123 Distributor Install - post-mortum, MPS was “bad”? But it isn’t? Options

[FlacaProductions]

Many of you followed and helped as I attempted to install a bluetooth 123 distributor in my 74 2.0 here:
http://www.914world.com/bbs2/index.php?sho...=368374&hl=

I can’t thank everyone enough for all of their input.

Car originally ran pretty well but I was installing the 123 to fix a running-warm situation due to a failed vacuum can on the stock distributor. (0231174011 with Pertronix Igniter II) MPS was a clearly opened/modified 0280100041 (done by PO).

The install proved difficult/frustrating (would NOT start) and everything from a bad 123 unit to not accurately finding TDC was suspected.

Luckily, I had recently picked up a stock/unopened 0280100043 MPS and after installing and re-installing the 123 multiple times, confirming TDC, etc, etc, I was desperate.

I know you’re not supposed to just “throw” parts at a problem, but in a last-ditch effort I dropped in the “new” 043 MPS and it immediately fired up. Runs GREAT.

This is where things get confusing:
The 041 tests ok out of the car - 15lbs of vac for 30 mins and I get 95 ohms across 7 and 15 and 345 ohms across 8 and 10.

The 041 had obviously been opened and I assume modified/repaired - but again - it ran fine in conjunction with the stock distributor w/Pertronix.

Why would it run just “fine” (outside of the conditions caused by the failed distributor vacuum can) with the stock distributor/041 MPS and yet not even come close to starting with the 123/041 combo, and then run great with the 123/043 setup?

Now i’m on to dialing in/playing with curves - I’ve found really nice performance with one that Pete Stout posted. Even though his is a 1.8, it made a noticeable difference to the point where my nephew remarked that it was really “snappy” now.

Other than that, I think i’m going to pop the 2 female pins out of the wiring harness that the 123 yellow and white wires plug into and shrink wrap them for a more solid connection. That seems like a weak link.

Additional questions:
- does my original distributor with Pertronix have value to anyone? The Pertronix itself is $100+ new. I can’t see needing to keep it as a backup when the vacuum can has tested bad and the 123’s are seemingly bulletproof once properly installed.
- does my 041 MPS have value? Should I open it up or have it tested and potentially rebuilt? As it sits, it totally immobilizes my 914 when installed. Is there potential to have it turned into a viable backup?

Again - thanks to The World. I learned a lot during this process and could NOT have gotten to the other side without all the input here!

[emerygt350]

You should map out the curve on the 041 mps, just for our collective d-jet knowledge.

I am starting to wish I bought the Bluetooth 123.. playing with curves sounds like fun.

[technicalninja]

I'd open it up for the experience ALONE!

I'd try to determine what failed and why.

Ninja proverb:
Hunt the ROOT, find it, and, if possible, come up with improvements.

I'd look at that diaphragm under magnification.

[technicalninja]

I'd mark the crap out of the housings and keep all hardware in their original positions.
I'd be methodical in my tear down as to allow "exact" reconstruction.
I'd take pictures...

Might not matter, but if it does, you'll be pissed at yourself for not indexing everything...

[FlacaProductions]

Yes - My Mityvac is in Indiana so I won't be able to do it until July but I will map it out to the best of my ability and that of my tools/meter.

I'd love to tear it down - yes - maybe a Tangerine MPS kit will bring it back to life depending on what I find.

Still curious as to why the 041/123 combo was DOA and the 043/123 is magic.

[Superhawk996]

I'd open it up for the experience ALONE!

(IMG:style_emoticons/default/agree.gif)

I’ve got one open at the moment.

Bad diaphragm being replaced. But I also found a stripped 4mm screw that holds and seals the diaphragm retaining ring. Someone was in here before (even though epoxy plug over adjustment screw was intact) and thought a 4mm screw needed about 100 lb-ft of torque? Stripped at factory? (IMG:style_emoticons/default/confused24.gif) There’s no telling what you might find.

Awaiting 4mm Heli-coil.

[Superhawk996]

Still curious as to why the 041/123 combo was DOA and the 043/123 is magic.

My bet is coincidental but simultaneous failure. Only way to validate is go back and try the OEM dizzy and your original 041 MPS. Should run if all is as stated.

[FlacaProductions]

It's interesting as my preliminary tests show it's "good" - you doing the replacement with the Tangerine diaphragm?

