Hi all:

1977 280z. Stock with 90k miles. Bought a year ago not running (I know, stupid). It would start, but die immediately.

The long version is detailed in my intro thread if you want to read it. http://www.classiczcars.com/index.php?/topic/53262-New-owner-of-'77-280z-from-Upstate-SC

The short version. Replaced fuel filter and lines, fuel pressure regulator, injectors, AFM, coil, plugs, plug wires and coolant temp sensor. Cleaned and verified coolant temp circuit function at ECU. Air gap between reluctor and pickup set to 0.012. Timing set to 10 degrees BTDC. All of this was done in response to various symptoms, such as low fuel pressure, misfire, etc. over the past year of off-and-on repairs interrupted by health problems.

Now it will idle roughly when cold. If I rev the engine it backfires and then revs okay. But it still runs roughly. Once the engine starts to warm up, it won't stay idling more than 15 seconds or so before sputtering to a stop. New plugs don't read yet. Old ones were sooty, even when fuel pressure was low.

I don't know what to do next.

Sent from my QTAQZ3 using Classic Zcar Club mobile

I picked up a gasket and made a block off plate for the EGR. I used a borrowed stud remover to try getting the studs out. But they wouldn't budge. Rather than break them off, I decided to just use the old EGR spacer on top of the block off plate.




No change in running, vacuum reading, etc.

I found the PCV hose under the intake. But I'll need double jointed elbows to get to the thing. I'll go at it from below on my next foray. But I ran out of time tonight.

Sent from my XT1254 using Classic Zcar Club mobile

Looks like a nice attempt at finding the leak, bad that it wasn't.  

There's a thing we know as the "yogurt cup test" from a very smart member with good common sense.  You shove a cup into the accordian hose between the AFM and the throttle body.  Pull the brake hose off and blow as hard as you can.  I put my valve cover gasket on upside down, straight side to the passengers side: wrong, and when I blew into the hose my hair moved.

You might try that and listen for the air.

Don't install the plate until you examine the inside of the EGR passages.  The problem that they have is that the metal between the two ports rots out.  So your plate might not do anything.  Stick your finger down there and make sure the metal is solid.  The EGR valve is controlling flow from the round hole to the square hole, gasket-shape-wise.  If the metal is solid, then focus on sealing the square hole.  The round hole won't matter if you've sealed off the tube from the exhaust manifold.

 

Just now, siteunseen said:

 Pull the brake hose off and blow as hard as you can.  I put my valve cover gasket on upside down, straight side to the passengers side: wrong, and when I blew into the hose my hair moved.

You might try that and listen for the air.

Hair only moves if you're a blowhard?  

Funny, but that test would probably work on the EGR system too, to see if the passages and valve are okay.

4 minutes ago, Zed Head said:

Hair only moves if you're a blowhard?  

Yes!  It was Presidential. 

Edited February 28, 20178 yr by siteunseen

Out of interest, did you try the double nut technique to remove the studs?  That is what worked for me when I did a lot of manifold work 3 or 4 years ago.  I did have the advantage of the manifold off the car though.   Wanted to replace the studs with ss bolts for a cleaner look with the block off plate.

Best of luck on your low vacuum issue.  Will be interesting to know what the ignition timing is currently at,  when you get to that

6,000th

 

1 minute ago, siteunseen said:

6,000th

Saved it for you.  

Thank you!  I'll save that. 

Zed Head I hooked a newer modem/router combo the renters left in my house.  Now getting a previous attachment, I have 46 pages, as soon as I click the whole page is downloaded.  It's amazing how much faster the downloads are.  Surf Board 6700.

Sorry to waste a post in your thread Tool Man.  I'll try to offer some help, ideas.

I did the yogurt cup test months ago. It would build pressure as it should. But it would probably be a good idea to repeat it.

I checked the web between the intake and exhaust ports for the EGR.  It's solid.  I was careful to clean the surface of the intake manifold so the new gasket wouldn't leak.  I did not plug the pipe from the exhaust.  So I wanted to make sure neither side would leak.

I tried double nutting the studs. But this required using an open end wrench to loosen them, which put a lot of bending on them. The extractor I borrowed uses cam driven rollers to grip the stud all around. I put a big ratchet handle on it and pulled pretty hard to the point where I think I yielded the studs a bit. In another thread I detailed my ordeal with snapped fuel injector screws. Rather than break these, I used the EGR spacer to let me put nuts on the existing studs. At some point I'll use heat to get them loose. But I'm moving on for now.

Timing is 10 deg. BTDC at idle. Vacuum advance seems to be working. But working alone I can't reliably correlate rpm and timing.

 

Sent from my XT1254 using Classic Zcar Club mobile

 

 

 

 

 

 

 

 

 

 

Edited February 28, 20178 yr by the_tool_man

I got one end of the PCV hose loose, so I could give it a good inspection. No apparent issues.

I've come up with a plan to use smoke to look for vacuum leaks. But I couldn't do that until a friend brings me his fog machine. So tonight I did a compression test. After warm-up:

1:152psi

2:152psi

3:158psi

4:155psi

5:155psi

6:150psi

An 8psi range (5℅) seems pretty good. Here's a pic of the plugs (in order 1-6 left to right):

They probably have about fifteen minutes of total run time on them.

No time for more than that. So I put everything back together and checked the firing order for the fourth time.

Of course there's always something that goes wrong. I have no fuel pressure now. Not sure how since I didn't touch the fuel pump circuit.

Sent from my XT1254 using Classic Zcar Club mobile

 

 

 

 

Edited March 1, 20178 yr by the_tool_man

Those look pretty dark for only 15 min of run time. The boot from the AFM to TB doesn't have any tears in it? Can you post a pic of the engine when you get a min? 

Edited March 1, 20178 yr by JSM