'90 851 Wiring Diagram

hindsight

Has anyone got a decent wiring diagram for a 851.. I'm trying to track down a peculiar fault..

History - replaced fuel hoses a few weeks ago. Ran the bike up to temperature last weekend, was running just fine. Tried to start it today, fuel pump primed (therefore kill switch working just fine), but no ignition: no sparks on either plugs. Can't meausre any voltage on the coil connections with the ignition on.

All fuses in the tail look fine, swapping the relays had no effect. I guess I now need to start checking component voltages and wire continuity.

Any advice (or a copy of a usable wiring diagram!) appreciated,

Thanks
Mike

wgsvintage

Would either of these help? Wiring diagram is on p.228. It's from '88 but probably applies. Crank position sensor can also cause your problems.
Bill

http://www.ducati851and888.com/showt...orkshop-Manual

http://www.ducati851and888.com/showt...Injection-Data

Mr.R

I've a genuine '89-'90 workshop manual that I could photocopy the wiring diagram for you if it helps?

Steve R

hindsight

wgsvintage wroteCrank position sensor can also cause your problems.

Thanks Bill - looks like it is exactly that. Remeasured voltage at the coil, and noted that I had missed that it was actually seeing current during the fuel priming cycle, suggesting that the circuit upstream of it is fine. Disonnected both sensors and measured - the timing sensor is 625 Ohm, the crank sensor is showing infinite resistance, suggesting that it's borked.

hindsight

Mr.R wroteI've a genuine '89-'90 workshop manual that I could photocopy the wiring diagram for you if it helps? Steve R

Appreciated, thanks Steve - but I think I'm there now.

hindsight

Just to close the loop on this one. Sensor ordered (SEN8E) and fitted, coil then starts to see voltage when the engine turns over as expected, and there is a nice strong spark from both plugs.

Fitted the plugs and the bike explodes into life. Curious timing (sic) for the sensor to expire, but hey ho.. everything will expire, given enough time - and this old girl is older than many others..

wgsvintage

A long time Ducati mechanic told me when my 748 was acting just like yours, that it was undoubtedly one of the two relays or the crank sensor and to just replace all three and be good to go for another 15 or 20 years.
Bill