Morning All,

Earlier in the year I was having problems with the fuel pump on my MK Blade (carbed), Fitted a brand new one and thought that was that. I was never quite sure about the new one as it ran all the time and was quite noisey, the old one used to shut off until fuel was needed and just tick every now and then

Gone to start it this morning and and its getting no fuel, slightly pressurised the tank to push fuel to the pump and it will then pump for a bit but gradually grind to a halt (still running all the time and noisey).

Any help would be greatly appreciated.

Hope I dont need another new one.

Kev

Sounds like the ECU??

The ECU should shut off the fuel pump when it has primed, then run it for a few seconds each revolution of the engine. Each revolution starts the timer again. If you stall the engine, it should run on for that time and stop.


ETA: Sorry, just realised its Carbs. Not sure in that case, but i would imagine it should work in a similar way.

[Edited on 14-8-10 by MakeEverything]

Sorry didnt say it was a 918rrv engine, were'nt they gravity fed from the tank on the bike?? so ECU does'nt know there's a pump. Its just there because the tanks not above the engine.

Stand to be corrected!

Kev

Yes i think youre right. Do you have a return from the carbs to your tank?

No return from the carbs, just tank breather and outlet to pump.

Kev

Sounds like the pump is pressurising the carbs and fighting against its own head pressure.
I would suggest that you need one with a pressure cut off switch, or a circulating pump with a return to the tank via a fuel pressure regulator. This way, it will run constantly, maintain pressure to the carbs without burning out the pump.

As far as I know most bike carb pumps simply use spring presure to pump. They suck in fuel from the tank with an electromagnet, but the actual pumping towards the carbs is handled by a spring.

Nothing to do with a ecu. The pump is powered during cranking and engine running.

But most of these pumps use contact points to make and break the circuit for the electro magnet. What does your pump look like? Most have a plastic cover at one end that can be taken off. I'd say the contacts on your new pump have got welded together... something that seems to happen to (older) pumps. They especially hate running dry.

As you said your old pump only clicks once in a while, but when running dry it will really buzz... way to fast, so the contacts get hot and stick, well actually spot welded.

There are some electronic after market pumps around. But they aren't 100% reliable either.

Another way that is used is to use the original (refurbed) pump. But use the contacts to switch a standard automotive relais, which switches the magnet. The relais is more durable, and much easier to replace when broken.

As further above, its gravity fed from the tank so always primed.

If you have an air leak it will click all the time, also if a bit of rubbish has gone into it. On bikes they last years so no reason why a new one would fail.

So is the pump on the floor/level with the bottom of the tank.

First thing I would do is remove and gently tap it to knock any rubbish out. Kit cars with hame made tanks tend to have little bits of swarf floating around.

I ran my carbs for a few years on one of these link

Regards Mark

The pump is one of the mitsubishi units with the black plastic cap as you described. There fitted to many of the carbed bikes.

I have looked at the Facet pumps but others have put me off saying there very noisey, is this true? There obviously much cheaper.

Kev

Thanks for all the replys.

Traced fault to dodgy cotton braided fuel hose from tank to pump. It's been drawing air through the pipe stopping the pump from being able to pressuries. I only noticed it when I pressurised the tank a bit more to force the fuel to the pump and it was pi**ing through the side of the pipe. New pump now works as it should and I am a happy bunny.

Who would have thought such a tiny hole could cause so much trouble.

Thanks again.

Kev