when replacing mass air flow meter,anything need to be reset?

[gblaine]

1975 280z will not crank,mechanic told me i need to replace mass air flow meter.Do I need to reset anything ,it still dosen't crank but turns over and I have compression and spark.

[m4xwellmurd3r]

have you tried just unplugging the AFM (air flow meter)

my 78 runs without, but runs like crap. do you have fuel? iirc, your car should kick the fuel pump on just with the movement of the flap.

[Mr Camouflage]

So, you mean it cranks but wont fire?

Do these have cold start valves like the 280ZX does? I'd start with that first.

[280~Master]

No Need to rest anything like newer cars just unclamp neg battery cable before doing an work and you will be fine.

[sblake01]

I'd be curious as to how his mechanic came to that conclusion. He says he has 'compression and spark' but no mention of fuel. There are so many things that will create that scenario but I've seldom seen an AFM cause that problem.

[gjfx1]

got fuel pressure?

[pbatura]

There is a switch in the AFM for the fuel pump, and is determined by the position of the flapper.

If you aren't hearing the fuel pump running when cranking the engine, this may be a place to check.

Good luck.

[m4xwellmurd3r]

that's why i said maybe try unpluging it. that would open the fuel pump circuit, AND the car should run with it unplugged (i've done it before, but it runs like arse)

[sblake01]

that's why i said maybe try unpluging it. that would open the fuel pump circuit, AND the car should run with it unplugged (i've done it before, but it runs like arse)

I've done a lot of research on this over the years. He has a 75 and you have a 78 as do I. The 78 S30 does not have fuel pump contacts in the AFM. It's the only year S30 that doesn't. It's setup like the later 79 and up S130, 810 and Maxima units (Pre ECCS). That's why the FSM cautions against using the 78 and later ECU or AFM in the 77 and earlier 280Zs. Unplugging the AFM on a 78 doesn't 'open the fuel pump circuit'. Compare these two scans. The only reason your car runs like 'arse' when you unplug the AFM is simply because you've unplugged the AFM. It really doesn't accomplish or help diagnose anything.

[m4xwellmurd3r]

sorry blake, i'm never good at explaining things.

when i looked at my plug, the plug has 2 contact points that are empty (no wires leading to them) I know that mine doesn't use the switch, but from my understanding, when the car is running, the switch is opened because the flap has moved. by unpluging the afm from the car, that switch would become an open circuit. that's all i was saying. (or, the easy way would just be shove a screwdriver to push the flap and see if it kicks the pump on.)

[sblake01]

I know that mine doesn't use the switch, but from my understanding, when the car is running, the switch is opened because the flap has moved.

What switch? There is no 'switch' in a 78 and up AFM as evidenced by the fact that there are no wires on the plug, as you said, that would correspond to the contacts on the earlier cars. Maybe you'll understand it better with these charts. On a 78 the position of the flap in the AFM has no effect on the operation of the fuel pump. That may work on his car but it won't on yours or mine.

[m4xwellmurd3r]

oops, i should've said doesn't have it instead of doesn't use it. i implied it doesn't have the switch by saying it doesn't use the switch.