Manifold Pressure Sensor

[Potter]

Anybody have a sense of the going rate ($$) on a used or new manifold pressure sensor. I believe mine has gone bad and will need to replace.

I checked one online catalog and the price listed was apparently not only for the part, but for the factory in which it was built, the college education of all of the children of the workers involved in it's production, as well as a substantial portion of the costs to "rebuild" Iraq. I nearly spooled through the bulkhead when I saw that number.

[anthony]

The going rate for a good used MPS seems to be around $100-200.

[Dave at Pelican Parts]

You may have spooled through the bulkhead, but that is the new price. I'm not sure that they're being made any more, and the price reflects their rarity. And some places charge more for 'em--and get it, sometimes.

The rebuilt ones are all done by Brett Industries, and they are "almost" right. The diaphragm inside is a different material, and the aneroids may be different as well. It responds close to the original, but not the same.

If you want new, you gotta pay the $$.

--DD

[jamcleod]

buyer beware!!!!

support our host!!!!

the following is for information only:

http://www.***********.com/action.lasso?-database=Items%20database&-layout=web&-response=search_results.lasso&-operator=eq&part%20number%20to%20search%20on=039%20906%20051&-maxrecords=10&-search

(let the flaming begin

(i was looking for that site where rebuilt ones were $200. it's not performanceproducts, GP&R. couldn't find it again but did find AA)

[Dave at Pelican Parts]

"New" for $650, and "Genuine" for over a grand?? Huh???

--DD

[tod914]

Yup I recently went through the same delemia.

[Otto]

They rarely go bad. You need to adjust it with an Allen wrench.Otto

[Jared at Pelican Parts]

You also need a C/O meter to properly adjust the sensor.

[Dave at Pelican Parts]

Originally posted by Otto
They rarely go bad. You need to adjust it with an Allen wrench.

Rarely?? Granted, not as often as they are blamed--but "rarely"?? Those bleeding copper diaphragms rip all the time... I've averaged about on in five which had total leak-down!

For info on how to adjust them, see: http://members.rennlist.com/pbanders .

--DD

[pbanders]

I'm with DD on this. Otto's got a lot of experience with 914's, but I beg to differ, MPS's go bad fairly frequently. The full-load diaphragm is flexed between the limit stops every time you open the throttle and every time you shut the car off. Eventually, the bronze diaphragm fails around the center adjusting flange due to metal fatigue. Big stress raiser at the edge of the flange, bad engineering, Bosch!! All they would have needed to have done was to chamfer the edge of the mounting flange and the thing never would have failed.

They also don't adjust with an allen wrench. Adjusting them correctly is a complex procedure, I don't recommend it unless you have access to the specialized measuremen tools I describe on my web pages.

I suggest that if you've got the money, drop it on a NOS Bosch MPS. Yes, it will cost a fortune but it's the only 100% sure way of getting the right thing. For the other 99% of 914 owners out there, buy a rebuilt (done by Bret Instruments) from Performance. PP doesn't sell them, AFAIK, maybe if you call them they'll decide to start carrying them. They're not perfect, but pretty good. They replace both the diaphragm and the aneriod cells with new parts of their own design, and the units are usually well-sealed. What they don't do so great is calibrate the unit - they have a single calibration standard. This works "pretty well" for most 1.7's and 2.0's, but would need to be tweeked for optimal performance - talk to Jeff Bowlsby about recalibration.

[jamcleod]

well, to quote the Porsche workshop manual, you could step up to the "more modern FI system"..... L-jet

i'm still searching for 912E FI part numbers: brain, fuel injectors, throttle body (as you know, 912E is 2.0L L-jet)

[Ron Meier]

I have a 2.0L Pressure Sensor on evilbay starting at $75.00 (shameless plug). I am a core supplier and have about 300 that are BAD - won't hold vacuum. Explain that Otto.

[Dave at Pelican Parts]

Originally posted by jamcleod
i'm still searching for 912E FI part numbers: brain, fuel injectors, throttle body (as you know, 912E is 2.0L L-jet)

Keeeeeep searching. There were only 2099 912E's made. EVER. Good luck in finding the 912E-specific parts.

When I get home I can look up the Bosch part numbers for you, but that won't make the parts any less rare. Several of the important ones are not used for any other car. (I believe the air flow meter and ECU are both 912E-only parts, and I know that the rubber intake boot/hose is and is very very hard to find. It cracks between "accordion pleats" all the time and is NLA.)

--DD

[mike_the_man]

After reading Brad Ander's web page (which is absolutley fantastic) about 12 times, I decided to try and calibrate some myself. I bought two good MPS's from Volvos for $50's, borrowed an inductance meter from the lab at my company, and recalibrated them. They seem to work pretty good, and it was pretty easy to do, once I understood how everything worked.

If you've got access to all the needed tools, I say give it a try. It's not hard, and you'll learn alot.

Good luck,

[jkeyzer]

Ron - you have THREE HUNDRED bad MPS's???

Wow.

[Otto]

Bad diaphram. How do you think they transfer manifold vacuum pressure into a signal that the ECU will understand.

[M. Hendrix]

Originally posted by jkeyzer
Ron - you have THREE HUNDRED bad MPS's???

Wow.

And that's just on the one car...



M

[pbanders]

Originally posted by Otto
Bad diaphram. How do you think they transfer manifold vacuum pressure into a signal that the ECU will understand.

Not sure I understand what you're saying here, Otto. If you look at the references in my web page below, there is ample description of how the ECU uses the inductance signal from the MPS to change the time constant of the loop circuit to establish the basic injection pulse duration.

When the diaphragm cracks, the MPS cannot hold a vacuum, hence the aneroid cells do not respond to manifold vacuum, and are in their fully relaxed state. As a result, the ECU interprets that the MPS is at WOT, setting the mixture very rich (e.g. 8 to 12 ms injection duration).

[M. Hendrix]

I got what he meant.. obviously, a busted diaphram is a no-go, if it holds vacuum, it can work.

I can translate here.



M

[Otto]

Miles, do you think anybody on this board understood what the technical analyzation of the MPS?