Electricky problems - fuse keeps blowing

Howdy all,

I posted the beginning of my problems in another related thread, but that seems to have been a red herring. I hope someone can help.

Bike started and ran fine after a lay up during the cold weather - little struggle to start but no more than I'd expect given the temperatures. Idled to warm, got a few hundred metres down the road, EFI light and oil light and limp-home mode. Turned off and on, problem cleared, rode fine for rest of the day (two journeys). Reading here this sounds like a sticky oil pressure switch - being a cheap part I've now swapped this, but this is what I was referring to as the red herring.

Next day, bike started first time, idled til warm. Wheeled off drive, just died, now the fuel pump doesn't prime at ignition on and won't turn over. Error codes 45 & 50 - starter and fuel pump circuits open/shorted. Battery is giving 13.5V, dropping to 11.7V when ignition on - I'm assuming because of lights drain. The 15A fuse for the starter/fuel pump circuit is blown; tried swapping it, but it blows instantly. Getting battery voltage across the terminals in the fuse box with ignition on. Alarm seems to be behaving normally. Optimate is giving green light.

Now I have a fair degree of mechanical experience, but none electrical, and I mostly hate anything that works by black magic. Are there any known issues that could cause this? Failing that, could someone give me an idiot's guide as to where to start looking for the problem, and how to check?

Any help would be much appreciated.
Chris.

Thanks Matt, will check and clean, to save me stripping half the bike (I've not worked on the Prilla), whereabouts is it located? Thanks.

Thanks Kev, how would I go about tracing the short? Beyond following the loom and looking for any obvious bared wires etc I'm a bit lost, as I said electrics aren't my thing! I have a multimeter and can strip the bike back, but where should I be testing from/to? Is it as simple as looking for continuity from the battery through the loom to the components and narrowing down based on lack of continuity until I find where's actually causing it? Or do you mean something inside the pump? I feel it is less likely to be the starter motor, based on the fact that I'm not pressing the starter button and therefore no current should be going to it? Or does the bike send power to it regardless?

Hey Ian,

In my case it was the speedo sensor, I can't remember the whys and wherefores now but I'd had a couple of instances of the clocks going mad over the previous few week so had ordered a new sensor anyhow; plugging the new one in solved the error codes, EFI and fuse-blowing. I think I probably spoke to an Aprilia dealer (or it might've been Griff) who recognised the symptoms, but it was a fairly cheap and painless fix in the end. Hope it's the same for you!