Mortortest Exhaust Gas Analyzer

Mortortest Exhaust Gas Analyzer

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v8s4me

Original Poster:

7,234 posts

218 months

Friday 5th February 2016
quotequote all
I've been given an old Mortortest Exhaust Gas Analyzer, model number 9030. It runs off a car battery.

When switched on the needle swings about halfway across the dial. Does anyone know how I can check whether is is working or not. I suspect it is faulty but it would be nice to check. Thanks in advance.






Edited by v8s4me on Saturday 6th February 10:38

Mroad

829 posts

214 months

Saturday 6th February 2016
quotequote all
Looks to be an earlier analogue dial version of this one:
http://www.motortest.de/english/9041_e.shtml
The two plastic pipes attach to the nipples on the respective corresponding clear window below, it looks like these have broken off?
There should be a paper filter element inside somewhere (probably behind the clear window), they trap unwanted particulates and moisture which would otherwise mess up the detector. The filter needs checking and probably replacing.
There is a membrane pump which should pull the gases through the detector, that needs to be checked if it's working (it should make a definite pumping noise when turned on).

Basic procedure for most CO meters is check filters are clean and pipework all intact and free from moisture.
Turn on and zero the scale in clean air (away from exhaust), use the knob on the right of yours to zero CO on the scale.
Yours has two scales, 0-2% and 0-10%, the scale is use is indicated by the green light, it might be auto scaling or the light might be a push button to switch between scales.
Stick the probe up the exhaust and a reading should appear on the dial after about 10-15 seconds.

v8s4me

Original Poster:

7,234 posts

218 months

Saturday 6th February 2016
quotequote all
Thanks for the response.

Mroad said:
...The two plastic pipes attach to the nipples on the respective corresponding clear window below, it looks like these have broken off?..There should be a paper filter element inside somewhere (probably behind the clear window),....
Yes, it looks like they have gone. The paper filters are there and clean though.

Mroad said:
...There is a membrane pump which should pull the gases through the detector, that needs to be checked if it's working (it should make a definite pumping noise when turned on).....
When I switch it on, there is a 'hum' but no pumping/sucking noise.

Mroad said:
...Turn on and zero the scale in clean air (away from exhaust), use the knob on the right of yours to zero CO on the scale.......
When I switch it on, the needle swings to the middle of the gauge, but turning the adjustment knob fully anti-clockwise will not re-set the needle back to zero.

Mroad said:
...Yours has two scales, 0-2% and 0-10%, the scale is use is indicated by the green light, it might be auto scaling or the light might be a push button to switch between scales....
Push-button on this one.

I'll try to ascertain why the pump isn't working, but it looks like this one might be heading for the scrap pile.

Thanks again for your help.


v8s4me

Original Poster:

7,234 posts

218 months

Sunday 7th February 2016
quotequote all
The pump works and the two tubes do connect to the front of the filter housings. But the air flow is a bit confusing:-



Exhaust gas flows (red arrow) into a plastic bottle and from there to the front of filter A. From there to a glass bottle (vapor separator?) and then to a T-piece. Fresh air appears to be drawn from inside the casing (green arrow) through filter B and then to the other side of the T-piece. The mixed gas (blue arrow) then goes to "can" 1, then out of "can" 2 and to atmosphere, out of the back of the unit.

Is this correct? Why is the exhaust gas being mixed with fresh air before it goes into the analyser?

glenrobbo

35,061 posts

149 months

Monday 8th February 2016
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v8s4me said:
Is this correct? Why is the exhaust gas being mixed with fresh air before it goes into the analyser?
It's probably meant for testing VWs Joe. An early version of the cunning emissions cheating plan.

getmecoat

Edited by glenrobbo on Monday 8th February 09:41

Mroad

829 posts

214 months

Monday 8th February 2016
quotequote all
I think it's a cunning plan so the pump is never pumping against a blocked off tube and ruining it, a sort of safety vent.
With the exhaust probe in fresh air and the pump running then it will draw air in via both tubes, exhaust and 'vent' atmospheric tube.
With the pump off and the probe up the exhaust the higher pressure exhaust gases will reverse flow out of the vent. With the pump on it will suck the higher pressure exhaust gases into the sensor. I don't think the pump is strong enough to suck in air via the vent as well as the higher pressure exhaust gas so the venturi effect doesn't come into practice.
I guess you treat the T piece as a diversion valve.
That's just my take on it, I could be wrong but try it up an exhaust.

