A little more on why the books are wrong (TVS adjustment)

[raygreenwood]

Ok, so I dropped out a few pictures last week in response to my rant that the books explain adjusting the throttle valve switch of D-jet (TVS) wrong. It ocoured to me, that everyone has different books. I think they all suck, but I will get to those. It also occoured to me that though I was careful to point out in the pictures that yes..I am adjusting using a brand new type 3 TVS, ....I was adjusting it on a type 4 TB. I just wanted to make sure there was no confusion.

Here are the exact adjusting notes quotes from various books....of which I will point out the defcets of each.

Bentley Brown type 3 book: Section 4, fuel system, page 25 of that section, paragragh 10.7 lower right hand.

"The throttle valve on 1968 and 1969 cars can be adjusted with ignition turned off. The ignition switch on later models must be turned on before adjustment is possible. Test stage 11 in the electronic test sequence can also be used to determine when the late-type switch operates.
Notes: The part about the ignition being on is only correct for the 1968/69 model. While you CAN adjust the late switch with the ignition on, there will be no "felt" click as they describe later in the text. Any click you HEAR...will be that of the injectors opening on the first step of the contact strip. Moving it two more degrees CAN in fact move the wiper arm to the correct location...but not always. The degree scale and the switch itself are not always of the same accuracy and syncronization...in fact...only about 50% of the time are they synchronous. They also do not mention that at no time should you allow the throttle to open.....or if you go to far on the first movement......to never rotate the TVS backwards. You must start over as moving backwards will reset the floating switch on later models to the wrong position skewing the adjustment.

back to the book:

To adjust:
(1) close the throttle valve. On 1970 and later models turn on the ignition.
(2) Loosen the screws on the throttle valve switch. Turn the switch slowly counterclockwise until a click is heard or felt.
(3)There is a degree scale on the switch. Turn the throttle valve one division (2*) further on the scale and tighten the locking screws. It should now be possible to open the throttle slightly before a click from the switch is heard.

Notes here: If you have a non-pressure switch style of D-jet system (meaning you have a copper diaphram in the MPS)...this method will rarely if ever result in a proper adjustment. There simply is no switch within the late TVS that makes a "click" either heard or felt. This book along with all others makes no visual references for inspection inside of the switch to ascertain whether this adjustment has put all of the affected parts into the proper location. I have literally dozens of brand new TVS's in boxes......several each of most of the common part #'s. I can assure you that rarely will any two adjust out exactly to the same 2* rotation specified. This is because they are rarely made that precisely. Maybe at one time....but not to the mid 80's....as most of these switches date to. On late switches....you must not only close the throttle plate as they suggest in section 1....and keep it tightly closed....but you must close the TVS plate itself all the way until the forked plastic throttle shaft bushing makes contact with the steel stop tang that is welded to the plate. This insures that (a) the throttle is closed or "zeroed" out...and the switch it contains is as well. This moves the rearward leaf of the forked copper switch located in the split plastic, floating bushing that is attached to the throttle shaft....toward the rearward post. It is off in that position and ....more importantly.....(b) the wiper contacts are in their respective correct "parked" areas of the circuit board. NOW...with the throttle plate still held tightly closed...you can move the TVS plate....toward open. That means...that the forked plastic bushing that is attached to the throttleshaft begins moving away from the steel stop tang. In only a couple of degrees of movement.......theoretically its 2*.....the forked copper switch in the bushing will move from the rear pin (off and fuel shut off) to the front pin (on enabling the wiper contact arm). The problem is that that even if that "theoretical 2*"....is perfect for that forked switch.....usually....it is not correct or identical for the position of the wiper arm. It is not useful at all....for that forked switch to be in the open position....if the wiper arm is still several degrees away from contacting its first enrichment segment on the circuit board. Unfortunately......the way the book tells it....if you are not careful...you are waiting to feel or hear a click. This book is largely correct on most other points in this section....but clarifys it poorly. To better explain.....with the throttle closed like they said....and the bushing against the stop tang ...like they didn't say....rotate the switch plate toward open until the forked contact is in contact with the foward "on" pin.......and keep roatating....until the little contact at the end of the wiper arm is in the green null area between its parking pad on the circuit...and the first segment of the contact strip. You will need to visually verify this...because on some circuit boards...the distance between each segment on the board for enrichment .....is greater than 2* The problem is.......that by the book method....they would have you rotate until you have touched that first contact.....with which you would hear a "snap".......as all four injectors opened and closed. ....and then they would have you move 2* more. If the forked switch is indeed synched in 2* encrements (rarely exact) to the wiper arm....that WOULD put you in the middle of the second null gap between the first and second segments of the wiper arm contact strip.
While this is actually good adjustment because it means that any 1-2* of throttle opening will result in contacting the next enrichment segment and giving you gas.........it makes sure that you....LOSE....the operation of the first enrichment segment of the wiper strip......and have quite a gap of throttle opening before you see any enrichment at all. They also do not instruct you to....after making adjustment.....tighten the screws on the TVS plate...and rotate the throttle open and closed and then recheck the TVS adjustment....which very nearly always shows a varaince that means mis adjustment...because the "slack" in the forked bushing and the gap between the contact pins of its switch.....are not nearly as uniform as they would have you believe.

