Air Flow Meter Fails Some Resistance Checks - Repairable?

[Zed Head]

The BCDD is an emissions device, but not the most effective. It's main purpose is to let a little extra air past the throttle blades to burn fuel on deceleration while in gear. According to the FSM (Emissions chapter) it should only be replaced as a unit.

They might still be available for only $252!

Datsun 280Z E.F.I.(2) -Air Flow- L28E

ASSY-BCDD :: Nissan Parts, NISMO and Nissan Accessories - Courtesyparts.com

[sscanf]

Here is a crack at it. Cut from a rubber glove (I have a laser :classic: )...

I'm not going to replace it but sandwich it with the broken diaphragm. The center has a thick rubber washer that I would need to replicate. I'm going to run with the bcdd disconnected for now. I just want to get the leak plugged and everything running right then come back to this. Probably will not get to the install until next weekend but who knows, I might get back to it before then.

[Captain Obvious]

Nice work! The only laser I have is strapped to a dolphin's head and I don't think I could train him to do such intricate work.

At one of my former employers we used to form diaphragms out of semi-vulcanized elastomeric sheet. Clamp them in a hot contoured clamshell mold, add heat, time, take out a little smoke, and presto... Formed diaphragm that is now fully vulcanized.

That diaphragm you made isn't roll formed like the original so it isn't going to perform the same, but it's sure a lot better than what you had in there before!! What glove material did you use? I'm thinking Nitrile?

[sscanf]

What glove material did you use? I'm thinking Nitrile?

After I did the art work for the diaphragm, I glanced about the office for rubber or similar and used the first thing I laid eyes on. From the manufacturer's web site:

"Playtex Living Gloves are trusted to provide the highest quality and protection for indoor and outdoor household chores. Premium gloves specially blended with

natural rubber latex and durable synthetic Neoprene

for greater resistance against harsh household chemicals. Playtex Living Gloves are strong more durable than ordinary latex gloves. Made with 4 layers to provide added protection against tears and punctures. Excellent protection from hot water. Super soft cotton, absorbent lining keeps hands dry and comfortable. Extra long Drip-Catch cuffs provide extended protection to forearms or can be folded up to stop water from dripping onto your arms. Deep palm pattern for added grip and control."

Hopefully the Z is not latex sensitive.

[EuroDat]

Any Nitrile butadiene rubber (NBR or Hydrogenated NBR) will do the job and last a long time too. Latex is a natural rubber and will not last long in the BCDD. If you can find some gloves made of NBR, that would be the way to go.

Natural rubber can be blended with polymers to create different sorts of Nitrile rubber like Europrene and Neoprene among other brand names.

Chas

[sscanf]

Any Nitrile butadiene rubber (NBR or Hydrogenated NBR) will do the job and last a long time too. Latex is a natural rubber and will not last long in the BCDD. If you can find some gloves made of NBR, that would be the way to go.

Thanks for the info. I have some nitrile gloves but they are thinner so I will double it up. One on each side. A real sandwich.

[sscanf]

Last night I did find the time to cut new diaphragms from nitrile gloves and install them in the BCDD. I sandwiched the old, torn diaphragm between the two new ones. I kept the old because it has a rubber washer in the middle that I can't really replicate. The plan is that the new diaphragms act as a patch to the old one.

I have no idea if this will work as a BCDD but it fixed the BCDD leak: My yoghurt cup test now goes well!

New Diaphragms

Jelly Side

Original

Peanut Butter Side

Mmmm....

My Yoghurt Cup Test Setup

While I'm at it, here is my setup in case anyone is looking for photos of this test (notice that mine is actually a sour cream test):

[EuroDat]

That turned out to be a neat repair when you consider how tiny and fiddly it is to work on. The Laser does a good job.

[FastWoman]

Regarding the sour cream test: That would actually be an appropriate post-Thanksgiving variant. Well done!

[sscanf]

Hey All ...

First off thanks again for all the help. I did manage to get it all put back together tonight, including a new GM HEI module. It is now running really really nicely once its warmed up. Smooth and idles perfectly at 800 RPM which I can now set with my perfectly functioning tachometer! The new HEI module certainly fixed the jumpy tach problem. I had no cut outs when I took it for a spin around the neighborhood (though that was a very intermittent problem).

The HEI module is a super easy install. I'll post some photos in the morning. I think all my vacuum leaks are now fixed (but the BCDD is not connected). I'll post some pics in the morning. My only complaint is that it still runs a little rough when cold - not terrible but not great either. Maybe an aux air problem. I still need to check the timing too.

Anyway, I'm really pleased with the progress and I LOVE that the tachometer is rock solid now.

[FastWoman]

Cool! Very well done!

BTW, I'm very impressed with your diaphragm!

[sscanf]

As I said last night, I got the HEI module installed. It was really easy after the prep work was done. The first thing I needed was a nice heat sink and, afters scouring the basement and considering attacking an old Western Electric telegraph test set with a hack saw, I laid eyes on a stack of these:

Which is an old tape format from the 80's/90's (we called the streamer tapes back in the day). I still have a SCSI drive that can read/write these things (but haven't tried in at least 10 years)... Anyway, these tapes are build like tanks, the back plate is .1 aluminum - I knew I saved them for a reason. The following pictures illustrate the transformation of one of these tapes into a nice heat sink for this HEI conversion project.

Add some quality time with a hack saw and drill to get a nice heat sink...

Yank the old ZX module (this 76 280Z had been given a ZX upgrade by PO):

Wire up like this (note: the left image was stolen from another thread):

Profit!

I do need to make a more permanent job of the wiring yet but its proven out as a nice, easy, inexpensive solution to my ignition module problem.

Thanks again for all the help.

Edited December 5, 2013 by sscanf