Printable Version of Topic

Posted by: MikeInMunich Jul 6 2018, 08:13 AM

Greetings once again from Munich gentlemen!

It started with a thought and no wood to knock on, seriously!

I was driving around Munich about 6 weeks ago and thought to myself, this car is running perfectly and needs nothing. What could go wrong? Then literally, less than a few minutes after that, it started. A light hesitation in the lower RPM range. Seemed like the car was choking a bit, or missing on once cylinder.

I was at a D-Jet workshop last year with Dr. D-Jet. See https://oldtimer.tips/de/

Volker is a great guy and knows as much about this system as anybody. He tested the vacuum on my MPS last year and informed me that it was "borderline". So that was the main culprit. I took it out, sent it to him and this year it was indeed worse and thus the main culprit. Volker disassembled it and replaced the copper diaphram. Now it's tight like new. Some may be surprised that this is possible and / or where he got a new diaphram from. He had them manufactured or perhaps, I'm not sure, manufactured them himself. PM me if you want / need one and I'll send you his email address.

So, with my restored MPS I hooked it up and, low and behold, the problem was quite the same, only about 10x worse!

Now, with the car immobile and Volker hundreds of km away, I'm practically on my own, with his and your advice, to try to track down the real problem.

Volker thinks that because the MPS was operating sub-optimally previous to my purchase of the car that the mechanic or the P.O. had compensated elsewhere to get the car to run properly and that now that the MPS is sending a different signal to the CPU, things are off.

More info:

Just before the problem started my milage was really bad
The CPU is the correct one for my MPS and working according to specs. Volker tested it.
Engine has about 5,000 miles on it. Was rebuilt and running GREAT.
Fuel pressure was set at 29 psi only about a year ago. I reckon it could have hardly changed on its own since then.
The engine was originally a 1,7 but is now 2liters with a “proper FI performance Webcam” (as stated by the mech ic who rebuilt the engine)

No adjustments were made to the FI to get it to run properly. It was running excellentwith a virtually perfect idle when warm and just slightly rough for the first 3 Miles or so.

TPS plate and air temp sensor are new.

What do y'all reckon could be the culprit? What should I be testing?

I'm taking it to a place to tell them what to test, including:

Fuel Pressure
Plugs
Compression
CO value
TPS setting
Timing & dwell
search for Vacuum leaks
grounds
Valve adjustment
Fuel filter
Relais
Injectors...

What else should I have them look for?

Thanks for your input!

With best regards from what was just ranked The Most Livable City in the World by Monocle Magazine,

Mike in Munich

Posted by: worn Jul 6 2018, 08:34 AM

I'm taking it to a place to tell them what to test, including:

Fuel Pressure
Plugs
Compression
CO value
TPS setting
Timing
search for Vacuum leaks

maybe add the cylinder head temperature sensor, coil, distributor timing points, and plug wires to your list. If you can get it to give a sign of the problem while not rolling, that will really help.

Good luck!

Posted by: Jeff Bowlsby Jul 6 2018, 09:06 AM

Trigger points function.
Have your injectors cleaned/flow tested, including the cold start valve.

Posted by: JamesM Jul 6 2018, 10:46 AM

It sounds like you already isolated the problem. Even though it has been rebuilt your MPS may still not be calibrated correctly for your car. I wouldn't spend any money on other troubleshooting until you have absolutely ruled out an MPS issue by swapping it with a compatible unit from a well running car.

In the mean time if you want to test individual components yourself I would recommend going over Brand Anders site

https://members.rennlist.com/pbanders/

specifically

https://members.rennlist.com/pbanders/DJetParts.htm

and

https://members.rennlist.com/pbanders/manifold_pressure_sensor.htm

While the dr-djet site appears to have good general d-jet information and troubleshooting it doesn't appear to have the in depth analysis of the different tuning parameters for components used over the course of 914 production.

Posted by: Amphicar770 Jul 6 2018, 11:22 AM

Had similar issue in my car. Connector to CHT was lose. Pushed it on tight and never had problem again.

Is your engine wiring harness original. That can be the source of many Gremlins.

