Now I know that Italian machines are famed for their "electrical systems" but mine is doing somthing a bit odd. When I use the pass button to flash the full headlights, it drops onto one cyclinder. Now when this happened before, I brought it to a guy with a Mathesis device and he said the only error on the ECU was horizontal cylinder misfire. Changed the coil for that cylinder and all was well. Now it is doing it again but worse, now sometimes when I turn on the full lights at night, it will drop onto one cylinder. To get it to come back again, I have to turn the lights off completely, throttle off and then on again and turn on the lights again. This is obviosuly a bit annoying ona a motorway at night. Does this sound familiar to anyone? Cheers, A
Doesn't sound like anything I have actually experienced myself - but the first place I would look is the big multi-pin plug on the left-hand side of the headstock. If any water gets in there it causes all sorts of strange things to happen... I got so fed up of it happening on my ST that I took the plug out all together and soldered the wires together instead... No strange electrical gremlins since...
Right, will check that. Have previously heard of issues with the one on the lower right side of the fairing, near the coolant bottle, but not this one. Will check it out.
The only thing that can affect only one cylinder is the ECU. Both coils are supplied by the fuel pump relay which is turned on the by the ECU, so you have power to both coils and the fuel pump or to none. The ECU fires each coil at the appropriate time by working out the timings from the pulses it receives from the crank sensor. There is only one sensor, not one for each cylinder so whatever is happening is within the ECU. A bad earth or a poor connection to it may be the cause. The tachometer is also driven by pulses from the ECU, derived from the crank sensor and is usually the first thing to behave erratically if there are voltage issues. Does the tacho behave normally when the bike goes onto one cylinder?
You are spot on Derek. The tacho does go all over the place and worse still, when I turn on the lights, the temperature read out on the dash jumps 3 degrees and with the full beams can jump 5 degrees! I have often seen the overheat warning on the dash but never once has the ECU stored a fault code for overheat, and the fan cuts in and out despite the dash reading silly temps. When it drops onto one, the tacho does not go mad, in fact I can't recall it doing anything abnormal in such instances. I have removed and cleaned the primary earth on numerous occasions to no avail.
It certainly appears to be an issue with either the supply or earth to the ECU. Check the ECU earth cable which is attached to one of it's mounting screws. Measure it's resistance back to the battery -ve, it should be nearly 0 Ω. As suggested above check the condition of the wires to the big multi-connector at the LH side below the fusebox. Water gets in and the wiring can rot from below.
I had a near identical problem with an old Volvo many years ago. In my instance the car would only run on high beam. Turned out the back of the fuse box was corroded and it was able to pull an earth supply via the high beam circuit.
I was thinking the other way actually. Thought TBH, I know fuck all about electrics. As another member on a forum says, if it can't be fixed with a hammer, it's electrical. Everything seems to be just fine with the ECU, as there are no error codes recorded there bar the running on one cylinder. I was thinking that the issue might be an earth somewhere that serves both the display and the lights.
Having read this post,at tick over if I put main beam on the tachometer reads zero.however same action but on the move sees tachometer read ok?
Right, had a look at this yesterday and it seems as if @philoldsmobile was pretty much spot on. I took the cover off the fuse box and immediately there was a problem. The 20A fuse for the lights was melted! Somehow, the plastic casing had become so hot that it had melted into a big clumps, but somehow the element inside was still connected. I took it out with some difficulty as there was a fair bit of corrosion around the connectors. I disconnected the box from the mounts and managed to clean the seats of all the fuses and replaced any fuses that had corrosion on them. Having remounted the fuse box, I fired it up and cycled through the lights and everything seemed OK, there even seemed to be less jumping around by the tacho needle when going from running lights to dipped beam. So, I can only conclude that a poor connection in the fuse box, due to corroded contacts had caused the plastic casing of the fuse to melt and that the bad contacts were causing the gremlins shown. I did not get a chance to take it out for a spin yesterday but I’ll report tomorrow. The only odd thing is the pass switch to flash the high beam does not work at all. Ah, well… A
Maybe the pass switch or its wiring was the cause of the fault? It may have chafed a wire, causing a short which caused the current drain and the melting electrics.
Yeah, good point. Will have to investigate further when time allows. Update: well, the spin to work this mornign was uneventful, which is good All worked as it should and there were no issues. Oh well, I suppose one must put up with these thigns on an 11 year old bike heading for 50k miles.
Right, here's an update on this zombie thread. The bike still did the weird thing of dropping on one cylinder when in 5th gear and I went from dipped to full beam. It also used to jump anything from 3-5 degrees on the temp read out as electrical loads came on. So, as the dipped beam came on, as the fan came on, as the main beam came on. Also, at tick over, the tacho read fine around 1000, to 1100rpm. Then when the dipped beam was turned on, the tacho often dropped to zero until you went took off and rev'ed the engine beyond the 1500 rpm range. This drove me nuts for ages until I was looking at something totally different and I copped the ECU earth. The ECU earth is a small circular electrical contact that bolts to the battery box. Not the metal frame, not the engine casing, but the plastic fucking battery box. When I realised that the ECU had its own earth, my limited knowledge of electrickery suddenly made sense of the situation. Basically, the earth was corroded and whatever earthing was offered via its bolt and sleeve in a rubber grommet was buggered. I gave the earth a good clean and turned on the bike until it would tick over on its own without fast idle. I then turned on the parking lights. temp display and tacho were unchanged. I turned on the main beam, ditto. High beam too, no change. I even flicked the fan on and off (manual fan switch) and all was well. Now I didn't have a chance yet to take it for a spin and get her up to 120kph and do the pass button trick, but I'm optimistic. So if your ST suffers any of these issues, try the ECU earth and see if it sorts it out. A
