Captain Obvious

Ewwwwwwww!

I don't have the ZX manuals downloaded. Anyone know what is the unlabeled device between 8 and 6?

Not sure this adds anything to the discussion, but I once cut up a stock pulley/dampers on my lathe to reduce the number of pulleys. I was just messing around at the time, but if you were concerned with the accuracy (I wasn't), it wouldn't add a lot of time. Here's a pic: More pics and some details here: http://www.classiczcars.com/topic/50727-a-project-is-brewing/?page=2#comment-46928

Won't you take me to..... Welcome aboard!

Based on my understanding of the system, I believe you nailed it. Needing that vacuum line at the back of the car kinda negates some of the advantages of moving the can though, doesn't it?

Cool. Glad you got to the bottom of the issue. I second the call for an autopsy of the screwy throttle body. Send it to me if you don't want to do it yourself. I'll open that sucker up! Dave, I would expect the same thing. With the wire off, you might discern a longer time to return to idle if you blip the throttle. Probably not a lot longer, but you might notice some difference. While you were in there messing around, were you able to determine if there was any change in idle speed with the wire connected vs. disconnected?

Zed, I dont know how large the passageways involved are, but yes... If my understanding is correct, it could/should result in a small decrease in idle speed if you were to disconnect the wire at idle. And yes, it would just be baked into the idle screw position. JSM, good luck with the investigation!

I don't know about new new cars, but they used the same basic concept in the 2000's. Couple differences though. The cans weren't always round, but were shaped to fit whatever tiny odd shaped space was available, and another difference is that the actuation was usually electrical through the use of a solenoid valve instead of the vacuum driven valve built into the cap on top of the can. They used the control brain to purge the can under the desired conditions instead of a vacuum signal. And diagnostics were incorporated into the system as well.

Well moving the carbon canister to somewhere else ought to be no problem. I think getting rid of the tank behind that rear quarter panel would be a little more risk. You do not, under any circumstances, want to push liquid gasoline into your carbon canister. My read on that overflow tank behind the quarter panel is that it is the highest highest highest point that liquid could ever ever reach. And then they pull a line off higher than that for the vapor recovery system.

Zed, the BCDD operation, as I understand it, goes like this... Chamber #17 is a pneumatic amplifier. If there is enough vacuum in chamber #17, it will lift plunger #9 off it's seat and allow some vacuum into chamber #18. And then if there is enough vacuum in chamber #18, it will lift plunger #13 off it's seat and allow air to pass around the throttle butterfly. So some points of interest... The further run in the adjustment screw on the bottom, the easier it is to lift #9 off it's seat. That's why the BCDD will operate at a lower vacuum. When the solenoid is energized (and the pin is retracted) this defeats build up of vacuum in chamber #17. This is because vacuum pulled into chamber #17 from the intake manifold side is just bled off by pulling in air from the upstream side of the throttle body. In order to enable the BCDD, they block the bleed passage on the upstream side of #17 and allow the vacuum from the intake manifold to build up in chamber #17. If that vacuum gets high enough, it will lift the plunger off it's seat. Keep in mind that I didn't design the thing, but that's my read.

Disconnecting the wire will enable the BCDD (which is the wrong direction and not what you want). If you want to completely disable the BCDD, turn the adjustment screw (#6 above) counterclockwise (when looking at the screw head). In fact, you can take that screw completely out. If the diaphragms inside are intact, the BCDD should be disabled completely. Of course, if one or more of the diaphragms has a hole in it, there's no telling what that thing is gonna do. Could disable, or enable it. Also, if there is a goober of carbon gunk holding one of the BCDD valves open, then things get unpredictable as well. To test if your problem is the BCDD, you could probably take off the rubber boot on the front of the throttle body and put a small piece of tape over the BCDD holes. Put the boot back on and start the engine. I wouldn't rev the engine for fear of sucking the tape off and down into the engine, but as long as the throttle butterfly stays closed, you would be OK for just a test. We'll figure this out!

Sorry, but I'm not sure I'm understanding... You are correct that as long as it's plumbed the same as the stock can, then that Sentra can should work just fine. You need three connections to the carb can. A vapor IN connection, a vapor OUT connection, and a CONTROL signal connection. The vapor IN connects to the overflow/separator tank thingie inside the right rear quarter panel. The vapor OUT connects to any constant always present vacuum source like the intake manifold, or the balance tube (if you're running carbs). The CONTROL signal connects to the ported vacuum signal that is also used to control distributor vacuum advance (high vacuum just above idle and no vacuum at other throttle positions). If you've got those three connections to it, I don't think the physical location of the can matters. I was just questioning if you were planning to have access to that ported vacuum signal. I wasn't sure if you were planning to run the original throttle body, or switch to carbs that did not have that signal available.

Well then I'm not sure I understand your question when you asked "To remove the BCDD is simply plugging all the vac lines to it?" I thought you were asking if you could remove it from the system (disable it) by plugging the vac lines that go to it. Were you suggesting a way to disable it, or are you suggesting taking it completely off the bottom of the throttle body and replacing it with a solid block-off plate?

