CIS Fuel/Air adjusting hole Plug

Just FYI, if you’re looking for a way to plug this hole and it’s a must if you don’t have this, after searching around google seems like only two places has them for sale but I’m sure there are other places you can get this but it’s just not showing. Anyway I ordered a couple from DMC as you can see the difference in price compare to Pelican’s.

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Hmm, on my Euro QV fuel distributor that hole is threaded, and a M3 (iirc) bolt about 5mm long fits perfectly.

Gordon

 

I know from the factory the hole is plug with an aluminum piece that’s press fitted in, sometimes when people punch them out from the underside, they then tap a thread to plug it with a set screw, but with this type of plug you dont have to do that, but i think it will still work even if it’s threaded.

 

Hey Mike,
Rock on. Thanks bra.
I was looking for a spare. Mine is a one person shop, but you lose that. ,,?? Your up a creek w/o a paddle.

 

Without it you will have vacuum leak

 

At that location, the real problem with a leak is that it means unmetered air is coming in, due to the fact that we have a downdraft CIS system on our cars, and the leak would be after the metering plate. On cars with an updraft CIS system (which was more typical I believe) the leak would be before the metering plate, so the leak air would be metered and have no effect. That would be of no consequence really, other than unfiltered air coming in.

When I got my 328, I found a rather rudimentary homemade plug in that hole. I replaced it with a silicone rubber plug that can be grabbed with a dental pick. This plug with handle looks like a much better option!

 

I remove that screw....(yes, that hole is threaded) before going to the MOT. With the screw in place Gas analyzer showes 3.5 and without it 1.2....engine still running smooth.

 

That just shows that your car is tweaked up into a rich condition. You could adjust the mixture screw a bit CCW to give the 1.2% CO result with the access hole closed. It's not too fussy on a non-cat car as IC engines run very well a little rich. On a cat-equipped car, at 3.5% CO the cat would overheat. What is the max % CO limit that you need to meet in your MOT test?

 

For oldtimers (more then 30 years) max. 2.5...over here. When touching that mixture screw even the smallest amount, CO will drop drasticly. So prefer not to touch and leave it a bit rich. Spark plugs showing perfectly and running great. No cats ...

 

2.5% CO max is a generous spec that should be easy to meet. You seem a bit fearful, but adjusting to something like 1.5~2.0% CO (with the access hole closed) would still be nicely just a little rich.

 

Other thing I did not mention,...on the left muffler pipe, its 1.8 with the screw in ....so only the right pipe is higher. And when the car is really well driven, that 3.5 amount is also lower. So that problem of 3.5 is only when the car is not used that much (and maybe only just before going to the MOT). My car has its own mind I'm sure.