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Posted by: bowzer Aug 16 2018, 10:34 AM

Im looking for info on possibly repairing my MPS, and what better way to gain info than this site.The wealth of knowledge Ive learned on here in a short time is priceless,and fun.everyone likes a short story,so..several years ago I picked up a pretty nice 73 1.7.and with the help of several on here I got it in really good condition,for a driver.Im a Honda-Acura mechanic so I pretty much know my way around most related issues.after several years of ownership,I got the idea that a 2.0 would be a sweet swap from the 1.7.problem that I found was that most had been changed to carb.fast forward,I was just browsing this site and came across a complete 2.0 with the F I intact.The sellers description was that it was a strong,non smoking engine,so i jumped on it.It was a pretty enjoyable swap,super easy as everything fell in place, and it fired right up to boot.so a couple weeks ago,on the hottest day in Olympia I drove it home.The hp bump was just enough to make me feel that I made the right decision,except for slight hesitation that I attributed to just needing some tweaking.come to find out that the 1.7 MPS is not compatible with the 1976 2.0 system.I didnt even really know what that grernady looking thing was really.The seller of the 2.0 sent me the correct sensor.I got it yesterday,sucked thru it and wouldnt you know,no vacuum.so....couple of questions.thinking that if its only a matter of replacing the Diaphragm,how hard can that be?its the final adjustment that has led me to ask for anyone who has been down this road,how did you do it?If I could find a good used one,that would be a good option but i do like repairing things if it is an option.as a final thought.tangerine has the kit as well as a spacer that will make a 1.7 MPS compatible with the 2.0 ECU.has anyone used that?I know this is the long way to getting to the question,but its all related reading material.thank you.

Posted by: worn Aug 16 2018, 02:39 PM

QUOTE(bowzer @ Aug 16 2018, 09:34 AM)

Posted by: 76-914 Aug 16 2018, 02:49 PM

Replacing the diaphragm is a piece of cake. Dialing it in is a Horse of a different Color. AFAIK, there are two members here that have the equipment and knowledge to calibrate an MPS. One is Jeff Bowsly. I forget the other but he has a green BW Bus as his avatar and lives in WA. Or you can try it yourself with trial & error approach. There are 3 adjustments. An inner, an outer and one that moves both in unison.

Posted by: Jeff Bowlsby Aug 16 2018, 03:40 PM

Bolting in a new diaphragm is mechanically easy, but is challenging to get the MPS case not to leak (maintain a solid vacuum). I spend most of my time dealing withe various leakage conditions when rebuilding these MPSs and sometime the core is not possible to seal. The coil side and the front end cover of the 1.7L MPS is physically different than the 2.0L , and I have never used the extension ring on a 1.7L to be sure that is will convert to the 2.0L values. It might...I have just never tried it.

You need a Wavetek inductance meter to get reasonably close to the calibration needed (Anders values are not close enough), and ultimately some dyno time or an exhaust gas analyzer to get it spot on for your engine, because of the multitude of variables.

Posted by: BeatNavy Aug 16 2018, 04:12 PM

I think Bleyseng also calibrates these (for a very modest fee). I purchased a cheap Inductance meter and used Anders' values as a baseline. Not long ago I was finally able to secure an unmolested 043 that still held a vacuum, and I used that to baseline my values against Anders' values. I'm not sure how much inductance meters can vary, but I found the values of that stock MPS to be significantly different than his values (posted here, for reference: https://members.rennlist.com/pbanders/manifold_pressure_sensor.htm).

Anyway, I never dyno'ed my car, but I do have an O2 / AFM and used that to try to dial it in reasonably close. I'm happy with the performance.

So I agree - the mechanical part of repairing is not necessarily that hard - although you do need to exercise care to not mess up the WOT stop screw during disassembly. But adjusting it to optimum takes tools, patience, and willingness to experiment. Having someone like Jeff or Bleyseng adjust it for you will get it pretty close.