Ikarus

I don't think so. I figured out what the deal was by re-wiring the power based on how the ignition switch is supposed to function. Sort of, anyway.

EDIT:

I can't figure this thing out. The voltage to the PCM during cranking keeps dropping to between 8-10V, and the ignition exciter 5V is only showing ~200mV. I think this battery may be toast, although it does the same thing with jumper cables and a running vehicle connected. I've checked all my grounds, again, and nothing. I'm still trying to figure out the wiring to the firewall fuse block, because interior lights stay on when the accessories are turning off. But I've got the PCM and everything hooked to a wire that is supposed to be hot in run and crank, per the switch wiring diagram, which is the pink coil wire.

1989GTA

What size cable are you running from the battery+ to the starter? What size cable are you running from the battery to where the power is for the ECM? What size are your ground cables?

Ikarus

Battery to starter is 6 gauge (i think). The battery to ecm power at the same post is 10 gauge. The ignition relay wire is 18 or 20 gauge. That's what came with the harness. The ground cable from the block to body is 6 or 8 gauge, and the battery to chassis is the same as battery positive. The block to chassis is a thick metal ground strap. The grounds on the back of the head are internal to the harness.

jimmyg

Put switched power directly to battery and see if she starts you prob need an ignition switch. They are cheap mine was 11$ for my 83 cutlass

1989GTA

"Battery to starter is 6 gauge (i think). The battery to ecm power at the same post is 10 gauge. The ignition relay wire is 18 or 20 gauge. That's what came with the harness"

When you say same post, is that the battery post?

Ikarus

Battery to starter is 4 gauge. and I just tried moving the battery cable to a junction block and powering it from there, same story. I've tried basically hotwiring the PSI ignition cable to the battery and it doesn't seem to make a difference. I think maybe the PCM has something internally wrong with it, where it can be programmed but it won't send the right start signals to the coils.

Ikarus

Welp, finally got it fired up tonight. Despite what the wiring diagrams said, a wire that was listed as "coils" needs to be hot at all times, as does a wire that was supposed to be going to the alternator.

Started up and it's super smokey, and after a minute or so of running it sounds like it has a pretty pronounced rod knock or something. I'm not sure, I only know what lifter tick sounds like. Guess I'll have to figure that out when I get it all buttoned up.

Thanks for the help, guys. I'll post a video once it's all going smoothly.

Ikarus

Judging by what I've read on here tonight, the piston slap is a "normal" problem with a lot of Vortec motors. I'm going to Seafoam it this weekend to see if it goes away. It's also been sitting unused for a few months now, so even after I changed the oil, there's going to be a lot of gunk built up. Also, the smoke may be my new LT headers burning in the ceramic coating I sprayed on. They came uncoated, and I used the spray-on ceramic coating. Starting it with open headers made it eye-watering and headache inducing after a minute or so in a half-open garage.

This weekend is going to be a lot of buttoning up of wires, installing of some Dakota Digital gauges, and putting the truck back together. So glad I finally figured out how to get it started. Now I just have to figure out where in the circuit to put the alternator, and it should be all good.

1989GTA

Glad you found your problem. Also let us hope and pray it is only piston slap.

Ikarus

Agreed. Just hoping it's not a blown head gasket or something. Although if that's what it is, I'll replace it myself.

truckdoug

iTrader: (25)

what kinda oil pressure do you have on start up?

Ikarus

I'll check when I start it again in about 30 minutes to an hour and let you know.

Ikarus

Seems like I spoke too soon. I went to start it again, and it did the same thing. Crank all day, and nothing. For two days. Then at one point today it randomly started and ran for a bit. When I turned it off, I couldn't get it started again. ******* ******* truck.

truckdoug

iTrader: (25)

swap your relays out for known good ones.

verify fuel at the rail

noid light on the injectors

noid light on individual spark plugs

I have had these same issues man, you just gotta keep grinding at it.

Ikarus

I've done all those things. More than once. And it's just driving me nuts that it fires up fine for a while, then just decides not to, even though nothing's changed.

This is probably another red herring, but I've got 12-13 ohms of resistance from my battery negative post to any of my grounds, or the frame, block, or body itself. Bad battery, maybe?

Ikarus

I don't know if it's normal or not, but that resistance only exists when the positive side of the battery is actually connected. When it's not, the negative side gets zero resistance to any ground.

LarryBoy71

Ikarus...Im in NW Arkansas (Rogers) and for 3 weeks now I have been dealing with a similar issue. Difference for me though is that I cant get my injectors to fire! So glad I found this thread...Im going to go back in and try all the things that were recommended to you on mine. Please keep me in mind if you have any fixes and would appreciate any help from the forum. This is my 1st resto with an LS too. 1971 C-10 w/2002 5.3. Another difference is I built my own harness from LT1swap.com. My resto is about 90% complete and I should have already been attending some shows, so I truly feel your frustration!!! This smiley shows how im feeling about right now... "whipped" haha

Ikarus

Nice. Good luck. I definitely didn't have the patience for that. I bet that thing is gorgeous.

So after all of the crap with this truck, I decided to replace the cam position sensor just on a whim. Knowing it should've started anyway, I didn't have high hopes. I really didn't have high hopes after having to remove the water pump to drill out the old CPS that was ******* jammed in the block.

It works now.

Every time. And everything is wired up correctly (the way I originally had it), and it runs perfectly. Except the piston slap/lifter tick noise. I've tried Seafoam, and it hasn't really helped. I'm not getting the usual "massive white smoke out the exhaust" from the Seafoam though, so maybe I'm not using enough. I also need to figure something out with the radiator until I can buy a nice double-pass. Either way, right now, it works.

truckdoug

iTrader: (25)

I seem to find something really common (that no one else does apparently) is the rocker arm tips/pushrod ends having extreme wear. I'd look there first.

Next I'd look and see if there is glitter in the oil. If it's a rod bearing it'll make glitter.

My current 5.3 is a '01 and it cold slaps badly for a couple minutes in the morning, but goes away after a minute or so.

But you have cleared all the major hurdles IMO. If it's a mechanical issue it can be fixed with more bolt turning.

Ikarus

The slap doesn't seem to go away when I let it run for a few minutes. It's all new oil. when I pulled the old, it was clean, though.

Then again, I also haven't actually taken it out to drive yet. I've just revved it up to about 2k RPM for a couple of seconds. Other than that, it's only been at idle.