Posted by: 76-914 Jul 6 2018, 11:23 AM

Possibly the diaphragm itself if not made with the same material. Chris Foley went to great lengths finding the correct material which IIRC contains beryllium. I know it's a long shot.

Posted by: dr914@autoatlanta.com Jul 6 2018, 11:31 AM

will the car no longer start and run at all now?

Posted by: saigon71 Jul 6 2018, 01:09 PM

It certainly sounds like it could be an MPS issue. Was it calibrated after he replaced the diaphragm?

I had similar problems to what you describe when my D-Jet trigger points got oily. It would be a cheap and relatively easy thing to check.

Posted by: Bartlett 914 Jul 6 2018, 02:07 PM

This is a very suspect point.

Since the MPS made things worse, I would assume it was not repaired properly and out of calibration. Does it hold vacuum?

Posted by: Dave_Darling Jul 7 2018, 02:23 AM

Start with compression and then move on to ignition. Problems with either one (especially ignition!) have masqueraded as fuel injection problems over the years many many many times. Compression also includes your valve clearances, BTW.

Then move on to the FI system. Check all wires and hoses; make sure everything is plugged in solidly where it is supposed to go, and nothing is cracking apart or leaking.

Fuel pressure can change rapidly if something clogs up the intake, or a hose kinks.

A bad ground can cause all kinds of strange problems.

--DD

Posted by: r_towle Jul 7 2018, 09:12 AM

Not enough information.
Car is stumbling at light throttle? Is that it?
What makes you think it’s Djet versus fouled plugs?
Are you still running points?
What is the dwell and timing?

Replace plugs, points, and distributor cap at least annually.
If the car sits unused for more than a few months in the winter, replace the fuel filter annually.

I came back from a trip recently to find my FIL P 1800 Volvo in my shop “dead”
Fuel filter replaced, 14 dollars, car runs perfect.

Posted by: r_towle Jul 7 2018, 09:32 AM

Djet parts
MPS....100k miles, you fixed that, it ran great
TPS, 100k miles, will produce conditions you can change depending upon the position of the gas pedal
Temp sensors, 100k miles. Car will run bad at every rpm, gas consumption will go up, will not start right....or at all
Fuel pressure regulator, 100k miles
Computer....lifetime (works or does not)

The rest of the parts are ignition
Plugs...6 months
Points...6 months
Distributor cap...6 months
Ignition wires...annual

Outlier...throttle body, 100k, shaft bearings wear out.

So, my advice is get a full tune (plugs, points, cap, wires)up and a new fuel filter.
Spend money there first, before you suspect DJet

Posted by: nordfisch Jul 8 2018, 07:07 PM

Hi Mike <and all others interested in this topic>,

you can be absolutely sure the MPS and the ECU you got from Dr-DJet are fully functional and correctly adjusted.

The new diaphragms he uses are NOS types he bought directly from the former producer and he adjusts the MPSs as fine as even possible using his own equipment and value-tables more exactly than the OEM can do this today.
In addition, he uses the original equipment and data the OEM used and uses for this task.
He owns this very rare equipment and tools and is a perfectionist.

He doesn't open the seal of the MPS to do this but reopens it some more times if neccessary to adjust it from the inside.

You will not get the parts back from him in perfect optical condition - he is a hobbyist and doesn't waste time doing things others can do - but does make a perfect technical service.

In addition, he gave you a second MPS and a second ECU for testing, both with the correct part #.

Yes - I saw and registrated you in Erlangen / Nürnberg only two weeks ago, but we didn't talk to each other, because you were in a hurry and up and away before I could talk to you. Maybe you saw my blue Opel Diplomat...
We had email-contact some months ago and I remember some of the problems you had with your car...

----

Please do exactly what Dave says.
Do it in full. Don't leave anything out.

Add opening the D-Jet main-relay carefully to the to-do-list. Maybe it has become weak as it happened once at my own car. Maybe you see brittled contacts...

And don't forget: Do all the testing and measuring at the ECU-connector. The wiring harness and ground connections are so often defective. One missing or bad contact can be the reason for all of your problems.