Simply put...these switches are dirt simple to adjust if you actually know what you are looking for ...visually....and electronically.....when they are adjusted properly.

I hadn't figured the explaination would take this much space.
I also have the Haynes for 411/412
The Elfrink manual
Chiltons repair and tune-up guide for all models 1970-81 (ugh)
And the muir book.

I'm still looking for my haynes for type 3. If someone wants to e-mail that books version to me....I would be happy to go through it.
You guys will have to tell me if there is enough interest in going through the rest of these books with this same critique. Don't want to waste your time. I was appalled at the sloppiness of the Benley manual on this subject though.

The Muir book is totally apalling in its TVS adjustment. Not one useful piece of information concerning late model....and sketchy on the others.

The Elfrink is the best....but here is what ALL of the books confuse you with: The same forked switch that late model TVS use as fuel shut-off on over-run....from switch # 311 906 11 C as Elfrink states.....is also your enrichment switch. There is no difference between the TVS for fuel shut off and not. the only difference is whether you USE that contact for fuel shut-off.
Four and five wire TVS are fully interchangeable...fully! Even if your does not have fuel shut-off..it uses the same eact switch for mixture enrichment. Why is this? Because that switch is FORKED. It has two contacts. When the fork shifts to the rear.....it not only contacts a rearward pole to signal fuel shut off.....it also....in order to make contact with teh shut off pole....must be out of contact with the forward enrichment pole.....so it shuts down enrichment as the wiper travels in reverse over the contact strips toward closed. I can and have used 311 906 B, C and D interchangeably with all function perfect. You can use almost all of the type 4 switches (which are actually just numbered with Bosch numbers but are the same parts)....in type 3's. This may help open up teh parts availability some for you guys. Occasionally with some switch...you may have to plug a four wire plug into a five pin TVS. So what. That fifth pin is simply a ground. Plug in starting on the left at pin #9. There are a few switches for other D-jet cars that are also otherwise identical but you may need to swap a wire around in your plug.

The drawing in the Elfink manual shows a diagram if 311 906 111 C on page 49 in the late modifications section. The part that can confuse you.....is that there is labled a switch ...a....and a switch ...b. Those are actually the same switch. They are the "floating" fork switch. It is simply ONE switch with two possible poles. In can never ever be ON or OFF in both poles at once. It must be one or the other.
Also....you can simply disconnect the fuel shut off portion on any car that has a decelleration valve....and actually solve many "bucking" issues at part throttle.

The part in Elfrinks manual on page 53 with refrence to adjusting TVS's with or without fuel shut-off....is ludicrous. The adjustment is the same. The switch is the same. Your systems usage of said switch with reference to its wire harness inputs are all that is different. Sorry for the length. Ray

[Tram]

The "Idiot Manual" is called that for a reason, I've always said. Back in the '70s, I brought a copy in for my German tech buddies to get a look at. These guys were like the Nick Burns (SNL) of VWs. You'd have thought it was a joke book. One of them got creative and made a poster on the Xerox machine, and retitled it "How To Get Fired From The Repair Dept. At Your VW Dealer, A Step- By- Step.... etc." We hung it in the break room.
_________________
Give A Pal a Hand!
www.happytrailsfarm.org
May 4, 1970... Never Forget.

