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raygreenwood
Samba Member
Joined: November 24, 2008
Posts: 21512
Location: Oklahoma City
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 Posted: Mon Mar 15, 2021 8:58 am Post subject: Re: FI Idling issues, fuel or Ignition or both? |
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| digg75 wrote: |
So, I got a tip to look at the TS2 sensor and its resistance.
`
Had a broken one before and installed it new last summer. I`ve checke the resistance on it and it`s good.
However, I was told that it came with extra an added resistance on 914:ns.
I added a "5w 300 ohm" resistance ant tried to start it up.
First clip, idel without extra resistance.
https://www.youtube.com/watch?v=z4DhIsPxwRM
Second clip with....!!!
https://www.youtube.com/watch?v=MrQUqkNnt1Q
When running I tried to remowe the plug in the AAR hose. Reacted with bad idling. Plugged it again.
Then unplugging the TS1, runs ok with or without it.
It even reacts to airscrew adjustments now. |
Yes!.....we spoke earlier in this thread about the ballast resistor for the TS-2.
And for the record.....its not just a 914 thing. Its pretty much every aircooled engine with D-jet.
The problem is that the TS-2.....the cylinder head temperature sensor.....has a flaw. In order to have the cortevt UPPER end range.....the thermistor used in them also has to have EXCESSIVE lower end range. It drops to far down in reaistance as it heats up.
With D-jet.....as resistance drops on the TS-2.....it leans out the mixture. For best tuning...tbe TS-2 should never drop below about 125 to 175 ohms. But...it routinely drops to about 75 ohms.
What I am about to say next.....is MOST IMPORTANT.
The ECU.... does not have the capability of leaning out the mixture any more...past about 200 ohms. So what tbis causes when the TS-2 drops down ti about 75 ohms......is that it has to come back up in resistance.....to far......to aow a clean "hot start".
This means.....that lets say you drive it on the highway for an hour and stop for lunch for 30 minutes. The TS-2.....which was fully warmed up.....but had air flowing over it and the heads while the engine was running......was at about 125-150 ohms when you shut down. And now the cooling air is instantly ahut off.
The residual heat in the heads and the valves .....now soaks into the TS-2. And.....its resistance RAPIDLY drops.....to the minimun of 70-ish ohms.
You come out 30 minutes later after lunch......and IN A PERFECT WORLD ......the engine has cooled SLIGHTLY. And the TS-2 "SHOULD" haave come back up to say.....200 to 250 ohms....just to give you enough fuel mixture for easy starting.
But it has not.....it was too far down below the minimum enrichment threshold....to give you any extra fuel........so it caused what has been known as the "hot starting" syndrome.
WARNING WARNING!
The syndrome listed above.....is ALL the 200-300 ohm ballast resistor was designed to fix.
It should NOT be the item that changes the way the engine RUNS when its fully warmed up.
If it does.....if the engine requires that, 300 ohm hallast to run semi normally......what it is indicating......is that your baseline fuel mixture is incorrect. This means you need to adjust the MPS.
Ray |
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digg75
Samba Member
Joined: April 11, 2017
Posts: 105
Location: Sweden
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| Posted: Mon Mar 22, 2021 1:41 am Post subject: Re: FI Idling issues, fuel or Ignition or both? |
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@Ray,
Thanks for input.
So I`ve to get hold of someone that can look at my MPS.
Don`t know if I can get it right my self. I coluld learn though 
Tried to swap the ECU this weekend. Just wanted to see if there`s any difference to the previous setup (though I know the ECU`s rarely breaks). The ECU i changed to is a NOS, never used.
This is how it sounds with the added resistance & TS1 disconnected:
https://youtu.be/lKAmUrTYKyg
And here with TS1 connected.
https://youtu.be/VcedmPpI1iM
Sounds as if it`s "counting". Drops a couple of rmp every 5-6 seconds.
Answers "clean" when revving it. Does`nt stall after revving as it did before.
But after giving some throttle, as soon as i let go of the throttle it increases in rpm for a second and then back to idling.
When connecting TS1 it runs on lower RPM`s and sounds if it runs "heavier".
