Newbie electrical question - Ducati.ms

Drdds · Jan 6th, 2012, 12:50 pm

So recently acquired a '94 900SS project and already have an electrical problem. I knew the battery it came with was totally dead, but it was the weekend and I really wanted to try and start it, so I jumped it to my car battery, upon thumbing the starter, it turned over once or twice very slowly then blew the #2 fuse (ignition and fuel pump). Maybe it is stupid to jump a bike with a car battery huh? Whoops. At any rate, bought a brand new battery, put it on the battery tender until full charge was there, replaced the fuse and "pop" goes the same fuse again. So now here I am, with a new fuse installed, and the ignition switched on, the fuel pump runs fine, if I depress the starter button, there's a large current draw (light dims, fuel pump slows) and if you hold it down for more than about 1 second, the fuse goes. I STFA and couldn't find any similar issues, but I did find some things I'm trying now. I pulled all the starter wires to clean contacts and replace them with heavier duty set (I'd love the Motolectric set, but the budget is getting thin with other issues that need addressing on a higher priority, so i made some new cables my self with welding cable and swaged copper lugs. Haven't had a chance to get them installed yet but am hoping that had something to do with it. Replacing both battery cables, frame to engine ground, and starter moter lead as that one was pretty dirty/greasy just in case.

On a side note, I can compression start it and it runs like a dream, so I'm pretty much thinking its a short to ground in the starter circuit somewhere.

Anyone with thoughts or similar problem?

Thanks so much

jimc2 · Jan 6th, 2012, 12:57 pm

my guess is starter motor bushings.
try the starter off the bike..

bananaboat · Jan 6th, 2012, 2:57 pm

Check starter solenoid and starter motor. If your wires to those are good and not shorting to ground, it's probably something wrong inside one of those. Good news - no computers to deal with. You have a wiring diagram I hope?

Drdds · Jan 6th, 2012, 3:34 pm

Thanks to both of you for the suggestions. I do have the wiring diagram. I have the factory service manual but not any of the others yet. I'll reinstall my new cables this weekend and see what happens. I had a thought after I posted this. The small white cable that goes in to the starter relay was pretty loose or may have been out when I pulled the relay, so that would explain the starter not working, but if that little guy was some how grounded to the frame or relay housing or something else near by, could that explain the blown fuses? I'll have to make sure that goes in correctly when I reassemble.

Thanks again both of you for the replies. I'll update when I can.

*edit*
by the way, are there procedures for checking the starter and starter relay?
thanks

Joe-B · Jan 6th, 2012, 4:34 pm

I had the same symptoms at a track day a month ago. Press starter, second fuse (ignition and fuel pump) blows. Turned out to be a faulty starter button. I removed the orange button and was able to start the bike by grounding the contacts with a flat tip screwdriver. Second time it's happened (2 different sets of switch gear).

Shazaam · Jan 6th, 2012, 6:02 pm

The fuel pump is powered by a DC motor that draws a fairly-high current and a dirty/clogged fuel filter will causes the motor to work harder and draw a much higher current. A pump feeding fuel through a clean filter will draw about 2 amps, but this figure can rise to 10 amps with a dirty filter, perhaps high enough with other loads to blow the fuse.

944SS · Jan 6th, 2012, 6:38 pm

Good replies so far. I also had the same symptoms you describe; turned out it was a cracked and twisted plastic grommet on the positive terminal of the starter itself forcing a ground of the pos cable to the housing.

This terminal is notoriously corroded since it sits in a spray prone area and it has a rubber boot that can trap water and dirt inside. So if you or the PO tried to tighten or loosen that nut and instead twisted the plastic grommet inside the starter, it could still be grounded to the housing. In my case, it was self inflicted in that I had changed the cables and got over exuberant in tightening it back down. Easy fix if it's the case, any chunk of abs plastic can be used as the grommet.

Drdds · Jan 8th, 2012, 2:08 pm

So I got my new cables finished and installed, made sure all contacts were clean and connections tight, buttoned it up and the starter works like a champ now. Fires up after only a second or so. Great news for me! I suspect it was the lead fom the starter switch to the solenoid grounding, because on reinstalling, that cable was really loose. I pinched the little pins inside the white connector just a little to tighten it up and that seemed much better. So not totally sure what it was, but sure glad to have it working now!
Thanks to all who replied, this forum is a tremendous resource to those of us new to Ducati. Cheers.