RIPRW

"Hell is- other people."- Jean- Paul Sartre

[raygreenwood]

Tram...I agree. I do keep it around because I appreciate it...for what it was. Its a survivors manual for those without money, without mechanical skills and without any real desire to gain those skills. It can help in a lot of situations...simply by informing you of what you can do to get around not having money or tools or correct parts.......when you lack the imagination, training or drive to figure that out for yourself.
But...they did do quite well in collecting baseline information and re-quoting it. The cross match and timing information is excellent. I keep it around because of the illustrations alone, the cross match and the history of it are just good reading.
In this day and age......with the scarcity of good new parts and the fact that the yards with vast seas of newly wrecked ACVW's are long gone.....if the Muir book is all you are going by....you are in trouble. Ray

[KTPhil]

[KTPhil]

Haynes Type 3 manual:



Brief as you'd expect since EFI was rarer in England than in the USA.

Same mistake as most others; they forget to tell you to first rotate it counter-clockwise, THEN clockwise as you listen for clicks or watch the meter.

[raygreenwood]

But...that is almost the most complete one I have seen. Thank you for including it!
It seems the wildcard is actually the degree of variability on the late models....of how many thousands of an inch of slack there is in the floating plastic switch fork with relation to how far the wiper arm moves. I spent an hour or so last night measuring the slack and sloppiness of about a dozen brand new late model switches...with reference to the level of float of the forked plastic bushings and their fit to the hole in the plate.

Its not that Bosch started building the plate, circuit board, plug and wiper arm assembly sloppy. If anything those parts got better over the years. It appears that whoever was molding theork changed a few details. Its not that the switches should abeled defective and thrown out either. They simply need to be categorized as different than spec and repaired or modified.
that modification I showed in the series of pictures where the enrichment contact for the forked switch was enlarge...made that particular switch superb in adjustment and response.

There are also at least two variations of manufacturing technology that went into tehse switches...so there was more than one OEM manufacturer. I have some example of what I call the "wire type" switch...wherin the floating contacts are not stamped copper...but copper or copper plated wire of about .010" or less. Those are miserable for getting out of adjustment.

There are also three basic designs of TVS. Ther very early two wire or 001...which is simply a micro switch with a tang that activates it, the four wire early which has a copper leaf switch and a semi-floating plastic shaft bushing similar in some ways to the late four wire and the late four and five wire switches with the floating copper fork. Ray

[blues90]

I can tell you the bently manual is completely crap the way it describes the TVS adjustment . First off they tell you to rotate the switch counter clock wise until you hear a click and then one mark further counter clock wise or 2 degrees. Well how can you move it counter clock wise when in fact the switch is against the stop . They should tell you to have the throttle closed move the switch clock wise then counter clockwise .

I was told by a fellow who worked for Porsch to look at the metal stop and there is a tang , bend that until the wiper is just before the first gap of the stepped circuit board contact with the fuel on/off contact against the off , then hold the throttle closed and turn the TVS counter clock wise just until you feel it hit the stop tighten the screws . This way you are on fuel and just before the first stepped contact . To explain, if you look at the off fuel wiper there is a gap on the circuit board , with the off fuel wiper on the contact just behind this gap is a board contact and strip that goes to pin #14 which is the idle circuit , when the throttle is just open the movement of the pivot contacts you are just now on fuel and the on fuel wiper is just at the edge of the board contact gap ready for the first contact just after the first gap . They have that stop set different on all of them . I have one on the car that has the wide copper on/off contact and one with the thin copper wire and I chose the one with the wide copper strip . Even still there is enough play in that pivot that the degree scale is not accurate . Doing it this way when the throttle is closed you on off fuel and when the throttle is moved just a tiny bit say 2 degrees you are on fuel and just right before the first contact on the circuit board .

He came over when he was working at ford with me as the shop foreman and I was trying to pass smog and adjusting the TVS as I always did . if you are one bit off the car will not idle using the degree marks . The older 4 wire TVS did not use #14 on the ECU .

