Fuel injection relief here!

[raygreenwood]

Ok…..so by request, I was asked to measure the gap between the 12mm bushing which is the inner stop…and the inner stop plate which is that steel dished plate with the “keyhole” shaped hole in it.

I had measured quite a few of one particular type a few years back. So today I measured four different part #’s of diaphragm type MPS. All of them were known to be unmolested from the outside. It was a very enlightening day.

By the way....I have used all of these part #'s with great success in my 411 and 412's . They just need to be adjusted for the engine you are running them on.

Here are the part #’s:

0280-100-037
022-905-051C Brown paint mark

0280-100-027
022-906-051B Yellow paint mark

0280-100-049
022-906-051-E (standard for 411/412)

0280-100-049 Porsche 914 1.7L

OK…a few things before we start. A year ago in the D-jet thread I was asked to start working on an MPS tuning guide. A lot of the pertinent info is in this thread. I am sorry I am so poor at posting pictures. I will get there.
But…I am taking pictures and took many today. But for the moment…..if you want to follow along and if you are going to be tuning any MPS….it is 100% required that you should at some point disassemble one of the type you are going to be working on so that you will be familiar with the parts for this discussion. If you are familiar and have one open.....you will not be confused at all by what I am saying.

Before I get into the findings I am going to list the parts in order so that you can visualize what is going on and what I am measuring today.

First: The front of the MPS is the end where the vacuum line and plug attaches. The back of the MPS has the epoxy anti-tamper seal and the adjusting screw. For today we will only be talking about the back half of the unit.

Back section Parts:
(1) Epoxy seal
(2) Aluminum screw (13mm) called the outer full load stop
(3) Back cover (aluminum casting)

!!!!!!!!!!!!!VERY IMPORTANT ASSEMBLY ORDER VARIATION COMES NEXT. !!!!!!!!!!!THIS WILL BE IMPORTANT LATER!!!!!!!!!

(4) Paper gasket
(5) Copper diaphragm assembly
(6) .024”-.026” Steel spacer ring (this order is for the 049 from the 914 1.7L)
(7) Inner stop plate with keyhole slot

OR……..

( Paper gasket
(9) .024”-.026” Steel Spacer ring
(10) Copper diaphragm Assembly
(11) Inner stop plate with keyhole slot

Notice the difference in where the steel spacer ring is. It is important.
So….There are two ways to measure the gap.

First....What we are actually measuring is NOT the gap between the 12mm bushing and the stop plate. What we are measuring is how much thread on the 12mm bushing is protruding above the 24mm steel flange that is crimped into the center of the copper diaphragm assembly.

In fact…once you remove the rear cover and the spring pressure is removed from the diaphragm….the copper plate goes to the neutral position and the 12mm bushing comes up against the stop plate.
So that gap cannot be measured and that will not help you anyway. The amount of thread that protrudes above the diaphragm assembly is what governs how far the plate can flex inward to add spring pressure to the armature stack when vacuum is high.

Method #1: The difficult way.

(1) With the back cover assembly in you hand, screws still in holding the keyhole plate down

(2) Use a fingernail or small screwdriver to lift the button on the center screw in the copper diaphragm so that the 12mm bushing comes in contact firmly with the stop plate.

(3) With a digital or dial caliper with its depth measuring rod extended through the long leg of the keyhole slot you can measure the depth to the flange on the copper diaphragm

(4) Now measure the depth to the top of the 12mm thread bushing.
(5) Subtract.

Method #2: the easier way

(1) Remove the four screws that hold the keyhole stop plate down.

(2) Use an 0-ring pick through one of the small vent holes to lift the
keyhole plate out.

(3) Lift the copper diaphragm assembly out.

(4) You can now use the caliper depth rod directly on the 12mm bushing and measure to the flange it is screwed through to determine how far the 12mm bushing has been screwed through it.

What I found:

Years ago, I had measured a handful of 049’s from 914’s. I found that the thread depth of the 12mm bushing was very uniform. It was between .063”-.067” very close. For reference all of these units had the same main spring length on the front of the case.

So a while back I had noted that the setting should be around .065” FOR ALL MPS"S….that was an error..... and I will get into it a bit more after I post the measurements. It is for the MPS with specific assembly order ONLY!

0280-100-037
022-905-051C Bushing thread height: .037” and .035” (Measured two units)

0280-100-027
022-906-051B Bushing thread height: .036”

0280-100-049
022-906-051-E Bushing thread height: .036” and .035” (Measured two units)

0280-100-049 (914 1.7L) Bushing thread height: .063”

THE KEY TO THE LARGER GAP ON THE 914 model 049…..is that the .026” spacer is between the copper diaphragm and the stop plate. When you subtract the .026” spacer…you have .037”…just like the others.

This is not this way because its special for the 914, I also have at least one example of each of the part #’s above that have the spacer swapped…and use a thread height on the 12mm bushing of .063”-.067” like I found years ago on the 049's.

