trigger issue Rotax 4-tec

[Tiger771]

Could someone please provide me with what kind of sensors is used for the crank and cam on the skidoo 1200... Is the crank vr and the cam hall

[Adamw]

Crank is VR, 36-2, cam is a single pulse, hall.

[therealkeal]

Did we ever establish a fix for this? I think I'm encountering the same issue, Vipec V88 Seadoo Rotax 1500cc refusing to start. Unless I'm missing something.

Checked timing offset and it was perfect, has spark, fuel, ISC operating, everything appears to be working. But no action happening, it also seems to be firing the plugs after the starter shuts off which is creating some ridiculous backfires. It almost, occassionally fires while cranking. 

I realised my MAP sensor is faulty, but you wouldn't think that would stop it running.

Is there any way to get support on these? I'm happy to pay someone to get this figured out. 

 

Seadoo GTX Rotax 4tec NA - Saved.pcl Starting Issue Log Vipec V88.llg

[Adamw]

No, you dont have the same issue, you have an initial spike of RPM as the engine first starts to crank but otherwise it is staying in sync, the RPM and dwell are stable when cranking which means the ecu is happy with the trigger.

What size injectors does it have?  Have you tried a squirt of starter fluid while cranking to confirm it is not a fuel issue?

[therealkeal]

That's a relief. 

They are the stock injectors, I think around 370cc, but the base map was for 1000cc, the fuel trim was 6ms, so I increased to 12ms to account for the smaller injectors. I did try some starter fluid but it seems to result in huge backfires, I suppose I could try it again. Its so odd its like the timing is out but I've double checked the base timing and its bang on. 

[Vaughan]

13 minutes ago, therealkeal said:

They are the stock injectors, I think around 370cc, but the base map was for 1000cc, the fuel trim was 6ms, so I increased to 12ms to account for the smaller injectors

probably want more like 18ms if your injectors are 1/3 the size

[therealkeal]

I've tried again with starter fluid, and a number of attempts with more fueling, different injector timing. I'm more and more convinced I'm getting trigger issues, today I was barely able to get stable RPM unlike the other day. It seems incredibly hit and miss, particularly when starting with fuel. I am getting a couple of attempted fires and kickbacks. 

When the plugs are out the timing is bang on and no errors. When they are in it seems to be all over the place. 

Do you guys mind taking another look?

Start attempts 27-8.llg Log 27-08-22 8;46;24 am - plugs removed.llg Seadoo GTX Rotax 4tec NA - Saved 27-8.pcl

[Adamw]

Yes you have trigger errors in that most recent log.  If you have very uneven cranking speed then the ecu will have trouble detecting the missing tooth.  Your battery voltage drops down to 9.7V on the first couple of tries, so see if you can improve that.  The starter clutches have a habit of slipping too so possibly consider replacing that.  

[therealkeal]

I think I'm starting to run out of things to try with these trigger issues. Have replaced the starter and tested using a jumper pack to keep the cranking voltage up. Tried a number of different filters on triggers, still getting inconsistent RPM and trigger errors. Is there anything left to try? 

When it is reading the RPM correctly I'm getting ~400RPM which I think is all the starter can do. 

Cranking - Strong battery.llg Cranking Strong Battery 2.llg Cranking Strong Battery 3.llg

[therealkeal]

The other thing that seems incredibly odd is, I had the ignition offset at -300BTDC and the timing seemed to be right (this matches what it should be according to some base maps I've found), then coming back to it a week or so later, I had to set it to +60BTDC to get the timing to fire correctly. The timing is off a mark on the Camshaft pulley too, so it should only be one ignition per rotation, so it physically cant be 360 degrees out as if I was doing it off the crank.

Is there any explanation for why the ECU would do that? I double checked that all of the settings were the same from an earlier saved map and they were. 

If I go back to -300BTDC the timing is way off. 

[Adamw]

40 minutes ago, therealkeal said:

I had the ignition offset at -300BTDC and the timing seemed to be right (this matches what it should be according to some base maps I've found), then coming back to it a week or so later, I had to set it to +60BTDC to get the timing to fire correctly.

This would suggest it is mis-syncing - the cam sensor isnt working or isnt being seen so it will sync on the correct crank rotation approx 50% of start attempts and on the wrong phase the other 50% of attempts (roughly).  

You really need to get an oscilloscope on the crank and cam sensor to see what is going on. 

[therealkeal]

Ok will try to get my hands on an oscilloscope. Would be so much easier if this ECU had the scope, it's a real early model by the looks. 

The CAP sensor has a 12V supply, and I have one pos sensor wire and ground going to sensor ground. I've attached the wiring diagram of the sensor if you dont mind taking a look, just to check I've not done something wrong. I've tried reversing the pos and ground sensor wires and it definitely doesnt seem to work in that configuration.

