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> MPS, Rebuilding the MPS
Ron914
post May 8 2025, 05:06 PM
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From: Huntington Beach,Ca
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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 .
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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 .
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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 .
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Ron914
post Sep 8 2025, 12:05 PM
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From: Huntington Beach,Ca
Member No.: 26,487
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Getting back to my D-Jet issue , walking away is what I do when things get a bit frustrating , coming up with another plan .
Well I purchased this test device for D-Jet from a member here . Although I have tested with my DVM these connections /values it really made it easier to take the readings .
I noticed when I checked my fuel pressure after 5 minutes I had a loss of 2 psi , not sure if this indicates a leak somewhere but I do still have a gassy smell inside my car . I have replaced the old plastic lines with SS ones and all fuel hose has been replaced with Cohline braided hose from the bird . The fuel tank was also removed and checked but I did not do a pressure test on it , the gasket inside the fuel cap was also replaced .( this is a separate issue and doubt it is the reason for my engine cutting out at 212F) .
I also figured out why my Dakota digital was reading so low ( it was in Celsius mode ) so when I said the motor quits running at 100 that really is 212F . I had to call their customer service and have them send out a new plug as one of the sensor leads has come out of the factory plug .I have videos of motor start up and bad running but I don't think I will use YouTube to post as this makes all videos public . My coil seemed hot but I figured this was probably due to leaving my ignition on too long during voltage checks .I currently have the decel valve disconnected and bypassed , vacuum line disconnected from distributor . I can send a email or text the video to @Superhawk996 or @emerygt350 if you would like.

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My test results
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Ron914   MPS   May 8 2025, 05:06 PM
Superhawk996   There you have it, now you know why it was a leake...   May 8 2025, 06:36 PM
Ron914   There you have it, now you know why it was a leak...   May 8 2025, 06:58 PM
MDTerp   There you have it, now you know why it was a leak...   May 8 2025, 08:17 PM
Ron914   Well all done . I must say it was easier than I th...   May 8 2025, 08:30 PM
JeffBowlsby   Another documented case of a completely fractured ...   May 8 2025, 10:15 PM
emerygt350   Way to go. I mean you are disassembling the most ...   May 9 2025, 06:57 AM
rjames   Crazy that it could hold vacuum at all!   May 9 2025, 10:01 AM
Superhawk996   Crazy that it could hold vacuum at all! Mine...   May 9 2025, 01:24 PM
Ron914   Well I was optimistic that my car was going to run...   May 9 2025, 05:37 PM
emerygt350   You can pull the wires one at a time till you find...   May 9 2025, 06:09 PM
Superhawk996   This is going to be a tough love post. When you ...   May 9 2025, 07:26 PM
Ron914   This is going to be a tough love post. When you...   May 12 2025, 03:17 PM
Superhawk996   I’m going to post this over here This is anoth...   May 9 2025, 07:53 PM
rjames   What Hawk said. And you just rebuilt your MPS, so...   May 9 2025, 08:17 PM
