I have read with interest and sympthy many of the long term problems people have encountered with this delightful car. The most difficult are the ones surrounding the fuel injection. Water leaks, handling problems and other issues are easy by comparison. Built prior to OBD standards, the ECU provides no help in our troubleshooting. We don't know what's going in or what's coming out.

I did troubleshooting for 22 years on corporate wide area networks. The various bits of equipment on the network never told the whole story. I had to tap the circuit with something to see all the messages going back and forth and then it was usually pretty clear what was broken.

Has anyone thought about a device to plug into the ECU that connects to an app on a phone via blue tooth so we have better information for our troubleshooting? We spend a great deal of time swapping parts and relying on solutions that worked for other people with a similar problem. I am not smart enough to build such an interface, but I can assure you that Porsche had something like it when they were building this car. So, it is feasible.

The economics of such a project could daunting. Assuming that such a device does not already exist, maybe we could find the right guy or team for the job and pool our resources to get one built.

I look forward to hearing from the experts on this idea.

I remember someone posting a thread about hooking the cpu up to scopes to see pulses. Seems these cpus don’t fail often and if they do, probably easier to swap out than to replace electronic components. But it would be cool to know what they’re doing…

Bosch and some others developed analog diagnostic testers for D-Jet. Both Jeff Bowlsby and Brad Anders are probably the authorities here on those. This is from Brad's site where he documents them:

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

It would be very cool to have a digital one that was a D-Jet equivalent of OBD II.

I beg to differ.

A DMM and very basic oscilloscope will tell you both.

The issue at hand is to confuse analog electronics with digital electronics. Trying to create OBD for an analog control circuit like a 914 ECU would be prohibitively labor and capital intensive. First order of business would be to put Analog to Digital converters in front of all the analog inputs and ECU outputs. Then there would be a need for a a digital ECU like a Rasherry PI to do all the controls work within. Write the code. Provide output interface to phone or PC.

All this work to replace what can pretty much be done with a digital multi meter.

If you want modern digital control, there are a multitude of options. Otherwise vintage analog control like a 914 ECU is a thing of beauty unto itself that predates the digital world.

The previous link to Brad Anders site pretty much is a wealth of information if you wish to understand how the analog ECU operates and how to troubleshoot the analog inputs to the ECU. The output of the ECU is nothing more than PWM voltage pulses to the injectors.

More info on the analog ECU and how to troubleshoot D-jet
https://jetronic.org/en/d-jetronic/ecu

Ahhhhh...yep

It has been my experience that 95 % of the problems is NOT with ECU but the old, brittle wire harness. ECU just won't work right IF the signal is not getting there.

Interposers inserted between the ECU and FI harness and the 12 pin connector and Ignition harness, with some kind of VooDoo box that transmits signals to a phone app could be interesting. Most of the cars already have the gauges for volts, oil temp. More sensors for oil pressure, CHT could be useful.

The interposer hardware is easy enough - who can do the VooDoo boxes?

Thanks for posting this TJ

bosch test unit for sale currently on ebay.de currently, but my German is poor and its going to be too dear for me, agree with above once you have a scope and the right test leads / knowledge or wave forms you can check almost everything ECU / sensor related.

https://www.ebay.de/itm/184890988632?_trkpa...8a0de%7Ciid%3A1

Here's the factory D-Jet ECU tester in use this evening with @ClayPerrine .

Click to view attachment

Click to view attachment

It doesn't give you a readout of what the ECU is actually doing, but it allows you to check all of the basic functions via a pass/fail test. In trying to troubleshoot some running issues, we were testing the ECU in the car as well as some of the spares. It turns out my spare makes a pitiful spare as it failed 3 of the 16 tests. Oops!

Glad to see there is a box.
Could I rent it when I get to the point of firing up my 914? I had a horrible issue with the prior motor and it would good to know the ECU was able to pass the GO/NO GO testing of this box.

Tim

I have that VW1218 above and other testers to evaluate the D-Jet ECU and offer group testing sessions from time to time. My last session a few months ago included 17 ECUs and I offer them as grousp session to keep the cost and turn around time minimal. My next session is planned for April but it has not been announced yet. Look for the announcement first week of April.

So, just to be clear:

The D-Jetronic (and L-Jetronic, for that matter!) fuel injection systems in our 914s used analog electronics to work, not digital. So you've got to be good with analog computing to suss out what the "brain" is doing. The Brad Anders page above talks about the details, and as a (retired) software engineer I can confidently say that I have no idea WTF he is talking about.

