I started my 88 K100RT yesterday arvo. Usual thing, turn on the ignition, hear the fuel pump going, press the button and it goes. Then it cuts out. Try again. No pump noise but it will start, but stop immediately. So the problem is that the fuel pump isnt going. I checked the lights etc all good there. Checked the fuses, likewise.

Now, I do have the instrument pod off for repairs to the odometer, but that shouldnt affect it, and I have moved the ignition switch holder around a bit while changing steering head bearings (another story, it was all over the place in the twisties on the Snowys trip and on a recent run down through Dorrigo). So a loose connection off the switch is possible, but everything else works.

So what I need to know is how to check the fuel pump is getting power. It seems to me I could check the connection at the back of the tank to see If power is getting there, but I'm not sure which pins. I'm sure someone here will know.

fi relay ?

The fuel pump should not run immediately the key is turned on. If that is happening there is a fault on it's own but check because maybe it actually isn't. It should run when the start button is pressed and for 1.5 seconds after the start button is released. The pump will keep running once the ICU gets signals from the Hall sensors.
The fuel pump is fed by a Green/white wire which comes from fuse #6  and fuse #6 is fed from the Fuel injection relay on a red/green wire which is on #87b of the FI relay.
You need to use an anologue meter so you will see a flick of the needle when voltage is applied.
Hold the start button on once the engine has started and see if it keeps running (you wont do any damage, the starter cant run once engine revs exceed 711rpm), if it does keep running then you need to look at the ICU plug to check it is connected properly.

RicK G wrote:The fuel pump should not run immediately the key is turned on. If that is happening there is a fault on it's own but check because maybe it actually isn't. It should run when the start button is pressed and for 1.5 seconds after the start button is released. The pump will keep running once the ICU gets signals from the Hall sensors.
The fuel pump is fed by a Green/white wire which comes from fuse #6  and fuse #6 is fed from the Fuel injection relay on a red/green wire which is on #87b of the FI relay.
You need to use an anologue meter so you will see a flick of the needle when voltage is applied.
Hold the start button on once the engine has started and see if it keeps running (you wont do any damage, the starter cant run once engine revs exceed 711rpm), if it does keep running then you need to look at the ICU plug to check it is connected properly.

Thats interesting Rick. The pump has always run when I turned the ignition on and I thought it was normal. I dont have an analogue meter but I'll make up a test lamp. I should be able to see a little flash.

Ha - forget all that. I disconnected and reconnected the plug at the back of the tank and it started and ran as normal, so it was just a loose/dirty connection. But, the pump still runs when I turn the ignition on before I start it. I'm tempted to leave it alone as its been like that since I've had it and its never been a problem.

Interesting does it shut off after 1.5 seconds.

RicK G wrote:Interesting does it shut off after 1.5 seconds.

Nope - just keeps running

Someone has had a play with it, possibly because the ICU is or was thought to be faulty.

I'm just going to let it be as I cant see that it would do any harm. The fuel would just cycle. Its not as if I'd leave it with the ignition on for a long time.

I suppose the other thought is that its the fuel pressure regulator not shutting it off when it gets up to pressure??

yeah id recon someone had a play

possibly putting in a wrong relay ...or something .

only dangerous if you have a buster and are laying underneath ....but ...I would make sure ...for sure that all rubber bits in the fuel line are defiantly good and new ....I think we have seen a few fires caused by dicky fuel hoses ...

charlie99 wrote:yeah id recon someone had a play

possibly putting in a wrong relay ...or something .

only dangerous if you have a buster and are laying underneath ....but ...I would make sure ...for sure that all rubber bits in the fuel line are defiantly good and new ....I think we have seen a few fires caused by dicky fuel hoses ...

I replaced all the rubbery bits a few months ago so all good there.

I suppose the other thought is that its the fuel pressure regulator not shutting it off when it gets up to pressure??

How does that happen?

I was expecting to find that in Bert's troubleshooting guide but don' t seem to find a mention.

I don't have mine coming on with the key but the pump is failing to cut off, this leads to the starter motor not getting energised.

The fuel pump should only start when the FI relay is energized. (When you push the starter button)
Try removing the FI relay. The pump should stop running.
If that doesn't stop the pump, remove fuse #6.
If the pump is still running, somebody had modified the circuit.
Check my diagrams there. It may help you to troubleshoot your problem.

CF

Rockman wrote:........
I suppose the other thought is that its the fuel pressure regulator not shutting it off when it gets up to pressure??

Fuel pressure regulator does not shut the fuel off. It only maintains 36psi at the fuel rail and returns excess to the tank, providing there is a head pressure of 60psi from the pump.