Possible fuel / pump issue

[fredouille]

Hi I got my old vmax stopping at the middle of a ride , impossible to restart even no sign of some ignition

I finaly discovered that the fuel pump might be the issue, I was not hearing pumping when turning ignition key

I got the pump out, put 12v and it was turning not good, I cleaned the contacts, contact cleaner + sand paper and it is turning now fast with normal noise that I was used to hear

I put back on the bike.. each time I put ignition with the key, the pump works as it should for some seconds, but whatever the number of on / off with the key, it is still pumping, I understood that when the circuit is pressured, it should not do this ?
I still can't start of course
I checked, inside the pipes fuel went through, but I suspect not enough pressure.. could be filter of finaly the pump dead

what are your thoughts ?

ps : could be also ignition, but all 4 plugs failing at the same time it is unlikely..

 

[MaxMidnight]

The fuel pump is controlled by the fuel pump relay which will cause the pump to run when the ignition is turned on. If the start button isn't pressed it will run for about five seconds before cutting out.
As there is no feedback from the carburettor float chamber it will keep trying to prime every time the ignition is switched on.
I guess Yamaha assumed that after turning the ignition on the next step would be to start the bike so didn't make provision for the scenario you are experiencing.

If the bike won't start then you need to investigate the systems that can prevent this: (in no particular order) - the interlock system that cuts the engine if you try to select a gear without pulling in the clutch or the side stand is still down; failure of the ignition control unit or associated wiring (don't forget the fuse); pick-up coil(s).

 

[fredouille]

The fuel pump is controlled by the fuel pump relay which will cause the pump to run when the ignition is turned on. If the start button isn't pressed it will run for about five seconds before cutting out.
As there is no feedback from the carburettor float chamber it will keep trying to prime every time the ignition is switched on.
I guess Yamaha assumed that after turning the ignition on the next step would be to start the bike so didn't make provision for the scenario you are experiencing.

If the bike won't start then you need to investigate the systems that can prevent this: (in no particular order) - the interlock system that cuts the engine if you try to select a gear without pulling in the clutch or the side stand is still down; failure of the ignition control unit or associated wiring (don't forget the fuse); pick-up coil(s).

thanks for your answer, I understand that the circuit can't know if there is fuel in the carbs, I assumed that the pump is stopping itself when there is pressure enough in the circuit.. it looks like this

the bike make a small ignition noise, so there is progress, I wait the full reload of the battery, I assume after getting the pump out and the full out of the circuit going to the carb, it requires a bit of time to fill the circuit to be able to start.
I still suspect an old fuel filter giving a too small quantity of full but lets see, or the pump not strong enough, but while testing i was feeling air being sucked inside

 

[Fire-medic]

The fuel filter can be checked by blowing through it. If you can't, easily, then time to change it. I cut-open my fuel filter to see what accumulated there.

On a Ford full-size van I had, the truck wouldn't get up to speed on the highway, yes, a clogged fuel filter.

 

[fredouille]

The fuel filter can be checked by blowing through it. If you can't, easily, then time to change it. I cut-open my fuel filter to see what accumulated there.

On a Ford full-size van I had, the truck wouldn't get up to speed on the highway, yes, a clogged fuel filter.

yes but need to remove pipes, get fluel everywhere and so one ... at the price of the stuff, I will change it whatever, I guess it is more than 10 years old, it is not original even

 

[MaxMidnight]

thanks for your answer, I understand that the circuit can't know if there is fuel in the carbs, I assumed that the pump is stopping itself when there is pressure enough in the circuit.. it looks like this

No, the fuel pump relay will cut the feed to the pump unless there is power from the ignition control unit.
It does not sense pressurein the system.

 

[fredouille]

No, the fuel pump relay will cut the feed to the pump unless there is power from the ignition control unit.
It does not sense pressurein the system.

ok let me rephrase, what happens on your bike when you switch on/off several times the contact key ? 5 sec of pump each time with the same noise or at 1 point the pump doesn't pump anymore because there is enough fuel in the line ?

 

[Fire-medic]

The latter. The fuel quantity and pressure is sufficient , and the pump stops.

 

[fredouille]

The latter. The fuel quantity and pressure is sufficient , and the pump stops.

thanks this is what I see, take a bit of time with empty circuit to get the right pressure it looks

 

[02GF74]

No, the fuel pump relay will cut the feed to the pump unless there is power from the ignition control unit.
It does not sense pressurein the system.

That's not quite correct.

There is a spring inside the fuel pump that determines the fuel pressure and pushes the solenoid plunger away from the solenoid contacts. When pressure drops, the contacts close and the solenoid plunger draws fuel from the tank into the pump. The spring presses against the now larger volume of fuel and keeps it under pressure. (a rubber diaphragm allows the volume to change).

When that happens, you hear clicking from the pump.

As stated previously, the fuel pump relay will provide power to the pump for about 5 seconds unless the engine is running.

Typically when turning on the ignition, you will hear clicking from the pump for 5 seconds or less.

If you repeatedly turn off the ignition, turn it on again, the clicking from the pump stops indicating the pump is unable to overcome the pressure in the fuel lines, which are closed by the floats pushing on the needle valves.

 

[fredouille]

If you repeatedly turn off the ignition, turn it on again, the clicking from the pump stops indicating the pump is unable to overcome the pressure in the fuel lines, which are closed by the floats pushing on the needle valves.

-> then it means that the pump is working fine. so I have another issue

 

[02GF74]

... back to the original.

How long after riding does it cut out?
There should be a vent for the fuel tank. Ad the fuel pump draws fuel, air gets sucked in. If the vent is blocked, the pump will struggle to suck fuel out. If you remove the fuel cap, youll hear air sucked in.

Also when it stops, undo one of the drain screws, catch the fuel, the fuel should start pumping (clicking).

If it's not fuel, you'll have to investigate the ignition system

 

[fredouille]

How long after riding does it cut out?

-> 5 min around

There should be a vent for the fuel tank. Ad the fuel pump draws fuel, air gets sucked in. If the vent is blocked, the pump will struggle to suck fuel out. If you remove the fuel cap, youll hear air sucked in.

-> I guess no issue here, no low presure in fuel tank, vent is not blocked

Also when it stops, undo one of the drain screws, catch the fuel, the fuel should start pumping (clicking).

-> which drain screw ?

If it's not fuel, you'll have to investigate the ignition system

-> yes I suspect now ignition.. but at the middle of a ride, strange..

 

[Dorney]

Yes the pump only runs for around 5 seconds. But if you keep turning the ignition on & off the pump will run until the bowls are full & the system builds pressure.

 

[02GF74]

How long after riding does it cut out?

-> 5 min around

There should be a vent for the fuel tank. Ad the fuel pump draws fuel, air gets sucked in. If the vent is blocked, the pump

How long after riding does it cut out?

-> 5 min around

That's not long.

When it cuts out, is it like turning the ignition off or does it run erratically before that? The latter would tend to point to fuel starvation as the fuel pumps stops delivering fuel.

Bear in mind that by this time parts (electronics, ignition coils and fuel pump) will have gotten hot and all of them can fail due to heat.

Are you able to leave the bike idling to see if it cuts out?
It may take more than 5 minutes.

There are small cross headed screws that drain the bowls, you'd need to search the forum or consult the manual. See attached photo, the best I can do for now.

The idea is when the cut out occurs, with ignition off, undo one screw, if no fuel comes out, it's the pump.

Refit the drain screw, turn on the ignition and you should hear the pump clicking.