Don't forget the grounds... dont only check them visual or by multimeter, but pull them off at the engine or screw them off at the relais board and elsewhere, clean them and the ground-point, too.

I saw your original ECU laying on the table in Erlangen, it was covered with underbody protection material. Maybe the relais-board-area looks similar. Paint = no electrical connection!

Regards
Norbert

Posted by: MikeInMunich Jul 10 2018, 05:17 AM

Indeed! I have now done this and it apparently IS the MPS! Apropos calibration...how is that done??

Posted by: MikeInMunich Jul 10 2018, 05:20 AM

Thanks for the feedback Norbert! Do you know which Relais is for the D-jet?

Posted by: MikeInMunich Jul 10 2018, 05:22 AM

Thanks for the input! Any idea where I can get a new CHTS? I want to change that out in any case.

Posted by: MikeInMunich Jul 10 2018, 05:24 AM

Thanks a lot for the input again Dave!

Posted by: MikeInMunich Jul 10 2018, 05:26 AM

It holds vacuum, but swapping it out proved your suspicion correct. Apparently it’s not calibrated properly.

Thanks for the input!

Posted by: Philip W. Jul 10 2018, 10:24 AM

this is not unusual, I had to re-adjust my MPS after it was set to factory specs, it was very lean running, but I have a A/F meter to see the fuel mix and once I readjusted it the car ran fine, but at stock setting my A/F meter was running like 14 and up to 17 on hard acceleration , and it should be closer to 13 or so.

Phil.

Posted by: Bartlett 914 Jul 10 2018, 11:04 AM

I have rebuilt a couple of these. I was very successful at matching the one in my car so I know I have a working spare. I did another with the same settings and it did not do so well on my friends car. The adjustment on these is a little tricky and each car may be a little different or so it seems. I will tune the last one on my friends car at a later date (it is just for spare purposes)

Posted by: Bleyseng Jul 10 2018, 12:38 PM

The MPS was adjusted back to Factory specs..... Hmm, is your engine brand new with all new parts, no. I have fixed and adjusted maybe 30 Mps's over the years and the "Specs" are a starting point. Get a A/F mix meter and adjust the MPS to your engine.

Posted by: Jeff Bowlsby Jul 10 2018, 01:36 PM

Exactly. Every engine today is unique in its configuration and wear characteristics. the exact fuel requirements for any two 2.0Ls are not alike. On top of that I personally own a few NOS MPS and have characterized many others that...guess what...are calibrated differently.

The best and really only way to get an optimal calibration is by using an exhaust gas analyzer, WB02 meter or Dyno on YOUR ENGINE. Inductance calibrations on the MPS with the Wavetek can only get you close. Using the caliper depth gauge method is also only an estimation because the calibration adjustment parameters are extremely fine for accuracy.

Posted by: Dr-DJet Jul 10 2018, 03:53 PM

Hi,

Mike did not mention to you and to me that he does not have the original engine installed. He had his 1.7 engine bore increased to 2.0l and changed cam to unknwon spec.

It is of course not possible that any open loop control ECU and MPS will notice that. Even a closed loop injection system would have trouble with that. His previous MPS lost vacuum and thus saw far too low vacuum enriching A/F mixture artificially. When it is back to factory spec what happens? Of course mixture is far too lean for an engine that has 25% more air volume and a total different volumetric efficiency and fuel need. Both are hard coded into each ECU and each MPS.

I do not understand how Mike could forget to mention this fact . If he is lucky he now has an engine similar to an original 2.0l engine. Then he could use components from that engine. But without knowing engine mechanics and his specific cam changes in detail, that is impossible to say.

My weeks of support for this trouble case is over. I learned of the total engine changes today. I am surprised what speculations have built up here in 914world why a factory spec MPS should not fit a normal engine. Bosch has supplied 10s of thousands of MPS as spares (and 100s of thousands originally). How would Bosch workshops have survived if they would have had to retune each spare MPS in field? Do not create such fairy tales. Bosch Classic delivers repairs of MPS to their spec until today for many car models with Mercedes-Benz still being the largest user of D-Jetronic MPS. So please do not base wrong speculations on such a case where someone tries to fit original components on a total different and unknown engine.

