EFI advanved timing and APV measurement?

Bearcat · Jan 25, 2016

800 EFI limp mode/drops one cylinder

Edit: changed the topic name as this seems to be limp mode issue.

I have ZR 800 EFI based mountain sled. Does anybody have experience about advancing the timing in EFI engine? I've advanced the timing 4.5 degrees and now I have issues getting it to rev above 6000 rpm. It drops out one cylinder :/

I had this same issues last year when it was turboed. Turbo turned to be too small so I took it out. Sled has worked quite ok this winter except week ago it started to die at top. Yesterday the thing got worse and it didn't want to rev over 6000 rpm anymore. EGTs drop in one cylinder totally, kind of loosing spark/plug totally but it will wake up when letting off throttle. Really weird issue.

I'm using modified PCV and I'll test today with stock ignition without PCV to see if those are the issue. I've leaned out whole fuel range about 3-6 numbers and idle is at -15.

The engine is -03 model. I've understood APV length should be about 30.5mm. The cables in otherhand are almost too short (adjustment thingy just barey stays on thread) for that measurement. -04 says 36.5mm for adjustment and that seems to be better for the cables. Funny thing is I've tried both setups and sled works the same. No error code either case. Weird?

Bearcat · Feb 1, 2016

This situation is still on. I've checked various places without success:
- Changed plugs
- Changed injectors, tested them too separately with extra fuel pump and gas
- Took out the mods: timing key and Power Commander
- Eliminated the kill switch
- Took out the stator, tested and checked it. Also rewelded the wires so no bad connections there
- Tested APV servo and installed wrong way it on purpose to see if I get Error 6. Yep, get it. So installed it back right way. Still the right cable measurement is question mark? What is the right measurement for ZR 800 EFI 2003?
- Tried different regulator. It wasn't similar in the sled though.

Sled seems to be in Limp Mode. It starts good, runs good up to 5000 rpm. Then it start to miss spark and above 6000 rpm it runs on one cylinder. When letting off the gas and letting it to settle down it runs good again until 6000 rpm is reached. There' isn't any error codes.

I read from Service Manual there's a Limp Mode in these sleds. This can be from bad voltage/amps. But can it be also from bad APV cable adjustment?

I'm totally lost here :/

Bearcat · Feb 1, 2016

Yesterday had some time in carage swapping parts. The list goes on without success:
- Changed APV wiring harness
- Changed ECU wiring harness
- Changed ground wire between motor and chassis
- Changed fuel pump

Next thing will be another ECU and chassis wiring harness. After that all electric parts are changed or checked...

Bearcat · Feb 4, 2016

Tested another ecu and another wiring harness. Still bogs. Also opened those small harnesses connectors to check if there's something weird. Could not find anything.

Light harness voltage of seems to be bit low to me: below 11V at idle and it won't go over 12V even at engagement rpm. This is probably the reason for bog - but what causes that?

Sledbrain2 · Feb 5, 2016

many times the stator will check out fine but it your issue, I had an 02 800 efi, my running issue was it would not start back up after running for a bit, once I re-wound the stator it never did it again, I did have a tps fail, I had to put current to the injectors to get it to start, other running was erratic rpm could not get it to hold a constant rpm, might something to check, can make your own tester. There is a crank senor that can also go bad next to flywheel. Other than that I think you covered everything else.

Bearcat · Feb 8, 2016

Thanks. I need to pay attention to stator. I tested M1000 regulator yesterday without success. I'm starting to believe it's the stator. Need to find one from somewhere. Luckily F6/7 -03..-04 seems to have quite same stator and those are easier to find around here. Need to get one and test it out.

Bearcat · Feb 13, 2016

Changed the stator today. No success. Damned. This starts to really piss me off!!! We have the best snow at the moment for a years and sled doesn't work. Really really frustrating!

Found that old Wildcat EFI has the same stator except wiring is different. So I replaced the wires from current stator.