However….the difference is that the units that have the spacer between diaphragm and stop plate...and use .063-.067" all appear to have the copper diaphragm that uses three thin pressed corrugated rings.

The units with the spacer between the copper diaphragm and the gasket on the opposite side of the plate all use a diaphram that has three wider flatter rings...and all appear to use .035" average thread height

All I can ascertain is that the thinner ringed diaphragms were more flexible under vacuum and probably needed more room between themselves and the stop plate.

So a good starting place for the height of the thread of the 12mm bushing protruding above the flange on the diaphragm is .035-.037 if the spacer is on the backside of the diaphragm …and .063” to ..065” if the spacer ring is between stop plate and the diaphragm.


Oh...and an important note:......the outer full load stop screw...Cannot...cannot...cannot....be adjusted unless the car is running at idle with a steady and correct idle when the engine is warmed up.

If you try to adjust the outer full load stop with the engine off...it will cause you to make the setting far too tight....keeping the copper diaphram from moving at all....and creating a lean condition.

To adjust the full load stop:

1) have engine warmed up with timing and valves adjusted and idle to factory or best running spec.

2) Make sure the threads are clean and the aluminum plug turns very easily.

3) turn the aluminum screw inward until it is felt that you just barely make contact with the copper diaphram. You will know for sure because even 1/6th of a turn further will disturb the idle and cause the car to want to stall.

4) once you have contact, back the screw out 1/2 to 3/4 turn. Start with 1.2 and work your way outward in 1/5th to 1.8th turn increments. You must test drive in between.

5) always mark the position of the screw. Once it is working properly, secure teh screw with a small drop of superglue. Ray

Ray

[knewknew]

Hey guys, hope everyone's summer is going well.

I am having a bit of idling trouble with my square and could use some advice. The car was running great for a few months, but now will not idle at a stop without me putting my foot on the gas pedal slightly.


-I have tried turning the 'idle adjustment screw' on the throttle body and noticed no difference whether it was all the way out or in.

-I tried taking the slack out of the throttle cable, but the pin at the end of the cable is already maxed out.

-The idle position sensor seems to be adjusted properly according to the manual: Depress the pedal slightly and hear 'clicks' from the sensor, right?


What else can I try? any suggestions? Thanks.
_________________
1970 Squareback

[Mike Fisher]

Do you have 14 volts revving the engine? You could have a bad voltage regulator?
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http://s169.photobucket.com/albums/u236/mr_bojangles500/
69 FI/AT square Daily Driver
66 sunroof,67,71,71,71 AT,72,72 AT Parts
56 & 57 oval ragtop $2,500

[OmniscientVWpunk]

1969 SQBK

So guys I need help as to wear the four wires of the ignition go. I have the red wire going to the B+ terminal on the head light switch and the black wire to the fuse panel but I have no idea wear the gary wire goes or the black/red wire goes any thoughts. I'll put picture if need.
Thanks for the help.

Jeffrey

[Bobnotch]

[OmniscientVWpunk]

Bobnotch
I know that is is to the starter but is it a cable connector or through some other switch. Also is the wire that it connects to black or white?
Thanks for the help and any comments.

[Bobnotch]

[Type3Noob]

Just want to say a BIG "THANK YOU!!!" tomTram for his introductory 101 on rejuvenating the Fuel Pump.

[crustychief]

Hello, I have been reading this forum for the last couple of days. I have a friend that has a 69 squareback. He says it will not start without starting fluid. after it starts it runs like a champ. He drove it from his house to his garage " hangar" ( about 28 miles ) he says it ran great. I searched the thread and started reading ( I am about 35% through it)
I am going to look at the car soon and wanted some ideas. I am intimately familiar with CIS, and have a good working knowledge of Motronic ( p car guy)but know very little about the system on his car. BTW it does not have a cold start injector. I would appreciate any help, a point in the right direction, or just a link to a thread! Sorry for the long intro!
I do have a 71 bus.

[OB Customs]

Hey there,
I just started reading the FI relief thread and have yet to find anything like my symptoms... As of this weekend My 69 Square started this weird pulse, hunt or buck as I was getting on the freeway. This car is a very low mile survivor and has ran mostly very well, a little rich on idle however. As I started down the freeway to get off the next exit it was able to make 60 then all of a sudden it was fine and I drove it another 10 miles with no problem made 3 different stops all fine. And then just as I returned to the freeway on ramp it started again. From what I have read on the web my first guess is Throttle Switch, followed by trigger points. Any advice would be great.
Regards
Spencer

[Tram]

[Woreign]

I suspect that the fuel pump is cutting out. I had the same problem with my Notch. The ECU would turn off the pump about 5 minutes into my drive, every day. I bypassed the ECU pump relay ground and and it has run fine ever since.

But as Tram said, check everything else first...
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[OB Customs]

[greg hord]

Recently aquired a one owner 1970 squareback and I am getting fuel to the engine bay but not to the injectors. Any suggestions on this one. Thanks, Greg

[Tram]

[OB Customs]

[Tram]

[OB Customs]

[Tram]

[Tram]