1977 280z prepup for smog check

[Zed Head]

Make sure that your gauge is good, maybe doublecheck with a different one.

But, yes, pressure is supposed to be about 36.3 (actually 2.5 bar, converted). 

[240zadmire]

Look like need to pull the whole fuel rail and injectors to replace the regulator.  Say, will the fuel rail and regulator of 1978 works?  I might have access to that set.  For sure the regulator of ‘78 won’t fit ‘77 but I might be able to buy the complete set.

thanks and regards

 

[Zed Head]

A 78 rail with regulator would swap right over, bolt-on.  It's actually a better rail it has fewer hose connections.

But you should be able to change the FPR without removing the rail.  Cut the hoses to get it off and slide the hoses back and forth to get it on.

But, again, if you have the old hoses on your 77 it might be a good time to change them, so the 78 rail would be a good option.  Always more work to do and decisions to make.  

Edited October 7, 2020 by Zed Head

[240zadmire]

Hoses on the rail are new.  Injectors seals are new as well. 
It was a pain to put the regulator last time even though it was off the car.

the ‘78 rail is definitely have less hose.  The hoses to connect the regulator is definitely longer, which make it easier to remove/replace.

 

say, the vacuum hose from the regulator to the intake manifold, there is no clamp.  It looks loose.  Does it need tight vacuum?

 

regards

 

[Dave WM]

are the injectors stock? also how did the remove the valve cover oil cap go, typically at idle it should stumble and maybe die. what's the vacuum reading while idling.

[240zadmire]

@Dave WM, As far as I can tell, the injectors are stock.  4 of them are faded green and the other 2 are more bright green.  I think  the  2 brighter green were replaced at some point.  Remove the oil cap and oil dipstick does stumble/lower RPM a bit but definitely car won't die.   Remove  oil dipstick alone does show lower RPM but not significant.

I don't have a vacuum gauge, though all hoses are new.  I guess I can take a look into the vacuum gauge next.

 

regards

 

 

[Dave WM]

6 minutes ago, 240zadmire said:

@Dave WM, As far as I can tell, the injectors are stock.  4 of them are faded green and the other 2 are more bright green.  I think  the  2 brighter green were replaced at some point.  Remove the oil cap and oil dipstick does stumble/lower RPM a bit but definitely car won't die.   Remove  oil dipstick alone does show lower RPM but not significant.

I don't have a vacuum gauge, though all hoses are new.  I guess I can take a look into the vacuum gauge next.

 

regards

 

 

if everything else is sorted you maybe able to lean out the idle air bypass on the AFM to get a lower CO emission, if that is where its failing. You would need to remove the plastic plug on the AFM CCW the screw (its prob stuck) to bypass more air AT IDLE 800rpm. I would not do this unless you have a way to test the CO while adjust to see if it actually helps. Once the car is fully warmed up the temp sensor in the t stat should not be enriching iirc it stops at about 140f. Going to be tough with out a way to monitor what is going on while making tweeks.

[Zed Head]

He's in CA where they do the rolling 15 and 25 mph tests.  The idle air bypass probably won't help much, I'd guess.

He's so close, I'd bet that an FPR that has correct pressure would get him in spec.  40 psi is 10% high.  Whenever I worked on my car to pass emissions (idle only) I would get CO and HC numbers that were much higher than he's getting and could get them to drop with small changes in fuel pressure (I had an adjustable FPR).  He just needs a tiny change to get his CO numbers down I think.  Tiny.  Maybe, in the same vein as the idle air bypass, he could just open up one of the vacuum ports on the manifold.  Maybe the one for the heater controls.  The FPR is probably more effective though.

Edited October 8, 2020 by Zed Head

[Dave WM]

think that works the other way, higher (more) vacuum lower FP, maybe a bit more ign advance for more complete combustion, (and more vacuum for that mater).

I would like to see the baseline vacuum, tweek the dist a few degrees more advance. the 40/32 sounds like he is about normal vac though.

 

Edited October 8, 2020 by Dave WM

[Zed Head]

Good point.  I was thinking in terms of unmetered air not intake manifold vacuum.

Another reason to just get an FPR that is in spec.

[Dave WM]

1 minute ago, Zed Head said:

Good point.  I was thinking in terms of unmetered air not intake manifold vacuum.

Another reason to just get an FPR that is in spec.

agreed that is the best starting point get a good static pressure.

[Dave WM]

just for grins, remove the fuel return line for the metal hard line that goes to the tank, and just have it dump into a container. then to a engine off pump on test (solenoid disconnect, ign key to start) get a reading see if you still have 40psi. want to make sure you don't have a restriction in that return line to the tank.