breakdown of what I did:
- Disconnected the fuel hose that connects to the fuel pressure line on top of the intake manifold plenum (the arrow in the photo points to the hose).
- Connected the fuel pressure gauge to this hose using a T fitting (that's included in the fuel pressure gauge kit).
- Connected the other end of the T fitting to the fuel line leading to the fuel injectors with the fuel hose included in the kit.
- I tightened all of the hose clamps and then cranked the engine as I observed the fuel pressure gauge needle.
Well, it turned out that the fuel pump was producing the correct amount of pressure. So, now knowing that the fuel pump was not the cause of the 'no start' problem, I needed to make sure that the engine was getting spark.
STEP 2: Checking All Ignition Coils For Spark
After having checked and confirmed that the fuel pump was not behind the no-start condition on the Nissan Sentra, the next step was to make sure that the ignition coils were sparking.
I accomplished this test by using a dedicated spark tester. The spark tester that I use is the HEI spark tester. This spark tester is the only one I trust to give me an accurate spark test result. Basically, if the ignition coil makes the HEI spark tester spark, then that ignition coil is functioning correctly period.
You can check out this spark tester here: HEI Spark Tester (at: easyautodiagnostics.com).
Here's the breakdown of what I did:
- I unplugged and removed the #4 cylinder ignition coil.
- Once the coil was removed, I reconnected it to its connector.
- I connected the HEI spark tester to the ignition coil.
- I grounded the HEI spark tester directly to the battery negative (-) post using a jump start cable.
- Asked my friend to crank the engine as I observed the spark tester.
The result was no spark. I tested the other 3 ignition coils and none sparked.
Since it's nearly impossible for all four ignition coils to go bad at once, these test results told me that the problem was not due defective ignition coils.
So far, I had eliminated the fuel pump and the ignition coils as the cause behind the no-start, my next test was to see if the fuel injection computer was activating the fuel injectors.
STEP 3: Checking That The Fuel Injectors Are Being Activated
So far, in my testing, I had eliminated the fuel pump as bad and the ignition coils as being defective. So now I was curious to see if the fuel injection computer was activating the fuel injectors.
To find out, this is what I did:
- Disconnected the #4 cylinder fuel injector from its connector.
- Inserted the appropriate Noid light to the fuel injector connector.
- Had my friend crank the engine while I eye-balled the Noid light.
What I was looking for here was for the Noid light to blink on and off as the engine was cranking.
Well it turned out that the Noid light did not blink on and off (connected to the #4 fuel injector connector), so checked the other three. None made the Noid light blink on and off.
These four test results (no fuel injector activation on each cylinder) and the no-spark test results of the previous tests now told me that the most likely cause of the no-start problem was probably due to a bad crankshaft position sensor. But before I tested the crankshaft position sensor, I got out my generic scan tool and checked for trouble codes.