Check engine light trouble

So... I'm hoping you guys can shed some light on this issue. I've got a 2000 Tacoma 2.7l 4WD. The engine was recently rebuilt and now the truck won't start; here's a quick rundown. Motor was finished last weekend, started, ran great and then shut off by me due to a belt tensioner locking up. I replaced the belt tensioner, went to start it and it won't fire up at all. I'm getting fuel (but I don't think enough), spark and compression but it just won't start (it just sputters). It'll kick over and try to run but won't. Here's the interesting part. When I take the key out of the ignition the check engine light stays on (very faint)and the temp gauge spikes all the way up. I have to disconnect the battery to get it to go off. I'm thinking ECM but wanted to see if anyone has dealt with this before.

 

Hook it up to an OBDII scanner or take it over to an auto parts store and have them pull the code for you, should point you in the right direction or at least give you a place to start from. Hard to know how to narrow it down without the code.

 

all of this sounds like bad grounds... one between the negative battery post and the block, another from negative post and the chassis, another from the fire wall to the back of the motor and yet more on the block/intake for the injection/ignition. Just because they are physically "tight" does not mean that they are a good ground.

 

Yeah I thought about the ground connections and double checked them. I'm going to have someone go behind me and check them again just to be 100% It's very frustrating since it ran and ran really good!

 

when I first fired up my motor after replacing it I didnt hook up the cable from the alternator to the battery or the plug and there were all kinds of wierd lights on the instrument panel that shouldnt have been on.

 

Another bad ground proponent, here.

There is a ground on the back of the engine that is easily overlooked. Check and verify it is in place.