Failed CO emissions - all controls removed - where to start?

[thetwood]

33 minutes ago, Dave WM said:

oh just noticed no AAR either (kinda slow today, recovering from hurricane prepitis), that sux. must be fun to start on a cold morning. Just don't get why folks have to remove stuff.

He was a high school kid. Why do they do anything? I know my high schooler doesn't always make the best of decisions... But wish it would have been left closer to stock.

Edited August 31, 2019 by thetwood

[Zed Head]

1 hour ago, thetwood said:

So maybe the fuel pressure gauge is bad (was in the car when we got it), but at idle it's sitting around 15 psi without the vacuum hooked up. With the vacuum hooked up, it's at 4 psi. I can look at replacing the gauge to see if that's indeed the problem...

In actual forward progress, I purchased and put on a new fuel cap, so at least I should pass that one.

Returning to stock seems daunting. With a swapped engine, new fuel rail and other non-stock items added in, I'm not even totally sure where to start. The Service Manual shows where things should basically be, but I'll have to read through further to see if I can really understand how to rebuild all of the missing. Then would have to start finding all the parts as well.

Check the injectors.  Take a closeup and post it.  It might have turbo injectors.

Also, check the kick panel by the left of the driver's leg.  Make sure the stock ECU is there.  Who knows, it might have Megasquirt or one of the other aftermarket systems.

Know what you are working with before you get carried away.  The engine has had a lot of modifications done but that doesn't mean it's hopeless.  The key is to be systematic and persistent.  You don't have a one-shot fix ahead of you.  On the plus side though, it's a great opportunity to learn about how EFI and engines work.  It's a classroom in an engine bay.  Good reason to buy and learn new tools.  The fundamentals you need to work on these engines work everywhere in life.

[Dave WM]

indeed, I did a lot of stupid stuff in HS..

Those pressures make no since at all, I would get that gauge out of there, get a reg temporary  pressure gauge, check again see if you can get the pressure right before anything else. As mentioned start with a engine off pressure 36psi, once that is right you want to see the response to the vacuum, dropping to around 30 psi at idle. You may want to get a vacuum gauge hooked up (you certainly have enough extra ports) as well. It maybe as little as an adjustment to the AFM bypass to get the HC working, but I don't know how you can really do that with out a way to read it while adjusting. I played with that bypass while reading the vacuum. If you assume the vacuum is a good measure of engine efficiency then you can watch the vacuum and see how tweeking things effect it. The most vacuum at idle. once you have it at the highest vacuum reading a bit of tweeking on the bypass to lean out the mix will reduce the vacuum a bit, that should be about the best setting for low HC. IIRC I would get a vacuum of about 19 inHg, then lean the bypass a 1/2 turn or so and it would go to about 17 inHg. At that setting removing the oil cap would kill the engine. If I left it optimized for 19inHg, removing the cap would have no effect.

Edited August 31, 2019 by Dave WM

[Dave WM]

good point about the ECU ZH, did not even think about that.

[Zed Head]

No offense Dave, but I think he needs to consider the whole system before doing too much else.  Here's another possibility for the low pressures - the FPR diaphragm is blown.  He could spend a lot of time getting the pressure back up just find that the other parts are wrong.  He is far away from the delicate tuning, he has major things going on.

Different methodologies.  I would ID and catalog all of the critical parts first.  

[siteunseen]

To throw another kink in that set up...

The afm has a weighted sweeper vane on a contact pad that figures air to fuel ratios. With that one mounted horizontal instead of vertical what kind of accuracy can he expect from the weighted sweeper vane? 

[Dave WM]

Yes he does have a lot of major stuff going on. On the ECU, I would think its a stock unit, based the OE style AFM (I assume aftermarkets use something else but I don't know for sure), but checking under the panel would be a good start. I can see now there will be a need for a lot of pics of just about everything to try and unravel remotely.

I am guessing the car drives well? starts ok? smooth idle? etc.. are we just talking failing the HC

[Dave WM]

1 minute ago, siteunseen said:

To throw another kink in that set up...

The afm has a weighted sweeper vane on a contact pad that figures air to fuel ratios. With that one mounted horizontal instead of vertical what kind of accuracy can he expect from the weighted sweeper vane? 

I orig thought that, but checked my test stand setup and noticed it was off kilter to and seemed ok.

[siteunseen]

Lets see the spark plugs. Are they black and sooty?

Whats the air filter look like? Cold air cone or stock? I bet cold air k&n. 

[siteunseen]

Zed Head.  My 9/76 had a non webbed n47 intake like this guys.

[Zed Head]

I was guessing on the switchover, either 77 or 78.  But I know that 78 had the webbed.  Also, there's no serial number on the engine bay plate in 1978 so that won't help him ID his engine.  I thought he might have a 79 ZX, since the emissions guy wrote ZX on the test paper, but I see the 280Z access door on the side in his pictures.  ZX's didn't have those did they?

He has a blend of parts, some not even Nissan, like the FPR and the header.  We can all guess away but really, he's going to have to dig in to each part to see what he has.  Look at what CO ended up with and his engine looked factory stock.

[Pilgrim]

Not to beat a dead horse, but I think the owner is going to have to decide how much closer to stock it's reasonable to take this engine..because that's the only starting point you can find references for.  Maybe not too close is necessary.

Personally, I think I'd be checking body and engine serial numbers to confirm which year each of them really is, and then getting as close to stock as I can, even if it means stripping the needed stuff off a dead engine I find somewhere.

You may be able to turn around and re-use some of the extra stuff that's on there, but until you have a driveable and legally license-capable car, you don't have a very good starting point.

Edited September 1, 2019 by Pilgrim