Air measuring Unit - Suggestions

[furry dice]

I think my one is bu**ered, I was stranded on the M40 this weekend, eventually managed to struggle home by a mixture of fiddling and luck.
It appears to me that the AMU (the AIR MEASURING UNIT that sits on the nearside wing) is faulty. When cold the car starts fine (i'm guessing that the ECU effectively ignores the AMU to apply a degree of choke to the engine) When warm the engine refuses to restart, or if it fires its just an instantenous fire then stops. After a bit of investigation and something remembered from a previous car I tried to start the car with the AMU disconected, low and behold it fires and seems to run ok-ish, afer further experimentation it appears it doesn't matter if I re-connect the AMU after the engine is running or leave it unplugged.
I am now assuming that the ECU will ignore the AMU if its not there when the engine starts, the only trouble is I reckon the car is just pouring petrol into the cylinders, as it appears to be running very very rich (slight hestiation at 4K revs and above, very black exhaust and smells slightly odd.)

Now I was wondering if anyone knows how theses units work and how to test them, if there's any other possible solution.

Cheers

[davidn]

Here you go Furry,
www.rpiv8.com/carbs-2.htm#setting-up
Hope it helps
David

[tahiti450]

I always thought it was an AFM (air flow meter)... And how exactly did it get buTTered??
but seriously, I hope you get it sorted, and let us know.

>> Edited by tahiti450 on Monday 26th July 13:36

>> Edited by tahiti450 on Monday 26th July 13:36

[furry dice]

Further info required,
Measured the volts coming out of the AFM this evening, not really sure if this is conclusive or not, but the bible talks about volts being between 0.5V and 4.5V the most I got form my AFM was 1.46V at 4Krevs.

Has anyone out there made any similar measurements.

I did this by sticking needles into the wires as it's impossible to be sure of getting the voltage meter probes on the wires in the connector, and there's no way I can get the cover of the cables at the ECU end.

Secondly does anyone know how the standard ECU works, as when the engine is stone sold it starts fine, but once its warmed up a bit it won't start, I'm wondering what the ECU does differntly in these 2 conditions.

Thanks in advance
Furry

[tahiti450]

Section 5 of the bible covers this whole area in some detail including giving typical values for AFM voltages and some diagnostic tests for the ECU.

I'm assuming you have the hot-wire AFM. As regards getting access to the terminals on the plug have you tried inserting a fine probe into the back of the plug (into the hole where the lead in question enters the plug). Once in far enough this should meet the contact within the plug for that lead. Some plugs will have a rubber boot on the back covering the lead entry and this would have to be peeled back carefully. The great advantage of this is that you can measure voltages whilst all the components are connected or even under running conditions (though you need to be careful that you dont use an analogue meter which may produce currents potentiallly harmful to some circuits - or so i've heard). Digital multimeter and oscilloscope make the ideal combination for most diagnostics.

>> Edited by tahiti450 on Monday 26th July 21:48

[shpub]

Temperature sensor?