At least at this point it runs better but not great.
//Ken |
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raygreenwood
Samba Member
Joined: November 24, 2008
Posts: 21512
Location: Oklahoma City
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| Posted: Mon Mar 22, 2021 7:04 am Post subject: Re: FI Idling issues, fuel or Ignition or both? |
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| digg75 wrote: |
@Ray,
Thanks for input.
So I`ve to get hold of someone that can look at my MPS.
Don`t know if I can get it right my self. I coluld learn though
Tried to swap the ECU this weekend. Just wanted to see if there`s any difference to the previous setup (though I know the ECU`s rarely breaks). The ECU i changed to is a NOS, never used.
This is how it sounds with the added resistance & TS1 disconnected:
https://youtu.be/lKAmUrTYKyg
And here with TS1 connected.
https://youtu.be/VcedmPpI1iM
Sounds as if it`s "counting". Drops a couple of rmp every 5-6 seconds.
Answers "clean" when revving it. Does`nt stall after revving as it did before.
But after giving some throttle, as soon as i let go of the throttle it increases in rpm for a second and then back to idling.
When connecting TS1 it runs on lower RPM`s and sounds if it runs "heavier".
At least at this point it runs better but not great.
//Ken |
Yes.....this "TS-1" plugged and unplugged test......is a good indicator that your MAIN fuel mixture as adjusted at the MPS is sligjtly off.
I make the above statement......based on these conditions:
The fuel pressure is correct within factory +/- specification and STABLE.
It is known that there are no vacuum leaks
Ignition timing, spark plug gap, spark plug wire connections, rotor quality, cap quality and distributor function (including centricugal and vacuum advance function) are all cordect within factory specs.
Voltage to coil and EFI system is correct and not LOW.
Valves are properly adjusted.
The wiring harness and ground system is known and tested to have clean, tight connections.
So in other words.....everything else in the system must be KNOWN to not be causing issues.....if one is to be diagnosing the effect......for idle and running quality ......of the MPS and Ts-1 and Ts-2.
For idle purposes....not driving and shifting......I have purposely not mentioned the throttle valve switch (TVS) or the full load switch on models that have one.....because unless they are grossly misadjusted or broken..... or have a vacuum leak in the case of the full load switch......they do not affect idle.
In the D-jet system......variable sensor wise.......the MPS is responsible for roughly 100% of your baseline fuel mixture at any given time.
I say roughly......because ......the Ts-1and TS-2......are variable ambient condition adjustments to your fuel mixture.....and.....fuel pressure, while it has considerable effect on fuel mixture across the board.....is "supposed" to be a fixed quantity. It is treated kind of like a hardware part by the system. It is supposed to stay the same within a narrow spec while the ECU and sensors work around that "fact".
As noted.....MPS .....IS your fuel mixture setting. The Ts-1 and Ts-2 simply add and sutract from that setting based on incoming air temp conditions and somewhat....combustion chamber temp conditions based on a rough estimate of head temperature.
So both TS-1 and Ts-2.....and numbers are hard to find......each one can dial in ....meaning add or subtract depending on temperature.......a range of about 10-15%.... which means a,+/- of about 5-7% on each side of 0.
I will have to review my notes......but i think disconnecting TS-1.....meaning open circuit......gives a default reading or effect.....of maximum lean.....which would be about 5-7% lean. I will check that. I cannot remember without checking .....whether the ts-1 drops resistance as inlet air temp rises (just like TS-2).....or whether it gains resistance as temp rises.
So if you disconnect TS-1 and your engine is responding positively to a reduction of about 5-7% less fuel......and all of the above engine settings are normal.......then you need a small tweak to the central armature screw on the MPS.
I would NOT take this to someone else to adjust. This is something you should do yourself. In reality....if you observe a couple of precautions like marking the adjusting screws with a sharpy......and ballasting the TS-2 connection.......adjusting the MPS is a procedure that is BEST done by driving and feeling the effect on acceleration, idling and shift transitions....and NOT with an exhaust sniffer....which rarely works because of the exhaust system design and the fact that when the system is idling and throttle is closed.....several parameters of enrichment are locked out by the ECU.