Does it zero in fresh air? It's possible the small white line on the meter is the zeroing point although it's sitting on 4.5% or 0.9%, neither of which make much sense.
Checking an online manual my old Gunson EGA is supposed to be zeroed in fresh air at 2% CO which still doesn't make much sense as I don't think atmospheric CO is anywhere near that.
Zero it on the white line (does the needle actually move when zeroing?) then stick up an exhaust, you'll know if it's doing anything as on a modern motor running correctly and warmed up the CO reading should be very low, practically zero.

v8s4me

Original Poster:

7,234 posts

218 months

Monday 8th February 2016
quotequote all
Mroad said:
.....Does it zero in fresh air? It's possible the small white line on the meter is the zeroing point although it's sitting on 4.5% or 0.9%, neither of which make much sense.
Here is a better picture of the dial.



As you can see, the white line in the middle is actually a '1' on the '0' to '2' scale. This is where the needle sits when the unit is switched on. Turing the zero adjuster anti-clockwise will not make it move back any further.

kev b

2,708 posts

165 months

Monday 8th February 2016
quotequote all
I have one of these but slightly later with an led readout., it is branded as Snap On.

Mine needs a new sensor and as far as I know they are unavailable, rendering it useless.

It was a really useful piece of portable kit back when the K Jetronic equipped XR3i and Golf Gti were current, I wish mine still worked. I used it to check CO% before sending cars for MOT when the new fangled emission test was introduced.

These days I could still find a use for it on classic cars and carbed motorbikes.

The sensors were not long lasting at the best of times and you needed patience as it took fifteen seconds to react to a change in mixture.

v8s4me

Original Poster:

7,234 posts

218 months

Monday 8th February 2016
quotequote all
kev b said:
....Mine needs a new sensor and as far as I know they are unavailable, rendering it useless..
How would I know if the sensor on mine is faulty?

Here is a picture of the dial with the unit switched on and "breathing" fresh air.


kev b

2,708 posts

165 months

Monday 8th February 2016
quotequote all
Mine has a knob on the front to set the display to zero whilst sampling fresh air, when it is no longer possible to achieve zero then it is likely the sensor is u/s.

The paper filters also need to be clean as well for best results.

v8s4me

Original Poster:

7,234 posts

218 months

Monday 8th February 2016
quotequote all
kev b said:
...Mine has a knob on the front to set the display to zero whilst sampling fresh air, when it is no longer possible to achieve zero then it is likely the sensor is u/s.....
Mine does that, so it looks like it is scrap then?

kev b

2,708 posts

165 months

Monday 8th February 2016
quotequote all
Yes I am afraid so, however I hung on to mine in case a sensor turned up somewhere, I trawled Ebay UK, USA, Germany and Googled until I was dizzy with no luck.

I tried our Snap On rep man but he can't supply parts for a guaranteed for life ratchet of the same age let alone a bought in rebranded item.

My only hope is that an electronic expert could make a sensor, maybe there is one on PH who likes a challenge?

Krikkit

26,500 posts

180 months

Monday 8th February 2016
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Some pictures of the sensor circuitry may yield results, worth a go!

kev b

2,708 posts

165 months

Monday 8th February 2016
quotequote all
Just googled motortest de and found they still make a very similar product!

Perhaps an email might be worth a try, hope they speak English though as my German is only good for ordering food and asking directions.

v8s4me

Original Poster:

7,234 posts

218 months

Monday 8th February 2016
quotequote all
Krikkit said:
Some pictures of the sensor circuitry may yield results, worth a go!
Any help?


kev b

2,708 posts

165 months

Tuesday 9th February 2016
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I will try and look at mine out today, it is at a friends place, the insides look very similar to how I remember mine.

v8s4me

Original Poster:

7,234 posts

218 months

Wednesday 24th February 2016
quotequote all
I've tweaked the component (variable resistor?) pointed out here....



... this has zeroed the gauge.



So I suppose the only way to test it is to stick the tube up the exhaust pipe. What sort of reading should I expect from a warmed up Rover V8 (7000 miles on a full rebuild).

Mr2Mike

20,143 posts

254 months

Wednesday 24th February 2016
quotequote all
v8s4me said:
Is this correct? Why is the exhaust gas being mixed with fresh air before it goes into the analyser?
Probably because these basic CO meters often use a catalytic sensor that measures the temperature rise when CO is oxidised. Obviously you need oxygen to do this.

kev b

2,708 posts

165 months

Wednesday 24th February 2016
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I would expect a properly tuned Rover V8 on carbs to show around 3% at idle.

v8s4me

Original Poster:

7,234 posts

218 months

Wednesday 24th February 2016
quotequote all
kev b said:
I would expect a properly tuned Rover V8 on carbs to show around 3% at idle.
Mine is a fuel injected 3.9. What would you expect on that please?