MPS: tested, is it good? Options

[jhadler]

To all you uber experts:

I dug up three MPS's from the crate and tested them

1) 043 MPS. Lost 6 inches Hg over 5 minutes. Tested at 91 and 338 ohms.

2) 049 MPS. Lost 4 inches Hg over 5 minutes. Tested at 89.7 and 328 ohms.

3) 043 MPS. Would not pull any vacuum, toast.

...

So, is #1 any good? If not, can I use the 049 on a 2.0L?

Thanks!

-Josh2

[bd1308]

I would think that not holding all of the vaccuum for 5 minutes would indicte a failing sensor. It's supposed to only loose like 2-3 over 15-20 minutes or something like that.

b

[JeffBowlsby]

#1 and #2 are failing, but probably serviceable, the leaks are not that bad. A good MPS is rock solid, no vacuum loss at 15 inhg forever. Because the MPS diaphragm is held by intake manifold vacuum pulses, it never sees a constant steady vacuum in reality. An MPS with a slight vacuum leak will work fine, sometimes for several years, before it does not adequately function. They fail going too rich.

#3 is a goner.

[Bleyseng]

(IMG:http://www.914world.com/bbs2/html/emoticons/agree.gif)

Alot of the times the slow leakers are due to old gaskets that aren't sealing perfectly anymore. I take the apart and reseal them and they work fine.

You can use a 049 (1.7l MPS) on a 2.0l to limp it home but don't drive too much with it as it is set up too lean. = Heat.

[jhadler]

Thanks!

I plan on converting the car to Megasquirt withing a year or two, so that's as far as the MPS needs to take me. The car will mostly serve autox duty in that time with occasional sunny day drives and track duty now and then. So is #1 safe to use? Sounds like it's okay, but not to expect it to last too much longer?

Thanks,

-Josh2

[jhadler]

If the leak is slow, I would think that the longer it idles the richer it will get. Does that sound right? If that's the case, then I would have a justifiable reason for revving the motor at a stop light (or staging line) right?

Max vacuum will be closed throttle at high rpms, which never lasts long. So that wouldn't be the big concern, but minutes at idle would definitely make it run richer and richer if I'm thinking about this properly right?

I guess my question is this: Will I harm the motor (the bigger investment right now) by running the stock FI with this MPS for a year or two of track/autox events?

-Josh2

[Bleyseng]

NO

At idle the engine vacuum (15hg) will overcome any leak down unless its blown. It has to be a pretty good leaker to effect the mix much, mostly it just effects transion from cruise to idle or off idle to cruise. The response just isn't crisp like it should be.

[jhadler]

QUOTE (Bleyseng @ Apr 7 2006, 03:40 PM)

NO At idle the engine vacuum (15hg) will overcome any leak down unless its blown. It has to be a pretty good leaker to effect the mix much, mostly it just effects transion from cruise to idle or off idle to cruise. The response just isn't crisp like it should be.

Okay. Then it sounds like it's even less of a problem. idle/cruise transition isn't my chief concern. If part-to-full throttle transitions aren't badly impacted, then I don't think I care too much. The car will spend very little of it's life (from now on) at cruise throttle...

Thanks for the info!!

-Josh2