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Discussion Starter · #1 ·
Runs on vertical cylinder only. Pulled the air box to see down each throttle body. On startup the horizontal cylinder gets two squirts of fuel and then stops. I swapped the fuel injectors and the same thing happens again on the horizontal cylinder. When running on the vertical cylinder, when I squirt a little starting fluid in the horizontal cylinder the front cylinder runs for a few seconds. So I have spark and compression but no signal on the horizontal fuel injection other than two squirts at start up. I don’t know where to go from here. The problem was intermittent at first but now it is chronic. Please help. Thx.
 

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Hi and welcome to Ducati.ms. We are super happy to have you here.

I will post a copy of your post about the issue you are having in the Sport Touring forum so you have a lot more exposure.

Please fill in your location information in the UserCP Edit Your Details section, that can help if there might be someone local to you give a hand or find new friends to take a ride.
 

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Your issue is identical to mine same bike same year same cylinder. I tried everything over two and a half years including HT leads and checking the LT and swapping everything out. I also checked all lines to the ECU. It turned out to be the Loom although there was contact it wasn't good enough to give a reliable strong spark.

Check your main connector and fuse box and also the connectors to the LT side of the coils after that you need to look at earthing points and possibly a replacement loom
 

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Back when the 2002 ST4s was a current model, was there existing dealer diagnostic equipment capable of narrowing down the cause of such failure? If so, it could be worth the cost of getting a diagnosis at the height of the riding season. S
 

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Discussion Starter · #6 ·
Running on one cylinder at start up issue resolved. I followed the advice above to check the wiring loom. I stripped the fairings and went about inspecting the wiring loom with a dental mirror and a good flashlight. Disconnected every engine related connector and douched both female and male ends with electrical cleaner. Didn’t really see anything suspicious. I then went about disconnecting and cleaning every battery and ground connection. I think this may have been part of the issue as two of the grounding connections looked as though they had been handled with dirty greasy hands where they mate to the grounding surface. I cleaned everything spotless and reconnected. I had earlier purchased the HICAP thick copper wire battery leads from Mototek. I noticed that the prior owner had already installed a set of these HICAP wires (but connected them with dirty, greasy hands I guess?). I noticed the new HICAP wire kit includes brackets to double up the wires. I suppose it is serious over kill but I was able to fit the new HICAP leads in parallel with the old set. The bike starts in an instant on both cylinders. Because I didn’t check the bike after each operation I don’t know with certainty which was the real issue but I’m thrilled it starts and runs so darn good. I just got back from riding up and down the Feather River Canyon on highway 70 north of Oroville, California. Is there anything better than a great road in the morning on a perfect running Duc?
 

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Congrats on your efforts and results!! Nothing is better than a great running machine arising from your detailed efforts. Welcome to the forum and enjoy the Super Duc!! Ride safe!! STeve
 

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So pleased for you, and a little bit happy I made a contribution. My fault was found by the dealer when he attached the diagnosit lead and the loom started to somke. He also found that some of the connections to the earth point(around six wires into one crimp) were not good
 

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Discussion Starter · #9 ·
Yes, thank you so much for sharing your experience in getting your Duc issue resolved. I don’t know what we would do without this forum. In reading hours of posts on our older Ducs I see a repeated theme of how critically important it is to maintain a nearly perfect electrical system. Where my dozens and dozens of previous Japanese bikes rarely seemed to be particularly sensitive to marginal grounds, batteries, connections etc., my 16 year old Duc demands perfection. But we put up with more extensive maintenance requirements because the riding experience is worth it. I have 4 bikes, 3 Japanese bikes and my ST4s. Any guesses as to which one I prefer to ride on a nice day in the twisties of the Sierra Nevada mountains? I’m addicted to Duc magic! Again, many thanks to all who contribute to this valuable resource to exchange useful knowledge among so many owners with common interests. ?
 

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I just got back from riding up and down the Feather River Canyon on highway 70 north of Oroville, California. Is there anything better than a great road in the morning on a perfect running Duc?
I hope you took some photos of the trains.
 
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