Its best done by first setting everything stable.....and driving a set circuit....stop and make a tweak to the MPS with a small screwdriver while its running....do this 2-3 times only.....then turn off car and let it cool 15 minutes max......see if it starts and idles normally.....then adjust some more if needed. Then take a break and let it cool down to cold. Then start and make sure it starts, idles and warms up normally. Only when you find the performance is acceptable.....should you then connect the car to an 02 sensor or tailpipe sensor.....to make sure the readings are nominal for idle.
So you adjust for driveability by feel.....and double check with the exhaust sniffer. And it must be a narrow band and not a modern wideband.
The problem of trying to use a wideband exhaust sniffer is that unlike modern injection....D-jet will not run what modern injection considers normal and even across the entire running range. The system and sensors do not,have enough inputs or resolution to do so.
When its running properly....to start, shift and drive properly......D-jet typically runs slightly lean at idle.....has overly rich bumps right off the line is fat through the midrange and leans out as rpm rises.
People who start with the sniffer.....usually end up getting as close as possible by the numbers at certain rpm ranges.....but the car drives and starts poorly.
Before we get any deeper into the how to of adjusting.....post your MPS part,number and a picture of it from the side.
Ray |
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Tram
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Joined: May 02, 2003
Posts: 22711
Location: Still Feelin' the Bern- Once you've felt it you can't un- feel it.
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| Posted: Tue Mar 23, 2021 9:57 am Post subject: Re: FI Idling issues, fuel or Ignition or both? |
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Digg- when you put a timing light on it, how does it react? Steady light on the mark, or does the mark "dance" a little. I swear that second video sounds like a wobbly breaker plate in the distributor.
_________________
Немає виправдання для війни! Я з Україною.
| Bryan67 wrote: |
| Just my hands. And a little lube. No tools. |
To best contact me, please use the EMAIL function in my profile |
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KTPhil 
Samba Member
Joined: April 06, 2006
Posts: 34003
Location: Conejo Valley, CA
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| Posted: Tue Mar 23, 2021 4:15 pm Post subject: Re: FI Idling issues, fuel or Ignition or both? |
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| Tram wrote: |
| Digg- when you put a timing light on it, how does it react? Steady light on the mark, or does the mark "dance" a little. I swear that second video sounds like a wobbly breaker plate in the distributor. |
Asked but not yet answered...
| KTPhil wrote: |
| Have you checked ignition advance and stability with your timing light? If your distributor is wearing out, the unsteady firing can make it run roughly, and also disturb your idle injection timing. |
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raygreenwood
Samba Member
Joined: November 24, 2008
Posts: 21512
Location: Oklahoma City
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| Posted: Wed Mar 24, 2021 7:26 am Post subject: Re: FI Idling issues, fuel or Ignition or both? |
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| Tram wrote: |
| Digg- when you put a timing light on it, how does it react? Steady light on the mark, or does the mark "dance" a little. I swear that second video sounds like a wobbly breaker plate in the distributor. |
Yes! It very well could be.
I keep saying this to all D-jet people. .....any engine setting or component.....that has the ability to "CHANGE" how the engine idles or runs.....even by a very small/minute amount....an amount that is so small that it would generally go unnoticed by twin carbs.....or by the later L-jet fuel injection system..................... causes changes to the VACUUM SIGNATURE of the engine.
The MPS of the D-jet system IS....IS.....IS.....sensitive enough to react to very small vacuum signature changes that most carb systems and flap based injection systems.....do not even see to react to.
D-jet then AMPLIFIES the changes in vaccum signature by altering injection pulsewidth......which is an order of magnitude in scale. A very tiny vacuum change .....that probably did not even change idle......gets MAGNIFIED when the MPS adjusts fuel based on it.
That adjustment to fuel....makes an even bigger change to vacuum.....for an even bigger change to delivered fuel.....for an even bigger change in vacuum.....for an even bigger change in fuel........see the point?
And.....in my last post....I noted that everything else must be PERFECT.....BEFORE we start to adjust fuel mixture at the MPS.
Trams comment/observation is spot on.
