I have heard stories about sticky AFM's in the past, but I have never held one in my own two hands. Until now.

So I've got this AFM here that has a binding sticky spot right in the middle of it's travel. I have looked it over very carefully and cannot see any visible explanation for the sticky spot. I'm thinking maybe the damper section of the vane may be making contact up in the belfry area, or the main shaft may be bent.

At this point, I'm toying with the prospect of taking the back cover off. I remember some discussion about doing this in the past, but don't remember if anyone has actually gone through with it.

Has anyone taken this back side cover off? Mine has two screws at the bottom and a whole bunch of glue around the entire perimeter:

Has anyone gone through the operation, and did the patient survive? I mean... This thing is worthless to me in it's current state, but it would be nice if this was more than just an autopsy.

56 minutes ago, HusseinHolland said:

I took the front cover off mine to check the needle track - on Fiats' version it can develop carbon buildup that throws the values off at differing points of the scale. Lookig at it again, I think mine is original in terms of spring setting.  I haven't driven the car enough to know whether it's performing at it should. I do know the fuel pressure at the rail is low (30psi) once the motor has been run for a awhile, during warmup I noted 34-36psi. I'll start a thread on that when I get to testing / checking the fuel pump, etc.,.

I can't seem to find the tutorial site, but it might be a good idea for you to scoot the board with the black sweeper track down a bit so that the sweeper arm is going over a fresh/flat/non-ground down track.  All you do is loosen those 3 screws that hold the board to the afm housing and push the board down towards the bottom of the housing a tiny bit.  Even the tiniest amount will get the contact points out of the carved area.

Edited June 2, 20231 yr by chaseincats

I've seen that before too.  Contact cleaner or Deoxit ia also a good idea.  Deoxit is good everywhere actually. 

 

https://caig.com/deoxit-d-series/

 

This might be helpful.

https://www.atlanticz.ca/zclub/techtips/EFI&fuel.htm

I bought a '76 that would crank and idle but wouldn't take fuel.

$1,000 for a perfect car with faded paint and carpet that had a spider web on the sweeper vain. Cleaned that and ran like new.

 

 

If your car runs OK and you don't have any reason to believe the traces inside the AFM are a problem, then I'd just let it alone. I wouldn't move the board around unless you have a reason to do so.

Can you tell (by looking at the silicone blobs) if your AFM has been "adjusted" by a previous owner?

22 hours ago, Captain Obvious said:

If your car runs OK and you don't have any reason to believe the traces inside the AFM are a problem, then I'd just let it alone. I wouldn't move the board around unless you have a reason to do so.

Can you tell (by looking at the silicone blobs) if your AFM has been "adjusted" by a previous owner?

I'm gonna say it's not been messed with

40 minutes ago, HusseinHolland said:

I'm gonna say it's not been messed with

Actually there are a couple different spots that can be messed with on the AFM and the one you pictured is not commonly messed with (thankfully).

The most common adjustment is to muck with the spring tension by moving the big black gear. There should be a silicone blob on the locking screw for the gear. In you pic, it would be hidden behind the counterweight. If you rotate the vane arm open some, it'll expose the blob I'm talking about. If it's still there.

Swing the arm and look here:

 

 

The only time folks should mess with the AFM is if they have a widrband sensor to tune it with IMO

@Captain Obvious - looks like it may have been tweaked then - there is no blob on the clamp

6 minutes ago, HusseinHolland said:

@Captain Obvious - looks like it may have been tweaked then - there is no blob on the clamp

it's definitely been played with, the stock bolt has a Phillips head carved into it

hhhmm... I don't see any blobs on the black gear that would assist in determining where the original setting was 😞

2 hours ago, chaseincats said:

it's definitely been played with, the stock bolt has a Phillips head carved into it

I was going to suggest that as well, but this is a 75 he's working on and most of my experience is with the later years. I can confirm the later years used a "Phillips" head hex on the clamp, but I've never personally been inside a 75 AFM.

Can you confirm that they used the same hardware in 75 that they did in the later years? It certainly doesn't look like any other hardware I've seen on a Z, but can you confirm?

Just for reference, here's the insides of my 77, It's different in a bunch of ways:

The other bolt on my counterweight is different as well. And both his and mine look like they have not been messed with: