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.

[Ron914]

I can dig around tomorrow and find them.

Hello Emery,
@emerygt350 , @Superhawk996 @JeffBowlsby @rjames
I found my notes with the settings from Chris you gave me . I decided to take the MPS apart again and set to those values and put the MPS back together and low and behold for unknown reasons it now holds a vacuum . Pulled 17InHg and waited , it took 1.5hrs to drop to 15 then it continued to drop slowly after a total of 3.5hrs it still read 12InHg . I installed it in my car and tried to start , it started but was running poorly so like that squirrel on meth I started turning the inner screw a bit and this made no difference so I turned CW & CCW more until I no longer knew where I was at . So I took the MPS apart again ( probably my 30th time or more) reset to Chris's starting point of Large screw protruding 0.40"/1mm and center pin/inner screw to 0.200"/5mm beyond the big screw and once again the MPS will not hold pressure . Side note I was able to secure a proper flat o-ring from a member here. I really think this car has a demon ,took it apart several times and still cannot get it to hold vacuum any more.
:
Ok let's move on :
My Questions:

. I was able to borrow from another local members spare MPS and ECU for testing so I can eliminate the MPS or ECU from being the cause of a bad to not starting motor . I need some expert advise before I go any further .
I have a 1976 2.0L D-jet set up , my MPS has the number 0280 100 043
I have to swap out a !.7L D-Jet MPS # 0280 100 049
Is it ok to use them for testing ?
My ECU has been rebuilt from sticker on it and has VW part # 039 906 021AV or 0280 000 052 is what it looks like on the tag
The part I have to substitute is #039 906 021 or 0 280 000 044

[rjames]

If I’m reading the chart on Ander’s site correctly, the your substitute MPS will work but not the ECU.

After you got your MPS to seal and you tried adjusting the inner screw with it in the car, were you using the adjustment tools to make sure that the outer screw wasn’t turning while adjusting the inner screw?
If you really only adjusted the inner screw, unless the MPS was set for way too rich a mixture and you only turned the screw counter clockwise (or vice versa), you should’ve noticed a change, suggesting another cause, but still not ruling out the MPS yet.

BTW, I don’t trust any MPS or ECU that has a rebuilt sticker on it. The ones I’ve seen weee done some time ago and none of them worked. Especially true of the MPSs that were rebuilt before quality replacement diaphragms were available. I’d only trust a rebuilt MPS if one of our esteemed members here had rebuilt it.

[emerygt350]

I think we need more info as well. Not well can mean so many things. I suspect there is something outside the mps at this point. As I have said before, my car idles and runs without the vacuum even connected to the mps. Not great but not so bad I notice before I back out of the driveway.

Also, if I spray starter fluid down the throttle body, the car (any car) should run like a champ. If your car runs badly with a spritz of starter fluid that really points more toward an ignition or timing issue. Luckily for us (unlike my mustang) the ECU has nothing to do with spark, so if it runs badly on starter fluid you can provisionally exclude the ECU as the culprit and really focus on timing, ignition, and other valve train or bottom end (shudder) induced issues.

Did you ever get the afr set up?

Oh and as far as mps leaks... Yikes. How are you tightening it? Does it appear warped in any way?

[Ron914]

If I’m reading the chart on Ander’s site correctly, the your substitute MPS will work but not the ECU.

After you got your MPS to seal and you tried adjusting the inner screw with it in the car, were you using the adjustment tools to make sure that the outer screw wasn’t turning while adjusting the inner screw?
If you really only adjusted the inner screw, unless the MPS was set for way too rich a mixture and you only turned the screw counter clockwise (or vice versa), you should’ve noticed a change, suggesting another cause, but still not ruling out the MPS yet.

BTW, I don’t trust any MPS or ECU that has a rebuilt sticker on it. The ones I’ve seen weee done some time ago and none of them worked. Especially true of the MPSs that were rebuilt before quality replacement diaphragms were available. I’d only trust a rebuilt MPS if one of our esteemed members here had rebuilt it.

Moving the inner screw both CW & CCW seemed to have no effect on the motor so I agree the MPS might not be the problem . I read here that ECU's rarely go bad . I gave it the smell test and cannot smell burned components .I have the 270 ohm resistor purchased from Auto Atlanta , if I added this to the CHT circuit would I be able to use the 1'7 ECU?

[emerygt350]

I would say absolutely. It such an easy test that I would just give it a go.

[JeffBowlsby]

These should be useful as substitutes for testing in your 1976 2.0L:

0280 100 043 MPS (factory correct for 1976 2.0L)
0280 000 052 ECU (factory correct for 1976 2.0L)
0280 000 044 (factory correct for a 1974 2.0L - It is functionally compatible and as far as I know the only functional difference is that it does not have the overrun fuel cut-off feature of the 052 ECU)

[Ron914]

I think we need more info as well. Not well can mean so many things. I suspect there is something outside the mps at this point. As I have said before, my car idles and runs without the vacuum even connected to the mps. Not great but not so bad I notice before I back out of the driveway.

Also, if I spray starter fluid down the throttle body, the car (any car) should run like a champ. If your car runs badly with a spritz of starter fluid that really points more toward an ignition or timing issue. Luckily for us (unlike my mustang) the ECU has nothing to do with spark, so if it runs badly on starter fluid you can provisionally exclude the ECU as the culprit and really focus on timing, ignition, and other valve train or bottom end (shudder) induced issues.

Did you ever get the afr set up?

Oh and as far as mps leaks... Yikes. How are you tightening it? Does it appear warped in any way?

I am tightening it as tight as I can hoping not to break a screw and cause a new problem . I purchased SS screws and nuts for the outer cases . I am getting ready to build my own wiring harness just need to locate a local source if possible for the connectors . Before I put the motor back in after rebuilding I did purchase a kit from 914 Rubber and redid all the end connectors with new plug housings and boots hoping to avoid the problems I am now expieriencing
I need to drive the car to a muffler shop to have a bung welded in and its all wired in and ready to go .
Back to the fuel pressure issue I spoke of while doing tests . If I activate the pump I see ~29psi its only when I shut off the pump that I see a 2psi drop after ~5 minutes so as long as the pump is running I don't believe I have that 2psi drop . I have also checked all over my car and can find no evidence of a fuel leak. I replaced the old plastic lines with SS and all hosing for both fuel and vacuum .

[Ron914]

These should be useful as substitutes for testing in your 1976 2.0L:

0280 100 043 MPS (factory correct for 1976 2.0L)
0280 000 052 ECU (factory correct for 1976 2.0L)
0280 000 044 (factory correct for a 1974 2.0L - It is functionally compatible and as far as I know the only functional difference is that it does not have the overrun fuel cut-off feature of the 052 ECU)

Thanks for the reply Jeff

[emerygt350]

I would try the 1.7, if that changes nothing, go back to basics. See if it runs on ether.