MPS Options

[pbanders]

I'm sure people have gotten lucky and bought good MPS's off of Ebay, but my suggestion is don't do it. Most of them are junk - they leak, they're rebuilts that some one other than the rebuilder has been into (e.g. Bret seals one screw with a drop of epoxy, if yours has no seal, well...), have been drilled for "adjustment" (read: buggering), or are of unknown service life (could fail any time).

Before the price of OEM units went out of sight (~$1K right now), I would suggest a new OEM unit. Now, I think the way to go is a rebuilt exchange from Bret at about $~250 from Performance. May not be absolutely perfect, but it has new aneroid cells and a new full-load diaphragm.

Brad Anders

[pbanders]

Brad has given you the method of checking the vacuum seal and resistance on your MPS. IF you want to buy a different/rebuilt one, I saw this one on evilbay.
http://cgi.ebay.com/ebaymotors/ws/eBayISAP...&category=34198
L. McC

That's an interesting one, a rebuilder I haven't heard of. From the tag, it looks pretty old. No idea of what "rebuilding" was done.

Rebuilding an MPS requires two special parts - a paired set of aneroid cells, and a full-load diaphragm. Brett Instruments does the rebuilds for Performance, I've talked with the owner. He has a local jobber build his aneroid cells, and IIRC, they do the full-load diaphragm on site. Both items require good engineering to make sure they respond the same as the Bosch OEM parts. In Bret's case, they've done an OK job. The aneroid cells look identical to the OEM part, but are made of steel instead of bronze, so they likely have a different expansion rate. The diaphragm is made of bronze, but it's somewhat thicker and has a different pleat pattern.

Bret drills out the rivets, taps one side of the case, and installs screws. They also (on some of the units I've looked at) add an additonal case O-ring for sealing. They also use heavy grease on the full-load diaphragm gasket for sealing, kinda yucky.

Once you put it back together, it has to be calibrated. Bret does this by putting the MPS into a D-Jet simulator they built (a LONG time ago) and using a set of "golden values" to set the idle vacuum, transition, and full load levels. From what another guy on Rennlist said, Bret told him they calibrate ALL of the MPS's they sell to the exact same standard - not a good idea. The idle and part-load will be fine, but the full-load will likely not be to spec.

Brad Anders

[Bullet]

Well I know that im taking a risk at bidding on this "rebuilt, never installed" But ohh well we will see what happens. and yes it has the exact same part # as the one i pulled out of my car. I know that if this ends up being a bad MPS i will hear it from my Wife as i try to explain to her my "Logic". (IMG:style_emoticons/default/laugh.gif)

[lmcchesney]

you are bidding on the MPS posted by L McC, I won't bid.

Whoa there. N.B. Note well. I am not selling a MPS. I saw this on evilbay after reading your post. Brad, I thought this one seemed a reasonable risk in that it had a warranty with it. However, I have no idea who CBS is. Ray Green said he was manufacturing some cooper diaphgrams. Has anyone had follow up on this?
Geoff helped me renew mine. Just the thinest of gasket sealer to be used.
2wheeldrifter, it has been my teaching that the MPS's 037,043,049 are all the same with different partial open throttle and wide open throttle settings. Do you agree Brad? Also, Geoff appearently calibrates the MPS using impediance.
L. McC

[Bleyseng]

All MPS's are basically the same. Some are short nosed some are long nosed, some have different spring rates.
I use a Waveteck to calibrate them to my known data which is very similar to BradAnders data. I do have a NOS 043 that I use to check the wavetek everytime before I calibrate a unit.
The 037 (73 2.0l) has way different settings than the 049 and 043. The 049 and 043 are pretty much the same except for the WOT settings.
You can set up a MPS though and it will spec out perfectly then go for a drive and it runs like shit! These units are old so if you want perfect running car get a new one!
I harvest good diaphrams out of MPS's then rebuild them for 2.0l's.
The AA rebuilt MPS's I have seen are junk !

Geoff

[4WheelDrifter]

L McC, I didn't mean you listed the auction, just posted the link. Sorry about the confusion.

[lmcchesney]

My email was lighting up with questions.

[Bullet]

Well, I won the auction for the MPS. recived it in the mail today and installed it after work. I pulled a vacumm on it and it held 20in, i then did a resistance check and it was right as specs called for. My car is now not running ritch (IMG:style_emoticons/default/laugh.gif) . But it still has a missfire. and the vacumm guage bounces from 8in to 10in I started doing a cylinder power ballance test. by removing 1 injector at a time checking for rpm changes. all cylinders are affected except for Cylinder #3. I get no change whats so ever. So I pulled the plug wire and checked for spark (good), thrn pulled the Plug and checked for spark through the plug (good) removed injectors #3 and #4 and both are spraying in a good CONE pattern. I set the Dwell a few weeks ago, and dont think that has changed. All i have been able to do is set the timming to TDC to keep it running. I cant set it to 27 degrees at 3500 because the engine wont hold the RPM. I can get it to 3500 but it drops down to about 3000 when i hold the throttle in the same position. WTF am i doing Wrong? anyone have any ideas on what could be going Wrong? Also all my Vacumm hoses are routed acording to the Diagram on Pelicanparts.com.

[dmenche914]

there are different MPS for different years, and engine sizes, so be careful, also some have been tampered with (seal removed over the screw)

If you are on the cheap (and who isn't) , and do not want to pay new or rebuild price, then give HPH (Brad) a call, and see if he has any used ones, he should be able to get you the right one for your car. And coming from them, you should have no worry about it not working. e-bay is a crap shot, you may get a deal, you may not, seller could be dishonest (rare but happens) or honestly knows little about what he/she is selling. then again, it might be perfect, for really cheap, so bid accordingly, ask seller many question, make sure the tamper plug still is sealed, and check the part numbers, make sure seller performs the vacuum test, and resistance tests.

