98 VFR800 cranks with spark but no start... Advice?

My son recently bought a 98 VFR800 with 20K miles in average condition and running well. The previous owner claims to have replaced the fuel pump within 2K miles, and we just replaced the plugs and air filter.

The other day while warm, it stalled and would not restart. It has spark and the plugs were wet. No flashing from the FI light. If I cycle the key on, I can hear the sound of a pump priming and the FI light cycles with the pump. It will crank but no ignition. I've charged the battery and have half/tank of fuel.

I downloaded an FSM and reviewed their troubleshooting flowchart which suggests I check fuel pressure next?

Any advice is greatly appreciated.

 

When you turn the key on and the fuel pump cycles, does it (the pump) turn off when it reaches pressure? Do not hit the starter button and wait for the pump to kick off. Does it happen?

 

Yes, the pump runs for about 2 seconds, changes pitch like it's building pressure, and then stops.

 

check the battery voltage cuz sometimes it will crank ov er fine b ut not have enuff extra potential to power the spark system.

 

Have you taken the plugs out cleaned and dried them?

 

Yes, I should have mentioned that - When I checked the plugs, which have less than 500 miles on them, I dried them well. When I put a plug in the cap and hold it against a ground, the spark when cranking is pretty weak looking, but I don't have anything currently to compare it to. It's clearly sparking though.

I also have it on a charger, so it is at full voltage. I am stumped.

 

To check spark you need to see if it'll jump a 10mm gap. If it cannot, it won't fire under 170-200psi in the head.
I do not know what'd cause weak spark on all your plugs, but that's how you have to check spark if you want to know if it'll actually light off the fuel.

My suggestion is to disable the fuel pump and then try starting the bike on the residual fuel and then with a squirt of gas or starting fluid. Spray into a vacuum line if you want, that's easy. Then maybe we learn if you have too much fuel.

 

You say it stalled ...do you mean died?

If so that sounds like something failed, all fuses OK?

Rubbing a pencil lead on the plug electrodes causes the graphite to explode giving a big bang so it should spin the engine

 

Stalled = died. It was idling, then it stalled and hasn’t been able to restart. It has made several minor combustion pops, but won’t run. Battery is good, fuses are good.

 

I tried to start it on starting fluid, and nothing. I am now thinking spark.... What would make all the plugs spark weakly with no combustion? ECU?

 

I think now would be a good time to get a factory service manual, take a few deep breaths, and follow the recommended order of troubleshooting outlined in said manual. Randomly shooting a shotgun into the darkness is only going to cause more grief and confusion.

 

Yeah, agreed. Which is what leads me to think its time for an ECU....

 

I haven't seen "bad ECU" being a thing with VFRs.

Since this bike is "new to you" it might be worthwhile to give it a good going-through, just a way to really get to know and understand what you've got, to make it yours.

This has always been my approach to owning a used motorcycle, I just don't feel like it's mine until I've been through all of its subsystems.

There's every chance that during a refurbishment effort you'll either find the source of this fault or you'll correct it without realizing what it was.

 

Thank you! Your advise was excellent and helped reveal bad fuel to be the culprit! Fresh fuel had it running well again. I appreciate all who assisted. The internet really is awesome.

 

Bad fuel ? Old or contaminated ? It seems odd that it would run but then wouldn't on the original fuel . Any way glad that you got it running again.

 

I can believe that it was a fuel problem when those who "know best" regulate what is mixed in the fuel. I'm talking about the ethanol in your gas. It is amazing how fast "regular" gas can go bad. For my part I fill up with ethanol free gas as the weather begins to head toward winter.