Ducati Diagnostic Instrument

[icekube1]

Hi everyone

My back cylinder has gone quiet.

There's plenty of compression and spark, so am thinking there may be some kind of timing (crank angle sensor) or fuel issue.

My workshop manual talks about a diagnostic tool; blinking light variety, plugs in at the engine management unit, to check the condition of sensors. Does anyone know where I can source one, or how to make one up? Goofgling hasn't helped so far. I'm guessing the plug/cable is an industry standard type. Any advice would be much appreciated.

Thanks
Mike

[Derek]

Can't help you with the diagnostic but I think if the crank or timing sensor has failed it will affect the spark and injection to both cylinders.

[icekube1]

Can't help you with the diagnostic but I think if the crank or timing sensor has failed it will affect the spark and injection to both cylinders.

That makes sense, thanks.

[higgy]

seems to me I saw a diagram on one of the other Ducati forums on how to craft your own version, do a google search and you should be able to find it

[nickta]

There is a schematic on how to build one on here too. It works too! Takes about $10 of parts and about 20 minutes to solder up.

Cheers.

Nick.

[nickta]

Try this post:

http://forums.ducatipaso.org/viewtopic. ... hing+light

Cheers.

Nick.

[higgy]

chances are this tool is not going to help much, time to start check those connectors and grounds
concentrate on the ignition circuits and key switch

[higgy]

chances are this tool is not going to help much, time to start check those connectors and grounds
concentrate on the ignition circuits and key switch



From G

P750 engine running on one cylinder (occasionally)

The problem could be everything from
pick-ups (quite rare)
incorrect pick-up clearance to flywheel (air gap)
pick up wiring (can break where it enters the engine cover. The pick-ups will measure the correct resistance if a wire isn`t completely broken which makes it tricky)
ground connection to CDI units
CDI units (quite rare)
wiring to the coils (kill switch, ignition switch)
coils
spark plug (HT) wires
spark plugs, incorrect electrode gap
carb synchronization

HT wires can age and if a coil has cracks in the housing it can be affected by temperature or humidity.
The most common problem though is the wiring with bad connections and old wires with copper rust.
Measure the voltage at the coils and CDI units (orange wire) and if it isn`t nearly the same as the battery voltage clean the kill switch and all electrical connections (specially the main ground connections) then do the wiring mod.
https://app.box.com/s/waxvk1l9g47phfybd6n9
One indicator of low voltage at the coils is if the dropped out cylinders kicks in when rpms are increased.
Electrical resistance of bad connections does increase with heat btw.

To rule out parts like CDI units or coils swap them from one cylinder to the other (one part at a time) then see if the problem shifts to the other cylinder. If the problem remains the same the parts swapped are ok and the problem is somewhere else.

If the issue remains check compression and valve clearances.

[icekube1]

Thanks for the responses guys.

Haven't looked at the bike for a week or two now, although I did quickly run a compression test on the rear cylinder; 125psi. So that's doesn't seem likely to be the problem.

As I mentioned in my op, there is a big fat spark at the rear cylinder, so I'm discounting CDI/ignition circuit issues at the moment and am starting think about fuel. Bike is just sittng in the corner of the garage atm, with a sheet over it.