MPS Adjustment? Options

[torakki]

On my '74 2.0L, I'm having trouble getting the thing to lean out. It's running very rich (un-drivable) with black spark plugs. I'd rebuilt the MPS so it has been apart. I adjusted the fuel pressure regulator all the way lean and it runs better but still, way to rich. So, I "think" it may be the MPS needs adjusting. When I rebuilt it, i set the screw adjsutments to what it originaly was by measuring and counting threads. Now, I think I may need to remove the epoxy and adjust the two screws. I did an ohm meter test on the connectors and results, shown below. BTW - the part number ends in 049. But, How do I adjust the screws and get it correct, (without special tools)? Thanks for any suggestions.

[brant]

the original settings from the factory are no longer accurate
the mixture for gasoline has changed significantly in the last 40 years

on top of that.. your motor is likely not in exactly the same state of tune as it was 40 years ago


you either need to send it out to someone that has the correct meter to reset it

or better but more expensive... you need a wide band O2 meter... to set it to your actual engine condition while installed on your own car.

[ChrisFoley]

I adjusted the fuel pressure regulator all the way lean

You need to explain what you did more fully. The fuel pressure regulator should only be adjusted if you have a pressure gauge in the line to see what is the pressure you're setting.

Are you sure the MPS unit holds vacuum now?

Rebuilding it using the exact same measurements as original should make the engine run a little lean, not rich.

[JeffBowlsby]

A couple of simple things to check:

An 049 MPS is for a 1.7L 914. Your 74 2.0L needs the 043. Does it hold a steady vacuum, verified with a vacuum pump and a pressure gauge? If it leaks, it will be rich.

Have you checked all your other FI components as correct for a 74 2.0L - especially the ECU, TS2, and injectors? Leaking injectors, including the cold start valve, will cause a rich condition.

Is your harness in good serviceable condition or are the contacts worn/dirty/corroded?

Set your fuel pressure to factory specs and leave it alone, by adjusting it you may have added in another variable to the system which will mask the real problem(s). D-Jet is a balanced system and every part has its function and correct setting for the system to function as designed.

[cary]

Chris & Jeff are the brain trust.
You need special tools. Chris sells the tuning tool.
Jeff can reset it to spec for you.

Counting threads won't get you to the "promised land" waayyyy more precise than that.

[Bleyseng]

Check your cht sensor first if you have black plugs. They go bad super rich, I can reset the mps to spec

[torakki]

OK, where to start. From your comments, I did check vacuum and it holds but has a small leak. Goes from 10 inhg to 5 inhg in about 15 seconds. So, I need to take it apart agian and re-seal everything.
But - If mine is a 049 and I need a 043, am I wasting my time setting this one up? Or, will it work but not perfect?
I've done a number of things that Jeff mentioned. No leaking injectors, wires are clean and grounded (had the engine out and cleaned everything), cold start not leaking, I had the fuel pressure set at 27 lbs. before I "tried" to lean it out. Not sure if all FI parts are matching. I'll check CHT sensor today.
Yes, the rebuild kit came from Chris and maybe I need to contact Jeff for tuning. I'm at that sunset stage in my life were I don't want to buy any more expesive tools for one last car.
I'll do my last tests today before I start PM'ing people.
Thank for all feedback.

[Olympic 914]

Also have and MPS with a slow leak, similar to yours. it has a good diaphragm.

there are seals / o-rings in the inner screws that are not included in Chris's kits.

I suspect mine may be leaking there. possibly some heavy grease may reduce that leak.

[torakki]

Update: Yea, Olympic 914. I read somewhere that grease on the paper gasket would fix leaks.
I checked my CHT sensor and it reads 18.9 ohms and slowly drops. This is a cold engine and about 72 degrees in the garage. I disconnected the CHT and started it and didn't notice any difference. I'm ordering a new one today then start again. While waiting for the new part, I'll try and re-seal my MPS.
After that, I'll probably reach out for reseting the MPS.
Thanks for the help.

[Bleyseng]

OK, where to start. From your comments, I did check vacuum and it holds but has a small leak. Goes from 10 inhg to 5 inhg in about 15 seconds. So, I need to take it apart agian and re-seal everything.
But - If mine is a 049 and I need a 043, am I wasting my time setting this one up? Or, will it work but not perfect?
I've done a number of things that Jeff mentioned. No leaking injectors, wires are clean and grounded (had the engine out and cleaned everything), cold start not leaking, I had the fuel pressure set at 27 lbs. before I "tried" to lean it out. Not sure if all FI parts are matching. I'll check CHT sensor today.
Yes, the rebuild kit came from Chris and maybe I need to contact Jeff for tuning. I'm at that sunset stage in my life were I don't want to buy any more expesive tools for one last car.
I'll do my last tests today before I start PM'ing people.
Thank for all feedback.

