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4Rt Only Runs With Fuel Pump Disconnected!


thall1
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Hi Honda_Freak....I found another test procedure on a Yamaha forum....mine test's out ok...so I'm thinking its back to the capacitor now?...

I kicked the bike over before I took off the rectifier and did get it to fire a few times but again it was only with the fuel line off the injector and the fuel pump disconnected...

 

 

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just had a thought....if I connect the fuel pump to a separate 12v supply and try starting the bike would I need to do something to the fuel pump supply connector to fool the ECU into thinking its connected or is it not that clever? I could I suppose connect the pump supply connector to a 12v bulb in order to give it a small load?

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I have some progress.....if I kick the bike I get voltage at the fuel pump loom side connection of up to 12.5v...its not a constant, repeatable reading, sometimes its less at around 9v but as you continue to kick it increases to 12.5v. If I leave the meter to continue to read after I get 12.5v the voltage slowly drops away which I guess is the capacitor discharging?

I put a separate 12v supply to the fuel pump - you can hear the pump running & bike starts first/second kick....if I take a voltage reading at the loom side of the fuel pump connector when the bike is at idle I have 14.17v dropping to 13.57v when the fan cuts in so the bike when running produces plenty of voltage but not when initially kicked over...I have cut back the insulation on all the earths and positive feeds to check for any signs of wire corrosion as I found on the capacitor but none present.

with the fuel pump reconnected into the loom the connections via the 2pin connector appear fine either side with continuity and no high resistance..

as I said in an earlier post, the rectifier diodes check out ok using the check listed below found on a Yamaha forum....

1. Attach red lead to the Bat+ pin, touch black lead to each stator pin on the RR. Each pin should read "OL" (open circuit) on the meter.

2. Attach Black Lead to Bat+ pin, touch red lead to each stator pin. Each pin should read about .5 volt.

3. Attach red lead to Gnd- pin, touch black lead to each stator pin. Each pin should read about .5 volt.

4. Attach black lead to Gnd- pin, touch red lead to each stator pin. Each pin should read OL on the meter.

could it be that the capacitor/condenser is taking too much voltage from the system?

any thoughts would be appreciated -  as always!

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I've had mine for just over a year now, it's never been one to start first kick, but then sometimes it surprises me and does. I've always suspected the capacitor as they do loose efficiency.

However recently it became worse at starting, so did some investigation as to what this may be and found:-

  • The throttle body was filthy with soot both sides of the throttle valve, how does this happen? - anyway the throttle body got a good clean.
  • I checked resistance and voltages of various components, everything checked out ok to the manual specifications, but one thing I noticed was that when kicking it over, the voltage coming from the rectifier was the same as you are getting, various voltages between 9v and 12v
  • Voltage from each of the three yellow alternator wires was 4.5v AC

One of the checks recommended somewhere on the internet was to check for continuity between the yellow alternator wires and earth (with them disconnected from the loom) and that there should be none, it should be open circuit, I can't remember exactly what I found here but I have a feeling I did get some sort of reading.

My conclusion was that the alternator on kicking wasn't producing enough voltage for the bike to start first time, though I could be wrong of course.

 

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Hi thall1

Your rectifier/regulator result seems fine if you remembered to push a little on the terminals pins as I've told before is this part very vital for a correct result.

One thing about the fuel pump motor.

Since this is a DC motor it may have points on the commutator, which has higher resistance than the other, thereby having difficulty to start the fuel pump motor.

Can you meassure the electrical current to the fuel pump wit a DMM or a current clamp !!!

Have you tried with a new capacitor !!!

Regards
Honda Freak

Edited by honda_freak
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I can measure the current -will have a go in the morning but previously I have kicked the bike with the fuel line disconnected and fuel is 'pumped' out... I can only assume that during kicking there isn't enough current to power up all the bike... By putting a battery on the pump the overall load on the bikes system is reduced.. Capacitor is on order but won't be here till next week...

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new capacitor fitted.... started second kick with a nice slow push on the kick start! ran lovely and smooth....all sorted!...or so I thought!!

After letting it run until the fan cut in/out I stopped the bike...second time starting it was the same, 3rd time after refitting the air box it wouldn't start!

I put 12v onto the fuel pump as before, bike started fine and ran fine..

cleaned the air filter, plugged the pump back into the loom..it started but it wasn't as easy as before, put 12v onto the pump again and it started fine with an easy kick, reconnected the pump into the loom and after a few kicks it started but its not very smooth, coughing and puffing black smoke on flicking the throttle open-spark plug was all sooted up. I stripped the fuel pump, some corrosion in the pump sump bowl under the filter but otherwise all seemed ok. Resistance check from the 2pin connector back through the gland and up to the connector on top of the pump are both ok.

Bike wouldn't start after refitting tank!...put 12v on the tank and it started fine....put the tank back into the loom and it started but again with a stronger kick...

Might put a new temp sensor in as that's the only thing I can think of that would give a signal to the ecu to run rich...??

   

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Totally totally baffling

New capacitor fitted - starts ok - switch off - starts ok again - refit air box - won't start

Disconnect pump from loom - supply 12v to fuel pump - starts ok

Remove 12v supply from pump and reconnect to loom - will start but its a struggle and runs rough/rich

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According to wiring diagram

The pump is running constantly and is not switched via ECU

Red wire to injector is constantly fed with +12v

Pink wire from injector is switched to earth via ECU, the longer this wire is switched to earth the more fuel is delivered via injector.

-------------------------------------------------------------------------------------------------------------------------

If temperature sensor is at fault, why would supplying the pump with 12v make the ECU think differently?

 

Edited by ourian
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Is there any chance you have a friend with a different ECU/throttle body you could try on your bike with everything else as it sits to check your ECU isn't having issues? 

I don't remember if you are you running a hotter plug or not, if not maybe go to the hotter pug listed in the manual? 

 

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Currently running a hotter plug. Tried it yesterday and bike wouldn't run even with 12v on the pump. Pump was running and I had a spark .After checking various things over two hrs and kicking it in between it fired up and ran fine without coughing or running rich?.... After letting it run up it restarted fine while it was warm. However the longer I left it and the colder it got the harder it was to start...ecu, tank/pump, coil and injector assy have all been put on other bikes with no issues .... The test bike started and ran fine each time.

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37 minutes ago, thall1 said:

Currently running a hotter plug. Tried it yesterday and bike wouldn't run even with 12v on the pump. Pump was running and I had a spark .After checking various things over two hrs and kicking it in between it fired up and ran fine without coughing or running rich?.... After letting it run up it restarted fine while it was warm. However the longer I left it and the colder it got the harder it was to start...ecu, tank/pump, coil and injector assy have all been put on other bikes with no issues .... The test bike started and ran fine each time.

Has the generator been on another bike ?

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No it hasn't .... I'm getting 12v plus at the pump connector when it's being kicked over - it was lower than this with the old capacitor - and 14.2v when running. Rectifier has been bench tested- see earlier post... And it appears to be fine ... I guess proved by the Voltage output when running...

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