Bearcat · Feb 14, 2016

Tested the engine without belt. Pinned full throttle and rpms go up. After 6500 AVP opened ok. But right after that engine started to struggle like rpm limiter or lacking fuel from one cylinder. After this rpms drop and go below 6500 when valves close. After closing valves rpms go up again. This keeps going and going as long you keep throttle fully opened. WTF is going on? My pal has same issue with his Firecat 7 -05, except the critical rpm is 7100 in his sled.

vdo1948 · Feb 18, 2016

I'm not much of a mechanic but will note a couple of things. While it acts like power valves and limp mode, from everything I know if it goes into limp mode your ECU will throw a code and you said your not getting one. Wild guess, have you checked you Throttle Safety Switch? My old '99 EFI acted somewhat like that when the TSS went bad, though it was more intermittent than what you seem to be experiencing. That's all I've got.

Bearcat · Feb 19, 2016

Yes, I unplugged the handlebar connector so TSS, killswhitch etc were disconnected. No error codes. I tried all sensors also by disconnecting them one by one and I got all the error codes so by ECU everything is ok.

Changed new Wössner pistons yesterday as old were hit by my turbo testings. Also tested another APV servo from ZR 600 EFI -02. No success :/ Rechecked stock APV servo again and it seemed to be ok.

Only thing I can imagine is the ECU itself - even I tried another one I have laying in carage. They both can be broken. I'm guessing there's some condenser fried up or something which causes this weird condition.

Bearcat · Mar 6, 2016

No solution found yet.

Today got some progress: the engine works when I unplug the fuel pump connector and connect the fuel pump into separate battery. But why it works? When fuel pump is connected into sled the voltage is around 16 volts in the connector.

Bearcat · Mar 7, 2016

Finally some progress

I tested on stand with separate battery as said earlier and engine worked. I made a cable from sled battery charging wire to fuel pump and put condenser into the line and seems it works. So now the fuel pump is powered by light coil and there's nothing in fuel pump coil.

Haven't tested on snow yet as I took the front shock out. I'll report the results when get some

As there's only fuel pump coil, ECU and fuel pump in the fuel pumping side - seems both ECUs I have are broken.

EJ Reichenbach · Mar 7, 2016

Bearcat said:
Finally some progress I tested on stand with separate battery as said earlier and engine worked. I made a cable from sled battery charging wire to fuel pump and put condenser into the line and seems it works. So now the fuel pump is powered by light coil and there's nothing in fuel pump coil.

Haven't tested on snow yet as I took the front shock out. I'll report the results when get some

As there's only fuel pump coil, ECU and fuel pump in the fuel pumping side - seems both ECUs I have are broken.

Did you by chance check ohms resistance on fuel pump coil? If you'd like i can get u specs

Bearcat · Mar 7, 2016

Yes, I've checked all the resistances of stator coils. Everything was right (1.9 ohms for fuel pump coil) and I also have another stator which I tried. I do get 16 volts at idle from ECU to fuel pump but still engine goes into limp mode. I think something has broken inside ECU (example condenser fried?)

EJ Reichenbach · Mar 7, 2016

Injector coil should nbe 19ohms fuel pump coil 1.9ohms.

EJ Reichenbach · Mar 7, 2016

With 16 volts I wander if something Is trying to lean out or fail and ecu is saying no add fuel for fail safe mode.

Bearcat · Mar 8, 2016

Finally installed the shock back and went for test drive - still bogs. Damned! It works on stand but not on snow. Back to square one. Bad thing is those ECUs for this engine are really rare around here scandinavia :/

EJ Reichenbach · Mar 8, 2016

Bearcat said:
Finally installed the shock back and went for test drive - still bogs. Damned! It works on stand but not on snow. Back to square one. Bad thing is those ECUs for this engine are really rare around here scandinavia :/

Well here's a good way to test it unplug the temp sensor and see if light flashes cuz it should.

Bearcat · Mar 8, 2016

I've unplugged all the sensors one by one to see if I get the error code. And I did, so all the sensors are ok.

Bearcat · Mar 17, 2016

Finally found the problem: ECU was broken. Annoying thing was my both ECUs are f***ed. So it was hard to find even I changed the ECUs it acted same way.

I connected the sled into oscilloscope and started to check the pulses and noticed the pulses going to coil acted bit weird. There was a big pulse which "ate" one cylinder pulse at high rpm. I compared the pulses into working ZR 600 EFI -02 so the difference was easy to notice. Took some video of both, I'll post them some day to here.

I'm guessing there's some condenser fried up. I'll take apart one of failed ECUs and try to find what has broken.

EFI advanved timing and APV measurement?

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