[raygreenwood]

Yeah..I agree...most switches out of the box are way off...but be careful in what you do before you bend that tang.
The TVS on D-jet should not affect idle at all...unless you seriously have something bent and are shorting out. Its just not what it does. It is extra enrichment...and only has bearing on anything when its either fully closed, in motion or in mid stroke and in deceleration position (fuel cut-off).
If your foot is off the throttle.....and the switch is closed....it should have no bearing on idle.......unless its not adjusted and in enrich position. Even then...it must be moving across contacts. There are a few rare cases where bending that stop tang is necessary before you start....but you will rarely have need of that during most normal adjusting. In fact you need to adjust to see if you need to move the tang.
What I'm saying is that bending that stop tang is usually one of the last things you do. They are indeed set to different places. No two switches out of the box will have that tang in exactly the same place.

The issue is that there are differnces in each switch for exact location of the circuit board and where it is riveted onto the plate, differences in drag on the forked switch carrier, difference in spring and width to the forked copper switch etc. There are about 5-6 variables that make each switch different.

The thing to remember is that the metal stop tang is mainly an absolute stop to keep the switch unit from over-rotating...ever...and putting the wiper switch into an area it cannot go.
When the switch is properly adjusted.....the forked switch carrier should not be resting on that steel tang. The actual throttle plate is the stop...and the switch should be about 3-4 degress advanced of that.

The real issue with the metal stop tang is that it may not allow the correct starting point for adjusting. This can only be seen after you adjust the switch......then cycle the Throttle plate to full wide open throttle and then cully close the throttle plate. Only then can you see where all of the friction and difference in the floating/moving parts...puts the at rest wiper arm contact location. From there....about half the switches need a further adjustment (usually about another 2*). Only at this time can you note whether the tang is too far advanced to allow the correct starting point.

I would say about half the new switches need a stop tang adjustment. But you have to try to adjust them first to find this out. Ray

[blues90]

[raygreenwood]

Let me print this out and sit down with a couple of switches tonight. If you can tell me what part # switch you are looking at....I can make sure I am on the same switch. Though most are identical...I'm going to make sure.

I'm pretty sure we are looking at the same details. Most people go by teh book with the TVS....and when you go by the book you only really get two states of running (a) just average and functional....which most people take to mean perfectly adjusted and excellent and as good as it gets (which is not true) or (b) not so well and lots of off the line issues....which most people think is either something totally unrelated or is a bad switch...because they adjusted by the book.

A good portion of most switches have minor tolerance issues that make adjusting difficult. This is excessive gap between teh two poles at the forked switch and excessive drag on that plastic forked switch holder.
Usually the locations of the wiper arms are very good...in reference to each other....meaning rarely will the primary wiper arm be in perfect adjustment while the interior shorter ones are off....which is rarely correctable. Ray

[blues90]

[raygreenwood]

The thing to remember is that these TVS...fit numerous cars. I have examples of the five pin that have 14 listed in two locations.
The five pin is left to right: 9,20,12 or 47, 17,2 or 14. You notice that there are options for these pins in several locations.
The four pin is left to right: 9,20, 12 or 14, 17

Both of these TVS...are 199% interchangeable. All internals are the same.
The differences are that different cars had different harnesses...connecting ECU's whose 23 pins are doing the same thing in both cars.

To use a four wire harness in a five wire TVS.....I remove all four contacts in the 4 pin plug... then...from left to right...insert 9, 20, 14 and 17. It really depends on the system.
In most type 3 and 4 D-jet...the function of the main 23 pins is the same in each...so they go to the same corresponding numbers on the components. As long as the circuit paths are the same inside of the TVS...it should function. I know that sounds cryptic...but let me look at the diagrams tonite and i will see what I can straighten out. Ray

[blues90]

[KTPhil]

[raygreenwood]

Sorry for the long delay. Works been busy. Glad to be working...

OK. The cut-off pin is # 17. But lets take a minute here.

On both the four pin and five pin TVS...all of the first four pin positions and functions are the same. It gets confusing. You can use a four pin or a five pin TVS in a car whose systems and harness were made for a four pin. You might have to find a five pin plug and remove teh pins from your four pin plug and insert them into a five pin plug...but they are all the same. With a couple of changes you can use a four pin TVS within a five pin system as well.

So pin #'s #9 and # 20 are the two halves of the "zipper" enrichment circuit path that you see inside the TVS that the wiper arms run across...ok?.

