*video* 01 Qx4 Wont Start. Cranks hard, has fuel pressure

[CanuckQx4]

Hey guys, first time Ive ever had this issue, came out of work and my car wont start, just cranks and crank and cranks but no engine start or even attempt to fire. I veryfied I have fuel pressure at the fuel rail as I have an aftermarket gauge installed form when I put this reman engine in 2 years ago. Here is a video of what is happening

https://www.youtube.com/watch?v=B0jKn6W ... e=youtu.be

I tried disconnecting the battery for 20 min, and the car is now sitting on a battery charger. Im hoping to check spark and possibly timing if possible next, can you check spark on a coil pack car like a traditional car with a distributor/spark plug? I wasnt sure so I didnt want to try without verifying.

One thing I think I should mention is the car throws a P0505 idle air control valve error, and has for the last 4 years, it currently has no stored codes though. But Ive read to fix teh IACV you have to repair/replace a computer aswell, but the problem has been there for years, I just have to tap the gas when starting it as it hasnt had a high cold start idle since it threw P0505 so long ago.

I do have a code reader with a live data function, ive actually never used it, but maybe that could shed some useful information? Anything specific I should be watching?

I got the car towed home, and I will disconnect the battery overnight while I go to work, but Im doubtful that is going to help. Im open to all suggestions and will do them promptly. Thanks for the help!

[frapjap]

Hmmm, that is interesting!

To answer your first question- I'd verify spark and fuel.
Lets start with the basics.
Fuel- Confirm that you have it either by listening to the fuel pump prime with the key in the on position. If you hear that, confirm fuel delivery by pulling an injector and watching it run. You can also change the fuel filter if you haven't already. If you don't think you're getting fuel, try adding some through a vacuum line or using starting fluid sprayed into the throttle body. If it cranks right up, you have a fuel problem.
Spark- Test for spark by pulling out a plug wire boot and set it on top of the valve cover (away from other wires or anything flammable or electrical) and have someone crank the engine over. If you have spark, you should be able to literally see it arcing as it grounds out.
If you verify both fuel and spark, make sure you aren't getting TOO much fuel by pulling the fuel pump fuse and cranking for a while. If it starts up after a bit, you know you were flooding.

Give those a try and report back.

[CanuckQx4]

I certainly have fuel, the fuel pump primes, and my aftermarket fuel pressure gauge that is mounted on the feed line has 45psi.

As for checking spark, since this VQ35 is equipped with coil packs, can you simply uninstall one of the coils, put a spark plug in the end of it and try that, I didnt know if you could do that with a coil pack

[CanuckQx4]

Confirmed I have no spark today when a helper arrived to crank the car for me. I also verified with my code reader that the car is showing the rpm @ 200 when cranking, to me that would show the crank sensor registerring.

How would I be able to tell if the ecu was taken out by a bad IACV? Is this even a condition it would cause? (no spark)

[CanuckQx4]

I appreciate the info greatly. I have a bit of good news, I was slightly set in my mind that my IACV took out the PCM as I read quite a few posts on this happening in nissan/infiniti vq engines. I inquired with a seller on ebay that offerred the service specifically for our vehicles and this problem, he said when I removed the ecu to open the case and it would be obvious something has gone wrong, he even sent a few sample pics and all had the same resistor/cap explode inside the ecu. I openned mine up just now after a fight on my back in the rain to remove it and mine is sparkling new inside, no damage. So good new, but bads news is I still dont know whats wrong.

I honestly admit, after downloading the fsm last night, it seems over my head on the language they use, the signage, seemed daunting to me to troubleshoot my current problem, even your post mechanicalbaron about checking for start signal seems a little out of my knowledge base, Ive rebuilt newer car engines completely, and am sound mechanically, but these FSM's seem impossible to read without a degree.

Where would the best place to start be for me after now knowing I have no spark to #1 and #3 coil, aswell as confirming I am getting proper fuel pressure to the fuel rail.

[yeldogt]

Wish I could offer some help ... If this was a Mercedes the failure you have is exactly how the CPS dies on the MB V6

[frapjap]

If you don't have spark on 1 and 3, I'd swap the coils around to see if you get spark on 1 and 3 and not 2 and 4. That way you'll be able to isolate a dead coil.

[CanuckQx4]

All the coils werent sparking, 1 and 3 wqere just the first 2 I pulled to confirm.

I fixed the truck though, ended up being the crank position sensor. I had an extra off of the the old engine and decided to install it since it is very quick to swap and the truck fires right up. Got lucky on this one, wasted a few hours pulling the lower dash apart to tak the ECU out and testing spark etc though, oh well.

[yeldogt]

So now we know that the Nissan V6 dies like the Mercedes ... CPS in my post is the Crank Position Sensor.