MPS, Rebuilding the MPS Options

[Ron914]

Hello to all who have helped me with this project . @emerygt350 ,@TJB/914, @Superhawk996 , @ChrisFoley , @rjames , @MDTerp
I am in the middle of rebuilding my MPS and have a couple of comments and questions .
First when I opened up the unit I found the most difficult job was removing the rivets holding the two halves together.
When I removed the retainer plate to take out the old diaphragm it was in two pieces .

I needed to take two measurements since I was replacing the stop screw , I needed to measure the the stop screw protrusion into the housing . The instruction sheet sent to me by a member had the measurements he must have made when rebuilding his MPS . His stop screw protrusion was 1.97mm and mine only measured 1.72mm.
His inner/outer screw assembly depth in the old diaphragm measured 6.51mm .
Here's one of my questions ?
when I measured mine I got two measurements depth to inner/outer screw assembly was 4.03
and depth to the washer outside the inner/outer screw assembly was 5.46mm.
Again there is a difference and since mine was never accessed before (epoxy over screw was not disturbed) is the difference in measurements ok and which measurement should I use I will try to attach a photo or two to help with my question.
this one .

I have not touched either of these measurements yet and awaiting any help/comments.
I think it's this one to the washer on diaphragm .

[Superhawk996]

Hi Ron,

Glad you haven’t given up.

Two things come to mind:

“TS2 CHT -@68F 5.3K ohms
@79F 3.6K ohms
once the CHT temp gauge (Dakota digital) reaches 100-104F the car just shuts off and does not want to restart , @ this time my readings between terminal 23 & ground reads
74.1 ohms., once car cools down it will start again.”


These are some whacky values cold through warm up. CHT resistance is a little too high at 68F ambient, about right at 79F, but that it seems to drops way too much by 100F to 74 ohms on the Dakota is weird.

At 100F CHT the sensor should be more like 1200 ohms. If you are truly dropping to 74 ohms at 100F that is going to go lean and I wouldn’t be surprised it stalls.

Here’s the chart of how CHT should respond for the 012 CHT


1) Are you sure that you are measuring OHMs properly? Use your meter to measure a known resistor (like the ballast reaistor) and make sure the meter agrees with a known resistance.


2) Are you sure the Dakota is reading CHT properly? Use a secondary Infra Red thermometer or other thermometer to measure head temp and ensure your Dakota gauge is reading correctly.

The first thing I would do if all the above is true is swap the CHT for the new one. Before I install the new one, I’d check it on the bench to make sure it’s measuring properly. You can use a cup of boiling water to measure the new CHT resistance hot around 212F or so.