That said, you can absolutely make a break-out box so you can measure inputs and outputs. Doing the measurements can be challenging, because you have to know if you are measuring voltage or current or inductance or what. There have been several people who have made break-out boxes already, so we know it can be done.

If you hook them into something like an Arduino or Raspberry Pi or some such, you can convert them into digital and then send the info out via Bluetooth or whatever. Again, over my pay grade, but absolutely doable.

A read through Brad Anders' D-Jet ECU theory and operation page should give you some notion of what's going on. From what I can tell, there's a circuit in the ECU that flips from high to low voltage (I think!!) and that signal is sent out to one coil in the Manifold Pressure Sensor. The other coil is inductively coupled to the first coil through the core in the MPS which is moved by manifold pressure. The rise and fall of the voltage in the second coil is what sets the metering for the injectors.

There are additional factors that are added in after that, mostly to do with temperature compensation, throttle position, and so on.

Again, this is all analog, so our (or at least my!!) years of experience with digital electronics is not very useful.

--DD

Two year old thread. If you want the ECU validated on a Go/No-Go basis use Jeff’s testing service come April. Otherwise the ECU is still Analog . . . But another two years older and more impressive that analog circuits like this worked long before digital was a thing!


https://www.youtube.com/watch?v=6YkAnv8inQE


Welcome to cyberspace, I'm lost in the fog
Everything's digital I'm still analog
When something goes wrong
I don't have a clue
Some ten year old smart a** has to show me what to do
Sign on with high speed you don't have to wait
Sit there for days and vegetate
I access my email, read all my spam, I'm an analog man.

…

And, in the end..."why bother"? You're not going to change anything, so your knowledge of what's going on is not particularly valuable...

Maybe I'm being a bit of a noodge, but if that's what you're looking for - and I was - then what you're looking for is a D-Jet conversion to Microsquirt...and I did. - GA

I have one of those testers for sale in the classifieds.

I have two of them….but foleys first

Hot wire it to some sensors to measure volts
Send to app

Make a fortune

curious what the failure rate was on that batch you tested

I previously posted the exact numbers from that last ECU test group, but if I recall correctly, the 2 that tested bad were believed previous to the testing to be bad (I just wanted to see how they failed). 1 additional ECU was bad...really bad, non-op. So you could say 1 of 15 were bad, but this is a very limited data set to draw any systemic conclusions.

On one of the ECUs tested that was believed to be functional in every way with no known driveability issues before the testing, the VW1218 said had 2 bad sectors- basic mixture compensation and fuel pump control. Customer put it back in the car and he is driving just like before with no perceived issues. Amazing.

Now, to find a test unit and tester for the L-Jet ECU! It must exist, as used in several other Marques also?

That's the data I am interested in is the ECUs that were running/believed good but then tests failed. Knowing how far out of an ideal tune these cars can run at without the driver noticing I think I would side with the test equipment and replace the ECU.

it exists.

ratwell has info.

https://www.ratwell.com/technical/L-JetronicTester.html

pristine vintage items are for sale.
not cheap.

https://www.ebay.de/itm/125174393719

looked into it out of mild curiosity as an isolated aussie a few years back.
not sure what it gets you in the end when it comes to the ECU.
but you plug it in between the ECU and the AFM if i understand it right.
and it can test and diagnose everything.

it sure looks cute. and compact.

I have the EFI Associates L-Jet tester, but not a 1.8L car to perform the test on the ECU. Member Marty Yeoman and I played with his 1.8L recently with it, as I recall it tests the ECU and AFM, gives digital injection pulse width info and other characteristics. His FI tested in good shape.

The AFC tester is in the photo on the left.

Yay! If/when another 1.8 rolls by, just let me know (a long drive from NJ); I have a suspect one. The other in car one is fine but would like to have a reliable spare.

@JeffBowlsby very cool. What does that service cost?

The cost is $125. + return shipping cost with a brief report of what was tested and its results.

ok thats what i thought mr. b
somehow it tests both items together.

they are such cute looking little machines.
i might resume my search for one down here in north antarctica.
its going to be more obscure down here as we didn't really go full bore on EFI until the 80s. an L jet tester of that vintage is not the sort of thing that was common in aus.
i need to go full wonk mode to keep my rep intact is this neck of the woods.
the guy who told all the carbi conversion crew to go get $%^&#d.