Strange MPS issue, Lew's car Options

[914itis]

I am helping Brian with Lew's car. As most of you may know, it is a 2056 with djet.
The car was running fine, he drive it to CT one day and when he came back he noticed that the MPS was hanging. The car starts to run on 3 cylinders with #4 not firing. We checked for spark and injectors they are all fine, but if you remove spark wire #4, it had no effect.

The strange thing is if you elevate the mps about 6 inches up, it's all fine, even that 4th cyl works. All the electrical wires on the unit are fine

(IMG:style_emoticons/default/confused24.gif) ?

Dies the 2056 uses 1.7 or 2.0 MPS?

He would like to make it to Hershey.

[r_towle]

If he lifts up the MPS it runs fine?
Is there oil in the plenum from the long highway run?
Look inside the hose that goes to the mps and see if there is oil in there.

[JeffBowlsby]

a 2.0L MPS is necessary for the 2056 recalibration. The 1.7L MPS does not have enough room to adjust.

If #4 is intermittent it has nothing to do with the MPS. Check either the rest of the harness for wiring issues or perhaps the FI grounds at the top rear of the case.

[914itis]

I wouldn't say intermittent, it only runs right when holding the MpS about 6 inches up from the mounting location.

Rich, I will ask him to check the system for water.

[Mblizzard]

a 2.0L MPS is necessary for the 2056 recalibration. The 1.7L MPS does not have enough room to adjust.

If #4 is intermittent it has nothing to do with the MPS. Check either the rest of the harness for wiring issues or perhaps the FI grounds at the top rear of the case.

Jeff is there a general guidance for or someone that does the recalibrating the MPS for the 2056? I have read Paul Anders MPS article but I am not sure that I am experienced enough or have the equipment to attempt the adjustment. I am running FJ67 injectors that are slightly higher flow than stock.

[achman_73_2.0]

I wouldn't say intermittent, it only runs right when holding the MpS about 6 inches up from the mounting location.

Rich, I will ask him to check the system for water.

I'll check for water in the line. I did take the line off to check for obstructions/leaks and found none.

I found this on the buildsheet for the engine:

"043 MPS replaced with 037 to achieve richer mixture"

The engine did seem to lean out a bit at higher revs under load...some faint pinging was noticeable...

But the car has been perfect until now. Driven local and to NJ CT without issues. Idles slightly high even when warm but that is it.

[achman_73_2.0]

I wouldn't say intermittent, it only runs right when holding the MpS about 6 inches up from the mounting location.

Rich, I will ask him to check the system for water.

I'll check for water in the line. I did take the line off to check for obstructions/leaks and found none.

I found this on the buildsheet for the engine:

"043 MPS replaced with 037 to achieve richer mixture"

The engine did seem to lean out a bit at higher revs under load...some faint pinging was noticeable...

But the car has been perfect until now. Driven local and to NJ CT without issues. Idles slightly high even when warm but that is it.

[914_teener]

I have always thought the two MPS bodies of the 1.7 and 2.0 liter are the same.....the only difference was in the calibration and adjustment of the diaphragm? (IMG:style_emoticons/default/WTF.gif)

That looks like a Fuel Injection Corp rebuilt MPS.

My bet is that the MPS came off the mounting bracket and cracked one of the harness wires.

I would check those first.

[76-914]

EMF. It's sensitive to spark plug wires. Reroute #4 plug wire under the runner. IIRC, that is a rebuilt MPS.

Edit: post a pic of the engine psg side.

[914itis]

I have always thought the two MPS bodies of the 1.7 and 2.0 liter are the same.....the only difference was in the calibration and adjustment of the diaphragm? (IMG:style_emoticons/default/WTF.gif)

That looks like a Fuel Injection Corp rebuilt MPS.

My bet is that the MPS came off the mounting bracket and cracked one of the harness wires.

I would check those first.

Harness was checked and is intact.

[JeffBowlsby]

Those exposed wires in the harness concern me. Brittle or cracked? Is that red wire to the TS2 or is it added to the harness?

The 2.0L MPS has a spacer ring that the 12.7L MPS do not have, which allows greater diaphragm range and adjustability...a 2056 adjustment is at the limit f the 2.0L MPS range.

That is a rebuilt MPS...not one of the new Tangerine diaphragms...all bets are off on how it performs. All MPS with new diaphragms need to be calibrated with an exhaust gas analyzer, there are too many variables to determine a single calibration for every engine, even the factory calibrated every MPS to the specific engine. I have found Brad A's published calibrations are lean, I always must richen them up.

[Bleyseng]

Those exposed wires in the harness concern me. Brittle or cracked? Is that red wire to the TS2 or is it added to the harness?

