efi 125 starts then dies....

[thumpa]

hello!
i have a chinese made 125 efi bike and have a problem with it.
basically, it will start first push of the button but then dies (the pump primes at switch on and fuel is reaching the engine.
battery fully charged.
i have read the ecu and it shows no faults.
i tested the spark plug to see if it was sparking ok (removed and held to engine whilst turning it over) and discovered when i turn the engine over it sparks for a few seconds and then nothing until i switch off the ignition and back on again and then the same again... again... again.
i know the workings of an ecu are a dark art but i am assuming the ecu kills the ignition after a few seconds because it hasn't started in a set time?
can any one help?
thanks.

[JerryHawk250]

Welcome aboard! Please provide more information on the make and model of the bike. What engine it has?

[thumpa]

hi! sorry i should have said.


hanway 125 efi 2017


engine based on a honda cbf125 as far as i know.


thanks!

[JerryHawk250]

A couple of things to check. Make sure your ignition coil has a ground. Next you can remove the injector and see if it is working while cranking the engine.

[thumpa]

hi. no change when adding a separate earth to coil...


BUT..


i unclipped the fuel hose from the injector and turned ignition on.


1: usual priming squirt of fuel.


2: no fuel pumping when turning over.


thanks again.

[thumpa]

hello again. i did some more testing. same issue with starting and immdiately dying.
spark test shows only sparks for a few seconds before nio spark, will not spark again until ignition off and back on.
fuel pump ok - even tried hot wiring it so it stayed on.. no different.
tested injector - works.
to me it's like the ecu does not know the engine has started and cuts the ignition after a set time.

maybe i am barking up the wrong tree but maybe crank position sensor or even ecu not getting rpm info from engine?
scanned the ecu with various software makes.. no errors (apart from one that came up because i had disconnected the pump to hot wire it).

cheers!

[JerryHawk250]

It could possibly be a bad coil. A bad sensor would set off a code.

[thumpa]

hi jerry, good call. i did do an ohms check recently and it seemed to be within tolerances.
i guess the coil could be failing under load and dies after a few seconds and does the same thing every time ignition cycled off and on?

[J4Fun]

Hi guys, isn’t there a possibility that the fully charged battery is weak or sulfated enough to let the voltage drop during start meaning the ecu senses fault? And this is why it stops working? Just a thought here…

[thumpa]

hi there, thanks for the reply. the battery is fine. it's a year old lifepo4 battery which i have found very impressive for it's size. had it starting a 250 for a while with no problems.
i actually used scan software to monitor live data and it did not drop when turning over.
give me a carb and points or cdi anyday
cheers.

[J4Fun]

Originally Posted by thumpa

hi there, thanks for the reply. the battery is fine. it's a year old lifepo4 battery which i have found very impressive for it's size. had it starting a 250 for a while with no problems.
i actually used scan software to monitor live data and it did not drop when turning over.
give me a carb and points or cdi anyday
cheers.

I like the carb and points also, but you have to wonder if you make changes and things aren’t the same then why…

[thumpa]

hi j4. no changes made, just been stood a while.


cheers.

[clash 168cc]

Sounds like the computer. When modern cars start and then shut off they lose spark and or fuel pressure. Caused by chipped key immobilizer system. Chinese scooters don't have the chip in the key that I have heard. Same symptoms though. Check/watch fuel pressure if you haven't already. I believe the computer sends the + or - pulse for spark plug and fuel inj. No codes would be another indication of a bad computer.

[thumpa]

hi thanks for the suggestion. i hot wired the pump to stay on but same result. bad ecu is not a good thing for me as it will cost a few hundred and i will have to wait weeks.
talking of codes i did get one when i hot wired the pump as it detected the pump was not connected. also gave a code when i had unplugged the temp sensor yesterday to check the connector and hadn't plugged it in completely.
of course, it could just be the ignition circuit of the ecu that has gone faulty :(

thanks.

[clash 168cc]

Originally Posted by thumpa

hi thanks for the suggestion. i hot wired the pump to stay on but same result. bad ecu is not a good thing for me as it will cost a few hundred and i will have to wait weeks.
talking of codes i did get one when i hot wired the pump as it detected the pump was not connected. also gave a code when i had unplugged the temp sensor yesterday to check the connector and hadn't plugged it in completely.
of course, it could just be the ignition circuit of the ecu that has gone faulty :(

thanks.

Try disconnecting the injector wires and then the wires to the coil and see if you get a code. Also, If the pulse to the Inj or Coil, usually negative, from the computer, stops after a few seconds it's either the computer or maybe the stator overloading. Could also be bad coil but you would normally get a code for all of that. Corrosion also in the connections/bad fuses. There are wires that go to ground for shut off from switch and or computer. Find that and disconnect.