Snap-On Counselor II Gas Analyzer MT3100 O2 sensor?

[lschwarcz]

Hi Everyone,

I've seen a couple of posts here suggesting that the O2 sensor on the Snap-On MT3100 4-Gas Exhaust Analyzer would likely need to be replaced. I just bought one (along with the MT3000A, cart and most of the cables) and have no idea of the O2 sensor age.

The official part number, "MT3000-16" doesn't seem to be available at all.

Are there any equivalent substitutes out there? Anyone know any specific brand/models that would work in that application?

Thanks in advance!
Larry.

 

[engineer2]

Post up a picture of the old oxygen sensor.
Most used a screw-in sensor with 2 wires and a 0 to 2 volt output. They were chemical reaction based would only last about 6 months or so. Medical equipment used the same type of sensor. If you bought a new one it came in a tin that looked like a cat food can.

 

[lschwarcz]

Post up a picture of the old oxygen sensor.
Most used a screw-in sensor with 2 wires and a 0 to 2 volt output. They were chemical reaction based would only last about 6 months or so. Medical equipment used the same type of sensor. If you bought a new one it came in a tin that looked like a cat food can.

Here‘s a pic of it. I now realize, if I was smart, I should have unscrewed it a few degrees so the model number would be fully visible . Let me know if that would be useful and I’ll get another when I’m in the shop later today. Thanks!
Larry

 

[lschwarcz]

Post up a picture of the old oxygen sensor.
Most used a screw-in sensor with 2 wires and a 0 to 2 volt output. They were chemical reaction based would only last about 6 months or so. Medical equipment used the same type of sensor. If you bought a new one it came in a tin that looked like a cat food can.

OK, I took a few better pictures of the O2 sensor. A bit of Googling and it looks like I need to find a "Class R-22 Oxygen Sensor" that seem to run about $80 - $100! YIKES!



Does this sound correct to you? Any pointers on good places to buy replacements? How to test if it's still good? And does replacement time depend on frequency of use or time regardless of use?

Thanks again!
Larry.

 

[TurnipTruck]

I have tested/replaced/calibrated/verified many thousands of the industrial equivalent, and only $80-100 is cheap. Sensors like that have a very finite shelf life, even when still in their hermetically sealed OEM packaging, so your sensor is extremely likely to be dead or uncalibratable.
When in open air, the sensor should read 20.9% oxygen, and in pure nitrogen it should read 0%.
I expect that the sample is pumped/vacuumed from the exhaust pipe, and should go through a water trap to knock out any liquid. Watch for leaks diluting the actual reading.

The part number resembles older Industrial Scientific numbers.

 

[engineer2]

Yes, what you posted sounds right. 20 years ago they were $30. Sodium hydroxide chemical cell with a finite fife span.
If you didn't replace it you ended up with a 3 gas analyzer (HC, CO, CO2) You can get by without an O2 reading.
Without an air pump you usually had around 2-3% O2 if everything was working right. They key was to peak out CO2 readings if your A/F ratio is adjustable.

 

[belvedere]

You might check with this place to see if they carry something compatible.

Cables and Sensors - SpO2 Sensors, ECG Cables, EKG & NIBP Accessories | Cables and Sensors

The global leader in O2 sensors and ECG / EKG cables. Excellent customer service & same-day shipping. Click now to browse our huge selection & low prices.

www.cablesandsensors.com

 

[lschwarcz]

Yes, what you posted sounds right. 20 years ago they were $30. Sodium hydroxide chemical cell with a finite fife span.
If you didn't replace it you ended up with a 3 gas analyzer (HC, CO, CO2) You can get by without an O2 reading.
Without an air pump you usually had around 2-3% O2 if everything was working right. They key was to peak out CO2 readings if your A/F ratio is adjustable.

Thanks! This is really useful info!

Sorry if this makes me sound like a total idiot, but, here goes ...

Without the O2 readings, can I still get my air/fuel ratio using just HC, CO, CO2? That's my real goal for tuning my old MG and Triumph.

Thanks again!
Larry.

 

[engineer2]

Yes you can. Maximum CO2 will be at around a perfect 14.7:1 A/F ratio, but you may not want that.
Best economy is leaner than that, best power is richer than that.
Too rich and your CO and HC go up. Misfire or being way too lean can make HC go up. HC can also come from blowby on a worn engine.
You want minimum HC and CO, but how low you can go depends on a few things.
CO is a good indicator of how rich the mixture is. You want low CO, but some older engines won't tolerate a mixture that is too lean.
Do not tune to the highest idle vacuum. It is an outdated concept that will set you way too rich and the exhaust fumes will burn your eyes.
For a street car you want easy starting when cold, good driveability, and decent fuel economy. The distributor advance curve has to work hand-in-hand with the fuel curve. Basically rich mixtures burn faster and need less timing advance while lean mixtures burn slower and you need to light the fire earlier. It'll take a little trial and error, but that's what makes it fun.

 

[lschwarcz]

Yes you can. Maximum CO2 will be at around a perfect 14.7:1 A/F ratio, but you may not want that.
Best economy is leaner than that, best power is richer than that.
Too rich and your CO and HC go up. Misfire or being way too lean can make HC go up. HC can also come from blowby on a worn engine.
You want minimum HC and CO, but how low you can go depends on a few things.
CO is a good indicator of how rich the mixture is. You want low CO, but some older engines won't tolerate a mixture that is too lean.
Do not tune to the highest idle vacuum. It is an outdated concept that will set you way too rich and the exhaust fumes will burn your eyes.
For a street car you want easy starting when cold, good driveability, and decent fuel economy. The distributor advance curve has to work hand-in-hand with the fuel curve. Basically rich mixtures burn faster and need less timing advance while lean mixtures burn slower and you need to light the fire earlier. It'll take a little trial and error, but that's what makes it fun.

Outstanding! Thanks for this useful information! You just saved me a couple of hundred dollars a year in O2 sensors!

Now, all I need is to fabricate two cables for my MT3000A (Main Lead Assembly and the Inductive Pickup) and I can start using it! But, I think I've found someone who has these cables and is willing to get the info I need .

Thanks again!
Larry.

 

[engineer2]

There was another discussion here:

Snap On Counselor 2 Analyzer

Snap On Counselor 2 Analyzer any idea what these are, and what all they do. do they pull codes too. And do you know if it has the old time scope patterns for the secondary ignition system?

www.garagejournal.com

 

[bczee]

I just picked up a MT3000 w/MT3100 from a shop. Free !. came with a mess of cables and adapters.. I fired it up and it seems to be functioning with out any issue except the memory for the Date and etc are not saved on shut down and start up. And as reading this thread. The Self Diag is failing the O2 of the MT3100 4 gas analyzer as expected. I've used scopes in the past, but have not used this model (mostly SUNS), but its been a while. I got two manual for the MT3000.. so I am going through it to learn and relearn how to set up and use.

One question I have.. can the MT3000 be used on an 6 volt, Positive ground car ? If so. How to setup ?

Any good sources to find replacement parts and add on accessories ? O2 filters cheaply.. don't expect to used too much. might be a one and done before it gets used again.

I am going through all of the cables and adapters. I'll post up anything good or interesting.

Added a fee more pictures of all of the cables and attachments. And these is a few primary ones still attached.

 

[Jack_K]

The O2 sensor will be a Teledyne R-22a. I buy compatible ones from AliExpress for $30 AUD delivered in two weeks. The local distributor for the Teledyne version wanted $300 AUD and an 8-10 week wait.

On AliExpress search for either PTB18.10, AO2 or AO-02