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Just finished a motor swap on 08 Altima with 2.5l and now I have a crank no start issue. I have tried swapping out the crank sensor with no luck. Can anyone give me some direction on where to go from here? I am so disheartened over this.
 

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Since you already replaced the crankshaft position sensor, the camshaft position sensor may be bad. When replacing sensors, always use Nissan OEM parts from a Nissan dealer; aftermarket electronic items generally are not reliable, don't last long, and many times are DOA.

One of the first things to do is perform an ECU code readout with a portable scan tool to see if any fault codes are set. The tool can be purchased at most auto parts stores. Post the actual codes here on the forum so that we may be able to help you further. If there is one or more fault codes set, they can help point to the malfunction. If you have a copy of the FSM for your vehicle, the code readout procedure is described there along with a listing of codes. You can download a copy of the FSM from this web site: Owner's Manuals. The section EC.PDF is the one you need to read.

At this point you'll have to determine if there's an ignition or fuel delivery problem:

* Testing fuel delivery:
An easy way to test the fuel pump and filter is to disconnect the fuel feed hose from the fuel rail and connect it to a long length of spare hose with the other end draped over the fender going into a catch can placed on the ground. Now turn the ignition key to the run position but DO NOT START THE ENGINE. You should see fuel going into the can at a good rate for several seconds.

Tee-in a temporary fuel pressure gauge between the fuel feed hose and the fuel rail. Turn the ignition key to the run position but DO NOT TRY TO START THE ENGINE. The fuel pressure reading should be around 51 psi which would be a static reading.

The fuel injectors may not be firing. This can be tested with a "noid" light probe for each injector harness connector.

* Testing ignition:
Pull several coil packs to test; use a spare spark plug in the coil pack to test; ground the plug base with a jumper wire to the engine block; see if you're getting a spark while trying to start the engine.

* The cam timing may be incorrect:
Check for a broken or cracked chain guide causing the chain to skip some teeth.

* There may be a major intake system vacuum leak:
Check the intake manifold nuts to make sure they are tight. Also check the intake plenum bellows at the throttle valve and at the MAF for cracks or loose clamps.
 
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