The stability of the ignition in general.....and the breaker plates, weights and springs VERY SPECIFICALLY.......were some of the primary keys in getting my D-jet system back to factory smooth or better and getting rid of oscillating idle and off the line acceleration from stop issues......when all else was finally 100% correct.
Had I known two decades ago just how sensitive.....numbers and capability wise.....the MPS is......I would have set the distributor straight FIRST.....as Tram always reccomends  ......and could have saved months or troubleshooting in my life.
This is why about 3 years ago I made a thread precisely going over the issues of long term wear in the breaker plate assembly. Getting rid of slack. Fixing the divot from the ball and spring, fixing issues with the locating pin length of current generations of points. Getting rid of slack between the parts that can translate to excessive or loss of or un-timed points plate movement and timing changes.
None of this age related "fine tuning".....is in the Bentley manual. And.....for good reason. If your distributor is NEW or low miles.....you probably do not have these issues.
A good distributor does NOT just mean the bearings are tight and the points are new and the weights are well lubed and move freely.
Here.....This is a start.
https://www.thesamba.com/vw/forum/viewtopic.php?t=686352&highlight=breaker+plate
Ray |
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digg75
Samba Member
Joined: April 11, 2017
Posts: 105
Location: Sweden
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| Posted: Mon Mar 29, 2021 12:36 am Post subject: Re: FI Idling issues, fuel or Ignition or both? |
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@Tram, @KTPhil, @Ray
Regarding dancing. Getting it to run properly AND be able to use the timinglight has been a challenge. Yet alone, having it idling "stable"
However, when I`ve used the timinglight it has been dancing between 7 and 10 degrees. |
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raygreenwood
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Joined: November 24, 2008
Posts: 21512
Location: Oklahoma City
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| Posted: Mon Mar 29, 2021 6:16 am Post subject: Re: FI Idling issues, fuel or Ignition or both? |
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| digg75 wrote: |
@Tram, @KTPhil, @Ray
Regarding dancing. Getting it to run properly AND be able to use the timinglight has been a challenge. Yet alone, having it idling "stable"
However, when I`ve used the timinglight it has been dancing between 7 and 10 degrees. |
At what idle rpm?
This is with vacuum advance/retard hoses disconnected right?
If idle is normal......does slowing the idle speed down.... make the timing more stable? Does speeding it up make it more stable?
Note.....that the answer to that last question that i am looking for......is not necessarily where the idle timing mark goes to when you speed up idle. It really is about.....does it become stable.
So if dropping rpm causes timing to say.......stay down around 7° or 8° .....stable......instead of popping up and down between 7° and 10°.....that tells you something.
Likewise if speeding idle up to say....1000 or 1100.....causes the timing mark to jump up to 10° to 12°......but it becomes stable and does not dance around......its telling you something.
Most of what that level of sensitivity is telling you is that the mechanical portions of your distributor have wear, need to be cleaned and/or have slop.
After all these years it can also even be common wear in the lobes of the points cam. Having one or more lobes wearing enough to change shape/profile or being lower than the others .....will cause a variation in dwell on one or more cylinders. Thats a big effect on vacuum and fueling. Idle will not be stable....so timing will not be stable.
Also.....when you remove the distributor cap and twist the rotor on the shaft....its spring loaded. This is your advance springs in action. If it moves too far or no t far enough when you twist it.....or snaps back slowly or not fully.......you have issues with the weights and springs.
I would strip down the distributor and check everything. Ray |
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digg75
Samba Member
Joined: April 11, 2017
Posts: 105
Location: Sweden
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| Posted: Tue Mar 30, 2021 11:55 pm Post subject: Re: FI Idling issues, fuel or Ignition or both? |
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@Ray
1. Yes, adv.hose disconnected.
2. If speeding up and trying to keep idle stable, It`s not jumping around. I would say stable. If letting the engine run at rough idle, not giving throttle at all, its jumping around.
