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Hello all,

my bike has had new carb rubbers and balanced but there is a problem the fuel pump is only pumping while the starter button is pressed, i am enquiring if i hook it up so that the pump continuosly pumps when the ignition is on. and when ignition is off it switches of.

i will be using my bike for road use and generally do tend to be on the throttle a lot with me living in the countryside.

does anybody see a problem with this? wont burnt out and set me on fire or anything daft

thanks!

it's not a problem that is the way it is suppose to be.
Once the engine is running the pump will continue to pump as required


You can wire it so that the pump is on a live feed but this can burn out th little contact points inside

so if i turn the key to have electrics on without the bike started, and leave it (the fuel pump will be on at this point)

it wont cause any damage?
(bear with me just want to be sure i have understood that right)

thanks for the reply

I'm doing this from memory................

With a stock set up the fuel pump only starts to pump once the starter button is pressed when the engine starts it continues to pump under control of the fuel pump relay


So with a stock set up just turning the key to on will NOT start the fuel pump.




You can if you want feed the fuel pump from any live switched on by the key source however it will pump when the key is turned.

at the moment the pump will have power while i press the starter buton as soon as the bike is running and i release that starter button there is no power to the fuel pump

could this be fuel relay? or maybe something differant.

someone has been at the wiring on this bike and it seems any problems they might of made are going to be hidden in the mass of taped wires hiding around the bike

so if i was to have fuel pump hooked up to live cable and have that linked to the key turning on the ignition would this cause a problem i.e burning out the pump etc,

or would the fact that everytime i stop use the key to turn of ignition and pump be ok and not cause any damage

thanks for this help!

I might be wrong on this but IIRC the last time we discussed this didn't we conclude that the fuel pump only ran when there was insufficient static pressure in the system, i.e. with the tank level low or during prolonged high speed use? Normally the carbs are gravity fed. So with a fullish tank when you start the bike the fuel pump doesn't run at all.

You might be right.......cos once the float bowls are full the pump stops

well i had fuel in the tank and it was just using up all the fuel in carbs, i.e id rev to 10,000 for a overtake say thn pull in and puff no petrol in carb n die, then i restart it on starter and its good until it uses up the juice again my idea was that someone had rigged it to the live wire for the starter motor (if there is such a thing)

i thought the pump would have a pressure sensor within itself to overide the power input coming in and switch itself off when it hits a certain pressure within the pump and then whe the carbs use petrol and the float goes down, the resulting presure feeds through into the carbs and the pump will notice the loss in pressure and restart the pump and begin the process again?

or am i just making this up as i go along haha

What Tirpz said

On start up the pump kicks in - leave the fuel tap "off" and you will soon hear it. Once the bike is fired up it reverts to gravity feed unless your in reserve - putting the fuel tap to reserve will not make it permanently on ! If the carbs aren't getting filled up its most likely the relay is faulty - try giving it a short sharp shock and see if that gets it going again but don't take that as a fix but as a get you home trick If it cures it go and buy a new relay.

Of course that does not rule out that some one has arsed about with the electrrics I could see where it could have an advantage on a race bike running FCRs but a road bike with CVKs having the fuel pupmp running constant is overkill.

MM!

aye i think you hit the nail on the head with the relay, had it on reserve and it was running fine when relay was by passed had it back on relay it was intermittent if i tapped it i could hear a rattling noise as if something had gotten loose? wthier way im ordering a new one and will see if that causes the issue to dissapear. it seems to be ok as it is bypassed but id rather be safe than sorry

in the mean the mean time my rev-ometer have gotten a little optermistic, i had it at red line and it didnt come back down to around 1,500 rpm on idle it goes down to 4,500

i can tell it not reving that hign so im going to have a fiddle round the back of the clock to ensure nothing is loose etc. other than that it passed MOT with flying colours today

thanks for all your help guys!