Captain Obvious

Haha!! Good luck! So out of curiosity, what year are you working on anyway?

I was taught that if one foot on the floor didn't stop it, you should put two feet on the floor and get up. You aren't going to fall asleep anyway.

Great news on the polarity confirmation. And also great news that the engine is running well! Don't forget to put a timing light on it though. You do still have to set the base timing.

My son who recently graduated from VT went through that exact same thing. There was one class that was questionable up to the end and nobody could be 100% sure until the diploma arrived in the mail. Hope it all works out!!

Haha!! My engineering sense tells me that the boundary condition would be when/if the pendulum ever reaches forty-five degrees to horizontal. Beyond that, it would be unrecoverable because the force pulling down would be greater than the force you could ever create even if you moved it laterally at infinite speed. At least that's what the vectors in my head tell me. And you're right! It's beer time!! Right now! Good night folks!!

Can't wait. Hopefully we have a smoking gun. It's always a great feeling when that happens!

I also believe that the original ignition modules are looking for the negative to positive going transition. And as Zed Head mentioned, if you get them hooked up backwards, you end up with a lot of spark scatter and unpredictability. It's because you are spending a whole lot of time in the transition zone with a slow changing signal. Kinda like a very slow ramp on a CMOS input. They don't like it and can go indeterminate. You want the slope as vertical as possible and if you get it hooked up backwards, it can go metastable. The only predictable area is physical transition when the reluctor stops approaching and starts retreating. At that point, the magnetic field change reverses, and the induced current will reverse as well. And... If that's not all... (we talked about the amplitude before being proportional to the speed of rotation) When designed correctly, the signal slope at the transition point is relatively unaffected by the rotational speed unlike the slope elsewhere which is very dependent on rotational speed. If I haven't beaten this to death yet, here's a pic showing the waveform with the polarity switched. Note that the important positive going transitions are that flat indeterminate area with almost zero slope. Bad. What you really want is infinite slope on the positive going transitions. Here's the wrong polarity: And here's what the waveform should look like. Note that the positive going transitions are the vertical slope areas. Correct polarity:

I disagree. I know it's all past news now and doesn't even matter, but I would have done it differently. I would have ignored the motor, the drive amp, and all the rotational stuff at the left end of the track. I would have also ignored the viscous damping. Focus on the forces required to keep the pendulum vertical. Write those equations first in a perfect simplified world and then once you have that part done add in the complexity of the damping and a rotational drive. But to start, assume linear motion, frictionless surfaces, and no damping. First task is to just keep the pendulum upright. Once you have that, add in the other factors one at a time.

That's one of my favorite Far Side cartoons ever. I've even heard that "My brain is full" phrase uttered in technical project meetings. Maybe even by me...

You do know that the signal coming from those VR pickups is polarity dependent, right? Even though it's an A/C signal, the phasing is important. So my guess, based on what I'm reading. is that you had it hooked up backwards earlier on, but with all the alligator clipping and such, you "accidently" swapped the polarity and got it connected properly. And FYI... That's the reason they used two different sized lugs. That forces you to get the polarity correct when you make the connections to the terminal block. The posts in the terminal block are sized such that you can't connect it wrong. Poka-Yoke.

Sorry to hear that. Since you came to us two days before it was due, you were clearly desperate. (As evidenced by the fact that you came to us! ) Well it at least sounds like the grades going into that project were good enough such that even a poor grade on that one, there was enough cushion to maintain a passing grade for the semester. Hopefully that's the case. The wording of the assignment made it sound like it was a group project... Was there input from other team members? Or despite the description, was it an independent effort?

So how did this turn out? Or don't you want to talk about it?

Remember that engines don't want to run slow and they hate running at idle. They also hate running cold. So it wouldn't be unusual for it to run poorly until it warms up. But once it warms up, it should be much more robust. And once the engine warms up the WTS should be about 250 Ohms. So if it runs better at 2.5K even after warm-up, then there's something going on. If it wants a higher resistance on the WTS, then it sounds like you're running lean. But for confirmation, you should be able to do some quick and dirty tests to see if it's rich or lean. I know you already know this stuff, but just in case: I assume you've got some of the vacuum connections on the intake manifold blocked off with rubber caps? Like the brake booster connection? You can pull the cap off a tiny bit to manually modulate some additional air into the intake manifold and see how the engine reacts. If the speed goes up and it steadies out, then you're probably running rich. If it get's worse and starts to misfire, you're already lean and making it worse by letting extra unmetered air in. Move slowly though... A little bit of air here can make a big difference. You can also adjust the mixture by moving the AFM position around, but same thing... A little motion there can make a big difference. It's squirrely. Have you ever taken a measurement on the ATS? It should be reading about 2K Ohms at your ambient this time of year.