3. The rotor advancespring works ok. No delay or slow movement. Feels and sounds "clean" when turning it.
4. The engine and if not swapped, the distributor has appr. 70000 kilometers (7000 Swedish MIL) or 43000 miles on it.
I`ll look into the dist. But, "should" be fine. |
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raygreenwood
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Joined: November 24, 2008
Posts: 21512
Location: Oklahoma City
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| Posted: Wed Mar 31, 2021 10:19 pm Post subject: Re: FI Idling issues, fuel or Ignition or both? |
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| digg75 wrote: |
@Ray
1. Yes, adv.hose disconnected.
2. If speeding up and trying to keep idle stable, It`s not jumping around. I would say stable. If letting the engine run at rough idle, not giving throttle at all, its jumping around.
3. The rotor advancespring works ok. No delay or slow movement. Feels and sounds "clean" when turning it.
4. The engine and if not swapped, the distributor has appr. 70000 kilometers (7000 Swedish MIL) or 43000 miles on it.
I`ll look into the dist. But, "should" be fine. |
Mmmm....no. Its not just the miles....its the miles and teh time. Grease and oils in the distributor are good for only a few years at most. They change just with age even at "0" miles.
And thats still a lot of miles for a 40+ year old distributor. These also get rust on the weight and at the pivot and fulcrum points. You need to strip, clean and lubricate.
I tell people this all the time. If yu are working n D-jet and you have not personally changed/replaced, tested or cleaned a D-jet part on a car you have acquired ....or within the past 2-3 years you have owned it.......it is suspect automatically.
There is no such thing as "should" be ok...or "looks" ok...with D-jet parts and old VW distributors. Ray |
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digg75
Samba Member
Joined: April 11, 2017
Posts: 105
Location: Sweden
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| Posted: Wed Mar 31, 2021 11:52 pm Post subject: Re: FI Idling issues, fuel or Ignition or both? |
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@Ray,
I had a feeling you`ld say that
Lucky me it`s easter and got 4 days off and time to ollk into it.
Wish me luck & Happy Easter! |
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digg75
Samba Member
Joined: April 11, 2017
Posts: 105
Location: Sweden
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| Posted: Thu Apr 15, 2021 12:33 am Post subject: Re: FI Idling issues, fuel or Ignition or both? |
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So,
I`we had my MPS sent off and got it adjusted and tuned.
It was compared and measured against original specs and other MPS in a workin car with the same setup as mine.
My MPS was "off" compared to other MPS.
I`ve installed it made some tests.
At first it ran ok but had some problems when giving throttle. Did`nt answer to throttle as it should.
Ran better without TPS (throttle valve switch) connected.
Opened TVS and cleaned it up. Tried to measure ohms to se any faults but didnt get the readings i wanted.
Finally i noticed that one out of four cables was "hanging by one thread"... just touched it and i broke off.
Had it soldered back and got it back together.
This is the result so far:
1st startup. (warm engine)
https://youtu.be/xj8gF7OvdHk
1st Testrun
https://youtu.be/BgKhZfkdqgo
2nd Testrun
https://youtu.be/Y7SeMfq8T-4
Testdoc below.
A-H= Other MPS units. (H currently installed to the test vehicle).
KS OLD= My MPS before beeing tuned.
KS NEW= My MPS after beeing tuned.
At this point it runs good. Feels strong and responsive.
Runs better than it did when I bought it .
Ignition, with strobe, spot on at 0 degrees when idling. |
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raygreenwood
Samba Member
Joined: November 24, 2008
Posts: 21512
Location: Oklahoma City
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| Posted: Thu Apr 15, 2021 7:21 am Post subject: Re: FI Idling issues, fuel or Ignition or both? |
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A couple of notes:
1. Congrats! Good work! ....ok....so now you have at least one MPS that is set at.....some usable baseline?
Now.....onto the issues I see.  .......
2. The only usefulness of sending an MPS out to be "BENCH ADUUSTED".....which is what you did.....is when an MPS has been tampered with and it is so far out of adjustment that the engine will not run...and therefore the MPS cannot be tuned to that engine because its not running........or.........if you replaced any parts in the MPS like the copper diaphragm or the aneroid chamber resulting in the same issue.....non running so not tunable.