Ron914   Thank you Superhawk and emery ,You are correct in...   May 9 2025, 08:27 PM
emerygt350   Once it is all back together, remember that inner ...   May 10 2025, 04:22 AM
emerygt350   Don't worry about TDC, the distributor only go...   May 12 2025, 05:50 PM
Ron914   Don't worry about TDC, the distributor only g...   May 12 2025, 06:57 PM
fiacra   If only I didn't live in California I would b...   May 12 2025, 08:03 PM
Ron914   If only I didn't live in California I would ...   May 12 2025, 09:46 PM
Superhawk996   First on the to do list MPS is leaking down too ...   May 12 2025, 06:57 PM
Ron914   First on the to do list MPS is leaking down too...   May 12 2025, 09:44 PM
Superhawk996   Aren’t other guys in CA running 123’s? Regard...   May 12 2025, 07:00 PM
Superhawk996   Also with respect to the dizzy vs timing Yes - s...   May 12 2025, 07:19 PM
Ron914   As far as putting a 123 in my California car I was...   May 12 2025, 09:11 PM
Superhawk996   I would open the MPS back up. I can post time lap...   May 13 2025, 08:37 AM
Ron914   I would open the MPS back up. I can post time la...   May 13 2025, 10:19 AM
emerygt350   I agree with hawk. The first time I rebuilt mine ...   May 13 2025, 10:02 AM
fiacra   Ron got that Pertronix from me, and yes it is olde...   May 13 2025, 01:34 PM
Ron914   Ron got that Pertronix from me, and yes it is old...   May 13 2025, 03:25 PM
fiacra   If I was to eventually pass a smog test I could t...   May 13 2025, 07:00 PM
Superhawk996   Remote stater switch is about $15 and pricele...   May 13 2025, 01:35 PM
Superhawk996   Z0n2aTFRMiI?si=W8rg02X2Kwp4r_54 I cut this off at...   May 13 2025, 02:40 PM
rjames   There is an art (and likely some luck) in getting ...   May 13 2025, 03:00 PM
Ron914   There is an art (and likely some luck) in getting...   May 13 2025, 03:10 PM
SVG223   Good luck with this, my MPS is leaking too, watchi...   May 13 2025, 04:18 PM
Ron914   [quote name='SVG223' post='3205335...   May 13 2025, 09:01 PM
JeffBowlsby   Just a heads up, there are other places the MPS ca...   May 13 2025, 06:18 PM
JeffBowlsby   dbl dbl.   May 13 2025, 06:18 PM
Ron914   Well I opened my MPS and found that the order in w...   May 14 2025, 07:57 AM
ChrisFoley   I switched from a round o-ring to square in my kit...   May 14 2025, 10:45 AM
Ron914   I switched from a round o-ring to square in my ki...   May 14 2025, 12:07 PM
emerygt350   I think that is exactly what I did the first time ...   May 14 2025, 11:54 AM
Ron914   I think that is exactly what I did the first time...   May 14 2025, 12:08 PM
Ron914   I think that is exactly what I did the first time...   May 14 2025, 04:36 PM
emerygt350   I think that is exactly what I did the first tim...   May 14 2025, 04:48 PM
emerygt350   Although no leak is best. That leak is pretty slow...   May 14 2025, 12:29 PM
Superhawk996   Get rid of the adapters Go straight from vacuum ...   May 14 2025, 01:41 PM
Ron914   Get rid of the adapters Go straight from vacuum...   May 14 2025, 04:32 PM
Superhawk996   [quote name='Superhawk996' post='3205480' date='M...   May 14 2025, 05:58 PM
rjames   [quote name='Superhawk996' post='3205480' date='...   May 14 2025, 06:20 PM
Ron914   [quote name='Superhawk996' post='3205480' date='...   May 15 2025, 12:29 PM
SVG223   Mine takes 45 seconds to leak from 10 in/hg to 5 i...   May 14 2025, 03:12 PM
emerygt350   Mine takes 45 seconds to leak from 10 in/hg to 5 ...   May 14 2025, 04:18 PM
ChrisFoley   Problem with the old square o-ring is that it will...   May 15 2025, 08:57 AM
Ron914   Problem with the old square o-ring is that it wil...   May 18 2025, 01:41 PM
Superhawk996   :trophy: you’re getting there!   May 18 2025, 02:17 PM
