I don't know what symptoms a failed MPS exhibits other than running poorly as you describe. Have you tested your MPS ability to hold vacuum? The other test involves measuring resistance between terminals on the MPS:
350 ohms between terminal 8 and 10
90 ohms between terminal 7 and 15
Has you MPS been tampered with (adjustment screw cover missing)? I have experimented with several MPSs that have been tampered with comparing them to 2 on hand that have not been tampered with. In each case, the tampered with MPS had been adjusted by a huge amount in the wrong direction for normal wear and tear - tighter (clockwise) is not better on this device.
The very last tuning item that should be attempted on a D-Jet system is the MPS. It should only be made when absolutely everything else is in specifications. The fine tuning adjustment in this case would be a very slight (1/32) counterclockwise turn on a high mileage engine.
The MPS produces an inductance signal between the coils to the ECU. 5 years ago, I made inductance measurements on the 2 factory set MPSs I own. I would love to have a bigger sample size for this. I did this at ambient pressure, -4"Hg and -15"Hg to form a baseline for adjustment of mishandled MPSs. I then corrected that data for altitude since I am at 6000' in ABQ. I was able to revive 2 MPSs back to a decent operating status. That data is attached.
If your MPS passes a vacuum test and the resistance on the coils posted above is in spec, evaluate the possibility of your MPS being improperly adjusted. Source an inductance meter and have a look at your MPS against these numbers.
I am away from home at the moment. I cannot remember my method for taking the readings - across the coils as the resistance test is done, or between the coils 7 to 8; same as 10 to 15. I would have to put that meter on my spare to verify. The readings I took are packaged with each spare I have on hand so I can figure it out.
I will measure the values at the MPS and post the results.
The MPS has not been tempered with - it was running perfectly last time I started it 4 months ago.
It is probably related to fuel supply, but I'm not sure. Where should I test for fuel pressure and delivery and how can I short the fuel pump so it runs with the engine off?
Thanks for clearing up the method of measuring inductance - measure secondary coil at terminals 8 and 10.
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