1978 280z AFM question

[johnny haywire]

Amigos,

The AFM on my '78 has been messed with, the previous owner had it leaned out considerably (and it still ran quite rich, probably richer now that I recalibrated it - decreasing the tension about 10 teeth) and upon inspection, it appears that the counterweight has been removed from the wiper.

Luckily, I have found someone locally who said he has 5 AFMs, 3 working, 2 for cores, and I think I'm going to check them out this weekend but I have a few questions as the only ones I've ever seen the internals on are mine and the ones that Blue posted in his adjustment and calibration pages on the Atlantic Z site (many thanks, Blue, you saved my arse!).

The first question - do '78 AFMs have pins for 39 and 36 (the fuel cut-off)? The AFM I currently have (A31-601 000) does have the fuel cut-off contacts on the board and has pins 39 and 36, while my harness connector does not have anything there for pins 39 and 36.

And my other question - my '78 AFM is supposed to have a counterweight on the wiper mechanism, right? Here's how it currently looks:

Many thanks in advance!

[zKars]

The 78 AFM does NOT have the fuel pump contacts inside. Pins 39 and 36 should be either absent on the AFM connector or not hooked up internally if there.

Now, your wiring harness that plugs into the AFM may not have the mating pins since there is no wiring in the car that uses these pins, which is actually the good news, since ANY late 74-78 AFM will work on a 78 since your 78 wiring will ignore the fuel switch if its in the AFM. The opposite is of course not true, you CANNOT use a 78 AFM on late 74-77 since they REQUIRE the fuel cut switch.

And yes all AFM's are counter weighted....

[grantf]

I think I just noticed something else strange about your AFM. I am not trying to confuse your situation. But it does look like you current AFM has a cut off switch. whether it is used or not is another issue. I can see the switch arm in the upper right side of you upside down photo. My car uses that switch. yours probably does not. Just noting it that's all.

Good job on the AFM find though.

Edit: my AFM (early 77) is a A 31-605 000

Edited July 16, 2012 by grantf

[johnny haywire]

Many thanks for both of your replies - this is extremely helpful. I suspected it was the wrong year AFM due to the cut-off switch being there and the lack of female connectors on my harness plug (no wires or female connectors in the plug for 39 and 36).

Thanks also for the info on the counterweight - I will be much more educated when I go and check these AFMs out. I plan to test them all before pulling the trigger. Also great to know that any late '74-'78 AFM will work fine. I am going to shoot for a '78 version if possible, but I'll be happy enough to just get an unmolested one (if possible).

One other question - is the counterweight removable or has mine been broken off?

I got lucky finding the local guy with the AFMs - I just posted a WTB ad on the local Craigslist and got a response a day later. We still haven't met, though, so...fingers crossed, breath not held.

[johnny haywire]

Duplicate post - sorry!

Edited July 16, 2012 by johnny haywire
duplicate post

[Zed Head]

I had a 78 and its AFM had the cutoff contacts in the AFM. Not used, but they were there. The AFM looked original to the car. I now have the 78 AFM on my 76 car. I adjusted the contacts so that they worked correctly.

I would guess that there was a point in manufacturing where the old inventory ran out and the 1978 AFMs didn't have the contacts anymore. But some do. The 1978 FSM shows the pins in a drawing but labels them as "useless" or something similar. Kind of funny.

Just posting for a little clarity from another perspective.

[johnny haywire]

Excellent point. I thought I remembered reading about that in the '78 FSM. It makes perfect sense...vestigial tails.

I'll just be happy enough with a complete and working AFM, regardless of year. The difference in performance since I calibrated mine has been noticeable, so I imagine with the counterweight, it'll probably be even better.

Thanks again for all the insight on this, guys. If we ever meet, I'll be buying the rounds!

[Zed Head]

Just saw this thread over on Hybridz. You might have a turbo AFM. The counterweight may not be missing after all.

http://forums.hybridz.org/index.php/topic/108020-afm-does-this-look-right/page__pid__1010448#entry1010448

[johnny haywire]

Thanks for noticing that, Zed. The turbo AFM definitely has a closer resemblance. After looking at it some more, I'm thinking that the counterweight is removable, and that it perhaps attaches to the nut and bolt on the opposite side of the wiper?

I just checked MSA's web site and the numbers on my AFM correspond to a non-turbo AFM, though. However, I have no idea what was done to my AFM, so maybe it has a turbo board and wiper?

http://www.thezstore.com/page/TZS/PROD/SFC03A/11-304

Sadly, the local guy with the 5 AFMs never wrote me back. So...not sure what's next with this latest bump in the road.

Anyone out there with an extra AFM knocking around the garage?

[grantf]

http://www.datsunstore.com/product_info.php/pName/airflow-meter-7778

Anyhow it does look like you have a very strange AFM. I looked at the pictures of the turbo AFM and it looks like you have sort of a hybrid frankenstein monster one.

Edited July 20, 2012 by grantf

[zKars]

I have some spares. Drop me a note to z240@shaw.ca and we'll take it from there.

The turbo AFM has larger inlet and outlet diameters, your 280 boots wouldn't fit.

[johnny haywire]

Just a quick update to this post - the new AFM is in and she is running quite nicely. Pulls much smoother at higher RPMs than before and seems to pull harder in general. Thanks again for everyone's input!