MPS copper diaphgram problems, What now? Options

[lmcchesney]

Help guys,
I recieved my 2.0L D-jet FI system today. Cleaned and inspected. Measured resistance/ohms on the MPS and looks good. Large leak.
Marked casing. Casing number -----049. Ground off rivets. Opened casing and inside ink marked 52 on bellows and scribed on partition 52. Removed bellows. Unscrewed retaining ring and partition. Center of copper diaphgram falls out. The copper diaphgram completely seperated from rim. UGHHHHHH.
Question:
I have a good copper diaphgram from my old MPS ----039. Is this the same and can it be subsituted for the copper diaphgram in the ---049?
Is it a functional repair to braise/soder the rim of the diaphgram back to the center of the diaphgram?
Or do I just start all over in search for another ---049 MPS?
Thanks,
L. McChesney
lamcchesney@netzero.net

[Bleyseng]

An 049 MPS is for a 1.7l djet car as is the 039. There is no way to repair the copper diaphrams other to swap in a good one. For a 2.0l MPS you also need the spacer ring that spaces the inner stop to the correct position. I do have a couple of good MPS's left and can calibrate one to a stock setting (year of Djet depending) or a 2056cc motor one.
The 2.0l numbered MPS's are the 037 (73) or the 043 (74-76).

What year is the Djet FI you have? I am talking about the ECU numbers.

Geoff

[garyh]

No, you can't repair the diaphram.

Yes, you can build one MPS from parts from several.

The MPS must be re-calibrated after assembly. There's a couple-three on this list that can do it. (IIRC, Geoff, Brad Anders, and myself.)

And somewhere I have an MP3 of that John Denver song (IMG:style_emoticons/default/wink.gif)

G.

[ChrisReale]

Jeff Bowlsby does it also.

[lmcchesney]

Thanks Guys,
Geoff: The MPS SN# is 0280 100 049. Looked at Brad Anders site and yes it is a 1.7L.
Bought the system from Craig Laughin. Said it is from a functioning 73 2.0L. The rest of the system looks OK. Correct Plenum, TB/Switch, Pipes, green injectors, AAR, Decel valve and breather. The number on the ECU is worn off. the remiander of the system matches 73 2.0L except the fuel pump. Is is 0580 463 009, which does not match up with the list. Probably a pump for the Vagaon or other.
SO, now I have two 1.7L MPS's. One with a erroded diaphgram.

What is the difference between 2.0L and 1.7L MPS's. Are they able to be recalibrated to function?

I know there is a difference in the circuitry of the 2.0L ECU. Is there an internal marker to identify the 2.0L?

No complaints here. Just new challanges.

Thanks,
L. McChesney

[Bleyseng]

Visually, no different except for the spacer ring that moves the inner stop plate. I haven't ever checked the spring rates but there might be a slight difference there too. Other than that, just the calibration (IMG:style_emoticons/default/laugh.gif)

It seems that the 037 ECU is fine if you use a good corrected MPS for it. The 73 2.0ls ran richer accross the board, so using a 049 or any other 1.7l one is bad. The oil temps will run up much higher on a long drive and a several hour trip could be your last one with a dropped valve seat!

Look inside the ECU for a number as its stamped or a small tag on the board.

Geoff
Oh Gary, I didn't know you also recalibrated the MPS's, good to know. I know you have been into 914's for a long time and remember your posts from the old old forums. You have always been a great source of good solid info! Hope to meet you at the WCC.

[lmcchesney]

Avitar test

[JeffBowlsby]

The ECU Bosch number should also be embossed into the side of the case IIRC, to help ID the ECU. It may be faint or paint covered, but the numbers are large.

Dont forget that the 73 2.0L FI setup also has the 27 ohm resistor in series with the TS2.

[lmcchesney]

I pulled the ECU apart. Bosch number is 0 280 000 043
Which according to Brad's information is a 74 2.0L.
The rest of the numbers check out including the injectors Bosch 0 280 150 019.
The fuel pump is not listed but lies between 1.7 and 2.0L series Bosch 0580463009.
Ray says the copper diaphgrams are the same and explains how to switch them, but the terminology is such that I do not understand. Hopefully this picture will be excepted.
"Just make sure to measure the center metal pices which is the outer/inner stop flange to make sure everything is the same size. The, measure the old center while the screw are still in he center to get an idea of the adjustment. Then transfer your adjusting screws. It should be pretty close."
Any further suggestions? How do you calibrate a MPS for insertion with the plan for final tunning in the car?

[garyh]

How do you calibrate a MPS for insertion with the plan for final tunning in the car?

Just slap it together and see if it leaks. If you can't get it to stop leaking, give up and get a rebuild. If it doesn't leak, and the internals are working, the engine should run, just not well.