@Av8ferg, Where did you get the O-ring and lock ring for the fuel sender? I'd like to pull mine out and figure out why it's not accurate, but I would like have an O-ring and lock ring on hand before I take it apart. I'm assuming if I have new ones here, I'll be able to re-use the old ones.

Haha!!! Thanks for the coverage!!

I'm not a timing expert, but I wonder if you would even see much of an impact at no load condition even if the advance mechanisms (centrifugal and vacuum) were working at all. I mean, on the road under load, you'd be losing lots of power and would certainly notice it. But under no load conditions, I'm not sure you'd see much impact. I can't easily disable my mechanical advance, but maybe I'll try disconnecting my vacuum advance and seeing what happens. As for the distributor signal to the ignition module... The VR is just a changing magnetic field cutting through a coil. The faster it changes, the higher the induced current and the higher the voltage that could be generated in an attempt to push it. So yes... The output voltage is proportional to the rotation speed. That said, however, it has to work well enough at starter cranking RPM or the engine would never even start. And I'm assuming your starter spins a lot slower than even a low idle speed.

IIRC, there are no ground connections to the EFI harness other than the large wire that leads directly over to the battery. All the other connections (other than the thermotime) are derived inside the harness from that one single ground. I don't think the distributor pickup is supposed to be grounded in any way. In fact, in an effort to prevent noise pickup from any other sources in the car, it's twisted pair to reduce antenna loop area. I haven't looked at in depth though. On my 77, that terminal block does not connect either side to ground. Don't know for sure about 75. I also believe the electronics portion of the AFM is floating and not grounded inside the case. So if they ground the AFM case, it's most likely another interference prevention technique. Faraday cage. Grounding the ECU case as well would do the same thing. All the electronics inside are floating with respect to the metal shell, but it can help to reduce outside interference from things like the ignition flyback. In the end though... I doubt any of that is the root cause of the problems you're having. Sounds like it's getting better though!!! Step by step!

Can't touch this.

And for today's amusement, the part of Captain Obvious will be played by siteunseen.

Oh yeah. Got it. Duh.

What do you mean by that? Do you mean the same amount of fuel spritzing from each injector? If so, that's the way it's supposed to be. Why would that bug you?

I wanted the above to stand alone, but as to your other questions about the switch... You can get the key-in switch out of the rest of the assy without dismounting everything. The only tricky part is prying off the indicator ring that shows the key positions (LOCK - OFF - ACC, etc). If you can pry that off, you can pull the switch out and replace it without having to dig any deeper. Personally though, I'd just bite the bullet and pull the whole thing off the column and do it on the bench. It might be just as easy in the end.

You don't "need" the shear bolts. They are a theft resistant device intended to make it difficult to disable the steering lock by taking the whole lock assy off the steering column. But honestly, I don't think any thief is going to mess around with it at all. One or two well placed hammer whacks on the top of the assy would probably crack the lock assy right off the column regardless of what screws were used to hold it on. Even if all the screws were traditional "normal" hardware, I don't think a thief in a hurry is going to take the time to remove them. Just crack the whole thing right off the column. Whack. Done. Unless there's some non-stock additional theft resistance stuff installed, I bet I could steal most Z cars "gone in 60 seconds". I've not tested the theory, but I'm confident. it would cost me a window (if the doors were locked), a steering column clamshell, and an ignition switch assy. With nothing more than a hammer. Less than 60 seconds. Gone. Let everyone think about that and take the necessary precautions.

If I was desperate, I believe my conscience would allow me to re-use the outboard bearing even after pressing the stub back of once it had been installed. The outboard bore is sized such that it's a press fit, but not a uber tight one. That's why the slide hammer works. If it were a real tight press fit, you'd need hydraulics to take it apart because a slide hammer wouldn't cut it. However, I'm not sure I'd do that if they'd been assembled and disassembled ten times. In any event, it's academic since new ones are on order. I also really really doubt it's a bearing issue. Even without seeing the parts, I'm at 90% sure the issue is the stub axle and not the bearing. Just for the sake of the investigation, I hope you can eventually conclusively determine exactly what was going on. I like the forensic stuff!

Yeah, I definitely think there's something else going on. There's absolutely no reason you should need to disconnect the WTS to improve anything. Disconnecting that should do nothing but produce billowing clouds of eye burning rich fumes. Have you checked the timing with a timing light? Should be able to get a quick and dirty measurement if you can keep it running long enough. Are you sure you have the thermotime and WTS connectors in the correct positions (sorry, but have to ask). If you think you're looking for an intake leak, you could smoke the system. The injectors are powered through the dropping resistors as shown. Bank of four and back of two. On the low side, they are grounded in groups of three. (1, 2, 3) and (4, 5, 6) through the two output power transistors. Wish I was closer to give you a hand.