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Re: [T3] Newbie--more data on FI

On 17 Feb 2005 at 14:08, Jim Showker wrote:

> Checked the diaphragm in the pressure sensor (actually manifold vaccum
> sensor) and it seems like no leak.


> Checked the Temp Sensor I and Temp sensor II, they read 3.4K and 630 ohm at
> 35F ambient.

Sounds reasonable.

> Cleaned all connectors on the engine with Corrosion X, a miracle corrosion
> cleaner. Reconnected the two temp sensors.

Possibly unimportant, but can't hurt. One thing I find commonly is that the 
little famale connector pins for the injectors don't seem to be tight any more. 
I often carefully remove them from the white plastic connector bodies and 
squeeze them a TINY bit, just to tighten them up. Check them on an injector 
before you put them back in the connector body.

If you're not already familiar with how to remove pins like these, just ask 
before you mess something up.

> Started engine again.  Started right up this time. seemed a little rich, let
> it warm up to see if it was cold enrichment.  When warm the motor idled very
> well, with no black smoke.  If I would get in the throttle to rev it up, the
> exhaust would blacken, and do an overich backfire now and then.  While at
> fast idle, I pulled the hose off the pressure sensor and the engine
> immediately went very rich, black smoke like when we ran it before.  I
> pulled the connector off the pressure switch, no change.  Pulled the
> connector off the throttle switch, no change.  With the engine off I can
> hear the throttle switch click like it is suppose to when you move it off
> the stop.

You might want to check the pressure switch and verify that it actually has 2 
states, and that it is in the vacuum state with the engine running. I can never 
remember which way this goes, but as long as it changes you should be fine. You 
should also verify that it holds vacuum.  

> I studied the Bentley manual last night.  I understand fuel injection fairly
> well, as I have a plane I built with a two stroke fuel injected Hirth
> (german) engine in it.  I have modified that motor quite a bit and have
> completely reprogrammed the ECU (control module) to work with my mods.  It
> seems to me now that on this Squareback, that I basically checked everything
> and it's working or not affecting (pressure sw., throttle sw.) normal
> running.  The electrical connections were probly not up to snuff.  The only
> thing left to my inexperienced way of thinking at this point would be the
> fuel pressure regulator.  I don't think it's ever been changed and it seems
> to me it could be off after 36 years. The fuel pump has been changed.  If it
> were regulating fuel pressure to some higher level, all running ranges would
> be rich.

Yes, good point, but the pressure regulators don't seem to wear out. They DO, 
however, get misadjusted by people. You'll need a gauge that goes to 30 lbs or 
so to check this. Set it to 28 psi. You may find that it has been cranked to 40 
psi or so.

You might also want to check that the DC power getting to the FI system is what 
it should be. There are a pair of white FI wires in a double connector that 
pick up power from 2 wires from the main wiring harness. They are located at 
the LF corner of the engine compartment, maybe somewhere in front (front is 
front) of the pressure sensor. Measure the voltage there, just to be sure.

You should be getting 14.1-14.4V at med rpm. 

If you haven't already done it, it might be a good idea to adj the valves, dwell, and timing.

> However, what do you think? I am so happy that this is working out.

Sounds pretty promising to me.

> Thanks for your help.  Aren't news groups just the most amazing thing?

We've got a great group of people here.  ;-)

Jim Adney, jadney@vwtype3.org
Madison, Wisconsin, USA

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