I don't know if it can be adjusted mechanically. I always do it electronically. The procedure I use is similar to the one described on Brad Anders' page.

Final adjustment should be done on a dyno so you can set the O2 levels properly.

G.

[Bleyseng]

I also just use the Wavetek method because the inductance is what the ECU sees to set the injector firing.
Who cares about the mechancial measurments are as there is noway to adjust it that way.

For a "Seat of the pants" method to get the car driveable do this:

Start car and warm it up
Have a friend try and hold the rpms to 2500
Adjust the center screw without moving the outer screw so the car runs as best as it can. Should run pretty smoothly and the friend should be able to hold the rpms at 2500 with out spitting, backfireing etc.
Turn it a 1/4 turn richer
Good, now drive the car to the dyno shop where you can set the part load A/F mix correctly and also the WOT A/F mix before you burn it up.

If the car is a stock 1.7 and 2.0l use a recalibrated unit by Gary, Jeff and me and you are good to go. ALL others must adjust their engines with a dyno and O2 sensor.

If you are trying to adjust a 1.7 MPS to 2.0L use a 2.0l spacer to set the inner stop correctly.

Geoff (IMG:style_emoticons/default/mueba.gif)

[lmcchesney]

Got it done.
I removed the good copper diaphgram from 049 with the bad WOT plug and matched it to the 049 rear with the good WOT plug and adjusted the inner screw to approximate the 049 that came off a working 2.0L setup. The WOT plug was set at 10 turns in and is marked. The outer screw is set about the same in both. Hopefully, I'm in the ball park.
Anything else to do until I get the engine in the car?
And just to confirm my understanding, there is NO diffenence between the 049 MPS for the 1.7L and the 037/043 MPS for the 2.0L is JUST THE ADJUSTMENTS.
Unfortunately, I do not own a Wavetek LCR55.

Thanks,
L. McChesney

[Bleyseng]

The only physical difference I have ever noted is the additional spacer ring between the inner stop and diaphram. I think that there might be a slight difference in the springs.
Turns and such mean nothing as its all the inductance readings cuz thats what the ECU reads.
I have tried the measurment method and it wasn't too close.


Geoff

[lmcchesney]

Dear Geoff,
Thanks for the information.
Are these the spacer and inner stop?
The dome points away from the diaphgram, correct?
Is there a way to check the spring?
Thanks,
L. McChesney

[Bleyseng]

Yes, that is the spacer ring and inner stop. I seal the diaphram with a lite coating of grey sealant on both sides since the paper gasket is NLA. Let it dry before testing with a vacuum pump.

Have you removed the machined plug carefully? You will need to be able to remove and install it easily at the dyno shop when you adjust for A/f mix unless you get a O2 sensor and laptop.

Geoff

[lmcchesney]

Yes. Coated the diaphgram with sealant. The picture is from my spare parts MPS. Should I remove the spacer?
Removed the epoxy and marked the location of the WOT plug. It is at 10 turns in from engagement of the threads and the case is marked, "10 turns in."

L. McChesney

[Bleyseng]

No, on a 2.0l you need the spacer to set the inner stop to the correct location.

I don't care how many turns the plug is. You set the WOT plug by the WOT A/F ratio and it should be just touching and supporting the diaphram. If it isn't, the diaphram will over flex and crack in short order, trust me. At rest, the spring is pushing the diaphram out against the plug! Only under vacuum does the diaphram move inwards.

Geoff

[mike_the_man]

Aren't those MPS's confusing little things. I had to read Brad Anders's web page about 10 times before I totally understood how they worked. Now I think I have a pretty good understanding of them.

As far as setting the MPS by measuring the number of turns and such, I tried it, and it didn't work worth a pinch of shit. When I hooked it up to an inductance meter, it was way off. Don't bother trying that way. If you don't have the proper equipment, send it to somebody to get it done right.

Just my $.02.

[Bleyseng]

They are kinda cool electro-mechanical devices. Brad Anders figured out (with help of others) the way to adjust/calibrate the little buggers after 30 years of Mystery. If you have ever met Brad Anders, he is way cool and knows his shit when it comes to electrical engineering.
I have tried the measure method a few times and it doesnt work for shit. Each MPS has its own resistance that I can electrically measure. All the diaphrams have some differences, so with those two variables it don't effin work IF you want a MPS that is close to the right settings.
We know what the A/F is supposed to be as its published (by Porsche)
We know what the measured inductance is by measuring Factory sealed 1.7, 2.0l units.
We also have checked the A/F by dyno time (I have done this) to make sure of the settings.


Go ahead a measure something that doesn't matter and when your engine goes lean burn and drops a effin valve seat you will know why.

Geoff (IMG:style_emoticons/default/smash.gif) (IMG:style_emoticons/default/spank.gif)