Pse see 1st post for symptoms. This is what I did:
This Group & other Ducati forums helped me take an anlytical approach - essentially first look at fueling and electrics. Don't forget that more often than not the bike would start and run perfectly.
- Emptied tank, took out pump assembly, tested pump (it worked every time), changed fuel filter (it was clean), inspected lines (they were fine and firmly clamped on, both inside and outside the tank; I changed the inner ones anyway). All this meant that in theory at least fuel should reach the injectors.
- Disconnected, inspected, cleaned every connector I could find, including of course the injectors and ECU connections.
- Checked each relay (all 4 of them!) repeatedly
- Checked crank position sensor (CPS) air gap; was about 1mm instead of 0.6-0.8mm. By the way, front cylinder does not need to be at TDC for this; on the contrary, as when the front cyl is at TDC the CPS faces recessed teeth, it it more reliable to measure the gap when the teeth are 'full width'. Anyway, there were 2 x 0.6mm shims present; 2 were too much, one not enough, so I left as is.
- Ensured battery was charged to the hilt.
When I started the bike it fired off straight away and ticked over fine if slightly lumpilly. I tweaked the rear cyl air bleed open 1/4 turn (plug was slightly sooty) and engine idled beautifully.
While fiddling I disconnected each injector in turn and this resulted in the exact 'loss of power' symptoms. A chat with a friend pointed to a 'sticking' injector as the bike had not been used much for several months, so a dose of injector cleaner was poured into the tank.
Took it for a test ride (starting and running perfectly) and decided to drop in on Pro Twins, near Godstone, from whom I usually get my spares. A cuppa and a chat later and they agreed to slap their test equipment on the bike. They diagnosed a series of fault codes relating to a weak battery (weak battery on the ST4s means injectors not firing, coils not firing, and a few other gremlins), and that the throttle position sensor (TPS) was at 1.4 degrees on idle, instead of 2.6.
To cut a long story short, they took my bike in today and adjusted the throttle bodies spot on (TPS, balancing, CO2 levels). Bike now works like a dream.
I guess I will never know whether one action more than the others cured the problem, but the more I think about it, the more I think that the starting problems were due to a not fully charged battery and the loss of power problem was due to a 'sticking' injector.
Many heartfelt thanks to all contributors, and to ProTwins for their expertise and very friendly service.
Michael
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