Sorry guys, I normally do not write here, but this was just too much fairy tale on false ground. See you on oldtimer.tips if you like.

Best regards, Dr-DJet

Posted by: MikeInMunich Jul 10 2018, 04:16 PM

Hi Volker and fellow teener fans!

As one can see in previous posts of mine here I have only spoken incredibly highly of Volker / Dr. D-Jet.

When an expert makes a false assumption, as Volker here did, by assuming that my engine was stock instead of asking me, and then blames it on the (often naive) non-expert car owner for not sharing all pertinent information when one may not even know what pertinent is, then I think that’s a bit uncool because miscommunications happen in human interaction. We all know this, and usually, to be fair, both parties are responsible when sub optimal or sub sufficient communication takes place, not just one. So, in response I want to make clear here that I don’t appreciate being blamed in an aggressive manner as if I were either some kind of idiot who deserves no respect or as if I had (stupidly) withheld information because I wanted to piss Dr. D-Jet off on purpose. In other words, please, chill out.

Beyond this, I’m pretty darn sure I MUST have told Volker (Dr. D-Jet) last year at some point that the engine was indeed increased to 2.0 liters either personally or via his site Oldtimer.tips.de This new problem popped up AFTER the engine had been running FINE. The discussion about what changed didn’t include any questions or REPEAT of the information which should have in all cases been shared a year previously in Erlangen or via correspondence. So yes, as much as Volker ASSUMED that my engine was stock, it could also be said that I assumed that he knew it wasn’t because again, I’m pretty sure that that must have been clear and in any case, he as the EXPERT looking to help diagnose a problem should, as a professional, KNOW / ASK the (often naive) lay customer about such essential basic background information. I find the irate tone and the WTF actually embarrassing for Volker and encourage a retraction.

On top of this, I described the recent symptom via email without reminding Volker that the car was a 2.0 or, possibly, without having EVER mentioned at all, which wouldn’t have been the case if he had ever asked, which he obviously should have at some point if not straight away when we first met in person at his clinic in Erlangen in 2017. After describing the new symptom the talk was about a prime suspect, the quality of the seal in my MPS. I sent it to him and he determined that the diaphragm was DONE and replaced it, for which I paid him. He also tested my CPU and determined what its model number must be based on values. This was necessary because my CPU has no number on it anywhere. He also sold me his CPU so I would have one while he looked into what was up with mine. At the time it wasn’t clear if mine was compatible with the MPs because it has no number on it. So he spent his personal time helping me determine that my MPS and CPU are compatible and was paid for the rebuild of the MPS, as mentioned. The next step was for me to install the rebuilt MPS, with his CPU, because he still had/ has mine, which we KNEW was compatible with BOTH MPS mentioned here, and for me to determine if things were now OK, which I did, but the engine was running worse than before. Volker also gave me an extra MPS to test when I bought the CPU from him in Erlangen a few weeks ago. The engine seemed to function better with this „extra“ MPS, but only until the engine started to warm up, which is apparently due to the cold start valve enriching the mixture very temporarily. After only a half a mile the symptom returned, and I reported this to Volker this evening. That’s where we were. Confused and trying to move forward. Then Volker heard from someone that my engine wasn’t a stock 1,7 and decided to get all bent out of shape with me, as you can see. So, for the record, this is all that occurred and there is little more to it.

Volker, I like you and I’ve been very grateful for your knowledge and support. I’m really disappointed how you’ve practically acttacked me here personally and I’m sorry I have this far failed you as a student.

Mike

Posted by: Bartlett 914 Jul 10 2018, 05:06 PM

Dr=Djet
It seems you took this personally. I was not an attack on you or your ability. When I stated that the MPS made it worse, that was a statement from a troubleshooting stand point. It in fact turned out to be the case.

