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Ok so I had a chance to go out and test for trigger signal on vemstune. Here's what I got:
A big flat line on the reference pulses. Note, the first pic was with the engine cranking over. Don't get excited about the vertical lines; the screen was the exact same when the engine was not being cranked over.
Now onto the 2nd and 3rd pics. So upon going into the primary trigger settings menu and the reference trigger table, there seems to be some errors showing up. I moused over the 'X's' so you can see what the messages are. I'm not sure how to rectify these errors, and I don't know why I'm not getting any pulses. It's such a simple system in and of itself. Could the flywheel be the problem? Is the stock 951 flywheel a 60-2, missing tooth style?
I don't really have experience with VEMS, but I have a fair amount of experience with other standalones, but not on 944s. Anyway, what I would do is first save off the configuration that you have, so that if anything goes wrong, you can always go back to where you are right now. Then, I'd try using the "default" box on the bottom of the Primary Trigger dialog - in the version of VemsTune that I looked at, there's a default in the pulldown list for a Porsche 944 Turbo. When I used it, it looked like the trigger settings were different than what you have set. Then save that configuration off to a different file, store it in the ECU (if necessary), and try your trigger analyzer again...
I think all the stuff about getting a "tach bounce" is probably not applicable to your situation - it may come out of the Motronic ECU, but since you've replaced it with the VEMS ecu, it may or may not be there. I'd suggest just concentrating on the tools that your standalone supplies, like the trigger logger/analyzer.
Ok so I had a chance to go out and test for trigger signal on vemstune. Here's what I got:
A big flat line on the reference pulses. Note, the first pic was with the engine cranking over. Don't get excited about the vertical lines; the screen was the exact same when the engine was not being cranked over.
Now onto the 2nd and 3rd pics. So upon going into the primary trigger settings menu and the reference trigger table, there seems to be some errors showing up. I moused over the 'X's' so you can see what the messages are. I'm not sure how to rectify these errors, and I don't know why I'm not getting any pulses. It's such a simple system in and of itself. Could the flywheel be the problem? Is the stock 951 flywheel a 60-2, missing tooth style?
the 951 is 132 tooth ( starter ring ) and 3 ref points.
and you need to use magnetic sensors in the settings.
Do you use both oem sensors?
the 951 is 132 tooth ( starter ring ) and 3 ref points.
and you need to use magnetic sensors in the settings.
Do you use both oem sensors?
Ok thanks. I'll go in and change those settings. I'm anticipating running into similar errors as seen in the 2nd and 3rd pics. Any insight into settings these values correctly?
the 951 is 132 tooth ( starter ring ) and 3 ref points.
and you need to use magnetic sensors in the settings.
Do you use both oem sensors?
Of the 3 ref points you mention, as I imagine you know, only one is used by the DME and its sensors/wiring harness... The other two are for the diagnostic sensor that doesn't diagnose anything...
So I opened the drop down menu in the 2nd/3rd pics and selected the Porsche 944 turbo option. It changed the trigger type to 'coil type', and the values below changed to what I'm assuming is correct for that setup. I clicked on 'burn to ECU' and the settings where saved. As expected, there was no change when cranking the engine, but at least the settings are now hopefully correct.
I went under the hood and rechecked the sensor resistances as per clarks-garage instructions. So for the speed sensor, the resistance between 8-27 was ~970. Right in spec. I got the same reading for the reference sensor between 25-26. But for both sensors, I couldn't get a reading on 8-23 or 25-78. It needs to read greater than 1 mega ohm, which my meters don't have that high of a range. So without getting a reading to confirm these resistances could this be cause for concern? Keep in mind, I tested the resistance right off the sensors, not the DME plug.
.8mm. It wasn't a matter of changing the gap as much as it was juat rechecking over and over. It can drive a guy crazy!
It seems other people have had trigger issues running vems as well. The solution for those unfortunate souls seems to be to go the aftermarket crank trigger route. It just sucks that it's pretty expensive, and I'm hesistant to go that route only to find the problem isn't resolved.
The other option would be to try a late sensor bracket with sleeve to see if that solves it. Again, it's a pretty expensive trial and error science experiment. Although it should really have the late bracket anyways considering the bellhouse is notched.
So I opened the drop down menu in the 2nd/3rd pics and selected the Porsche 944 turbo option. It changed the trigger type to 'coil type', and the values below changed to what I'm assuming is correct for that setup. I clicked on 'burn to ECU' and the settings where saved. As expected, there was no change when cranking the engine, but at least the settings are now hopefully correct.
I went under the hood and rechecked the sensor resistances as per clarks-garage instructions. So for the speed sensor, the resistance between 8-27 was ~970. Right in spec. I got the same reading for the reference sensor between 25-26. But for both sensors, I couldn't get a reading on 8-23 or 25-78. It needs to read greater than 1 mega ohm, which my meters don't have that high of a range. So without getting a reading to confirm these resistances could this be cause for concern? Keep in mind, I tested the resistance right off the sensors, not the DME plug.
On the sensor plugs, you should see 970+/- across the two signal leads (middle and one of the outer pins). The third pin shouldn't be completely isolated and have no continuity (infinite ohms) to the other 2 pins. I really doubt that shielding the sensor will bring your motor to life. Your motor should fire up even if the signals were poorly shielded -- you'd just be getting occasional starter kick back and fussiness, but not a complete lack of ignition. If VEMS is that sensitive to noise, then I'd think the shielding sleeve isn't enough anyway. Did you not get support from your vendor when you bought the VEMS?
I bought the vems kit used. But I don't think this is a vems issue. But it would be nice to fix this problem, even if I later decided to go to a different trigger setup. I guess somewhere deep down inside me I'm just hoping there is something simple I'm missing.
First, focus on the fact that you don’t have a reference sensor signal - shielding is secondary. I’d try gapping the sensor a little tighter. Then, use your oscilloscope to see what sort of signal you get. Also, you can try pulling out the sensor and gently running a piece of steel across the top while watching the signal - you should see a pulse when you do that.
I've since removed the old sensors and put in a front mount trigger wheel, with a hall sensor. There is a trigger signal when cranking and the engine wants to start, but it just won't fire. I've messed around with the timing in VEMS, but I can't get it to run. The ECU was sent out for inspection last year. It was deemed good.
At this point, I'm considering inspecting/cleaning all the grounds, testing/replacing the entire wiring harness, and sending out the injectors. I would even consider lending someone my VEMS ECU to someone that is running VEMS, just to see if it will run their engine.
Other than that, I haven't touched the car in about 2 or 3 months. I have another car that needs work to get ready to sell. So I'm not sure when I'll get around to messing with this thing again for now.
05-23-2019, 11:14 PM