About the charcoal can... They use a ported vacuum source to actuate the canister purge. They don't want to pull air through the can at idle, or at WOT as it is essentially a controlled "vacuum leak" and could adversely affect stability at idle and performance at WOT. The only time they purge the can is at light cruise. So... With all the changes you're making, are you planning to still have access to a suitable ported vacuum source peaking at light cruise?

Well I did a little digging to try to refresh my memory on exactly where I removed metal to allow my parking brake handle to sit lower, and I still don't know. A little embarrassing. I took a couple pics of the assy on the car (with the parking brake removed), and it looks like I may have cut a new rack gear or two at the bottom of travel. Kinda hard to believe, because the teeth look perfect and I don't remember putting that much effort into it! If you want to wait, I've got a plan. This past summer, I bought a new rubber seal for the parking brake pivot ball under the car, and I'll take this off season opportunity to replace that seal. In order to put the new seal in, I'll pull the brake assy and take some pics. However, if you've got the ability and opportunity to lower yours by relocating the mounting bolt hole, then that should work great too!!

I don't know anything about 79, but for all the previous years, it's not a simple matter to disable the BCDD. 75-78 has one wire going to the BCDD, and that wire needs to have +12 on it to disable the BCDD. Meaning that if the wire is disconnected, the BCDD will be enabled. And as for vacuum connections... There are no externally accessible vacuum controls for the BCDD. There are two vacuum ports coming off the throttle body that LOOK like they might have something to do with the BCDD, but they do not. They are both ported vacuum sources that go to small holes in the throttle body bore to control distributor advance and EGR operation. Even though they look like they are for the BCDD, they are not. All the BCDD vacuum ports (both control signals and operation vents) are located internal to the throttle body casting and do not come out to the outside world at all. Like I said, I don't know 79's details, but if the BCDD is on the underside of the throttle body like 75-78, then I would assume it's pretty much the same.

Here's a sketch of what I did to the parking brake assy. Note that it's a hardened pawl on a hardened gear so a file will just skate. You can't do it with a simple file. I didn't trust myself with a grinder, so I used a small square profile diamond file. I'll see if I can get an actual pic of what I did, but in the meantime, this should describe it. So at the "new" bottom of travel it doesn't click because there aren't any teeth, but you can adjust the at rest position like this. After making this mod, it made the addition of my return spring (other thread) even more necessary:

I don't know what happened with the original pics, but here are some replacements. Top side: Bottom side: Close up:

Yeah, I agree. That's exactly why I went through the effort to move mine up there. I wanted to get rid of the rats nest of hoses under the dash and simplify everything under there. I figure the fewer separate hose lengths and fewer clamps, then the fewer leak sources. Only reason I would use to justify putting it under the dash is that I believe the Escort core and the newer plastic bodied ball valves to be more reliable than the old stuff. I think at this point, if I used a new style ball valve and figured out a way to stuff it under the dash, I don't think I'd ever have to mess with it again. It would become the new owners problem at some point hopefully long in the future.

No, I think it was material off the ratchet gear itself. I'll take a look today and see if I can refresh my memory. Sad part is I've done two of these now (mine and my buddy who was with me at your place), and I don't remember the exact process. Some stuff you just don't think is ever going to come up again...

1) One end goes to the charcoal canister, and the other end attaches to the complicated 74 balance tube. 2) Charcoal can could help with gas smell, but won't do anything for vapor lock. All years have gas tank venting one sort or another... The difference is what they did with the fumes. Prior to 74, they "stored" the gas fumes inside the engine block, and after 74, they routed them to be grabbed onto by activated charcoal in the carbon can. I'm not sure about the very early years (like 70), but prior to the carbon canister, they used a device called the "flow guide valve" which directed fumes into the non-running engine crankcase. In 74, they updated the system to the charcoal can. Does that help?

Oh, and I forgot... I didn't like the perpetual Viagra posture of my parking brake either and I lowered mine too, but I did it a little different. I ground a little material metal off the parking brake assy where the two parts come together and limit the down travel. So now mine still uses the original mounting holes, but it lowers a good bit farther down than original. I don't think I have any pics, but I'll take some when I get the chance. I thought I had some in my parking brake spring thread, but not only didn't I mention that, but all my picture links are dead: http://www.classiczcars.com/topic/49952-parking-brake-handle-return-spring/ Not sure what happened to the pics...

Whoa... They managed to stuff an angle grinder in the original harness? Those Germans thought of everything!!

I haven't tried it to confirm, but I believe the studious and creative Z owner would be able to find off the shelf molded hoses that could be modified to accomplish that.

That top tube is the purge line from the carbon canister system. I think the 73 still used the flow guide system and in 74 they updated to a full blown evaporative capture system. Meaning... I think that fuel rail is from a 74. But the bottom line is... Unless you're running a charcoal canister evap system in the stock location, you can cut off that top tube with no problem.