No spark

Tiny
SETH_
  • MEMBER
  • 2005 NISSAN ALTIMA
  • 2.5L
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 150,000 MILES
Cracked the head gasket while driving and I rebuilt the motor from the head up. I have compression and fuel to spark plugs, but just wont spark. I have no idea why.
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Tuesday, November 10th, 2020 AT 2:12 PM

2 Replies

Tiny
ASEMASTER6371
  • EXPERT
Good afternoon,

Did you check and make sure the crank sensor is hooked up?

https://www.2carpros.com/articles/how-to-test-an-ignition-system

https://www.2carpros.com/articles/symptoms-of-a-bad-crankshaft-sensor

https://www.2carpros.com/articles/crankshaft-angle-sensor-replacement

What is the compression?

https://www.2carpros.com/articles/how-to-test-engine-compression

Roy

The crankshaft position sensor (POS) is located on the cylinder block rear housing facing the gear teeth (cogs) of the signal plate at the end of the crankshaft. It detects the fluctuation of the engine revolution.

The sensor consists of a permanent magnet and Hall IC.
When the engine is running, the high and low parts of the teeth cause the gap with the sensor to change.

The changing gap causes the magnetic field near the sensor to change.
Due to the changing magnetic field, the voltage from the sensor changes.

The ECM receives the voltage signal and detects the fluctuation of the engine revolution.

ECM receives the signals as shown in the figure.
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Tuesday, November 10th, 2020 AT 2:22 PM
Tiny
KASEKENNY1
  • EXPERT
We need to start with checking voltage at the coils. You can just pick one and lets test voltage on each wire of the coil and see what we have. You should have 12 volts on the red wire. Then you should have a pulse signal on the control wire coming from the ECM. You can use a test light for this wire if you want to.

Basically we need to find out if we have a relay/fuse issue or a control issue with the ECM which could be a crank sensor issue. This will just tell us what path we need to take.

Take a look at the wiring diagram and let me know what you find. If those both check out we need to check the ground that is on the front of the engine. Just clip your test light to the positive battery terminal and touch the ground pin on the coil and the light should come on. If not, you have a ground issue.

Let me know this and we can go from there. Thanks
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Tuesday, November 10th, 2020 AT 2:25 PM

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