I am getting terrible milage (~18) in a D-jet 1.7, and individuals have suggested the MPS? Are there other symptons? How can I test? Anybody have a spare I can test?

first thing you can do is disconnect and plug the vaccum hose going to it and see if the car runs any different. If the MPS was messed up, chances are performance change would be noticable as well unless its just starting to go.

after that...you have to do the vaccuum pump bit which I'm not very knowledgable about, never had to do that. I think you have to pump it up no more than 15 in and it has to hold for awhile...

search the archives for specifics.

checks are to see if it holds a vacuum for "awhile" and electrical resistance between terminals. exact values i don't know.

The simple sure-fire test of the most likely MPS failure (bad diaphragm) is to just pull a vacuum on it and see if will hold.

A mityvac is worth buying. Handy tool to have around for other uses too.

You Want To Become Very Familar With This Site

1. see if it will hold a vacuum.
2. measure resistance- between outer pins on connector- 90 ohms (about)
3. resistance between the two center pins- 350 ohms (give or take)
4. resistance between either center pin and either outer pin- zero ohms.
5. resistance between either center pin and ground- zero ohms.
6. resistance between either outer pin and ground- zero ohms.

There's a good chance it won't hold a vacuum with those MPG numbers. If the diaphram is leaking, it'll fool the MPS into thinking, "hmmmm. He must be running WOT. I guess I'll richen up the mixture for him!"

If all these tests are OK, the MPS could still be bad. But you'd need an LC meter to go to the next step of testing.

Jim

After you've done the MPS thingy.....

1.) Fuel Pressure ... high pressure can override solenoid in injector....turns it into a constant injection

2.) Valve adjust

3.) timing

etc......,

Used my trusty MityVac to check the vacuum and it does not hold, as you suspected Jim! Now what? Can they be repaired? If not, what is a good source? I see at Pelican they are NLA? How successful have guys been buying used one?

bleyseng is the man...talk to him

I think I have sold about 40 rebuilt ones to club members. 037's, 043's and 049's.

just trying to keep em on the road with a REAL MPS calibrated to spec so you get a good drive.

I don't use silicone, duct tape or solder to repair diaphrams...

let's say someone had an LM-1. how do you adjust an MPS? not interested in the steps, just theory, what you're trying to do... i have an MPS with a small hole drilled to access a tiny screw under the outer cover screw. i bought it that way not really knowing about the hole.