Something blew up while trying to start supra

[pseudoduck]

Hey all. Got a 1986.5 Supra with a 7mge. I recently replaced the headgasket and just got it finished and assembled back together. I went to start it and it turned over, but barely. It started to run for a little bit on it's own but then died. I went to try to start it again and then there was a popping noise from the hood and a bunch of smoke coming from the front of the engine near the valve cover and the alternator. When I tried it again it drained my battery instantly and my tachometer went up to about 4000 rpms and then dropped. I found out I forgot to plug in a black plug on the throttle body. I got it plugged in now and I'm waiting for my battery to charge. Is my 7mge dead now? Should I try it again?

[pseudoduck]

Also, I think these could be another problem. I don't know where these wires were supposed to go. I figured they were ground wires so I bolted them to the intake manifold.

[MA70-3.0GT]

Think those should be earths (grounds) as you say, but can't see the wire colours to be 100%. not to insult your intelligence 'cos you already know the earths are black & lives red, but years of dirt can cover the true colour... Is it just possible that the alternator charge wire got hooked up to the earths by mistake (or an earth to the alternator output?) That upper terminal in the pic does look somewhat similar to the alternator wire...

A common problem is the fusible link in the battery cable failing although I'm not sure it'd give the same symptoms you had, it is in the general area you describe, perhaps check that it's intact & not corroded first off?

I guess you could just be unlucky in that your alternator just failed, they're not unknown to die in short order (no pun intended there!) sometimes related to using jump start/booster packs... And if a diode pack shorted out it could do something like that... maybe if that's suspect you could just disconnect the wires to it & try starting with fully charged battery to see what happens?

[pseudoduck]

Well the wire colors are brown and white. And I don't remember where I took them off of. But I did get my car running. I charged the battery back up and plugged in my throttle position sensor and it runs. But the idle is VERY ROUGH. And there is a kinda loud hissing noise coming from somewhere near the alternator.

[Sonyps307]

Looks like the grounds for the ecu they bolt to the bottom of the intake

[MA70-3.0GT]

Hissing from under the alternator would likely be a vacuum line off, I think there's 2 or 3 lines in that area. that would also throw the idle out.

[pseudoduck]

So a little update. I just drove it around the block just to see what would happen and every time I run the car something is burning inside my exhaust and the smoke goes up through it and out my hood. And when I pulled the dipstick out my oil smells like fuel. I went over my vacuum lines 2 more times to see if everything is connected and so did my dad and he says it's okay too (can never be too sure).

We didn't replace the seals on the injectors when we pulled them off. So we think maybe we have a bad seal and it's just leaking fuel or something. And maybe that's what the hissing noise is? Could also be what that pop and misty stuff was that shot out of the head.

[MA70-3.0GT]

burning inside the exhaust and coming out under the hood... Have you got your exhaust disconnected or a big leak or something? if it's inside the exhaust the smoke can only come out where it exits. I'd suggest more likely oil on the outside of the exhaust, when the turbo oil line or the power steering hose leaks it blows back onto the downpipe when on the move IIRC.
Hard to truly diagnose noises without hearing in person so afraid I can't suggest any more than being 110% that all vac lines are connected (and not split/perished). I didn't change my injector seals when I replaced my HG and was fine but guess that depends on how bad they were to start, a more likely source of hissing in that area would be either the plenum or lower intake manifold leaking through either bad gaskets or loose bolts. (you know what a pig some of them are to get to!)

Oil smelling of fuel needs changed ASAP as it could be thinned out enough that running the motor will damage the main bearings etc.

this could either just be old really contaminated oil or possibly cold start injector is leaking badly, probably cause rough running too but change oil/filter & make sure no air/vac leaks first, along with calibrating your TPS and we'll go from there

[abhattan]

have you checked the timing? I would have done that first. Almost sounds like it could be off a tooth or so. Or it was off to begin with and there has been damage and you are getting pressure where you shouldn't. Let's just hope not!