# 12...third pin over from left... is the ground half of the two "zipper" enrichment path circuits. Its what you hook your probe to when testing either #9 or # 20.
NOTE: You have some odd numbers on these TVS's because they were not made just for VW's. They fit a whole slew of cars.
For instance...wire #12 just happens to be the ground pin on the trigger points.....which just happens to govern the triggering of both pairs of injectors...right? Well the "zipper" strip in the TVS..also alternately triggers those same two injection channels...just out of time with the distributor trigger...get it?
So...the two circuits using pins #9 and #20 as grounded by pin #12 on the TVS..are simply and alternate external source of injection triggers. Thats how this works. Everything else in the TPS is a function of cutting injection off like when throttle is closed on overrun, or when cruising at high speed.
On some cars like late type 4...they ran a wire called # 47 from the third pin normally called #12...to ground together with the trigger points on the dizzy.
So you ask...if #12 is a ground and is technically the same as #12 on the trigger plate...why does # 12 run to the ECU? And why does # 12/14 from theTVS not run to the ECU. Because its a ground.
The #12 on the triggers runs to the ECU because the #12 inside of the trigger is grounded to the chassis of the distributor. It takes the ground for those two circuits into the brain.

The #12 on the TVS......is....actually (as we noted above)....the same as #14. . confused? Don't be!....Just remember its FUNCTION!!!
Its the same as #14.....because #14 is also a ground......and its a ground...because its hooked to #17!

To undertsand this you must look closely at the circuit diagram of the TVS. #17 is the ground that controls fuel cut-off....but is a ground nonetheless. It goes straight to the ECU...but is a ground through the chassis of the TVS. Pin 14 goes to wire #32 (at least on type 4) and hooks to the ground bundle where the injector grounds go. Its number 30 on the chart for 70-72 model type 3's with a four pin TVS.

The ECU's pin 14 is only used when controlling a EGR valve relay. Also...in that same case....the five pin TVS uses its pin #14 to do the throttle closed triggering of that relay when throttle is closed....which is when the floating forked switch...disconnects #14 from #17 and causes fuel shut-off.




Here is the important part.

For both four and five pin TVS's, looking right at the pins in the plug and reading from left to right:

Pin (1) is #9
Pin (2) is #20
Pin (3) will say #12 AND #14 on the four pin and #12 AND #47 on the five pin.
Pin (4) Is # 17

The only real difference in the five pin TVS is that the fifth pin is #2 and #17.

Let me explain this wierdness. You ask how these two TVS can be the same internally when # 14 appears in two differnt places?

Because...internally...#14 and #17 are connected together at one particular point by the forked switch in the housing. They have the same function...which is a ground.

I know this is confusing. But what you have to do...is simply understand what each pins function is...either positive or ground.

Yes you cans swap four and five pin TVS's on any system 70 model and on as long as it does not have an EGR. To make them work you will have to swap around in the plug...pins 14 and 17. Pins 9,20 and 12 stay the same. In one case...and this is from memory....you need to run both 12 and 14 from the third pin on the TVS which is #12/14.
I think that is when moving from a five pin late model with no EGR...to use a four pin late model switch from 70-72 type 3 or a 71-73 type 4 .

The factory did some of this for you....moving pins around in the plug to access the right functions...when you find late model cars with no EGR...that came with a five pin TVS.

All of the functions for 70-73 are included in both four and five pin plugs. You just have to plug your wires in correctly to access them.

The bucking sysndrome: I have a stack of pictures I sent to someone about two months ago. They show the sloppy parts of the factory TVS.

Its true that there is a "parking" area for the wiper arm as Blues90 mentioned. When the wiper is in that area...it means that the throttle is closed all the way. This is fuel shut-off position. The ground is broken.....so why do you still get idling? Because when teh TVS is porperly adjusted...the car gets its idle ground ...because at this point in the wiper strip....#17...is connected to #14....which is #12...which is a ground.

So.....you should be asking....when you are at part throttle cruising...and do not have the wiper in park....and the forked switch is in neutral or against teh rear pin....shut-off location...why does my car continue to run at highway cruise speed? Because...when the forked switch in in neutral or on the fowrad pole (enrich)....it is not breaking the contact between #17 and #14. So the car runs.

