CIS problem. Was: CIS help?

[Dan Cordon]

Konstantin Bogach wrote:

<snip>

> Are you saying that wetting with gasoline will ruin a spark plug and it never will produce a good spark again?

That has been my experience. Actually, most of the time when I've had a 
single fouled plug, just running the engine for a minute usually brings 
it up to temperature enough to start it going again. But if all the 
plugs are wet, cold starting could be an issue.

<snip>

> I does ignite the fuel but does not burn it completely.  Could poor atomization cause it?
> I have to wait for a dry weekend to continue testing.  Coming saturday probably looks good for now.
> 
> Thank you.
> Konstantin.

I'm still thinking that atomization is less the problem. With the CIS 
injection system, the injectors are running all the time. So for nearly 
3/4 of the engine cycle, the injectors are just firing against the back 
of a closed intake valve. Most of the fuel is considered to pool up 
there and enters the cylinder in a very rich state. Flow in the cylinder 
is turbulent enough to mix things up enough to ignite when it's time.

This is *not* to say that the injectors aren't the problem though. For 
instance, if one injector is flowing twice what the others are, that 
will throw off the measured air/fuel ratio at the O2 sensor by a lot. 
With all the CIS messages lately, I can't remember if you compared flow 
on the injectors or not.

Troubleshooting a rough/not running engine can be frustrating, but also 
highly rewarding too. One thing I learned from my dad as a kid was "It 
only takes three things for an engine to run. Fuel, Compression, and 
Spark." When troubleshooting, I always come back to those three things. 
Another thing he kept telling me (especially when I was buying large 
coils) was that it's the 'when' of the spark that's critical. The 'how 
big' of the spark is relatively unimportant for most driving conditions.

Of course, a weak spark in the presence of poorly mixed air/fuel is 
bound to be troublesome :o(  Let us know how things are going though, 
and what you find out from some more testing.

-- 
Dan Cordon
Mechanical Engineer
University of Idaho - Engine Research Facility