Diagnosing D-Jet Problem...solution & update, All of a sudden...loss of power... Options

[MikeInMunich]

Greetings once again from Munich gentlemen! (IMG:style_emoticons/default/bye1.gif)

It started with a thought and no wood to knock on, seriously! (IMG:style_emoticons/default/mad.gif)

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! (IMG:style_emoticons/default/hissyfit.gif)

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. (IMG:style_emoticons/default/idea.gif)
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

[worn]

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!

[JeffBowlsby]

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

[JamesM]

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/manif...sure_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.

[Amphicar770]

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.

[76-914]

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. (IMG:style_emoticons/default/idea.gif)

[dr914@autoatlanta.com]

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

Greetings once again from Munich gentlemen! (IMG:style_emoticons/default/bye1.gif)

It started with a thought and no wood to knock on, seriously! (IMG:style_emoticons/default/mad.gif)

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! (IMG:style_emoticons/default/hissyfit.gif)

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. (IMG:style_emoticons/default/idea.gif)

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
search for Vacuum leaks

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

[saigon71]

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.

[Bartlett 914]

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.

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

[Dave_Darling]

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

[r_towle]

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.

[r_towle]

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

[nordfisch]

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

[MikeInMunich]

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/manif...sure_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.

Indeed! I have now done this and it apparently IS the MPS! Apropos calibration...how is that done?? (IMG:style_emoticons/default/idea.gif)

[MikeInMunich]

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

Thanks for the feedback Norbert! Do you know which Relais is for the D-jet? (IMG:style_emoticons/default/idea.gif)

[MikeInMunich]

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

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

[MikeInMunich]

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

Thanks a lot for the input again Dave!

[MikeInMunich]

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.

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

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

Thanks for the input!

[DRPHIL914]

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.

[Bartlett 914]

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.

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)