Quote:
Originally Posted by psalt
tirwin,
Did the PO say it was set rich because of the broken WUR ? Control pressure offsets the deflection of the air flow plate and low control pressure increases the amount of fuel to the injectors. When cold the pressure is low and you get a higher plate and more fuel for warm up. Your pressure never increases and it should be running too rich when warm as a result. Your cold running problem is probably caused by something else and after your replace the WUR, I would be checking the mixture at hot idle in case it was adjusted to compensate.
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Previous owner didn't suspect the WUR to be bad.
If the BM strip has completely failed, then control pressure should never, ever increase, right?
But, what if the strip is just not getting power? In that case, it may be that the strip is still capable of doing it's job, it's just that it's not because it's not getting any current to warm it up. In that case, it would seem that heat from the engine would warm the BM strip and cause it to close the valve. In that case, I should see control pressure increase to a normal level.
If the control pressure is at a normal level with a warm engine, then the mixture should be at the "normal" setting (normal is of course relative, but let's not change any other variables at this point). If the control pressure never increases to a normal level with a warm engine, then what you are saying about that the mixture being too rich makes sense.
Sounds like I need to do two things: (1) check to make sure WUR is getting power and (2) run the engine for a little while and check the control pressure again to see if it's in the normal range.
Sorry if I'm being a bit thick but I do feel like I'm making progress. I'm still trying to sort this all out in my head and understand things. Hopefully it will help someone else.