If you are having a vacuum leak, then that will certainly effect your mixture, so hopefully this is your only problem.

Avoid the temptation to toss out the FI for carbs. An FI engine has a cam that works best with FI, not carbs, and a FI system that has been gone thru is very reliable, gets great milage (something I have not yet seen from carb conversions), requires less tweeking to keep in tune. I love my D-Jet. $800 on webders for a stock engine would be a waste.

Keep you grounds clean, and your fuel lines fresh, just keep on D-Jetting!


dave

[dmenche914]

Valve adjustment ????, compression test???? Is the plug oily??? It aint the trigger points, as they fire the injectors in pairs, you only have one dead cylinder.

you got spark and fuel, Could your spark plug wires be crossed??? A wrong wire to a plug, can allow the car to run poorly, so double cheak that. firing order 1432, note the #1 plug on the dizzie should be at the notch on the dizzie body, cylinders are labled on the shroud. i made this screw up before, oh well, live and learn.

hope it is something simple

dave

[Bullet]

It is a fresh rebuild. I adjusted the valves when i still had the engine out. I will double check the wire positions, but wouldnt that cuase 2 cylinders to Miss? Plug is clean. but i just put a new set in today. They all foulded up from the bad MPS. when i pulled the plugs out that i replaced I noticed that the #3 cylinder plug was the only one not saturated In fuel. al the other ones were completly Soaked. But that dont make since. considering that i have Physily seen the injectors all fire.

[pbanders]

What does the vacuum gauge guide tell you about a 8-10 variation? Sticky valve?

[nebreitling]

you have replaced the trigger points, no?

do it if not good luck

[mike_the_man]

Have you tested all of the injectors to make sure they're all flowng about the same? If number 3 wasn't wet, then maybe that injector isn't flowing enough. Pull all the injectors and put them all in graduated cylinders. Disconnect the coil wire, then floor the gas pedal and crank the car over for a 30 seconds or so. The level of fuel should be pretty close to even between all 4 graduated cylinders.

Good luck.

[Bullet]

What i came up with, Even though Injector #3 does Squirt when I moved it from #3 to #1 the miss followed the injector. Which is really Iritating beacuse this is the New injector I got a couple of weeks ago. Does anyone In the Portland Area No where I can get ahold of an Injector Tomorrow (satrday)? any help would be great.

[lmcchesney]

You are getting there Bullet. Just a little more.
Injectors have an electromagnet which opens the valves. Check the resistance on the injector. It should be 2-5ohms. Not 0 and less than 25 is listed as normal. If the resistance is acceptable, clean the injector. The injector is triggered by 3V and not 12V like the cold start valve. The intake portion of the injector has a filter screen. This sometimes obstructs with dibre. Recomendations include spraying them with Chremtrol, or carberator cleaner. On the board is a method of making a home ultrasonic-like injector cleaner using a vibrating scribe. Otherwise, a local mechanic would probably place the injector in a true ultrasonic cleaner and do it quickly/reasonably priced.
If this does not work, many have mixed findings on rebuild injectors. Similar to the MPS comments. Bus boys: has 023-906-031 new for $90 and rebuilt for $41.5 plus core exchange. HPH Brad mentioned a site for rebuild injectors for $55 as well.
Now that you have a working MPS you may also want to check the flow of the injectors as Mike said. They should flow 380ml/min.
Good Luck
L. McC

[Bullet]

Im about to give up on this car. It has to have a Demon! I got an injector that works now, All cylinders stumble when i disconnect the wires for the injectors. But it still runs like crap. I havent checked the flow of the injectors yet, but i have checked resistance on them and they all were the same 2-3 ohms. removed them all and checked the intake screens and they were clean. when it is running I can see that it is still missing, if i rev it up at part throttle it stats to hip-up or surge. now that i have that injector working my idle vacumm is between 12-15. I have gone through tons of brake clean trying to find a Vaccum leak and have not found one. Have gone through pinching lines to see if that made a differance at all, and have found nothing. I barowed a friends ECM form a 73 and that made no change for the better. it ran a little Worse with that ECM. My dwell is at 51-52 will that make a big differance? I have only staticly timed it, runs to bad to attemt to set that at 3500. Does any one have any idea's on were to go with this?

[Bullet]

I jsut went out side and fired it, Noticed that when i first started it it ran great for about 30 seconds with a steady vaccum of 15 but after 30 seconds it went to shit with a jumpy vaccum again.


I also have been checking resistance values of wires and componets, and when i mesure resistance of the outside air temp sensor I get an Infanite resistance Value. Could this cuase me a Running issue?

[Bullet]

I was reading through some stuff on pbanders site and I read that my pcv breather hose should not go to the top of my air box but it should go to the air distrubtion box? and the i looked at this picture and he has it routed to the air box. I ran outside and tried this. but found out that the pcv house is to big for the hoses conections on the intake. so i used a ruber house to make it work. Car runs a beter now but i get a really anoying whistle when i do this. is this normal?

(IMG:http://www.914world.com/bbs2/uploads/post-2-1082882279.jpg)

[Bleyseng]

It goes to the plenum via a rubber boot that has a decel hose connection on it too or just plug it in without the decel valve hose. Not enough vacuum when its hooked to the air cleaner.


Geoff