MPS rebuild, mission accomplished Options

[emerygt350]

I just used Chris Foley's excellent rebuild kit on my leaky MPS. After removing the spider webs and varnish it all went together nicely. Chris gave me some great tips on getting an initial set. I think it is there but I don't have any experience with how a well tuned djet 2.0 914 should run. I suspect there is probably 150k or so on this engine although it could be lower, I doubt higher unless it was cared for very very well. Impossible to know with the dead odometer. Compression is great on all cylinders with no variability.

I took a little video of a drive, start up, corners, and two pulls to 60 (of various quality). After the first 40 seconds I opened my sliding rear window so you can hear the engine sounds better.

https://youtu.be/Fi4vFCWhlCw

[jrmdir]

OP, I hope this doesn't amount to hijacking your thread but it seems we're all in the same boat with this topic. I, too have just finished rebuilding my MPS using Chris' great parts and tuning kit. (When I got the car the diaphragm was toast and it ran rich.)

I made the mistake of buying a very cheap LCR meter on Amazon and had some scary results that I HOPE are the fault of the meter. In all of the write ups the inductance varies from around 1.5 down to .7 ish. On mine, the highest reading never got above .95. Even with nothing touching the operating rod (case apart) Coil resistance is great and inductance changes smoothly across the range, but it just reads too low compared to published data.

Chris, then I read your seat of pants input here - set the outer screw to bottom out at around 5"Hg and put everything back together. And lo and behold the drivability is better than it ever was! Now I'm fine tuning and both the inner screw and the ECU knob make noticeable changes. But I'm not sure how to get the right balance. Idle is a bit too high even with the idle screw closed and the whiff test points to rich conditions. I've already ruled out other vacuum leaks and am still somewhat concerned about the low impedance measurements. As it seems that lowering the entire curve would add fuel across the range. But then it seems to drive very well and if I had a bad coil I'm not sure that would be the case.

Any thoughts or advice would be appreciated. And if anyone knows of a reference inductor component I could use to spot check the meter it might help.

Thanks,

Ron

[emerygt350]

I had the exact same inductance readings as well. Both on my original (before the leak developed) and the rebuild with parts from Chris (tangerineracing.com). A range from .6 ish up to a max of .92 no matter what I did. I probably bought the same cheap meter on Amazon. It actually seems like a pretty well made meter though. Would be interesting to check its accuracy, just no clue how to do that.

I adjusted the MPS on the bench as described by Chris (range of movement on the diaphragm running 0 to 7 hg). That is all adjustment of the outer screw. Chris likes the stop screw just starting to engage the diaphragm and I have tried to get that as close as I can since it is in the car now.

Just so people know what I am referring to..
I call the big one that plugs the back of the MPS the stop screw and it would normally be covered by epoxy. Chris sells a kit that has this plug screw hollowed out (so you can adjust the inner and outer screws without removing it) with a big 8mm alan for adjustment (and a nice rubber cap to seal it up when not adjusting it).

When I say inner screw I mean the tiny innermost screw.
When I say outer screw I mean the large screw the inner screw fits into.

Once it is on the car I have been adjusting only the inner screw. Chris has a very handy tool for holding the outer screw steady while you rotate the inner screw. (or reverse).