rjames   No need to crack it open again to adjust if you ha...   May 18 2025, 03:12 PM
Ron914   Well after putting the old square O ring back in ...   May 24 2025, 08:40 AM
rjames   Put the ecu knob back in the middle and adjust onl...   May 24 2025, 09:16 AM
Ron914   Put the ecu knob back in the middle and adjust on...   May 24 2025, 10:27 AM
rjames   Put the ecu knob back in the middle and adjust o...   May 27 2025, 06:30 PM
Superhawk996   I need to add that I must set my timing still , ...   May 28 2025, 05:36 AM
Ron914   I need to add that I must set my timing still ,...   May 29 2025, 06:25 PM
JeffBowlsby   Of those three pairs of wires, one is grounds for ...   May 24 2025, 10:49 AM
Ron914   Of those three pairs of wires, 1 iz grounds did t...   May 24 2025, 11:09 AM
Superhawk996   Those grounds are mighty crispy and corroded and a...   May 28 2025, 05:31 AM
Superhawk996   My bad Ron I completely forgot you were running P...   May 30 2025, 04:15 AM
Ron914   Hello to all that have been helping me getting my ...   Aug 19 2025, 03:10 PM
Superhawk996   Hi Ron, Glad you haven’t given up. Two thi...   Aug 19 2025, 04:35 PM
Superhawk996   Here’s a little experiment you can do before the...   Aug 19 2025, 04:46 PM
Ron914   I will try your suggestions later today and post t...   Aug 19 2025, 05:03 PM
emerygt350   I will try your suggestions later today and post ...   Aug 19 2025, 05:20 PM
Ron914   I will try your suggestions later today and post...   Aug 19 2025, 05:30 PM
Superhawk996   I will try your suggestions later today and post ...   Aug 19 2025, 07:50 PM
Ron914   @Superhawk996 I made the checks you requested and...   Aug 19 2025, 10:39 PM
ctc911ctc   Audio engineers Fluke! [b]@[url=http://www....   Aug 20 2025, 09:52 AM
Superhawk996   Good job and report out on the testing Ron. :head...   Aug 19 2025, 11:33 PM
Ron914   Good job and report out on the testing Ron. :hea...   Aug 20 2025, 08:12 AM
Ron914   I made the tool needed to remove my CHT and I noti...   Aug 25 2025, 12:30 PM
Ron914   I decided to verify the condition of the CHT wire ...   Aug 25 2025, 12:46 PM
Superhawk996   Flukes rarely go bad New leads are much cheaper ...   Aug 25 2025, 12:59 PM
ctc911ctc   Flukes rarely go bad ^^^^^^^^^^^^^^^^ :agree:...   Aug 25 2025, 01:27 PM
Ron914   Yes the car is still stalling after 5-10 minutes o...   Aug 25 2025, 01:44 PM
Superhawk996   Yes the car is still stalling after 5-10 minutes ...   Aug 25 2025, 03:54 PM
Ron914   Yes the car is still stalling after 5-10 minutes...   Aug 25 2025, 05:39 PM
emerygt350   Your not at a higher altitude are you? 16 isnt en...   Aug 25 2025, 02:04 PM
Ron914   Your not at a higher altitude are you? 16 isnt e...   Aug 25 2025, 02:32 PM
emerygt350   At the least you can resell it. Just remember, th...   Aug 25 2025, 03:22 PM
cgnj   I'm curious where these diaphragms are being s...   Aug 25 2025, 03:29 PM
emerygt350   Go for it! I love a carb too but this is like ...   Aug 25 2025, 03:44 PM
Superhawk996   Ah - OK so you have a good wire from sensor to ECU...   Aug 25 2025, 07:03 PM
emerygt350   I always do a visual before hand as well. Mps vac...   Aug 26 2025, 05:37 AM
Puebloswatcop   Where can I obtain a MPS re-build kit with a new d...   Aug 26 2025, 06:46 AM
FlacaProductions   Unless someone is going to sell you from their sta...   Aug 26 2025, 07:17 AM
Ron914   Getting back to my D-Jet issue , walking away is w...   Sep 8 2025, 12:05 PM
rjames   I'm confused (happens often). On August 19th y...   Sep 8 2025, 12:38 PM
Ron914   I'm confused (happens often). On August 19th ...   Sep 8 2025, 03:00 PM
emerygt350   A 2 psi drop would lean the mix quite a bit. That...   Sep 8 2025, 02:21 PM
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