2004 V6, crank, no start

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2ndGenToyotaFan

2ndGenToyotaFan

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I’m working on a 2004 4runner with the 4 L V6. Sometime around 2017 the engine was blown up and it sat until I bought it a year or so ago and I found a used engine out of a 06 tundra and put that in. Everything is back together and it cranks and will fire a few times, but it will not start and run or idle. I’ve gone over the wiring harnesses a few times and I don’t think anything‘s unplugged, but I’m also not getting any trouble codes. The security light is doing everything that it should so I don’t think the immobilizer is immobilizing it. I can hear the fuel pump running, but it turns off after a couple seconds in line with when the engine stops firing.

If anybody has any thoughts or has experienced something like this, let me know. Thanks a bunch!
 
I’m about to do that. I just checked ignition timing and it’s in the ballpark. I’m starting to suspect maybe a weak fuel pump that’s only putting in enough fuel up to make it sputter but won’t let it run. 🤷🏻‍♂️
 
I’m following, having the same issue
 
Where did you test the fuel pressure? Are you using Techstream? Generic OBD scanners won't show everything.

Generally would see a misfire code if there is a spark problem but not always if it's system-wide. I would make sure injectors are getting signal and coils/plugs are firing.

I've seen wiring for crankshaft position sensor cause a no-start/no-run without throwing a code.
 
I tested the fuel pressure where the hard line leaves the inner fender.

I had a mobile mechanic come by with a snap on obd unit and he couldn’t really find any problems either. I might have to find a way to get techstream and have a look at it.
 
The plot thickens…. For weeks I’ve been slowly checking and rechecking things. Oil pressure spiked to 50 psi while cranking. Oil pressure sender is good. Timing cover removed and timing chain checked. Valve timing checked…

Still cranks, fires and dies.

Then! I unplugged the crank sensor and cranked on it. It didn’t even try to fire, which makes sense. Plugged the crank sensor back in and unplugged the cam sensors. Hit the key and it fired right up and ran! I had the airbox off and the maf unplugged at the time. It was running at about 2000 rpm’s till I turned it off. It sounded great, not missing or stumbling at all.

Success right!?!?!? No. That was a week ago. I haven’t been able to replicate it since…

So I am more heavily leaning toward the ECU being bad. I took it apart and it looks brand new inside. However there are about 1000 solder joints that could have gone bad.
 
With intermittent success based on changes that are non-replicable, certainly sounds like more of an electronic/computer issue. Was the ECU ever wet? Possible there is a compatibility issue with one or more connectors as well. Did you compare all connectors on new engine to the old ones?
 
I’m pretty sure I reused all the sensors from the old engine with the exception of the crank sensor. But I’ve confirmed part number compatibility between the two and most of them are the same sensors with the exception of the camshaft position sensors which fit in the same hole in the head or timing cover, but are totally different sensors with different plugs. There is a coolant pipe manifold part that goes at the back of the block and it’s totally different between the two so I reuse the old one which had the temperature sensor in it. There’s no sign that the ECU has been wet, the inside looked brand new. The outside cover had some corrosion on it but nothing serious. I think I need to start looking at the ECU because even though it looks good, it doesn’t mean it’s good. I tried throwing a space heater on it to warm it up and see if that changed anything but I didn’t get any different results.
 
One more thought is the fuse box. I have had some very strange inconsistent issues due to poor connections in the fuse box. I agree that it sounds more like ECU though.
 
Well, it’s getting weirder. A friend gave me a hand today and we figured out that the truck will run with the passenger camshaft sensor unplugged. (I’ve tried various combinations of things unplugged, but never had repeated positive results…) But it dies immediately if you plug it in. Swapping cam sensors left right didn’t change anything and replacing the VVT solenoids didn’t change anything. So maybe it’s a bad wire? I’m about out of ideas though.
 
Sounds like you're on the right track if you're getting an isolated repeatable result. Wiring or connector issue sounds most likely. Slight possibility still that there is an issue with the ECU. You also noted previously that the cam position sensors that were in the engine were different...
 
The engine came out of a tundra, so there were a couple differences, one of them being the camshaft sensors. But the sensors from the 4runner are in the engine now, and the sensors from the tundra won’t plug into the 4runner harness. Physically, the heads and the timing cover are the same where the sensors mount. I sure hope I can get this sorted out soon, it’s been a real drag, having this thing not running.
 
It doesn’t appear that either of the two wires are grounded to anything. I haven’t checked them from the engine to the ECU yet. But I did drive it around town today. It drove fairly normal had a few hiccups, but never died. Of course, check engine light is on and there’s camshaft sensor codes.
 
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