Phil Hof phil.hof at ostronic.org
Thu Apr 27 20:36:34 PDT 2017

Before adjusting the MPS, make sure there are no vacuum leaks anywhere.  Missing even one and then adjusting the MPS will drive you batty and it won’t run right.  There are over a dozen potential leaks and they All matter, especially with an automatic.  Contrary to intuition, leaks that let in air will make it run richer, not leaner.

Next, check that the MPS holds vacuum, and also check all sensor and circuit resistances against the Bentley limits.

Then check that ignition is spot on (static, mechanical and vacuum portions, as well as steadiness), and that you aren’t running platinum plugs.

When all this is 100% set right, only then can you think of adjusting the MPS!

Altitude isn’t a factor on your car.  The ’71 has an aneroid barometer built into the MPS that compensates for altitude pretty well.

You will need an air-fuel meter, which will cost you a couple hundies and some friendly welder help..  It is hard enough with this, and harder to try “by ear.”

There are three somewhat interdependent adjustments, and it requires either partial disassembly each time, or a special kit with a hollow end plug/full load stop and a hollow wrench, plus a slim screwdriver that fits into it.  It’s part of a kit that includes a new copper diaphragm and runs about three bills.

So before you try to adjust the MPS, please describe how it is running rich… at idle, cruise, power, and/or transition?

Has this particular MPS been tampered with?  Is the epoxy over the plus/stop still there?


> ------------------------------
> Message: 4
> Date: Thu, 27 Apr 2017 16:22:53 -0400 (EDT)
> From: KENNETH ROGERS <kensue356 at cableone.net>
> To: type3 at vwtype3.org
> Message-ID:
> 	<1276577748.7467833.1493324573122.JavaMail.zimbra at cableone.net>
> Content-Type: text/plain; charset="utf-8"
> I am so happy to be communicating with this great group again. 
> Question: 
> The pressure sensor on a 1971 vw Type 3 FI squareback automatic, 1640cc stock everything. After setting fuel pressure regulator to 28 pounds and making sure throttle valve switch is in correct position and everything is correctly adjusted, can I fine tune this pressure sensor? It is running rich. 
> I have monkeyed with this in the past with a sick running motor so it is out of adjustment. 
> Who has experience on this? I found nothing in the books about adjusting it. Is this where I find a '14 to 1' or higher air ratio at 5000 feet altitude (I live at) using my Sun tail pipe sniffer? Or just find the sweet spot in dialing it in? 
> Kenny Rogers 
> *************************************************

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