Posted by: Dr-DJet Jul 11 2018, 02:26 AM

Hi,

yes I take it personally if I read so much bullshit in a case where someone completely changes his engine from 1.7 to 2.0l and everyone expects this to run well and doubts my trouble-shooting, Bosch factory specs etc.

And also the statement that the 2nd MPS makes the car run better is not correct. Mike got a second MAP sensor from me which was very richly adjusted (not by me and on the upper tolerance side). Just to help if there would be something odd with his own one. But also that one makes him drive just 800m as Mike wrote me yesterday evening. What does that tell us. Car runs with cold start valve and cold fuel enrichment then problems start. What a surprise!

My last statement in this case: A modified engine from 1.7 to 2.0 l will NEVER run well with 1.7 components. No matter how you tune or detune a MPS.

Posted by: MikeInMunich Jul 11 2018, 03:17 AM

Volker, what you clearly fail to realize is that we are mere mortals and not expwrts like you, at least not myself. Comments like, „what a surprise!“ show that you apparently expect us (all) to be at practically your level of advanced knowledge of this system when you understand it better than almost anyone on the goddam planet and have spent literally hundreds if not indeed thousands of hours(!) getting to your level of understanding of how it works. Sorry, but I’m still only on hour number 5 or so. Unless you WANT to sound the way you do (note description excluded) then I would (personally) keep cool and choose my tone and words more carefully. Nobody here, including myself naturally, is out to seem / be stupid and waste your time. You can correct us, help us, teach, etc. but expecting us to know everything that you practically consider common sense is a bit off, to say the least. This system is your hobby and passion. You spend a LOT of time annually putting on 3 workshops to meet, teach and help normal guys like me, both very technically inclined and talented as well as some slower learners who may prefer to pay a mechanic to test and help to diagnose a ghost in the machine, like myself. Some people / readers may have virtually ZERO understanding of the system or inclination to try to diagnose / fix a problem themselves, and they would surely think your comments here are WAY over their heads. I can’t even get a master mechanic in a Bosch Werkstatt to want to test this system without a tester designed specifically for it! And again, why be mad at me for „withholding“ information about the engine‘s displacement and take zero responsibility as the expert for not having asked? Come on! All we talked about was why, all of a sudden, was the car not running as well as it had been and went for the MPS and swapped it in and quickly came to where we are now. So be honest, how much time did you really lose / invest in helping me before someone ( Nordfisch?) said, hey Volker, are you aware that Mike has a 2.0 liter engine? I reckon compared to how much time you otherwise invest into this passion of yours, very, very little. I recommend considering a „so what now what“ attitude instead of getting pissed off at me. Again, I have greatly appreciated your support and let you know it constantly. Getting mad at a customer or student isn’t Master-like and I find it a shame. Since this is what you love doing and this thread can be extremely valuable to some people in the future, I propose a more measured and professional apparoach to sharing your knowledge with us. We would all appreciate it, especially myself.

Does it go against the grain for you to manipulate/ re-calibrate the MPS (MAP) because you believe that everything should remain stock, or would you like to perhaps describe for us here how to calibrate it? Otherwise, perhaps another member will do so.

I hope you calm down and forgive me for not making clear as this new problem popped up that I’m running a 2,0. I honestly don’t think that’s a good reason to get pissed off at me. Perhaps you’ll chose to take some responsibility for that wasted time upon yourself for having not asked. Again, after all, you’re the consultant / expert and you’re the one who made the false assumption, nicht wahr?

So, can we perhaps move forward, everyone, on how to get my system checked and calibrated nicely again? I would really, really appreciate it! As far as the claim that it will NEVER run well I can say that it WAS running very well for about 6,000 miles. What Bleyseng and Mr. Bowlsby have stated above lead me to believe that it’s far from impossible and that Dr. D-Jet may well be interested in expanding his experience and knowledge through this case and its potential / eventual solution rather than simply softly scream NEVER and sign off.

Thanks!

M.i.M.

