280z 280z 78 Wont idle, Running Rich, out of ideas.

[Cyrillink]

2 hours ago, Dave WM said:

The reason I asked if they are carbon fouled was the early post about running rich. Wet does not mean rich, could be just not igniting. I just wanted you to confirm the initial diagnosis that its running rich. Smelling fuel could be a fuel leak somewhere. I like to start with a new set of plugs, then run it for a few minutes, under varying loads if its drivable, maybe put 10 miles on them, and then pull and examine. A properly setup EFI on a 280z should result in nearly white insulators given that test. I just don't want to be chasing a false premise.  Poor running could be a massive vacuum leak that may not show up as leaking smoke under the hood, say if its a stuck EGR as an example.

 

Hey Dave,

Thanks for the feedback. I am going to put this thing together entirely and take it for a 10 to 15 mile spin warm it up properly.

than i will pull the plug send a photo.

[Cyrillink]

On 12/16/2019 at 4:22 PM, Cyrillink said:

Hey Dave,

Thanks for the feedback. I am going to put this thing together entirely and take it for a 10 to 15 mile spin warm it up properly.

than i will pull the plug send a photo.

Hey Team,

So i broke down and bought a really good leak down tester.

The valves are leaking badly. i think we have our diagnostic. 

[Zed Head]

Check valve lash.  It's the first procedure in the tuneup chapter.

[Cyrillink]

6 minutes ago, Zed Head said:

Check valve lash.  It's the first procedure in the tuneup chapter.

Yep, going to start the adjustments. right now

Cold:

Intake .008" Exhaust .010"

Yey FUN!

 

[Cyrillink]

2 hours ago, Zed Head said:

Check valve lash.  It's the first procedure in the tuneup chapter.

Looking very "Healthy"

[Cyrillink]

On 12/16/2019 at 2:13 PM, Dave WM said:

The reason I asked if they are carbon fouled was the early post about running rich. Wet does not mean rich, could be just not igniting. I just wanted you to confirm the initial diagnosis that its running rich. Smelling fuel could be a fuel leak somewhere. I like to start with a new set of plugs, then run it for a few minutes, under varying loads if its drivable, maybe put 10 miles on them, and then pull and examine. A properly setup EFI on a 280z should result in nearly white insulators given that test. I just don't want to be chasing a false premise.  Poor running could be a massive vacuum leak that may not show up as leaking smoke under the hood, say if its a stuck EGR as an example.

 

Due to valves not closing correctly the plugs have oil on them.

Hope this helps any one with a similar issues. Pretty comprehensive diagnostic. 

[Zed Head]

1 hour ago, Cyrillink said:

Looking very "Healthy"

Not so sure.  The base circle has wear marks, indicating that it had some force on it.  The base circle is usually dirty since it only has the force of the mouse trap spring on it when lash is correct.

I don't see a feeler gauge.

[Zed Head]

Like this one.

http://www.kangamotorsports.com/blog/2016/11/datsun-cylinder-head-disassembly

[Dave WM]

looks like the two in the middle may not be firing at all. Try a power test (disconnect the fuel injectors from the harness one at a time, see if there is any effect on the idle, should be a drop that is consistent as each plug is disconnected one by one. From the look of it the middle two will not have any effect on idle.

[Reptoid Overlords]

Has the head been off and or to a machine shop?

 

I'm wondering if it has been cleaned/rebuilt and reinstalled and run without setting valve lash. There's also the need to check and adjust after 100 miles or something.

 

 

 

 

[Cyrillink]

1 hour ago, Reptoid Overlords said:

Has the head been off and or to a machine shop?

 

I'm wondering if it has been cleaned/rebuilt and reinstalled and run without setting valve lash. There's also the need to check and adjust after 100 miles or something.

 

 

 

 

So speaking to the owner i found out they had a full engine rebuild like 2 years ago and then it was parked for rest of its life. The Owner took it out really really ran it hard and then this started.

[Cyrillink]

19 hours ago, Dave WM said:

looks like the two in the middle may not be firing at all. Try a power test (disconnect the fuel injectors from the harness one at a time, see if there is any effect on the idle, should be a drop that is consistent as each plug is disconnected one by one. From the look of it the middle two will not have any effect on idle.

I agree the 4 and 3 are not dirty at all and Cylinders have the most wear on the cam, barely had any valve lash, it was 0.002in and 0.001in barely fit.

I am taking the day off to relax and get over a nasty cold. Coming back to it tomorrow.

Also, i am going to double check the Valve timing tomorrow morning. I really thing the major issue is valve lash/valve timing.

When i ran a 70psi with a leak down tester i had 95% lose! 

Hey Guys,  Zed, Rep and David - PM me if you guys ever in NJ/NY beer is on me!

 

Edited December 19, 2019 by Cyrillink