Electric water pump problem

Hi I have a problem with my electric water pump on my italjet dragster 125.

Basically the water pump will work fine but when I start the scooter up and idle the pump works fine but if blip the throttle slightly the electric water pump will stop working. If I let the scooter idle the pump will sometimes start working again.
But every time I switch the ignition off and on the electric water pump run fine until I rev the scooter.

If I do this a couple of time for five mints the water pump will work find and I can ride off all day with no problems.

Any ideas ?

Thanks

 

The pump is wired from the battery using a relay and the ignition switch as a the switch for the relay.
Also when I wire the pump to the wiring off the scooter not directly off the battery the pump will still do the same.

 

Change the pump, relay to rule them out.

 

Yes I bought another pump also changed the relay first. it does the same.

 

Can you fit a seperate 12v battery to it and try ? could it be voltage sensitive ?

 

I can that is my other option to try something like a extra battery under the seat.
But the pump only draws 0.7 amp

I even used the spare pump just wired in to the carburettor heater wiring and when the pump running off the battery stopped so did the pump running off the carburettor heater wires.
It's a annoying problem because every time it stops working I checked the voltage and there is 14.8 volts every time plug it back in dose not work. switch the ignition off then back on and it will work fine when the engine is not running.

 

When you rev the bike, the harmonics from the bike is tripping the relay contacts to open, thereby shutting the pump off.
Move the relay to a more isolated position on the bike.
If you want to confirm this theory, take the relay and hold it in your hand off the bike completely, so it's touching nothing but your hand. then rev the bike, see if it cuts the pump.

 

The auto choke/heater is A/C voltage so not ideal. Are you using a thermostat in it ? I was thinking of trying a seperate tempory battery just to see if it's something on the scooter wiring ?

 

I have removed the thermostat now because of at fist I thought it was over heating due to coolant system or something. But then found out its the pump.

Yeah I could get another battery to test that. Its just really radom because it will not do it evey time.

 

Thermostat is good to keep it constant temp as long as by-pass hose is fitted.

 

Yes ideally I want the thermostat