I've been following this explanation and walkthrough of testing the MPS; https://members.rennlist.com/pbanders/manif...sure_sensor.htm, and I've come across a problem.

My MPS holds vacuum, I've got correct resistance readings on each of the coils, confirmed that they were isolated properly, so I moved on to adjusting. At 15 in. Hg, reading were correct (.71H). I found that I couldn't get the MPS to reach any higher than 0.9 H with my inductance meter at either the 4 in Hg or 0 in. Hg. I pulled the MPS apart, and measured again with it open (nothing pushing back on the main armature shaft with the armature shaft stops in place). The armature stops don't appear to be bent. With the armature shaft pushed in all the way, I get a reading of 0.45 H.

Any thoughts? Is this MPS toast? I can't figure out why it won't register more than 0.9 H, which i way off from 1.44 H.

I can tell you that the meter makes all the difference. My cheap meter #s were way low so I bought the LCR55A. Using the LCR55A I was able to calibrate to the PBanders numbers easily. And as I'm sure guys will point out, tuning to the PBanders #s won't necessarily tune the MPS to your specific engine.

This is quite literally where I am at with my car and had the same issue. #s way off with cheap meter, got the good meter, #s spot on, still runs like a turd.

I'm now in the process of installing a Fuel/Air Meter system this week to help get it dialed in.

Good luck!

For reference below, these were the #s I got with my cheap meter and wasn't able to adjust close to where I needed. The LCR55A solved that problem.

@PBanders Sea Level Numbers for 0"/4"/15" - 1.40/1.20/.74 @20H
My MPS ----------------------------- 0"/4"/15" - .95/.84/.63 @20H

I am not sure why because I know he accessed and characterized NOS and good used, unopened MPSs, but the Anders numbers are known to be too low, even withe the Wavetek meter.

BTW the better vacuum test and calibration uses data points up to 18inHg

Thanks. I wonder why that would make such a big difference. I bought a $35 meter off Amazon because it could arrive the next day and was inexpensive. Guess that was a mistake. At least it is giving me numbers so I have some frame of reference. I set the MPS to your lower set of numbers, and we'll see what happens. I've got a second MPS that is unopened, but leaks. It's numbers at the various test points are about the same as the ones from your cheap meter.

The MPS in the car (73' 2.0) currently is the one with the leak. The motor runs with it, but runs very lean (15-15.5 AFR). The spare, which I'm trying to calibrate, holds air, but someone had messed with the calibration screws. When hooked up to the car, it barely idles, but revs fine. My goal is to calibrate the spare back to stock so the car will run with it, then calibrate it for my engine using an LC-1.

In addition, I've got an ECU tester on the way incase the ECU is the problem. Hopefully it between the MPS testing/adjustment, and the ECU testing, I can get this running lean problem sorted out!

Which ECU tester did you get?

VW 1218 tester. Found it on eBay. Hopefully it works!

Thats a pretty good tester. It tests block functions of the ECU in a simplified way.

So do you have the correct 73 2.0L setup? 037 MPS, 037 ECU, 012 CHT and ballast resistor?

My readings for a 037 MPS at sea level are @15H-.74, 4H-1.26, 0H-1.52 . This is on a Wavetek model the same as Anders. Best way to setup a MPS is too use a O2 setup and adjust the MPS at partload to 13.5-14 AFR and at WOT to 11 AFR then idle to 13.5

Yes. All the correct parts for the 73' 2.0 (ECU, MPS, head temp sender, and ballast resistor. The quick calibration I did last night seemed to be a huge step in the right direction. Head temps reduced by 40-50 degrees (I've got a Dakota Digital cylinder head temp gauge installed). Now the temps are in the high 200s to low 300s for around town driving, and around 350 on the interstate. I've still got some more adjusting to do, but I'm really happy. Much better than before. I had been around 360 driving around town. Didn't even try to drive on the interstate.

Thank you for the AFR numbers! That will be a huge help when I hook the meter up to it for fine tuning.

did the head termperature decrease happen as a result of running a lower A/F ,or in other words more rich? were are your numbers now?
I had been watching the same on mine and now with my CHT adjust, TPS working and resetting my idle and part load a bit more rich (12.5-13.5 with WOT low 12) my head temps yesterday around town with lots of idle and stop go then hard acceleration and spirited driving was staying under 300, from 260-300 at most and oil temps right at 190-200. I think its finally about where it should be, but wont know until I can get out on the highway and also up in the hills too. nice to have the gauges so you know whats going on and if you are headed in the right direction!
anyway good luck keep us posted,

Phil

Yes. I only changed out the MPS, and the lower head temperatures were a result of a richer AFR. My original MPS which had a leak, was causing the engine to run around 15-15.5 AFR. Driving around town resulted in head temperatures around 350-360. Ambient temperatures are in the 90s.

With the rough calibration of my second MPS which doesn't leak, I've gotten head temps down to 295-315 driving around town when the engine is fully warmed up. The oil temperature takes longer now to hit the middle of the stock oil temp gauge (I think around 200 is the middle).

I've still got some fine tuning to do with an AFR meter, but I'm much happier with the temperatures. I also need to install the floor pan air deflectors as a previous owner removed them. That should improve cooling a little bit. My goal is to keep them under 300 for around town driving, but that may be difficult in Texas!

It is nice to have the gauges. I felt like it was a must in hotter climates, and I'm glad I installed them.