I'm not quite curious enough to put the OEM dizzy and 041 back in....i have PTSD from this install...

[Superhawk996]

It's interesting as my preliminary tests show it's "good" - you doing the replacement with the Tangerine diaphragm?

I'm not quite curious enough to put the OEM dizzy and 041 back in....i have PTSD from this install...

Yes - Tangerine diaphragm. Chris posted previously he’s seen instances of holds vacuum but had crack and didn’t respond correctly. I could see how this can happen from a hairline fatigue point that isn’t yet leaking but has substantially weakened the diaphragm. Likewise, full vacuum isn’t the same as starting/cranking and idle so full vacuum doesn’t “prove out” the whole operational range the MPS needs to run things properly. Who knows - possible that aneroid can has failed? That would only show up graphing the MPS curve across full range of vacuum? (IMG:style_emoticons/default/confused24.gif) I’m learning here too.


(IMG:style_emoticons/default/lol-2.gif) don’t blame you on the PTSD and not wanting to close out that experiment just to prove a point

[JeffBowlsby]

If I understand correctly, 3 items were replaced. Dizzy, trigger points, and a correct-for-a-1974-2.0L MPS. Car did not run previously, now it does. One or more of those three components or their combination, was bad. All three are crucial components, and if even one was bad the engine will not start. Whatever was done works now, with known good components, so leave it alone and drive!

[FlacaProductions]

Yeah - stuff that came out ain't goin' back in! I'll take a good look at what's out, though...

[FlacaProductions]

(FINAL?!) UPDATE:
My original intent was to install the 123 to replace the stock distributor because I thought that the vacuum can wasn't holding vacuum.

THIS HAS PROVEN TO BE AN UNTRUE/INACCURATE DIAGNOSIS.

I started looking at the distributor lately and discovered that I had replaced a missing attachment screw on the vacuum can with one that was too long and was not allowing the vacuum advance and retard to move the plates.

I have replaced the screw with one of appropriate length and all is good with the distributor.

It's now in the Classifieds for $125 - heck the Pertronix is $150 new!

Now - I'm not mad because the 123 is a great piece of kit and I ended up putting in the "correct" MPS and the car has never run better. I just wanted to put this in the thread because some things aren't always as they appear.....

[Superhawk996]

Appreciate the update. That helps make some sense of this.

I think one of the biggest issues that face all of us is that of false assumptions. In my career of 40+ years of troubleshooting both electronics and mechanical systems, false assumptions cause the most problems and are the largest waste of time.

Early on in USAF tech school we were taught to troubleshoot by starting with a “de-brief” of what the situation was, symptoms, tests done, etc. Basics were to re-verify what you were told before starting your own troubleshooting. If you immediately started trouble shooting based off the information given - you would be intentionally led astray and would fail the exercise either by coming to the wrong root cause conclusion or by simply running out of time chasing your tail thinking something you were told was true or had been verified and trying to make sense of conflicting symptoms.

The long screw serves as a brilliant example of how this happens. A good lesson for all of us to heed.

[914_teener]

Appreciate the update. That helps make some sense of this.

I think one of the biggest issues that face all of us is that of false assumptions. In my career of 40+ years of troubleshooting both electronics and mechanical systems, false assumptions cause the most problems and are the largest waste of time.

Early on in USAF tech school we were taught to troubleshoot by starting with a “de-brief” of what the situation was, symptoms, tests done, etc. Basics were to re-verify what you were told before starting your own troubleshooting. If you immediately started trouble shooting based off the information given - you would be intentionally led astray and would fail the exercise either by coming to the wrong root cause conclusion or by simply running out of time chasing your tail thinking something you were told was true or had been verified and trying to make sense of conflicting symptoms.

The long screw serves as a brilliant example of how this happens. A good lesson for all of us to heed.

In engineering school one of my classes was industrial engineering.

"Tribal knowledge" meaning an assumption without data ,can be very dangerous. Boeing has found that out the hard way.

So no inspection of the screw or investigation led to an assumption. If the vacumm can was suspected, a vacuum test would be performed (at a design HG) and leak down test ALONG with a visual to make sure the arm was advancing the plate enough.

Jeff said it simply as well.

Assumptions lead to testing and inspections and then data.


Now drive it like you stole it.