The problem with bucking is that there is sometimes slop and frictio ngetween teh two brass pins that the forked swicth contacts. So when you are at part throttkle with light pedal pressure....the forked contact switch instead of floating between the enrich and fuel shuut-off contacts...will contact the rearward pin beraking the ground and shutting the injection off for a split second (bucking). It can do this from engine vibration at part throttle.

Other times the gap between the two poles on the forked switch is excessive...so....it allows too much float time for each throttle movement from your foot...to cause a move toward the enrichemnt pole...and too much power/rpm loss....so when you contact that forward pin with the forked switch...you get a jolt of enrichment (bucking agin). A really sloppy switch gets bucking in both directions as the forked wwitch oscilates back and forth between the enrich and shut down poles.

By unplugging #17 wire....(let me check to make my latest harnesssure please cause it could be #14...cause they are all connected to #12).....it makes sure that the forked contact bouncing off of the fuel shut-off pin cannot cause bucking at cruise and overrun. If your switch is otherwise not sloppy...this gets rid of the bucking.
So you ask...if #17 is disconnected...how does it get its idle signal when the throttle is closed?....well...if your TVS is properly adjusted...it gets it through #12/14.

If your Forked switch is sloppy...this only gets rid of exactly 1/2 of your bucking. The rest must be corrected by minor surgery on the forward enrichment pole (mainmg it larger in diameter to get rid of excessive slop).

After all of this...really critical adjustment must be done. I have pictures of all of this. You will find throttle repsonse you never knew you had. Ray

[blues90]

post below

[blues90]

(On my TVS there is pin

9
20
12 & 47
17
2 & 14

14 only come into play with 17 closed throttle 17 being the only contact to ground if the forked contact is in contact with the of side on the forked lever contact 14 and 12 & 47 are ground always.

So you are saying that the fuel at idle is controlled by a ground circuit because at that point pin 9 and 20 are out of the circuit. For some odd reason the later 73 ECU uses pin 14 on the ECU . The EGR relay uses pin 14 and 17 from the TVS and are wired from pins 14 and 17 at the TVS then they are double wires in the same terminal at the EGR then go to the ECU.

The EGR relay was right by the ECU on the MPS bracket so I might be better to remover these spade connectors which are nothing more than a splice and make it a direct wire and also the EGR valve was on the front right of the engine and the EGR valve takes it's power off the fuel pump relay pin 87 as it is just a very long lead just looking to short out . i just left the EGR valve connector hang tapped off is is a good test point for power at the pump relay.

So you are saying the TVS idle circuit is basically a ground for the injectors and the trigger points at idle and the trigger points at idle alone provide the injector timing also considering the HTS and MPS signal ? )

[raygreenwood]

The later ECU uses #14 only for the EGR connection. You will notice that there is a pin # 14 on the EGR relay as well...so its a 3 way link between the ECU, EGR relay and TVS. Even when you have no EGR relay in the loop....the wire still goes to ground and stil goes to the ECU. Either way its still a ground. Its simply the other side of #17.

The interesting part is that certain systems have enough ground loops because of their wiring that you can literally unplug the TVS while the car is idling and it will have no effect. Of course you can't rev it because then it miss fires due to no extra enrichment. I am trying to remember if all of the late models do this.

"So you are saying the TVS idle circuit is basically a ground for the injectors and the trigger points at idle and the trigger points at idle alone provide the injector timing also considering the HTS and MPS signal ? )"
Yes..it is. Thats not saying that thats the only function. As Brad Anders had made clear to me, certain things function at certain times within the ECU and are limited by timing functions at certain points (warm-up etc.)

But...the TVS is really quite a bit simpler than everyone is making it....regardless of all of the "potential" things the TVS is designed to do or could do.

The EGR system is simply slaved onto...meaning is activated by....the TVS. It does not really make the TVS more complex. It is using circuit paths and switches that already exist in the 4 pin TVS. In fact. In less than a minute. I can rip the 4 pin plug from a TVS and install a five pin plug....and then use that TVS on a late type 3 or 4 with five pin harness and EGR system. that plug twists right off. Thats why it has spring terminals inside...instead of soldered connectors like older TVS.