 

CAPS Testing Seadoo Manual.pdf

 

[Adamw]

9 hours ago, therealkeal said:

Would be so much easier if this ECU had the scope, it's a real early model by the looks. 

Yes the V88 was released in 2009 and discontinued in 2013, a time when very few ECU's had enough memory for a scope function.  

 

For the cam sensor, if you "back probe" the trigger 2 pin at the ecu connector by poking a paperclip or similar down beside the wire so it touches the terminal, connect a voltmeter to that then watch voltage as you put a piece of iron (wrench or similar) in front of the sensor like your pic shows.  If sensor is working and wiring is ok then you should see high voltage (>4V) when there is nothing in front of the sensor, and close to 0V with iron in front of the sensor.    

 

[therealkeal]

Have tested the sensor, getting 4.6V open and 0.02 touching, around 0.3V or lower when right next to it. Haven't got an oscilloscope yet. Didn't have my laptop handy to log it cranking, but looks like the sensor itself is working OK. 

Assuming I'm still getting the same issues, what options are available to me? I feel as though I've tested every trigger setting available. 

Will report back when I get the oscilloscope onto it.

[therealkeal]

Here are the files from the oscilloscope. Still not getting consistent timing. Have done a couple cranking just off the battery and with jumper leads to try and get maximum rpm. 

[therealkeal]

Heres a link to the data from the scope https://docs.google.com/spreadsheets/d/1fjRY90KhYJ8BR8v4pNoCZzlIDGGs6pJd/edit?usp=sharing&ouid=106553184062656533192&rtpof=true&sd=true

I couldn't get all of the data for both triggers into one CSV, but let me know if you want the rest of the data for the cam trigger. But that doesnt look like the problem.

[therealkeal]

Any thoughts on the above? Appreciate the help.. 

[Adamw]

Yeah there are a couple of potential issues here.  

The first one is the crank speed variation.  Below is the calculated RPM over several teeth based on the 50ms/div time base.  So your crankshaft goes from rotating at 160RPM to 550RPM in the space of 3 crank teeth (30deg), it then slows back down to 160RPM in the space of 3 teeth.  That will make it pretty difficult for any ecu to determine where a missing tooth is when the time period between 2 teeth changes so drastically.  That seems pretty extreme - Are you sure the starter sprag isnt slipping during compression stroke?

 

The 2nd thing that doesnt look good is the big spike of noise that you have coming through both triggers occasionally.  Since it exceeds the arming threshold and crosses zero, this will make the ecu see extra teeth that arent actually there.  Im not sure which of these 2 potential issues is causing your trigger error (it may even be both).  I suspect that spike of noise is probably from coil voltage taking a path it shouldnt be, so you could try cranking it with the coils unplugged, if you still have a lot of trigger errors then you could say it is probably more the speed variation that is the issue, if your trigger errors improve with the coils disconnected then you could concentrate on finding the cause of the spike.

[therealkeal]

The starter clutch could be slipping I suppose. I only replaced the starter itself. 

It's a pretty big job but while I'm doing the clutch, I will have access to the Crank Trigger wheel, I could theoretically make changes to the trigger wheel at the same time if you think the ECU would prefer a different configuration. 

Would 36 teeth none missing, or 36-4 be more reliable? I've got a spare trigger wheel I can modify. 

I was reading an earlier post in this thread that 36 with none missing could be better because the ECU doesnt look for gaps? (which seems to be the root cause of the issue with this engine given the variable cranking speed)  

 

I also noticed that blip on the scope, though it only happened once, will try cranking with the coils unplugged. 

[therealkeal]

Any thoughts on the above regarding trigger wheels? 

[Adamw]

It could be worth trying a "no missing teeth" pattern but my gut feeling is it is unlikely to help.  Regardless of missing teeth or not the ecu still has to predict how fast TDC is approaching based on the time period between the last two teeth events.  When that time period changes by a factor of more than 300% in just a few teeth as it does in those scopes above then there is potential for a lot of error in predicted crank position.   

If I were going to do that I would grind off groups of 2 adjacent teeth, leaving every 3rd tooth to make it the existing 36-2 into 12 evenly spaced teeth.  

[therealkeal]

Thanks Adam, really appreciate it, have got a bit of work to do and see what happens in the coming weeks. 

[therealkeal]

Long time between drinks, have now changed the crank wheel over to twelve teeth, a new problem emerged that I didn't expect. Have a lot of noise on the crank trigger which wasn't there before, nothing else has change though. It's a bit intermittent. I'm planning on replacing the crank sensor, and rewiring to bypass the factory wiring incase it's aged. Anything else I should check?

When it does work I finally have zero trigger issues and stable rpm.

[therealkeal]

Hey Adam wondering if you can shed any light on this?? 

[Adamw]

No, you might have to give a bit more info about what the problem is.  That looks more like a possibly scope issue than a wiring issue to me, some of those cheap hanteks will do weird stuff if the laptop is plugged into AC etc.  .