Captain Obvious

I've never used a colortune so it was neat to see one in operation. Neat. I can provide one potential answer about one thing... There is an "after start enrichment" that adds a little extra gas for a little bit after the starter stops spinning. Lasts maybe thirty seconds or so? I found and poked around with the section of the ECU that performs that task, and it tapers off over the first 30 seconds or so. That might be why you aren't seeing the misfire until a little bit after you start the engine. (For those of you that geek out about this kind of stuff... It involves PNP transistors, film caps, and high value resistors. In other words... Bosch analog voodoo.) So about the colortune... On the video of #2. When you rev the engine and then release the throttle, I can see the bright blue ignition spark when the ignition spark is still occurring, but the mixture is too lean to ignite. The whole plug circle doesn't light up, but the narrow strip of the ignition spark gap still does. But on the video of #1 when you rev it and then release the throttle, I can't see that same phenomenon. Is there a healthy spark during deceleration that I just can't see? I'm just making sure we're hunting a fuel problem and not anything possibly having to do with ignition.

One heck of a shine? A huge ball?

Yeah, like I said, I would be happy to be wrong, but the A/C cars are really packed in there. I know I could take the control head out of my non-A/C car without pulling the whole dash, but I'm skeptical about the ones with A/C. I haven't tried. But pulling the dash isn't the end of the world. Gets easier every time. IMHO, draining the Freon out of the A/C system if necessary would be more of a problem...

I would be happy to be proven wrong, but I don't think you will be able to get enough stuff out of the way to get it out. I think you need to remove the whole heater control head at minimum. You have A/C, right? That makes it worse. I think even the evaporator box might be in the way.

Haha! Maybe next time we'll start with the beer. Might make troubleshooting a little more difficult though!

Yeah, the diagram for the 75 and 76 are the same, and what you suggested is exactly what I think happened. The original battery cables are long gone, and the replacement cables did not have provision for the pigtail firewall ground connection. That left only one tie point built into the body wiring harness that runs along the pass frame rail along the engine. One end or the other of that wiring harness tie point wasn't making good connection, so the body (and everything on the entire car that uses a body connection as ground) was floating. Stuff don't work so good like that.

My pleasure. Glad to help, and good seeing you again. For the record, when I left, his Z was not only running, but after we addressed a couple other issues, it was "running better than it ever had before". Haha! I'm happy with that as an afternoon's work. Sometimes you get lucky and it's the first or second thing you check. Sometimes not. This time, we got lucky. Only thing that went wrong is we never got to the beer! About the ground connections... After I got home, I looked at the two wiring diagrams for 76 and 77, and according to the schematics they definitely added more ground ties in 77. And also according to the 76 diagram, the only tie between the block and the body is that connection pair we identified yesterday. There is, however, a connection on the diagram right from the battery terminal to the body (like you are going to do with that ground strap I left with you). So the bottom line is that you might be missing a body ground connection that was built into the original factory battery cable, but other than that, yours is the way it's supposed to be for 76. And the inclusion of additional ties between body and block in 77 makes me think they weren't completely confident in the 76 design. And I'm not confident in that single Phillips screw on the back of the alternator either. I understand the purpose of single point grounding, but it seems questionable to count on that one single small connection to handle all the current from everything on the body. Headlights, brake lights, heater motor... everything. Through that one single Philips screw? I don't trust it. Good luck moving ahead from here, and looking forward to seeing you on the road!

Man... Seeing that thing up close and personal like that makes my skin crawl. Must be an primordial instinctive thing. If you're positive sure it's completely total unequivocally dead, you might want to cut it open? The internal construction is pretty fascinating.

Just make sure they aren't pics of you in the emergency room from getting stung 6000 times!!

Good thing you shut it down so quickly. I'm really curious as to why something like that would happen all of a sudden happen. You pulled this engine from one of your cars, right? Car was totaled, but engine was fine?

Yeah, that 8V thing is definitely a problem. Gotta be a bad connection somewhere. I don't think it's a huge drain dragging the battery down. If it was, you would have seen smoke by now. It's got to be a connection issue. I'll come take a look at it for you for beer. You got beer?

Thirded! It was a little chilling when I heard on the news. The administration in the area put out a directive... "If you aren't evacuating, then please write your Social Security number on your arm." If that don't tell you what they're expecting, then nothing does. Chilling. When I was there a couple months ago for Zcon, I took a day and went to Riverwalk in San Antonio. Here's to hoping there's still some "walk" in Riverwalk, and not just "River".

