[T3] Temp sensor and MPS problems on new motor

[Jim Adney]

On 29 Feb 2016 at 21:20, Jessica Chase wrote:

> Don´t worry - we don´t usually run it up to 40 in 2nd, but for the purposes of this test (checking AFR numbers under hard acceleration), we pushed it.  With this new fully balanced motor with a lightened flywheel, it was pretty easy to accelerate and keep on going. The motor didn´t flinch.  The owner´s manual says that we can safely o up to 43mph in2nd so maybe we were just short of redlining it :) WeTMve run performance Type 1 motors up to 5k rpm and the Type 3 at 40 in 2nd sounded not even close. 

I agree that 40 in 2nd is no problem for short times, especially with 
your new engine with counterweighted crank.

> We have a gas mileage log in the glove box that goes back 4 years.
> Mileage and fill ups are usually really regular (we drive the same
> route every week) and last week gave an anomalous 14mpg from 4 days of
> driving which is why I mentioned it.

Yes, 14 is bad. That's the number that we can understand.

> We didn´t ground wire 18 when doing our "unplug" tests yesterday.
> Where would be a good place to ground it to? What even is the true function of that wire? 

 Check the voltage on that wire when it is disconnected and the 
engine is running. I don't know if it goes high or low when 
disconnected. When connected, it is driven high when the solenoid is 
energized and held low (grounded thru the solenoid) at all other 
times. If it drifts high with the engine running and the wire 
disconnected, then you'll have to ground it to get meaningful 
results. You'll have to be creative about a ground. Just a little 
alligator clip lead from Radio Shack would do. You know you have a 
good ground if the voltage on the wire now measures zero with the 
engine running.

The pressure switch is supposed to give extra enrichment under full 
load (WOT.) There are 2 different versions of internal construction, 
and I've seen one with a broken spring inside. That would really 
screw things up. They are easy to open up, but you'll have to remove 
it to do that. It takes a 10 mm socket with a small OD to do this.

> Driving-wise, the only complaint we have is leaning out not under WOT
> but on the way up to WOT. With the AFR gauge installed we might see
> cruise #´s of 13-14 but acceleration #´s of 15-17 and then 12-14 when
> we assume the full load switch kicks in. But yesterday without the
> load switch connected we were richer under acceleration than with it
> connected! ItTMs all kind of dizzying and without a bunch of factory
> graphs and values to look at, itTMs all rather vague! 

Yeah, let's take a look inside the pressure switch! You can suck on 
the inlet and watch, and check, the switch action. There may be 
something weird going on there. If you can take some vacuum readings, 
I should be able to compare them with ones I have here. Sounds like 
yours could be switching later than it should. Or maybe it's 
switching back and forth randomly....  

Okay, all this weird info made me wonder if I had the pressure switch 
logic backwards, so I just went down and checked one. Here's what you 
should find:

Under vacuum the switch should be open, infinite resistance. This is 
what you should have at idle and most of the time while driving. 
Unplugging the electrical connector puts it in this state that's why 
I suggested that you unplug it.

At or near atmospheric pressure the switch should be closed, ~zero 
resistance. This is what you should have when the engine is not 
running or under hard acceleration. It's probably like this when 
cranking, trying to start, too.

Yeah, that's the way I thought it was.

Did you check this when you had the Bosch tester?

You adjusted the pressure sensor CCW. How far?

-- 
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Jim Adney, jadney at vwtype3.org
Madison, Wisconsin, USA
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