Tom Woods wrote:
My car has just failed its MOT test on emissions.

it is running a simple open loop gas kit with a mixer before the carb.

apprently it was

at 2500rpm - CO 0.07%, HC 3380ppm
at idle, HC 8000ppm+

Any suggestions as to how i should go about sorting this?

I have changed the air filter (which was 1 year old and dodnt look too
bad).
Before the MOT i set the points (which smoothed the idle out)

Can the timing being off affect it too?

I moved the dissy when doing the points and I cant recall what we set
it to when the converters first set it up - so i set it by guesswork
and how much go it had, and it felt fine to me just before its MOT.

The HBOL says 17btdc@idle - which is presumably for 4* since it is a
1980 car and an old haynes book
Assuming i should advance it a couple of degrees of advance for LPG,
this would put it at about 19btdc@idle

When i tested it just now it was at 30btdc@idle. would this affect my
HC levels?

Was recommended at the last MOT to test it on petrol, tester claimed frequent
failures on gas with high HCs, ours flew throigh on petrol.

--
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On or around Sun, 08 Oct 2006 14:50:36 +0100, Tom Woods
enlightened us thusly:

On Sun, 08 Oct 2006 13:45:38 GMT, "GbH"
wrote:

Was recommended at the last MOT to test it on petrol, tester claimed frequent
failures on gas with high HCs, ours flew throigh on petrol.

mine wont as the needle and jet are too worn and it always runs rich.
Not having to fix these was another plus point to the LPG conversion!

your timing figure sounds too advanced, and that might upset the burning.

You also get problems if the gas rig is incorrectly tuned; too lean or too
rich can produce too much HC.

Try tuning it with it attached to a decent analyser.
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