By-passed FPC now won't start!

[Rong]

Yesterday I had the dreaded FPC failure so bypassed it, fuel pump whirring away, enough fuel in tank for 28 miles but it refuses to fire. To be honest I did connect the pump round the wrong way to start with, blue wire to neutral, so could this have introduced some form of air lock in the system?
Bike's a 2004 1200 GS 20 thou. on clock.

Up until the FPC failure the bike was running perfectly OK.

Any advice would be welcome!

Ron

 

[Funners]

Blue wire to brown wire Yes ?? Yellow to Blue Green ?

I'd be tempted to pull a fuel line and see if it's actually pumping TBH....errr.poin it into a can eh ?
failing that I'd try the wires the other way round...

 

[Pukmeister]

You may have answered your own question there perhaps, however I believe the fuel pump is centrifugal rather than positive displacement so can't see how it would suck when running backwards, just cavitate.

Enough fuel for 28 miles?? I reckon you should throw a gallon of fresh petrol in there and try again, it could be sucking the last dregs from the tank for all you know.

Maybe you could try the TPS reset routine as you have nothing to lose, maybe it will give the ECU a bit of a clear-out?

Maybe the pump needs a bit of a run to build fuel pressure in the fuel rail to the injectors?

Have you checked for a spark in case you have more than one fault now?

I still reckon that adding more petrol to the tank may give the fuel pump a positive inlet head of fuel, allowing it to prime and then pressurise the fuel system to the injectors. It's not wasted money putting fuel in the tank as you'll use it eventually anyway when the bike runs.

 

[Wapping]

I would be very surprised if the pump sucks.

(a) Are you sure the tank wasn't simply empty? Try lobbing a reasonable amount of fuel in.

(b) I assume you are running the work around direct from the battery, with a suitable in-line fuse?

Has the fuse blown? I am told the pump draws 7 amps, so check the rating of the fuse.

It will NOT run powered from an auxiliary socket.

(c) You can easily tell if the pump is pumping and / or the injectors injecting.

Disconnect the 'fuel out' pipe. Fuel should be pumped out in a nice steady stream. It's not gallons per second but get a small plastic drinks bottle to catch it in.

and / or

Disconnect one of the fuel injectors. One small retaining bolt and gently pull the injector out. Spin the motor, using the starter button. The fuel should be coming out of the injector in spurts. To replace the injector, simply reverse the removal method. Be careful not to bash or get crap into the action end of the injector, so don't go poking at it. If it works put it back. If it doesn't work, put it back, too.

Don't spin the starter button for hours. You will flatten the battery or, worse, burn the starter motor out. It gets very hot!

 

[Rong]

Wapping, in answer to your queries:
a) 1/2 gallon
b) from aux power socket that is wired directly to the battery with fuse
c) fuse not blown as pump whirring away

New FPC arrived today from MotorWorks, fitted and fired up straight away so why didn't the by pass work, and yes I did try connecting wires both ways i.e. blue as hot and then white as hot.

 

[Wapping]

Wapping, in answer to your queries:
a) 1/2 gallon
b) from aux power socket that is wired directly to the battery with fuse
c) fuse not blown as pump whirring away

New FPC arrived today from MotorWorks, fitted and fired up straight away so why didn't the by pass work, and yes I did try connecting wires both ways i.e. blue as hot and then white as hot.

OK Good to know that you are up and running.

I can't think why it didn't work. It has certainly worked for me and for several others, including the intrepid Tim (see threads) who lashed one together in Morocco.

If the fuel pump is pumping and the system pressurised, there is only one place for the fuel to go, that is out of the injectors. Did the bike turn over but simply fail to fire up?

The only way to find out I guess, is (now that you know that the bike starts and runs) is to put the work around back in place and see if you can work out why it failed. In essence that is what I did when I took my reliable controller out to make the work around. The only thing I discovered that stopped it working was the Canbus tripping, but in your case we can exclude that possibility.

From memory, there is a brief whir noise on first engaging of the ignition. That, I think, is a pump to simply prime / pressurise the fuel system. There is then a separate continuous whir of the fuel pump running in an unregulated (the fuel pump controller is absent) state. That will - I assume - only pump enough fuel to fill the pipe between the pump and the injector heads. If the engine does not fire, the pump will simply whir, pumping nothing. If you were then to disconnect the 'fuel out' pipe it should simply pump the tank dry - a useful trick if you ever put diesel into the tank. So the questions is, why didn't it fire up if the fuel was arriving at the injectors? It's a mystery, I'm afraid.

 

[Wapping]

Just a thought.

From memory, there is a second plug and socket down in the recess where the controller sits. I don't know what it does. Is it possible that you dislodged it when installing the work around, only to nudge it back when installing the new controller?

Just an idea.

 

[Rong]

I did check the second plug (for the pressure sensor I think) when it wouldn't start before and it seemed to be seated OK.

Now that I know I have a running system I will do as you suggest and remove the new FPC and try, once again, with the bypass rig as I want to keep that in the toolkit for emergencies. Plus I don't like mysteries as there must be a reason why! but the more I think about it the more I think that there must have been some sort of airlock. The reason I say this is because I took off the fuel delivery hose and no fuel came out with the pump running.
I will post when I have an answer.