CO measurement on Gunsons tester

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Sat 13 Jan 2001 15:24
CO measurement on Gunsons tester - Andrew Hamilton
Help! I bought Gunsons Gastester Professional (£100). Now I followed the handbook and can now measure the revs and dwell. The tester is neat, easy to use, but cannot measure CO properly.
I am testing a 1983 Austin Metro Auto (No catalyst) which had failed emissions at 6% CO.
I followed Mr Haynes manual advice, to check timing, plugs, etc and weakened mixture until speed started to fall. Recommended CO is 2.5%+/-1%

Procedure is to stabilise at 2% reading in air (Seems odd but handbook said so. Takes ten minutes)
Insert in exhaust minimum 8 inches. Reading after stabilised was 0.1% CO
On removing probe to air reading went back to 2% after 10 min for fumes to leave tester.
I emailed gunson but they have not replied. The car would not run surely at 0.1% let alone at normal 750rpm idle which it did. Any suggestions gratefully received.
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Sun 14 Jan 2001 15:13
RE: CO measurement on Gunsons tester - peter thear
never had this problem with mine. did you insert the probe and just leave it? sometimes droplets of water condensing in the pipe that connects the probe to the machine effectively block it and prevent a true reading.
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Mon 15 Jan 2001 07:20
RE: CO measurement on Gunsons tester - Andrew Hamilton
Thanks for reply. No I made sure I followed handbook and pipe was never blocked. I could hear the pump pulsing all the time. I guess if yours worked the machine must have a problem.
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Tue 23 Jan 2001 21:16
RE: CO measurement on Gunsons tester - Andrew Hamilton
The Gunson Tester is accurate. I recorded 0.1% CO in an auto metro at idle 750rpm. The MOT test bore this out - 0.1%. So a 17 year metro can actually idle at such a low mixture - I was surprised.

I increased the mixture to read 2.2% CO when warmed up. When the garage tested again it got 4.14% but they did not wait for car to warm up properly.
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Sat 3 Feb 2001 19:35
RE: CO measurement on Gunsons tester - Andrew Moorey (Tune-Up Ltd.)
Its a toy.
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