Posted by: MikeInMunich Jul 11 2018, 04:13 AM

Good links on this subject... and a number of questions answered, such as how the MPS can be calibrated. Thanks...

https://web.archive.org/web/20050307014722fw_/http://www.914fan.net:80/djet.html

http://www.914world.com/bbs2/lofiversion/index.php?t318446.html

https://members.rennlist.com/pbanders/DJetParts.htm

https://oldtimer.tips/en/d-jetronic

Posted by: MikeInMunich Jul 11 2018, 05:22 AM

Why would you think that everyone doubts your trouble shooting, Bosch specs or that everyone expects a 2.0 to run well with an MPS calibrated to spec for 1.7 liter engine?? You’re jumping to illogical conclusions and getting defensive-aggressive unnecessarily. There’s certainly no reason at all to take anything written here personally.

Posted by: 914_teener Jul 11 2018, 08:54 AM

So.......


Guys, I.ll be in Bavaria in December cruising the Main.

Where are the best brewhouses in Frankfurt?

I.m serious.

Rob

Posted by: MikeInMunich Jul 11 2018, 09:31 AM

Hi Jeff, thanks for chiming in here. I just spoke with George Hussey about sending me a new CHTS and he was nice enough to take some time with me on the phone to discuss the problem. First off, he emphasized the challenges that often occur when changing the CHTS, such as getting the old one out without breaking it, and discouraged me from changing it unless I was sure that the one I have is faulty, which I am not. In fact, I’m pretty sure it’s OK. I will test it again with a multimeter.

But what I’m writing about is how George believes that the problem likely lies elsewhere altogether, like with timing, valve adjustment, dwell, fuel pressure, etc. and not with the MPS. He also said that the MPS adjustment screw is for FINE tuning mixture and that my problem seems way too severe for such fine tuning to be the potential solution, whereby you and Bleyseng seem to emphasize the adjustment of the MPS screw as the primary(?) way to change mixture. I’m not clear on this.

Also, can you offer me some info on what you mentioned about the cold start valve and flow testing? This valve only enriches the mixture while the engine is cold, no?

After we’ve ruled out all of the usual suspects, as mentioned above, if the problem persists and I’m hooked up to a CO / AFR sensor and can see if the car is running too lean or too rich, how should / can the mixture be adjusted? Primarily with the MPS screw? How else?

George also said that a camshaft can make a big difference, but the simple fact that the engine is 2.0 liter instead of 1.7 shouldn’t / doesn’t / in his experience has never been a problem. This is a far cry from Dr. D-Jet´s opinion on exactly that point and I’d say George has far more experience with the D Jet on 914s than Dr. D-Jet does.

Thanks again for your input. Hope to read a reply from you again.

Mike

Posted by: MikeInMunich Jul 11 2018, 09:36 AM

Neither the Main nor Franfurt are in Bavaria.

If you’re going to be in Munich, send me a PM if you want to get together.

As for your question here, refer to Trip Advisor! That’s your best resource, not I, nor likely not anybody else here. Wrong place for it anyway.

Best regards,

Mike in Munich

Posted by: rhodyguy Jul 11 2018, 09:41 AM

Perhaps a discussion of the engine spec is in order prior to a MPS refurbish.

Posted by: 914_teener Jul 11 2018, 10:30 AM

Thanks Mike.

Sorry to step on your thread.

Starting Pilsen....then Nurenberg...then Frankfurt. If I get to Munich I will surely look you up. Thanks for the offer.

BTW...I had Jeff B. Set up a MPS using Chris Foley.s replacement diaphram for my 2.0. Working great. I had to fiddle a bit with a wide band but it is running flawlessly. As far as the cht...I am using an reprop. that Mcmark.made now 914 rubber makes that uses a modern thermister and a seperate ground.

Hope that helps.

Posted by: MikeInMunich Jul 11 2018, 11:18 AM

Wow!

Calibrating the MPS seems pretty complicated. Brad Anders also states, in the link I’m posting here, that it should be considered a last resort. Dr. D-Jet seems to consider it a no-go altogether.

https://members.rennlist.com/pbanders/manifold_pressure_sensor.htm#Adjustments

Posted by: MikeInMunich Jul 11 2018, 11:20 AM

Thanks Rob. No worries. Don’t skip Munich!

