Chasing engine issue in my 73

[Zed Head]

1 hour ago, gundee said:

I am pretty positive that the 1973 had a TSB that included installing an electric fuel pump in the rear.

Maybe this one.

 

[Geoff's 240z]

11 hours ago, gundee said:

I am pretty positive that the 1973 had a TSB that included installing an electric fuel pump in the rear.

If yours has that mod then that is where the blockage is, if it is fuel issue. 

You may need to pull the filter from the pump and replace. Very common on those.

I've searched everywhere around the tank, no filter to be seen (or felt). Rubber hoses connect directly to the hardliners. Where specifically would it be?

[gundee]

2 hours ago, Geoff's 240z said:

I've searched everywhere around the tank, no filter to be seen (or felt). Rubber hoses connect directly to the hardliners. Where specifically would it be?

Then this may not apply to yours. Not all 73''s have that pump installed.

[Geoff's 240z]

Alright, so we've ruled out a pump issue at the tank. No cracked fuel lines. So are we down to either failing fuel pump (block) or float levels?

Thanks team!

[Zed Head]

I

On 2/22/2021 at 7:38 AM, Geoff's 240z said:

New fuel filter in the engine bay, checked plugs and they are fine. 280 block, head was redone about a year and a half ago, same time added new Ztherapy carbs. 280zx dizzy and standard coil. Any thoughts?

Has it ever worked right?   Never really said.

The "standard" coil might not be the right coil for the ZX distributor.  Or it might just be 50 years old.

Are you using the return line on your carb setup, and does it have the restrictor in it?  The restrictor actually keeps the fuel pump from over-drawing from the feed side.  I just realized this when you said your filter gets drawn down.  With the pusher pump at the tank you wouldn't have this problem.  But the mechanical pump is pulling and pushing.  If there's no restrictor it will be easier to push than to pull.  You might be starving your pump.

It's still kind of early here so my thinking could be off.

[Geoff's 240z]

6 minutes ago, Zed Head said:

I

Has it ever worked right?   Never really said.

The "standard" coil might not be the right coil for the ZX distributor.  Or it might just be 50 years old.

Are you using the return line on your carb setup, and does it have the restrictor in it?  The restrictor actually keeps the fuel pump from over-drawing from the feed side.  I just realized this when you said your filter gets drawn down.  With the pusher pump at the tank you wouldn't have this problem.  But the mechanical pump is pulling and pushing.  If there's no restrictor it will be easier to push than to pull.  You might be starving your pump.

It's still kind of early here so my thinking could be off.

Has always run great, this is a new issue. Yes on return line, no restrictor I can see.

[Zed Head]

On 2/22/2021 at 7:38 AM, Geoff's 240z said:

I have an on/off (random, every couple weeks recently) hesitation under load through all gears. Fine to idol and get off the line, but as I add more gas, it stumbles and feels like it is choking. I heard detonation under this while driving last night. I thought I'd limp home but it mysteriously fixed itself and full performance came back.

Intermittent problems are the hardest to solve.  I'd set some things up so that I can get information when the problem happens.  A fuel pressure gauge would tell you about fuel supply.  Watch your tachometer needle closely when the hesitation happens.  Could be a spark problem.  The fuel filter thing might be a red herring.

And, it's always good to start with a fresh tune-up when a new problem shows up.  

[Geoff's 240z]

All tuned up. Fuel pump pickup today, I'll report back after install.

[Geoff's 240z]

Problem solved, running great! FYI, consulted with a local Z expert and the fuel filter not being topped off is normal. Thanks all for help!

[Patcon]

Was it the fuel pump?

[siteunseen]

9 hours ago, Patcon said:

Was it the fuel pump?

Apparently so. He's been driving all day.

 

[Geoff's 240z]

13 hours ago, siteunseen said:

Apparently so. He's been driving all day.

 

Indeed!