The problem with "bench Adjustment" is that it can only set the MPS either to the manufacturers baseline.....if its known......or to a used sample MPS which may have wear, aged and stiffer copper plate, work hardened or leaking aneroid chamber etc.....and therefore is just a random sample.
Bench adjusting of an MPS.....is similar to trying to adjust a,carburetor.....while sitting in your backyard....sucking through it with a hose....to adjust it for an engine that you have not built yet.
Its not adjusted to YOUR engine.....and there are virtually "0" engines anywhere that at this age....match factory specs.....use factory fresh parts.....or even the same fuel.
So......you are LUCKY that it runs so well. Historically from what I have seen in my experience and in these and the Porsche and Shoptalk forums......there are equally as many people who send their MPS out for bench adjusting......get back their MPS.....and the car runs worse or not at all.....as those who get a good result.
This is because unless your engine is factory "nominal".....it has its own unique vacuum signature that you need to adjust the MPS to.
This really IS the same as adjusting a carburetor to an engine. Bench adjusting is the equivalent......of what Aircooled.net (and others) do....when they sell you a carburetor.....and they look at your cam profile, head type, valve size, exhaust size and type, gearing and ignition curve......and they can put in a good known size range of vents and jets.....to get you running......moderately well.
But you STILL have to adjust that carb to the engine once you install it. The MPS is no different.
A couple of notes about the TVS and wires in the EFI harness
3. It may just be your use of terminology......but there is NOTHING in any of the TVS that is measurable by measuring OHMS. This comment is also made for the benefit of others.
Several of the books note the use of reading the ohms or resistance of the tracks in the TVS.
This is 100% worthless (almost 100% worthless).....and is one of the numerous mistakes in what few books on D-jet that exist.
The TVS does not operate on resistance. It is simply a set of SWITCHES.
The ONLY function that testing a TVS for resistance serves.....and this is what the books are doing.....but they do not explain it.........is it a semi-OK test of the TVS....to check for extreme wear or corrosion.
If the circuit traces, switches or wipers are corroded or dirty/tarnished enough to create high resistance.....its going to operate poorly.....but not because the ECU reads high resistance....but simply because high resistance means poor CONNECTIVITY....and it slows or delays the signal.....response speed wise.
Another similar example:
This is the same issue with why the resistance balance between both channels of the trigger points is important. The trigger points are still going to operate and signal injection....no matter how high or low the resistance is.......but.....high resistance.....SLOWS down the response time. D-jet has no software. It is simply a set of resistance based timing circuits....and operates within the millisecond speed/time frame.
At 3000 rpm engine speed.....thats 1500 revs per minute of the distributor.....or 25 revs per second......or 12.5 cyles of opening and closing for each trigger point channel.
This means that at 3000 rpm.....each injector pair trigger set only has an "injectors on/open"....time window.....of 80 milliseconds maximum....within which to accomplish its entire injection dosage.....and that 80 milliseconds may not even match up to the valve speed of movement or opening cycle.
So.....having dirty, high resistance trigger points.....will not STOP injection from happening....but it will delay the start and finish of it. You may not get a complete injection...............because......resistance in D-jet = TIME delay.
Back to the subject.... .....a voltage/ohmeter is only used for adjusting a TVS in the "continuity" mode. Yes.....its good to do a quick ohm check just to see how dirty it might be....but after proper cleaning....adjusting is done by simple on/off continuity.
4. Last thing.......DO NOT SOLDER ANY WIRES IN THE FUEL INJECTION SYSTEM.
There is not one single SUCCESSFUL EFI system that has ever used solder on free hanging wires. Soldering ruins the temper of copper connectors ...which were poor in the first place in this system.....and they will fail due to looseness over time.
Soldering is a very poor connectivity system in higj vibration, high heat cycling, millivolt senaitive systems like automotive. It does not hold a candle to proper crimping.
There is a reason why all automobiles and aircraft use properly engineered crimp connectors.....and its not cost.....because crimp connectors are roughly 4X more expensive than automated machine soldering.
Soldering in automotive is only useful when terminating a flexible wire joint onto a rigid circuit board....because in this way one side of the joint is supported and the whole joint can be "potted" for strain relief and varnished for corrosion protection.
Ray |
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