Other than the fact that your system voltage drops to 8 volts when you get to the ON position, everything sounds pretty much normal. When the key is ON and engine is not running, you should see battery voltage on both sides of the injectors. The 8V level may be so low the your ignition module or ECU won't work right, so we'll have to get to the bottom of that. And the cross threaded stud on the starter could be part of the problem. You need a good tight connection between the starter cable and the smaller white wire which connects to the starter. If that cross threaded stud is preventing good connection between those two wires, then that could be part of the problem. Beyond that, some ideas? Bad battery. Bad connection(s). Blown fuse or fusible link. Something is drawing huge amounts of current and dragging the battery voltage down. Don't burn anything up before I get there.

What he said! I'm so glad to have had the chance to meet in Austin, and here's hoping to catch up in Atlanta as well!

Here's the pics I sent to Nick. A couple shots of my battery and cables. I'm using VW cables and I really like them. Here's the battery end of the cables. The two smaller connections power the EFI system: Here's the rest of the battery wiring. Unfortunately I had to use some of the yellow crimp connectors to put things together. I'll clean them out of there someday, but since it works (but is unsightly), it's lower on the priority list: Here I'm holding up the EFI fusible link: And here's where the positive cable connects to the starter solenoid. I'm holding a rubber insulating boot out of the way. Note the smaller white wire coming off the same terminal. The battery cable is on last hiding the smaller ring terminal of the white wire behind it. This white wire is how the rest of the car (minus the EFI) get's power: I'm not sure if it's something that changed with years, but I wouldn't make any assumption about the polarity of the EFI wires based on wire size. On my 77, I believe both wires are the same gauge, so I just wouldn't be comfortable without making measurements between the battery end and the ECU connector end. So cranking and getting spark is an improvement!

I don't think there's any way you would ever be able to consume 35 GPH. I don't think fuel pump capacity is the problem. Note that I'm not ruling out fuel starvation, but if there is starvation, I don't think it's because the pump is only rated for 35 GPH.

Haha!!

No, that's not a good sign. I just want to tell you both good luck. We're all counting on you.

Yeah, I'm hoping for some interesting forensic discovery... I'm just hoping it's not too gruesome. Any possibility that you starved something for lube with the oil pan changes you made?

Oh. Nevermind. I was confused by semantics and picturing you taking measurements somewhere else. (I'm a dirty skunk? I'm a dirty skunk?) Seems really odd that it would be both of those W/R wires though, doesn't it? Both ends disconnected, and they both still measure hard to ground?

Well I know you know this, but don't get hung up too much on "continuity to ground". Some things will appear to be shorted to ground, but are working as they should be. Like the headlights... If you are measuring continuity to ground through the headlight wire, it's not a problem. It's supposed to do that, and unless you have a good meter, you won't be able to tell the difference between a cold filament and a dead short.

My 77 had the carbon can removed before I got it, so I can't look for any of that restriction. Which tube is it in? 1) The tube that leads from the tank to the can 2) The tube that leads from the can to the intake manifold 3) The control line tube to the throttle body and distributor I believe my old 260 had a restriction between the can and the intake manifold.

I'm thinking the check valve on the CARB system is a smaller check valve with a lower cracking pressure than the one on the gas cap. But since the CARB system is under vacuum when the engine is running, they can't use that smaller check valve when driving. They still need the other one on the gas cap to break any potential vacuum in the tank as fuel is removed to run the engine. Again, just reverse engineering speculation.

Oh, and BTW, I think there are three W/R at C-5. One to the ignition switch, one to the headlights, and one to the ammeter. I hate the 260 wiring diagram...

Not sure, but my guess would be that they didn't want the system to continuously circulate. Think about this scenario... Car is sitting overnight with a half tank of gas and everything is cold. Then in the hot Arizona sun, the car heats up to 140 degrees at mid-afternoon and the vapor in the gas tank expands and cracks the check valve and pushes some vapor up into the carbon can. Then that night after the sun goes down, the car cools off to 60 degrees at 2:00AM and the vapor in the tank contracts and draws a vacuum on the tank. If the only way to reduce the vacuum is through the gas cap, then it will essentially form a one way path. Every day it will push into the carbon can, and every night it will suck in past the gas cap. Eventually, your tank will be empty, and your carbon can will be saturated. I wasn't there when they designed it, but my theory is that they didn't want that to happen. So they put in another way for air to get back into the tank to reduce that vacuum, and by pulling it back through the carbon can, they can put those vapors back into the tank where they belong. Essentially exhale and inhale through the same tube instead of inhaling through one and exhaling through a different one. Haha!! Far fetched maybe, but that's all I got?