Gunson gas tester

[Nick Triesch]

I bought a Gunson gas tester online and it arrived with no tubes or gas probe to hook it up . It will be returned. My question is how the the tester analyze the gas when the tubes just hook into the plastic piece on the back. In other words , I don’t see how any gas goes into the actual tester.

[Funracer]

Flex tubes plug into the fittings in the top pic and couple on to an aluminum tube that is inserted into the test port in the cars exhaust. That one you have there looks unusable the way it is. It looks like its been delivered by Ace Ventura!

[Funracer]

Maybe the disc is the collector and the big box is the analyzer? Mine broke and I tossed it. Kind of wish now I had cracked it open.

[Nick Triesch]

I see what you are saying but if you look at the picture, the plate part came unglued from the machine and I see no hole there for gas to get into machine to be analyzed. How could gas be analyzed if no gas gets into tester. You can see that both parts were together when new. The gas to be analyzed seems to me to go nowhere!!

[Nick Triesch]

I must be missing how this thing works. The part is just glued onto the back of the machine. I read that it is very common for it to come unglued. Anyway, it’s going back to the seller.

[Schulisco]

Refer the single page "manual", this shows the content of box and the hoses delivered with.

https://www.gunson.co.uk/product/G4125/Gastester-Digital

The sensor is in the round disc where the hoses getting connected. There's no pump sucking the exhausts in. They have to flow to the sensor when engine is idling. Therefore it rerquires a moment until measurement is possible. Simple, very cheap, but working. Unfortunately with a tolerance of 0,5% not sensitive enough for injection cars with catalyst, because they have to keep a CO value between 0,4-0,8%...

Thomas

[Nick Triesch]

Ok , the round disc is the sensor, but how does the information from the gas get to the digital readout on the tester when disc is not connected to the tester? My Gunson was delivered apart and there is no “ in “ port on the tester. So how does it read ?

[spuggy]

Originally Posted by Schulisco

Refer the single page "manual",

That's the product description. The "full instructions" they refer to in that description may be found online. This https://images-eu.ssl-images-amazon.com/images/I/91Ihi6jU31S.pdf worked for me.

Or there's a 7 page handbook: https://www.manualslib.com/manual/1482901/Gunson-Gastester-G4125.html#manual
and a 20 page handbook (eh? do what now?) https://www.manualslib.com/manual/1380847/Gunson-G4125.html
and a 2 page "supplementary adjustment procedure" document https://www.manualslib.com/manual/2226550/Gunson-Gastester-Digital-G4125.html#manual

Originally Posted by Schulisco

The sensor is in the round disc where the hoses getting connected. There's no pump sucking the exhausts in. They have to flow to the sensor when engine is idling. Therefore it rerquires a moment until measurement is possible. Simple, very cheap, but working. Unfortunately with a tolerance of 0,5% not sensitive enough for injection cars with catalyst, because they have to keep a CO value between 0,4-0,8%...

LOL - "a moment"... I had one, used it once. Seemed to agree with my wrench's 5 gas analyzer fairly closely - and, to be fair, didn't cost $5000...

That said, they are both inaccurate and slow... An initial 8-10 minutes for free air calibration (the "supplementary adjustment procedure says "allow to warm up for minimum of 15 minutes"), initial reading after 15 seconds, observe for another 1-3 minutes, allow "at least" 1 minute to stabilize between adjustments, leave powered up "at least" 10 minutes after motor shutdown for exhaust gas purge etc.

The stated accuracy of +/- 0.5% in the range 0.5% - 6.5% CO?

Although mine seemed somewhat better than that (actually, pretty much dead-on), that stated accuracy is the same difference between 3.0% CO and 3.5% CO - which, for idle on a CIS 930, was the difference between "runs correctly" and "cyclic lean surge on fixed throttle under light load".

[spuggy]

Originally Posted by Nick Triesch

Ok , the round disc is the sensor, but how does the information from the gas get to the digital readout on the tester when disc is not connected to the tester? My Gunson was delivered apart and there is no “ in “ port on the tester. So how does it read ?

This may help:

[Nick Triesch]

Again , no gas goes into the tester. How does the digital readout change ?

[911obgyn]

Magic!
I tried to use a friends tester gave up and bought a innovate wide band O2 kit and use the O2 bung.

[porschedude996]

The first one I bought was broken in transit. Not as bad as yours, mine had the water trap popped loose. I was worried that internally it may have sustained some damage. You and I can’t be the same ones. Even the Chinese package better than what I received. To rephrase, the Chinese company that made these is less proficient at packaging. It seems like they would have a better profit margin if they corrected their packaging.

[spuggy]

Originally Posted by Nick Triesch

Again , no gas goes into the tester. How does the digital readout change ?

The exhaust hose goes to the pulse pump/water trap. The actual sensor is in the "collector box" (the bit that came unglued that the pulse pump is mounted on). There's an electrical pigtail between that sensor and the main box that houses the display and the electronics.

[Nick Triesch]

Yes ! Was a terrible package. I bought from Mercari a site like eBay. They sent me a postage label to send it back. I however put it in a correct box. I’ll get my money back.

[Nick Triesch]

Got my money back !

[porschedude996]

Originally Posted by Nick Triesch

Got my money back !

Are you going to rebuy?

[Nick Triesch]

Yes ! When I can . The return worked smoothly.

[BSNMOE]

I have a good Gunson with instructions and 2 probes if you’re interested

[AndrewCologne]

Originally Posted by Schulisco

...Therefore it rerquires a moment until measurement is possible. Simple, very cheap, but working. Unfortunately with a tolerance of 0,5% not sensitive enough for injection cars with catalyst, because they have to keep a CO value between 0,4-0,8%...

Mine needs about 10 mins to calibrate itself in environment air, after that ist quite accurate and hits the final CO very close, compared with professional exhaust testing systems at emission testing shops like DEKRA/TÜV etc.
The values 0,4-0,8% are just for the initial setting, finally with active control at lambda 1 on these engines it results in up to approx 1.2 % CO where then the cat converts internally with up to 90% efficiency down to approx 0.1 % CO.

[ant7]

They do work pretty good for what they are, mine compared with the latest MOT test, was pretty much the same as how I set it!
I agree though, they can be a bit fiddly to use.