Left Stranded-Fuel Pump?

[Guest Scura Owner]

I was left stranded today. I had to double-up on my significant other's SV650S and leave the Scura. She is still laughing.

 

After stopping for a quick snack in the middle of a 200 mi ride, the Scura started fine, then went to one cylinder then died. I found a blown fuel pump fuse. I happened to be near an auto parts store, so I ended up buying 18 fuses and going through every one of them. Half the time the fuse would blow on turning on the ignition and the other half after I got the bike running on one cylinder and tried to give it some throttle. In order to trouble shoot, I had the tank off and the whole fuel system disconnected. I got flow through the filter. I got flow upto the pressure regulator. As soon as I connected the system back up, the fuse blows. I would think the pump is shorting but I do not understand why the engine will run on one cylinder (the left one). I also unconnected are reconnected all the wire connections I could find.

 

Any ideas?

[callison]

Sure, I have a few suggestions. The fuel pump fuse isn't just the fuel pump fuse. That circuit is shared by the ignition coils and the injectors as well. So, since the problem is on the right side you need to find out which component is giving problems, the right ignition coil or the right injector. Remove the connector from either one and then turn on the bike and see whether the fuse still blows. If it does, re-connect that connector and remove the other one and try again. Since the bike will run on one cylinder, it is not the fuel pump blowing the fuse. It could be an ignition coil, it could be an injector, or it could be the wiring. It is even conceivable that it is something on the left side of the bike, but that isn't as likely. Start with the easiest things first by unplugging components.

 

The following schematics are in color if that will help.

 

http://home.pacbell.net/guzzi007/schematic.../V11_Wiring.gif

http://home.pacbell.net/guzzi007/schematic.../V11_Legend.txt

[dlaing]

Never trust a significant other. She put a bobby pin in your ECU relay, just to get a laugh!

But seriously, it could be anywhere along that line, coils, spark plugs, fuel injectors, fuel pump, wiring, or relay. The relay is most likely to flake out, but Carl's diagnosis sounds good based on the running on one cylinder evidence.

It could be tough to diagnose because if you remove something from the circuit to see if it is the culprit, you may also be lightening the load on the fuse allowing it not to blow.

If you can compare the resistance of the left and right coils and the left and right fuel injectors, a gross difference may indicate a short. I imagine the primay resistance of the coils is probably about 3 Ohms. The Ohms don't have to match exactly. But if you get 3 Ohms in the left and 2 Ohms in the right, you'll know something is off. I have no idea what the Ohms for the fuel injector should be.

Best of luck,

[Guest Scura Owner]

Thanks your your input. I spent the day running back and forth and finally trucked the bike to dealer. I expect it to be a long wait as the dealer says he does not stock any of the likely culprits (pump, injector, or coil) since he has never heard of one of the items failing. Maybe this will fix the stumble and pinging.

 

Also carefull when using the wiring diagram in Callison post. The Lemans and Scura use a slightly different diagram where the F2 fuse powers the pump and ignition circuit (but with Guzzi I would not be suprised if neither of them were correct).

 

Thanks again.