My ST4S is only running on the vertical cylinder. I am not getting a spark on the horizontal cylinder. So far I have checked the horizontal plug on the vertical cylinder and it gives a spark. I have swapped the coils over and still no spark on the horizontal cylinder, but ok on the vertical cylinder with either coil. I have also swapped the plug leads over and again I get a spark on the vertical cylinder but not the horizontal cylinder. So from this I have concluded that the coil, HT lead and plug are all good. I assume the coil isn't getting a LT signal. But I'm now stuck! I don't know what to look at next any ideas?
Peter I don't know the ST4S but had a look at the wiring diagram, the one I have has an IAW 59M ECU. If plug, HT lead and coil are all good. It has to be something connected to the wiring, connector or (Gulp!!) ECU. The injection and both coils receive a pos supply via the injection relay and a common brown/white wire, which I ass-ume is paralleled at locally at the coils. The logical though forlorn hope is to check you have a pos 12 on that wire on the Horizontal cylinder. I think you will as its a commoned supply but you never know. You could use a test light or better a multimeter. The ground side for the horizontal is a blue/grey wire going back to ECU, you could check that for continuity. You cannot do much more that I can think of without diagnostic equipment or an Oscillisope. You could possibly check if anything is happening at the coil if you have (or can get a loan of) a multimeter that measures frequency. With that you should read frequency if the LT side of the coil is attempting to fire it. That's all I can think of right now, remember this is just from going from the wiring diagram, I wouldn't know an ST4S if one fell me. Hope its of some help John
as Jock says from the tests you have performed it would seem it has to be down to :- one connector check via brown wire from injectors (connector for that cylinder only), a continuity check of coil trigger wire (also brown?) running to long ECU connector plug - pin Number 1 assuming it's the same as 748/9** etc and a check for corrosion at the ECU plug at that pin number at the same time. Interesting that it's on the end so possibly more prone to moisture/corrosion. If none of this works you could even try carefully reseating chip as I know that this has been known to work occasionally - finally, it's 'borrow someone elses ECU time'. If yours does use a 16M type and you were closer you would be welcome.
Thanks for your advice folks, I may be getting in a bit too deep for my knowledge now, but when I get chance I will try and follow the suggestions above and look for anything obvious corrosion loose conections etc. With regard to the ECU the previous owner (who I know) had put a new ECU on the bike before he sold it, so I would hope that it's not that. As to which type of ECU, I have no idea, how do I go about identifying it?
Peter Its not that complicated to check if you are getting power to the coil. There is nothing particularly magic, the coils are fed +12V via a relay and have current flowing in them most of the time. The negative side goes to the ECU, when a spark is needed the ECU breaks the circuit on the negative side by opening the path to ground, this causes a voltage build up in the coil and a spark at the plug. To check for a positive supply, according to the diagram its a brown/white wire, take that cable off the coil and connect one side of a test light to it. Take the other side of the test light to the engine or frame. When you switch on the ignition the bulb will light if the supply is good. John
there you go - nothing like a bit of teamwork when someone's flailing about in the dark :smile: could you go a step further and tell Peter the corresponding pin number on the ECU for the trigger wire on horizontal cylinder John?
Hi Chris The diagram states that the Pin is Engine 38, the codes are split into Body and Engine, I'm unsure if the 2 types relate to the 2 plugs. The wire is Grey/Blue. Here is the link to the diagram I am looking at http://www.ducatiwiki.net/images/f/f5/ST4S_05(Colour).pdf Hope that helps John
Chris W, that is superb. I just did some quick Googling Motor - Engine Rahmen - Body Pin 38 Motor Horizontal Coil Trigger (Edit: Chris we posted at the same time) Pin 10 is the Vertical Coil trigger Peter - Just check it all ties up and the wiring colors correspond to the pins and you should be good Great when a few us pulling together can really help John
The side you are interested is the Schwarz (black) this relates to the colour of the ECU connector bases. I do all my ECU work on the Grey side so I am learning things from this post.
Ok quick test, remove sparkplug from broken cylinder. Plug it in to your spark plug wire, earth on engine and start the bike, should be sparking if all ok. Keep it away from the sparkplug hole as petrol might/will be shooting out. If it is sparking compression check would be my next guess.
SPIKE, no not checked the compression, but that is because I'm not getting a spark so thinking more electrical than mechanical. Lucaz, Yea, pretty much how I concluded I have no spark on the horizontal cylinder. Chris, ChrisW & John, Many thanks for this lot particularly the link to the colour wiring diagram and picture of the ECU, yes that looks like mine. However knowing what pin does what doesn't help me to much (probably 'cos I'm thick)! the connectors to the ECU are mould plugs with a clamp arrangement, so if its plugged in I cant get a multimeter on to the connectors to carry out any kind of checks. If I take the connector plugs off the pins are so small and close together I don't think I would be able to connect a meter to them without shorting against something and frying the ECU! So what am I not understanding here?
Peter You might need to buy a small testing prod, you can get them so they can clamp around small pins. Like these Probe Clip Test Leads : Test Leads & Accessories : Maplin Electronics or Test Lead Set with Probe Tip Covers : Test Leads & Accessories : Maplin Electronics I would take the plug off and and from the loom side of the removed plug check for resistance between the plug and the coil lead (remove the spade or pug or whatever off the coil as well). You should read a small resistance less than 5 Ohms I'd guess probably a good bit less. If you do that then you know the wiring is good from coil to ECU. If you already checked the pos 12 side and its good then you have pretty much narrowed it down to the ECU. Others may have better ideas but that's the way I'd approach it. With the plug out of the ECU I would not be too concerned about frying anything, the possibility always exists to a small degree, but its only when plugged into the ECU that you need to be super careful. John
Well it's bad news, it seems that it is the ECU, I have someone looking at it and after check through the wiring they tried a 999 ECU and it started on two cylinders. So does anyone know where I can source a replacement? ... Cheap! (Don't Laugh)