The 2.0L MPS has a spacer ring that the 12.7L MPS do not have, which allows greater diaphragm range and adjustability...a 2056 adjustment is at the limit f the 2.0L MPS range.

That is a rebuilt MPS...not one of the new Tangerine diaphragms...all bets are off on how it performs. All MPS with new diaphragms need to be calibrated with an exhaust gas analyzer, there are too many variables to determine a single calibration for every engine, even the factory calibrated every MPS to the specific engine. I have found Brad A's published calibrations are lean, I always must richen them up.

Early 1.7L MPS's have a WOT stop ring cast in the cover while 2.0L and late 1.7L MPS's don't. You need all the adjustment you can get for a 2056 using a exhaust O2 meter for the calibration. Using a stock 037 MPS will help get you closer but that's a rebuilt one so it's calibration is suspect IMHO.

[Dave_Darling]

One curious thing that I found--the MPS can be sensitive to shocks and sometimes even to orientation. It is an electro-mechanical device, and the core inside it can be moved by external forces and change the mixture.

I found this out by accident with the engine idling while messing about with the MPS mounting--the sensor fell down onto the engine tin, and the engine hiccupped when it hit. Naturally, I tried it a few more times, and tried jarring it a few other ways. It was most sensitive to being hit on the end.

That part was what led to the realization that the core could be moved relative to the windings by thumping on the MPS body...

--DD

[achman_73_2.0]

One curious thing that I found--the MPS can be sensitive to shocks and sometimes even to orientation. It is an electro-mechanical device, and the core inside it can be moved by external forces and change the mixture.

I found this out by accident with the engine idling while messing about with the MPS mounting--the sensor fell down onto the engine tin, and the engine hiccupped when it hit. Naturally, I tried it a few more times, and tried jarring it a few other ways. It was most sensitive to being hit on the end.

That part was what led to the realization that the core could be moved relative to the windings by thumping on the MPS body...

--DD

Hey Dave

This all started when I came home from a drive to NJ and popped the engine cover and found the MPS laying in the engine compartment on the tin. It had been jury-rig mounted and came off...but the car ran fine. issues started when I remounted correctly. So is the MPS toast?

[SLITS]

You need a vacuum pump and volt/ohm meter ..............

See if it holds 15" of vacuum for 5 mins.

4 pins on the MPS. Should be 90 Ohms between the two outer pins and 350 Ohms between the two inner ( or could be visa versa, don't remember but the values are correct). Check each pin for continuity to ground (the case).

[Dave_Darling]

This all started when I came home from a drive to NJ and popped the engine cover and found the MPS laying in the engine compartment on the tin. It had been jury-rig mounted and came off...but the car ran fine. issues started when I remounted correctly. So is the MPS toast?

No idea! I don't think the core inside the MPS should be able to get to where it won't move unless the MPS body is in a certain orientation, but it may be possible.

Do you have access to another MPS for testing purposes?

--DD

[914itis]

This all started when I came home from a drive to NJ and popped the engine cover and found the MPS laying in the engine compartment on the tin. It had been jury-rig mounted and came off...but the car ran fine. issues started when I remounted correctly. So is the MPS toast?

No idea! I don't think the core inside the MPS should be able to get to where it won't move unless the MPS body is in a certain orientation, but it may be possible.

Do you have access to another MPS for testing purposes?

--DD

He does not and I only have a few 1.7,s

[achman_73_2.0]

This all started when I came home from a drive to NJ and popped the engine cover and found the MPS laying in the engine compartment on the tin. It had been jury-rig mounted and came off...but the car ran fine. issues started when I remounted correctly. So is the MPS toast?

No idea! I don't think the core inside the MPS should be able to get to where it won't move unless the MPS body is in a certain orientation, but it may be possible.

Do you have access to another MPS for testing purposes?

--DD

He does not and I only have a few 1.7,s

Pretty bummed, but looks like I may be taking the normal car to Hershey. Where can I get a 2056 calibrated MPS?

[914_teener]

I would talk to Jeff Bowlsby....

Try and have him hook up a 2.0 core or the FIC rebuilt one with one of Chris Foley's replacement diaphrams. He can calibrate it for a 2.0 and then you can road test it.

You can play with the fuel pressure to try and up the mixture if you think it is lean. Maybe someone at Hershey has an portable Innovate AFM they can bring?

I personally think you are giving up too soon. Are you sure you "rung" out all the input wires on the harness for continuity?

Are you sure it isn't the connector on the trigger point in the harness as well?

[914_teener]

Did you test it as Slit's suggested?