1977 280z prepup for smog check

[240zadmire]

@Zed Head 

34 minutes ago, Zed Head said:

My brain is starting to hurt...

Your brain cannot go on holiday right now!

There is a screw at the end.  For sure it is for adjusting.  And there is a lock screw with a white paint marked.  I suppose that is a lock screw and was set at factory.

 

the wire schematic showed like a switch... but you already know what is it. Very interesting.  I’m glad the problem give you some challenge.  I have zero clue 😉 

[Dave WM]

maybe its been covered already, but does the car have a cat? if not just adding one maybe a simple solution. If it has an old one, perhaps it needs to be replaced? I don't know how you would test it for effectiveness, only if its clogged or not.

[Captain Obvious]

About the altitude compensator... All of the documentation I have indicates that the altitude compensator is an ON-OFF switch affair, and not an analog resistance device. I don't have one of those devices here for confirmation, but that's what the docs say. (Ref 77 FSM EF-15 and the 1980 FI bible page 85.) I wouldn't worry too much about a dramatic change in engine operation when the switch changed state. They can handle that in the electronics with smoothing and hysteresis.

As for the stuff inside the altitude switch... Don't knock that thing around too much. That "spring" inside is actually a hermetically sealed bellows chamber. It's very similar in construction and operation to the bellows in the throttle pull-pull off and the BCDD.

Here's a thread that's about the BCDD, but there are some good pics of the BCDD altitude compensating bellows that they used inside there. Looks like this:

Here's the thread where those pics came from:
https://www.classiczcars.com/forums/topic/58748-info-on-bcdd-boost-controlled-deceleration-device/

 

[Zed Head]

2 hours ago, Captain Obvious said:

About the altitude compensator... All of the documentation I have indicates that the altitude compensator is an ON-OFF switch affair, and not an analog resistance device. I don't have one of those devices here for confirmation, but that's what the docs say.

So you're saying that he should trust what the FSM says and go ahead and short that switch?  Assume that a direct short is fine and won't harm anything. 

Here's the post with the image showing the switch-like behavior.

 

[Zed Head]

Many of the jars that food comes in, like salad dressing and mayonnaise, have plastic lids that can be drilled and cut for use in the garage.  I had one that I set up as a liquid trap for when I wanted to pull nasty liquid using a vacuum.

Anyway, The shape of the device seems to lend itself to something like that. 

Here's a similar one, except it has a metal lid.  Just run your electrical wires in the other port, seal it well, suck on the hose, and you're at high elevation.  Don't let the cops see you though...

https://www.amazon.com/Liquid-collector-vacuum-trouble-getting/dp/B077BRRL59

Edited October 10, 2020 by Zed Head

[240zadmire]

Look like all information from other forums also pointing to connecting the wires together.  There’s not much info otherwise.  What indicator to know the jump wires take effect? Higher/lower rpm?

 

regards

 

[Zed Head]

The odds are in your favor.  But there is a risk.

You might hear a slight change in RPM.  6% less fuel.  If you do, then just keep the plug jumped and go get tested again.  You're so close before, it should pass.

[Captain Obvious]

8 hours ago, Zed Head said:

So you're saying that he should trust what the FSM says and go ahead and short that switch?  Assume that a direct short is fine and won't harm anything. 

Yes, that's what I'm saying. I have no reason to believe that thing is anything other than a simple pressure (or lack thereof) switch.

If it were my car, I would put that device in a jar and try to draw a vacuum on it and see what happened, but if I could not get that to work, I would just short the connections and see what happened. Unfortunately I don't know if you would hear or smell any difference... The effect may be subtle enough that you might only be able to see it with diagnostic equipment.

[240zadmire]

Well, got the ‘78 fuel rail and regulator.  It actually a bit worse.  Without solenoid/cranking the car, 42ish PSI and 34PSI on idle. 
another thing “weird” is that open the oil cap, the car takes few seconds before it starts to stumble and die.   Also, the original, ‘77 fuel regulator, the vacuum hose to the intake manifold was not sealed completely on the intake manifold.  There is quite a suction on that hose too.

also, I did jump the wire on the altitude switch.  I can’t tell the different on the engine sound/exhaust smell where the jumped wire work or not.

 

the exhaust still smell a bit of gas for sure.

is there anyway to lower the pressure? Change the hose to be smaller from the fuel filter to the rail?

 

 

 

[240zadmire]

Come to think of it, the vacuum hose to the original FPR wasn’t tight enough.  That explains when I open the oil cap, rpm lower but not stumble and die.  With the tight vacuum hose and the ‘78 FPR, open the oil cap made the engine stumbled and die.  However, oil dip made no different.  Does that means the vacuum now tight? No more leak?  I’ll have to see the CSV once more time 

[240zadmire]

Ladies and Gents,

it’s a wonderful day today.  My Datsun has finally pass the smog test.

Last night I readjusted the valves and was careful to have all within the same “resistance” when sliding in the feeler.

Took the fuel pressure test again using different rental showed 30psi at idle... drove the car at least 30 miles on freeway before brought her in... the rest is history.

 

much appreciate all the suggestions and guidances from everyone.  We will deal with this again in 2 years . 😉 but for now I’m a enjoying it.

more other little things here and there but at least I can drive the car now.

 

thanks

 

[Captain Obvious]

That's fantastic!  Enjoy the car and drive safe!