failed deq 78 620

[DattoChinook]

I have a 78 620. This is my first Datsun and I dont know much about egr and vacuum lines.  I bought this in February.  It has always ran good but always had a small exhaust leak coming from near under the hood and it has always idled where it seems like it is gonna die every 20 seconds or so but doesnt.  The guy I bought it from installed this weber carb himself.  I always knew something wasnt right about how everything was hooked up, as it looks like it is missing vacuum lines.  It ran ok so I ignored it.  I always thought the exhaust leak was from the header gasket...

 

Today I failed deq with high HC and CO.  I started looking at things closely under the hood.  I am sure I found my exhaust leak.  This tube is capped with a rubber cap and it has what seems like exhaust coming out of it where pressure increases when I give it gas.  Its obvious that it has been leaking through that rubber cap.  A bunch of other stuff has to not be right. 

 

Any help is appreciated.  I want this to pass deq and get back on the road.

 

 

 

[KlassicMotion]

Go here:  http://www.datsun510.com/manuals/

 

Download the 1977 manual.  It should have a diagram of where all the hoses go to.

 

I'd say just remove that air rail all together, but you may need to buy an air pump and put it back on to pass the emmisions test.

[Tristin]

I had the same exact exhaust leak... the cap finally blew off mine and I just said fuck it. Luckily Im in a no smog area with a car 25+. Hopefully you get it sorted out. 

[DattoChinook]

I had the same exact exhaust leak... the cap finally blew off mine and I just said fuck it. Luckily Im in a no smog area with a car 25+. Hopefully you get it sorted out. 

So I dont understand...  There is just supposed to be a cap on that or was something originally supposed to hook up to it?

[flatcat19]

HC is unburnt fuel. You are running rich. 

Even with an exhaust leak. 

 

Check your ignition. 

Plugs, wires, cap, rotor, timing. 

Run again. 

[DattoChinook]

HC is unburnt fuel. You are running rich. 

Even with an exhaust leak. 

 

Check your ignition. 

Plugs, wires, cap, rotor, timing. 

Run again. 

Ok thanks.  I am not that experienced to do anything more than changing out the plugs or wires.  Wires are newer.  Not sure about plugs.  I planned on getting a regular air filter for next time I test and ditch the k&n.  Was gonna also do an oil change.

[DattoChinook]

Can someone please tell me what the pipe coming out with the rubber cap on it is (in the last 2 pics - 3rd to last shows it with the rubber cap removed)?  What is it for originally?  It obviously wasnt meant to be capped by a rubber cap right?

[Tristin]

That is suppose to go to a series of hoses and if I remember right it should plumb back into the air cleaner via a pcv valve. 

[DattoChinook]

Deq readings...  Second idle is after he revved the engine for a minute.

 

First Idle:        HC (220 or below)   466   CO (1 or below) 1.2519

Second Idle:   HC (220 or below)   343   CO (1 or below) 5.8469

[flatcat19]

That is suppose to go to a series of hoses and if I remember right it should plumb back into the air cleaner via a pcv valve. 

 

PCV valve should come straight from engine to valve mounted in intake. Nothing else. 

Positive Crankcase Ventilation. 

 

Bonus about living where you are-you have a million Datsun owners able to help you. 

[KlassicMotion]

I believe the plugged pipe on your air rail went to a pump like this one below:

 

This one is free plus shipping if you find you need one.  But get your engine and carb tuned first.  Here is a link for tuning your Weber:  http://www.redlineweber.com/html/Tech/carburetor_set_up_and_lean_best_.htm

 

[Tristin]

PCV valve should come straight from engine to valve mounted in intake. Nothing else. 

Positive Crankcase Ventilation. 

 

Bonus about living where you are-you have a million Datsun owners able to help you. 

 

I know normally... thats how mine is set up. I was pretty certain that when I looked it up months ago (when the cap blew off the same exact pipe), I was able to trace the hoses to a PCV valve. Let me retrace my steps and see what I can come up with. 

[flatcat19]

There should be nothing more to a PCV system. 

 

What did your NOX numbers look like?

Do you have a catalytic converter?

[Tristin]

I followed the link Klassic posted up and here is what their diagrams have:

 

 

Blue circle is the pipe were talking about

Green line is the hose that is missing from that capped pipe

Red circle is where the green line ends

Red oval lists it as a PCV

 

 

 

 

All that shit was missing on mine so I cant say first hand where everything goes... just know thats what the manual says.  :confused:

[flatcat19]

That is not it. 

Those big rubber cap is for air pump. 

 

In the last picture OP posted...below the air cleaner is a bent, brass hose. That is the PCV.

No it's not. The valve is on the firewall side of the IM though. 

 

 

Do you have an air pump?

It should be opposite the alternator. 

 

You are missing a lot of the needed vacuum routing. 

Fuck old cars and DEQ. 

 

You have so many emissions options that all need to work to pass. 

Argh!

[Tristin]

Per that manual it sure looks like it... 

[DattoChinook]

There should be nothing more to a PCV system. 

 

What did your NOX numbers look like?

Do you have a catalytic converter?

Yes Cat.  Not sure if it works though.  Could be the original.  Not sure what NOX numbers were.

[DattoChinook]

So I dont have an airpump then.  Can I not pass deq without one? 

[flatcat19]

Life would be easier had you a working air pump. 

 

You are reading high amounts of fuel. 

The air pump pumps O2 into the exhaust to lower the PPM of the HC and CO. 

 

The canister you should should collect fuel vapor to help out also. 

 

Find the vacuum routing diagram and get that nailed. See how it does. 

 

 

The numbers you posted, second idle looks like the car was cold. 

Was the car super hot when going through? And I mean blazing hot!

 

I used to take trouble cars in to the testing station for customers. 

I would do hot laps in the neighborhood to get them hot. 

Fail. Adjust fuel and timing. Repeat until passed. 

Tune car back to running well after passing. 

[flatcat19]

I'm so happy to live in an area not requiring emission testing. 

[KlassicMotion]

Yeah, that diagram from the '77 doesn't look right....   I"m looking for a better diagram......

[datsunaholic]

The pipe that had the plug on it was the inlet to the air injection rail.  There used to be a check valve there, it's missing so now you just have a big exhaust leak, which other than being noisy is routing exhaust into the cab through the usually leaky firewall. 

 

It has nothing to do with the PCV system.  The rearward hose originally went to the anti-backfire valve, which routed the hose very close to the PCV system.  But they aren't connected together.

[KlassicMotion]

Here is that check valve datsunaholic said your missing:

 

[DattoChinook]

The pipe that had the plug on it was the inlet to the air injection rail.  There used to be a check valve there, it's missing so now you just have a big exhaust leak, which other than being noisy is routing exhaust into the cab through the usually leaky firewall. 

 

It has nothing to do with the PCV system.  The rearward hose originally went to the anti-backfire valve, which routed the hose very close to the PCV system.  But they aren't connected together.

Thanks.

[cruznude]

So good to know an mechanic/emissions guy. My pump never was hooked up  and I just seemed to pass.  Low and behold.  Good luck with all that shit man.  I live in a smog area and it sucks.  I ripped all that shit out of there and have a real fuckin clean motor now.  I'll deal with the emission shit when the time comes.  Hope you get it down.