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Griso 8v fuse 'C' [or is it 'B'?] blowing on start

V

Vince C

Just got it firing!
Joined
Jul 20, 2013
Messages
12
Location
Wilmslow
I've only had the bike a couple of weeks, but last week on starting fuse 'C' blew, so no start. I replaced the fuse with a good one, and all was well and the bike ran and started OK until tonight.

This evening I went to start it and it blew the fuse again (it's a 15a fuse). So I replaced the fuse, tried again - it blew again! On the third try it started and ran OK. I'll need a big supply of spare 15A fuses at this rate!

Anyone any idea why it might be doing this?
 
Re: Griso 8v fuse 'C' blowing on start

On that diagram it's shown as Fuse 3 (but that diagram doesn't seem to show it as 15A, which it is and should be). It feeds (via the contactor in relay 28, the Main Injection Relay) the fuel pump, both injectors, and both coils.
 
Re: Griso 8v fuse 'C' blowing on start

Vince C said:
On that diagram it's shown as Fuse 3 (but that diagram doesn't seem to show it as 15A, which it is and should be). It feeds (via the contactor in relay 28, the Main Injection Relay) the fuel pump, both injectors, and both coils.
Click to expand...

OK, Checked the schematic. Check the harness to the fuel pump, if it looks OK then disconnect the pump and see if it blows the fuse when you turn the key on. Could be bad harness,or pump. If it doesn't blow the fuse, then it is a dodgy pump. Also it could be the harness to the injectors or coils and these components, but those items are less likely. Intermittent problems like these are hard to determine. You have identified the circuit items the fuse supplies. Now it is a matter of isolating the fault.
 
Re: Griso 8v fuse 'C' blowing on start

Check the wiring loom directly under the injection relays. These are behind the RH side panel right behind end of tank. Take out all the screws underneath and on the side to get access. A bear to get in there good. I have fixed 3 or 4 that had a pinched loom at that location. Worth a check see.
 
Re: Griso 8v fuse 'C' blowing on start

Most electric stuff draws quite a big pulse of current upon energization and their running current is much less than these first moments of power-on. As said, a pump that has a bit higher friction due to debris accumulation or wear sounds as the most logical reason for an excessive startup current pulse. Of course mama could have put the loads on different circuits to avoid such glitches.

Yada-yada alert:
The only way I can think of checking such pulses is through some instrument with memory of current readings during the transient power on period. Maybe measuring the resistance accross subsystem connectors/loom or even adding some 0.05 or so ohms resistor in series and then taking a transient voltage memory measurement accross said resistance points with proper Vmeter or cheapo pocket oscilloscope. Voltage/resistance gives current drawn at specific timepoint. With all these transient related trouble , having benchmark values by a good bike would be quite handy for diagnosis of anything out of the ordinary. Such electrical gremlins are hard to properly diagnose otherwise.
 
Arrgh! Another fuse blew on starting - checked carefully before replacing, and .....it's fuse 'B'!

Could I have been wrong about the other fuse blows? Was it 'B' all along and I was looking at fuse box from the wrong end and thought it was 'C'? Or are they both blowing?

I'm going to assume for now that I'm an idiot and has been fuse 'B' all along. Unless fuse 'C' really does blow in future! I hope it is just 'B', as that at least seems to be well understood.

I think!

Took off Starter motor today to clean any stiff old grease out of the solenoid cyclinder and off the solenoid plunger (there wasn't much in there and it didn't look too 'stiff'). Wiped it all clean and replaced the grease with a smear of clean engine oil on the plunger and the cylinder walls.

Even if that cures fuse 'B' blowing, I intend to do the start relay mod once I find out how to get to it! (See other thread on side panel removal) as I don't like the idea of high current going through the ignition switch.

Something I have noticed is all the fasteners are coming out 'dry'. One of the starter motor mounting bolts (the lower one) was showing the beginnings of corrosion on the bolt shaft and threads. Everything is going back with a smear of Coppaslip grease on it.
 
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