There is no difference between a 049 and a 043 except for the Wot settings. But you should adjust it after resealing it. I use a slight bit of gasket sealer on the paper gasket

[914_teener]

Update: Yea, Olympic 914. I read somewhere that grease on the paper gasket would fix leaks.
I checked my CHT sensor and it reads 18.9 ohms and slowly drops. This is a cold engine and about 72 degrees in the garage. I disconnected the CHT and started it and didn't notice any difference. I'm ordering a new one today then start again. While waiting for the new part, I'll try and re-seal my MPS.
After that, I'll probably reach out for reseting the MPS.
Thanks for the help.

A disconnecterd CHT lead will not allow the car to start. The lead needs to be grounded for the car to run. The CHT is unlikley the issue. What sometimes happens becuase the sensor is threaded to the head, oxides build up and deposits cause the grounding resistance to change as the thermister heats causing a bad resistive signal to the ECU.

If the MPS leaks like apparently as you have posted....the leak needs to be fixed and then the MPS adjusted with the right tools and instruments. Crusty is gone but I'm still here...grease is not the right way to fix this leak and at 15 HG likely to make things worse.

I agree....Jeff and Chris are the experts here. I used Chris Foleys made diaphram and ended up having Jeff calibrate it on my last T1V engine. Ran flawlessly once done.

Good luck.

[Jonathan Livesay]

OK, where to start. From your comments, I did check vacuum and it holds but has a small leak. Goes from 10 inhg to 5 inhg in about 15 seconds. So, I need to take it apart agian and re-seal everything.
But - If mine is a 049 and I need a 043, am I wasting my time setting this one up? Or, will it work but not perfect?
I've done a number of things that Jeff mentioned. No leaking injectors, wires are clean and grounded (had the engine out and cleaned everything), cold start not leaking, I had the fuel pressure set at 27 lbs. before I "tried" to lean it out. Not sure if all FI parts are matching. I'll check CHT sensor today.
Yes, the rebuild kit came from Chris and maybe I need to contact Jeff for tuning. I'm at that sunset stage in my life were I don't want to buy any more expesive tools for one last car.
I'll do my last tests today before I start PM'ing people.
Thank for all feedback.

There is no difference between a 049 and a 043 except for the Wot settings. But you should adjust it after resealing it. I use a slight bit of gasket sealer on the paper gasket

I seem to recall reading that the difference between 043 and 049 was a spacer ring under the diaphragm. Am I remembering wrong?

[Eric_Shea]

How do I adjust the screws and get it correct, (without special tools)?

You don't.

[JeffBowlsby]

There is no difference between a 049 and a 043 except for the Wot settings. But you should adjust it after resealing it. I use a slight bit of gasket sealer on the paper gasket

Not sure that you meant this as it reads Geoff. There are several differences.

[Bartlett 914]

Update: Yea, Olympic 914. I read somewhere that grease on the paper gasket would fix leaks.
I checked my CHT sensor and it reads 18.9 ohms and slowly drops. This is a cold engine and about 72 degrees in the garage. I disconnected the CHT and started it and didn't notice any difference. I'm ordering a new one today then start again. While waiting for the new part, I'll try and re-seal my MPS.
After that, I'll probably reach out for reseting the MPS.
Thanks for the help.

The CHT should read 1.8K ohms cold. It drops to about 100 ohms when hot. A loose connection could cause the ECU to see a cold engine and make it run rich. A leaking MPS and the incorrect one is an issue but I still question the CHT.

[Bleyseng]

There is no difference between a 049 and a 043 except for the Wot settings. But you should adjust it after resealing it. I use a slight bit of gasket sealer on the paper gasket

Not sure that you meant this as it reads Geoff. There are several differences.

The basic MPS is totally the same, the 043 has the metal spacer although I have seen 049 MPS's with the spacer. The differences are the calibrations and number stamp. I have made many 040 MPS's out of 049 units. People get hung up on the stamp number as it's the calibration that matters. I am sure at the factory some worker had a box of MPS's they assembled and then used the pre-stamped cover to put them together finally calibrating then with whatever they used.

[riogato]

There is a very comprehensive article I found a few years back. All you ever wanted to know about the MPS including very detailed adjustment procedures. Other areas are also covered in great detail. I cannot attach the file here (the original link is long dead) but if you e-mail me I'll send it to you. It is just under 1mb in size.


UPDATE

After a search I found the site again. It has been updated and so has some of the info.

Here's the link: https://members.rennlist.com/pbanders/

[torakki]

Yes, I've seen the site that riogato mentions. It help when I rebuilt the MPS.
For my update, I have two things. I ordered the CHT and installed it. I checked ohms but don't recall the exact number but believe it was close to 1.8k as Bartlett states. I also took apart the MPS and used a non-hardining sealer on the gasket and now, I let it sit for about 4 minutes, at 10 inhg and no measurable lose in vacuum. I haven't tried to sart it yet. I've been distracted, installing a new security camera system here at home. But, I'll try tomorrow. I'll still get the MPS set up correctly. Will send PM's. Thanks for all the feedback.