M.

Posted by: BeatNavy Jul 11 2018, 11:57 AM

It's not that complicated - if you have an inductance meter and appropriate tools for adjusting. But it does take some trial and error, and, as a minimum, an O2 sensor. I think adjustment is necessary if the MPS has been repaired, as it's very difficult to get it close to correct through other means (e.g., measuring depth of inner / outer stops, etc.).

This topic has been discussed in many different ways over many different threads. I agree with Jeff B - no two engines are exactly alike -- but I also agree with Dr D-Jet that stock calibration should get you close enough for a corresponding / matching engine if it is stock. They were sealed from the factory for a reason. So in that regard, I also agree with George - an MPS that's "in the ballpark" for a given engine is not going to make that car undriveable. It may not be optimized, but it may also feel just fine. I've futzed with my MPS's enough to know that at this point.

Posted by: MikeInMunich Jul 12 2018, 04:21 AM

Absolutely. Had I discussed or even mentioned this to Dr. D-Jet he would have been happy to not have anything to do with this case and not unhappy about trying to help where he otherwise would have chosen to distance himself.

Posted by: Dr-DJet Jul 13 2018, 06:57 AM

Well after Mike and me agreed on real facts that he had told me it would be an original 1.7 engine and that both MPS (one originally closed with rivets, vacuum tight etc) do not work for more than cold start enrichment (800 meters) and that he has also tried 2 ECUs:

I have references for 94% of all MPS, rough ones from Bosch and very precise ones measured myself. I always adjust MPS to references. And that is what makes cars going. To the opposite: A leaking MPS (and the first one was losing vacuum in 4 seconds) should create a very rich mixture with bad motor run in idle and part-load. If it was running well with that, then there were earlier other problems already.

I cannot know the revised engine specs but I can tell you that the ECU is used both on 1.7 and 2.0 engine. But 2.0 engines were never equipped with this MPS. It was equipped with 0280100 037 (sorry I do not work with Volkswagen no.s) in combination with this ECU. As a registered user u find all that information on https://oldtimer.tips/de/d-jetronic/druckfuehler#Liste. Anonymous surfing gives u only limited info.

So if we have 2 ECUs and 2 MPS not solving the problem, it is time to follow my original advice from the beginning when I learned it is a modified engine:

1. What specs is this revised engine? Bore, stroke, compression and valve timing.
2. If it is like original 2.0 engine, I would recommend to try 0 280 100 037 factory spec MPS. It is much richer than the 049 for 1.7 engines.
3. If it is not like original 2.0 engine, well then you have to do trial and error.

Regarding detuning MPS: You might know type 3 MPS from Mercedes-Benz, Opel, late Volvo etc. with black cap. Underneath is an easily accessible screw. (this one has just one screw and not 3 as it has no diaphragm and no full-load transition. Full-load is handled via a contact in throttle switch). I see a habit in the US to detune them. And later they are sold as core in ebay or completely with bad running car to someone else. Many MB 450 SL make it to Germany like that. And it a nightmare to fix it. They have altitude compensation and need to be checked at 750 and 600 Torr environmental pressure with differential vacuum applied to that environmental pressure.

Fortunately we do not have such a tradition of detuning MPS in Germany. I am doubtful that you can adjust all 3 screws on your MPS simultaneously while riding a car and watching A/F meter. That is why I recommend not to do so. Tuning screws on MPS are VERY SENSITIVE. Regarding swapping MPS from one engine to a different engine: Normally then MPS have different slopes in their curves and you cannot reach it via screw tuning. It would need a change of springs inside plus proper tuning.

Hope that clarifies the subject and please apologize if I got disturbed by "alternative facts" as they were first stated by Mike. It is good that he has changed that view and I accept that.

BTW: In April local Porsche 914 club had invited me to Karlsruhe for a workshop with 18 Porsche 914s teaching only D-Jetronic and engine testing. It was a lovely event and they have asked to have Obelix and me again next year in another region.