The later "builds" of TVS....got a lot more universal. I realize that earlier on, there were variants of TVS taht seemed to be made specifically for one system and were slightly differnt enough that they couldn't be used on other systems. This is not so much part # related....but date of manufacture related.
In the early days of D-jet....say 67-69..there were not as many cars using D-jet. Most if not all were VW. Then Renault, mercedes and others. There began to be a lot of unique parts. If you look at enough TVS's...early...then look at those same parts that wrere manufactured up until recently by Bosch....you will notcie that they consolidated a few parts. The vast majority of TVS for 70 models and later that used D-jet...have only a couple of differnt circuit board part #'s inside. The number of actions that TVS's carry out is a pretty short list...and all of them that I know of can be carried out within one style of 5 pin housing.
Its just a matter of where you attach wires and what they go to.

Also...I'm not nearly 100% knowledgable about everything that goes on inside of Each ECU. Most are actually fairly the same except for some differences in resistance....and of course what harness is hooked up to it to use a particular sequence of paths.

Its worth it to remember that Pin # 14..connects to pin # 12 (which we know to be a ground).....through pin # 17....only when the throttle is closed and teh fuel cut-off pin is activated on the 024 TVS. That means that when throttle is closed...wire # 14 is supplying ground to the EGR relay and the ECU simultaneously. We know that at idle...is not where you want EGR to operate....and we also know that EGR is a richening factor....or is supposed to be.
Pin # 17 goes to the EGR relay as well. Also wire #26 from teh EGR relay goes to a thermotime switch just like the cold start valve does (a seperate one). Generally the TTS provides a ground signal. wire # 28 from the EGR goes to a ground bundle. It internally supplies ground across a switch inside of the EGR relay to pin #30 on that relay which takes this ground to the EGR valve . The EGR valve appears to take its positive from the fuel pump relay and also supply that positive back to pin # 29 on the EGR relay.

So...it appears that you have a whole series of grunds and several resistors inside of the relay. The gorunds iwould suspect...are deesigned to tell the relay all of the different point...when it is NOT allowed to be open. In short...with a constant "hot condition"...the EGR relay is constantly on supplying power to the EGR valve when the fuel pump is running....except for all of the areas when its contacts are grounded out and switched to the other pole...which means no power to the EGR valve.

The nifty thing is that #14 on the four pin TPS...is simply a ground. That means that on teh EGR circuit...since it is no longer physically a ground...its either getting its physical ground from pin #14 on teh ECU and taking it to the EGR relay and then relaying it back to the TVS....or its getting it from terminal #17 on the EGR relay an supply it to both the TVSand the ECU at terminal #14.

Either way.....if you don't want to use the EGR...simply pull the #14 wire out of the ECU socket and off of the EGR relay and run #14 to ground at the injector bundle...and it will function as a non-EGR system. Ray

[blues90]

Have you noticed that when the throttle is wide open there is not ground on 14/47 or 14 in the TVS? In the cover there is a stop and on the forked contact that the fork switch uses as a common for both fuel on and fuel off there is a double wiper one ahead of the other at full throttle the rear slidding contact meets a gap on the board and the forward contact is also off pin 14"s strip.

This would really depend on how the TVS was adjusted at it's starting point but it does seem like at the wide open throttle the fuel would shut off as at that point 20 and 9 have no ground at all.

[raygreenwood]

Yes...you are right...at wide open throttle the contact strips of 20 and 9 would have no ground on certain TVS...but that makes no difference to the injection system because the two injector channels are getting their constant ground at pin #12 on the trigger set....thats whay it keeps running
Remember...the third pin is 12/14 on the TVS.....and simply ADDS into the trigger set signal. It is not in place of it.

All this limits....is the extra enrichment injection signals that the TVS was sending....not the rpm and trigger signals that the triggers are sending.

The TVS is only momentary impulse enrichment.....meant for throttle resposne as the TB is opening. Its transitional response. The baseline main enrichment is still being set at WOT as you wind the throttle out....by a combination of MPS reading, rpm signal from triggers....and CHT baseline reading. I will have to read up...but its also possible that extra max enrichment is being signaled whne you are at the end of the TVS contact strip....by signaling WOT to the ECU. Ray