MPS mystery, huh Options

[r3dplanet]

Last winter I had some fun rebuilding my MPS unit, which is for a '73 1.7 liter engine. The MPS part number ends with 049.

According to the calibration tests on the pbanders website in conjunction with my trusty Meterman LCR55 and MityVac, the unit is perfectly calibrated. It holds vacuum without issue. The readings at 15, 4, and 0 in.Hg all match perfectly. And I mean perfectly. No variation from what the LCR55 shows to the pbanders table.

The mystery is that when I hook it up to the car the engine won't start. It tries to start and I can sort of force to keep going by blipping the gas, but it won't idle on its own. However, when I install another verified trashed out unit, the car starts right up and idles and climbs smoothly.

Um. Huh. I'm hoping that there's some other adjustment elsewhere in the system that my tired brain won't remember. Somehow maybe my car is adjusted to work around the (leaky) old MPS? Or maybe I didn't rebuild the MPS correctly. But it was in and out of the thing for days and I'm convinced the physical operation is correct. But I'm always willing to be wrong.

Confused.

-m.

[stugray]

I assume the 'known signal into the primary' means setting the vacuum at known levels

No, what I mean is that you would inject a sinusoid drive signal into the primary side inputs and look at the amplitude of the signal that comes out of the secondary, then adjust the vacuum like you did before to the three vacuum levels.

Of course the experiment would need to be done with a NOS MPS just like Paul Anders did.

Sounds like you are deeper into the theory and electronics than me

Sorry to sound like a nerd, but I helped test the board that measures the LVDTs that are used to focus the Kepler spacecraft telescope. They can meause linear changes at the micron level.

Oh wait, how is your CHT? hooked up, right reading at cold???

I just measured the CHT sensor and determined that it is a type 2252 Thermistor if anyone is interested. That means it should read 2252 Ohms at 25 degrees C.

Stu