Posted by: Dr-DJet Jul 16 2018, 04:35 AM

Hi,

and the last puzzle piece also unmasks the lie that you can simply use 1.7 components on an engine increased to 2.0 l. Such a statement is not only alternative facts, it is directly fake news.

A 2.0l does not only have a richer MPS it also has injectors with 20% higher static flow rate. Yellow ones have 265 cm³/min on 1.7s, green ones on 2.0s have 318 cm³/min .

And guess which ones Mike just reported to me about his car? Yellow ones. But the company who did the engine volume increase claims that they have compensated everything by a changed cam. What magic would that be? Cams can change air flow but never compensate for insufficient amount of injected fuel in intake manifold.

Mike, get the company in Texas to tell you exactly bore, stroke, valve timing, compression and compare to an original 2.0 engine. Only if it is the same, get green injectors 0 280 150 019 (or other green ones) and an 0 280 100 037 MPS. Or swap that engine to an original 2.0 one.

Posted by: MikeInMunich Jul 16 2018, 10:36 AM

Update...

I'm taking Volker‘s advice and will have the injectors changed. I am pretty sure the car is running too lean. Will have CO tested ASAP and will attempt compensation via increasing fuel pressure to 31 psi, then 32...

Meanwhile, all other basics will be taken care of...valves, timing, fuel lines and filter checked, grounds checked, cap and rotor were already changed by myself, vacuum lines checked, TPS re-set, plugs changed and compression checked. I’ll report back CO and fuel pressure values prior to and after adjustments to the valves and prior to and after swapping the injectors from yellows (for 1.7) to greens (for 2.0).

Thanks, especially to Volker, again.

Mike

Posted by: Dave_Darling Jul 16 2018, 11:44 AM

A wide-band O2 meter would be a decent way to get real-time readings of the mixture. That way you could confirm that it is too lean.

--DD

Posted by: Philip W. Jul 16 2018, 11:53 AM

-- pretty sure I said that on post #19 - Got mine from Summit Racing, had the O2 bung welded in to the proper place on the Triad and ran the line for the gauge - WOW was I lean- and when the diaphragm on theMPS went bad before it went all the way I knew it was going because I was very rich suddenly- anyway - you wont be guessing---

Phil

Posted by: brant Jul 16 2018, 03:28 PM

also,

I wouldn't really increase fuel pressure past 31
just my opinion.

but you can more easily change mixture through MPS calibration (there are actually 3 things to adjust.... not one... at the end of the MPS)

you have to have a wide band to adjust mixture

Posted by: MikeInMunich Sep 10 2018, 03:08 PM

I decided to take Volker‘s (Dr. D-Jet‘s) advice and change the injectors from the yellow (for 1.7 liter) to the green (for 2.0) from Bosch. Found a few at reasonable prices, used. Bought 6, 2 were defective.

Car is now running great. MPS is from 1.7 and was restored by Volker. It has a new diaphragm and holds vacuum tightly.

CO value is at about 3.5% and my mileage on my first trip with girlfriend and luggage was about 18 MPG, which was pretty disappointing. Most of that was highway or at least in 5th gear. Thoughts?

I think it’s running too rich and mileage should be about 40% better / closer to 25 MPG. For my European friends, that was 13 liters / 100 km (this is how we measure gas mileage over here).

I purchased 4 MP sensors for 2.0 liter engines for about 60€ apiece. They all worked but gave higher CO values, one being as high as about 5%.

Compression was 116 PSI on 3 cylinders and 123 on the other. Valves were adjusted, though they weren’t off by much a5 all. Timing checked / set at 25 degrees BTDC. Ignition is good. Cap and rotor in electronic distributor were changed. Fuel pressure is still at 29 psi / 2 bar.

Next step, open up MPS and through trial and error adjust to get a lower CO value, goal being 2%. When successful, I hope my mileage is at least 30% better. Gas costs $6 a gallon over here!

BTW. The CO value with the same MPS and the yellow injectors for the 1.7 was 0.5%. The car was running way too lean and quite badly, though I never did determine what was causing the ORIGINAL hesitation.

Thoughts and feedback?

Thanks!

Mike in Munich