MPS, Rebuilding the MPS Options

[FlacaProductions]

If you get really stuck - let me know.
I'm in Santa Monica/Brentwood - happy to meet you somewhere half way and I'll bring my stuff and we'll see if we can get your MPS back to zero/stock setting. I know what it's like to get way off and not be able to find your way back. I now have an LCR meter to get it back to "normal" as a starting point.
Lemme know...

[emerygt350]

If you get really stuck - let me know.
I'm in Santa Monica/Brentwood - happy to meet you somewhere half way and I'll bring my stuff and we'll see if we can get your MPS back to zero/stock setting. I know what it's like to get way off and not be able to find your way back. I now have an LCR meter to get it back to "normal" as a starting point.
Lemme know...

I think this would be a great idea. You have been fighting the same battles. Ron, Chris Foley has some nice instructions as far as getting your mps to a starting point. Did I send those to you? It's just measuring the relationship of the screws to each other. 30 minutes to leak down is good enough for this. Your car should run unless there is a crack and then it would be rich but running.

[Ron914]

A 2 psi drop would lean the mix quite a bit.

That cannot be excluded as a problem. Maybe not 'the' problem but I wonder about it.

Is this very, very repeatable? 212ish every time? Sputters and dies the same way?

Anybody remember the minimum pressure for these injectors? I seem to remember something about not even being able to fire if the psi fall to a particular level.

When the motor cools down I will do another test but nothing is very consistent with this car . I do feel most of my issues now are coming from my MPS .It still does not hold good vacuum for very long . My plug for the Dakota digital needs to be replaced , they are sending me a new one so when I get it installed I will add photos of temp when it stalls .

[Ron914]

If you get really stuck - let me know.
I'm in Santa Monica/Brentwood - happy to meet you somewhere half way and I'll bring my stuff and we'll see if we can get your MPS back to zero/stock setting. I know what it's like to get way off and not be able to find your way back. I now have an LCR meter to get it back to "normal" as a starting point.
Lemme know...

Thank you for the offer . I want to keep messing with it some more and will get back to you if I run into a wall with this . I have a mighty vac and an LCR also but need some values to shoot for to get back to normal .

[FlacaProductions]

Ah - ok - missed the part that you have an LCR.
That - to me - is the key to getting back to zero.

I'm sure you know this already but this is what I did to reset:
https://pbanders.synology.me/914/manifold_p...sure_sensor.htm

page down to: Electronic Calibration Method then go to step 10.

[emerygt350]

Just remember, no faith in the actual lcrs. They are great if you knew what they were when it was running with the lcr in your hand, but trying to use another person's lcrs... Yeah, not so much. They do let you construct a curve, which you can tune to look like anders published curves and then tune to taste using the inner screw.

[rjames]

I'm confused (happens often).
On August 19th you posted:

Car was idling good and I drove it 10-15 miles before removing the MPS to rebuild it . I rebuilt my MPS because it leaked and would not hold vacuum for very long and was told I might as well replace the diaphragm with Chris's rebuild kit since I will need to properly tune my MPS because of the 2056 motor upgrade

I don't see any follow up posts stating that the MPS is not leaking anymore and that you tried tuning before moving on to suspecting the CHT.
If it was running ok before the MPS rebuilt, I'd go back to the MPS.
If it doesn't hold vacuum or is out of tune (usually the case after a rebuild) then it's still suspect as at least a partial cause for your issues.

If I've followed along correctly, when cold, the car starts, the AAR opens, and engine runs at 1400 rpm as expected. After the car warms up and the AAR closes, the idle drops to ~1000 rpms as expected, but stalls soon after and you notice a fuel smell like it's overly rich.

If the MPS is out of tune, or won't hold vacuum, that could be the cause of your overly rich mixture. And it would make sense that with the AAR open it wouldn't stall despite being overly rich because the AAR is adding enough air to compensate. When the AAR closes though, the car is too rich to keep running and stalls.

What am I missing?

An easy way to check the above would be to turn just the inner screw of the MPS clockwise ~1/2 a turn or so to lean it out and see if allows the engine to keep running after the AAR closes. This assumes that your MPS holds vacuum.

My MPS follow up was in page 3 of this long post maybe I should start a new one . I was able to locate a square edged ring and tried replacing to see if it helped my MPS leak down any better but it has not .It stills leaks down from 15inhg to 3 in about 30 minutes . My concern is I have messed with the inner screw settings enough I no longer trust the position it is at .Basically I am still baffled as to why the car doesn't run well after the MPS rebuild ,I suspect the MPS is no longer functioning correctly . I will try your suggestion of turning the inner screw 1/2 turn CW .

After a rebuild, the MPS needs to be tuned! Small adjustments can have a HUGE impact on fuel mixture and can result in exactly what you're experiencing. If it truly takes 30 minutes to lose vacuum, then you should be able to get the car running ok, but idle may not be steady.

The outer screw is best set on the bench and the inner screw best set while the car is running. From there, fine tune with an wide-band sensor. That said, just turning the inner screw clockwise a bit should offer clues as to if it was just running too rich or not with the MPS being the cause or at least a contributor. You will need the adjustment tools to ensure you're only turning the inner screw and not turning both the inner screw and outer screw at the same time. (note that the outer screw is not the same as the full-load stop screw).

[Superhawk996]

Ron I’m late to this post. Don’t really have anything to add. Focus on the MPS as Has been suggested.

If necessary - retune it on the bench per the initial set up instructions & Anders curve and then tweak it in car as Rjames has suggested and see what symptoms change.

The find on the Dakota reading in Celsius makes perfect sense. Depending on what lead is loose, you may actually be running a bit warmer than what the gauge was saying and when fixed I’m betting your CHT measured temp, measured resistance, and oil temp begin to converge in a sensible way. Just keep in mind oil temps lag head temp by tens of minutes if not longer when cold starting and idling.

Can’t remember do you have a Wideband O2 sensor installed to monitor?

[Ron914]

Ron I’m late to this post. Don’t really have anything to add. Focus on the MPS as Has been suggested.

If necessary - retune it on the bench per the initial set up instructions & Anders curve and then tweak it in car as Rjames has suggested and see what symptoms change.

The find on the Dakota reading in Celsius makes perfect sense. Depending on what lead is loose, you may actually be running a bit warmer than what the gauge was saying and when fixed I’m betting your CHT measured temp, measured resistance, and oil temp begin to converge in a sensible way. Just keep in mind oil temps lag head temp by tens of minutes if not longer when cold starting and idling.

Can’t remember do you have a Wideband O2 sensor installed to monitor?

I need to be able to drive the car to a muffler shop to have a bung welded in still so No

[Ron914]

If you get really stuck - let me know.
I'm in Santa Monica/Brentwood - happy to meet you somewhere half way and I'll bring my stuff and we'll see if we can get your MPS back to zero/stock setting. I know what it's like to get way off and not be able to find your way back. I now have an LCR meter to get it back to "normal" as a starting point.
Lemme know...

I think this would be a great idea. You have been fighting the same battles. Ron, Chris Foley has some nice instructions as far as getting your mps to a starting point. Did I send those to you? It's just measuring the relationship of the screws to each other. 30 minutes to leak down is good enough for this. Your car should run unless there is a crack and then it would be rich but running.

@emerygt350
I know you sent them but I cannot find the email ,coud you send it again please .
Thank you

[emerygt350]

I can dig around tomorrow and find them.