Captain Obvious

Haha!! I'm disappointed! It's solid state and not tubes!! Hope none of your neighbors are listening to the radio or they're gonna hear you testing your injectors.

Chas, That's exactly what I did as well. I used the starter for about ten seconds and decided I needed to do something different. That's when I got the signal generator out and used it to drive a relay that pulled the lower side of the coil to ground. That way, I could also test the ignition system and verify the one injector opening for every three sparks, as well as vary the frequency. A little crude, but it worked. I only mentioned the sig gen because I'm sure Dave has one. Probably vacuum tube, but I'm positive he's got one there somewhere.

Zed Head, Now that I think about it, I bet you are right in that they are steel and not aluminum. I was jumping to conclusions because I don't think they rust. And with that in mind, I bet they are stainless. I suspect the rust you have seen is "embedded" into the shim by the piston, but not growing out of it. I don't have any spares and the only ones I have are on my car. Next time I'm in there I'll investigate a little deeper. Do you have any spares laying loose? Are they magnetic?

Haha! Well the arrow doesn't necessarily point towards the front of the vehicle (because the caliper doesn't mount exactly on the top of the rotor), but it does point in the direction of wheel rotation (when the car is moving forward). When the calipers are mounted on the car, the shims contact the piston from approximately the 8:00 position to the 4:00 position. (Does that make sense?) I don't know for sure what material they use for the OEM shims, but I don't think they rust, so they are probably stainless steel or thin aluminum. I don't know what grade, but it is not one of the dead soft malleable grades. There's a temper to it. They would be a breeze to cut using water-jet or laser. You could mill them on the CNC, but water-jet or laser would be much faster and easier.

EdwardZ (David), Welcome aboard!! I hope you like it here. You got a wonderful car, and I hope you enjoy it as much as the previous owner did!

When I first got my car, the front brakes squealed. When I dug into it, I found that my PO had put the anti-squeal shims in backwards. I switched them around to the proper direction and the squeal went away like magic. Poof.... One way they squealed, the other they did not. The point being... Yes, which part of the piston that is covered by the shim DOES make a difference.

Dave, Yeah, it's not as bad as it sounds. You can get the whole rail off as a unit, and that will also give you the opportunity to take a look at your lower injector seals. If they're dried out and shrinked up, they might not be sealing well. And that certainly isn't going to help a lean misfire at idle when the vacuum is so high and the amount of fuel is so low. Chas, Haha! That sure does look familiar! I don't remember, but I probably got the idea from seeing what you did! Out of curiosity, how did you get the injectors to fire?

And about injector testing... I checked my injector balance a little while ago. I bought a pack of small plastic containers. I think it was an eight or twelve pack of containers from the dollar store. I used a small hole punch to cut a hole in the lid of six of them: I weighed them empty to get the tare weight. Thankfully they were all the same (at least to the resolution and accuracy of my cheapo HF digital scale) at seven grams empty: Numbered them up so I knew which was for each cylinder: Disconnected the fuel rail from the head and thankfully there was enough flexibility to get the cups onto the ends of the injectors: fired the injectors a bunch (I used a sig gen tied into the ignition system) and collected samples: Weighed them up again and verified they were the same (again to the resolution and accuracy of my cheapo HF digital scale), so I'm happy:

Dave, I don't know if there was an ignition problem or not, but I was just pointing out something different on the two videos. Maybe it was just different indexing of the colortune when threaded into the two holes. Maybe on cylinder 2, the spark gap was on the visible side and hidden when installed in cylinder 1? There's a dark spot in the ring on cylinder 1 video. Maybe that's the shadow cast by the ground strap electrode strap? If that's the case, then the spark would be 180 degrees from that and would be hidden by the plug boot? Would be neat to have two (or six!) colortunes installed at the same time for easier comparison in real time.

Well I certainly would try to get it out without pulling the dash first. Maybe you'll get lucky and can manage to get enough stuff out of the way. That copper tube goes about three inches or so into the airbox and then is formed into a coil about an inch in diameter. The point is, you need direct straight on access, not only to get the two screws out, but also to pull the assy out of the airbox. It's incredibly easy if there's nothing in front, but like you said... you have to disassemble so much to access two tiny sheet metal screws. Good luck and keep us posted!

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!