Fuel pump & reserve level - Inexplicable problem

Hi all,

I have a problem that's driving me crazy

I bought a month ago my '09 TE 510, and it seems that the bike can't consume the last 2 liters of fuel. I realized that when after 60km the motor died without showing any reserve light, and I thought the thermistor was broken.

Today I drained the tank, I disassembled the fuel pump and I tested the resistance of the sensor, and the thermistor works very well, keeping a hand on it makes the resistance goes down and viceversa. The pump assembly was ok, all the cables and the components seemed in its place, and the lower filter seemed to be ok.

So i reassembled all, and I poured 1 liter of fuel in the tank.
Turning on the key, the pump primed regularly as usual, but the sound was like it is sucking air and not fuel, and obviously the motor didn't start.

I poured another half liter, and again the same.
So I poured another half liter for a total amount of 2 liters, and then turning the key on I finally heard the right sound of a pump sucking fuel, and the motor started regularly.

Taking stock of the situation:
1) the pump doesn't dry the reserve (1.8 liters)
2) the fuel light doesn't turn on because the motor die before reaching the reserve level

What's going on???
The fuel entry point is where the manufacturer put it, I can't figure out why the tank doesn't dry completely

Has that fuel pump slip out that rack, when i can drive my fuel tank empty, not that empty, but can recall there was half litre left in there

Hi Mik-3, the fuel pump is correctly placed in its holder.
Yesterday I talked with a local dealer and he told me that the problem is a bad tank design that affect 2008/2009 EFI models.

In short, it seems that the tank was bad engineered and the only way to make empy the tank is to invent some pump modification that move lower the fuel entry point....

Ok, then i dont know. But i can i drive like 5-10km after fuel light is coming on, i mean need to ride, pretty upraised so fuel pump dont suck air, when that is the most bad thing, it will kill fuel pump on time. I have ride only like two times, that fuel light has come on, when i know you can only get about 5-10km, so no bueno

it aint the tank unless it is badly deformed at the sump for some reason. the light should come on even if there is some fuel left 'hiding' in the tank somewhere.

in-tank pumps require submersion and are actually 'semi-gravity fed' to maintain prime they need a column of fuel smothering them to operate properly. so modifiying a stock pump simply won't work- at all.

that said if ya gots almost 2ltr's left, no light, pump is submerged and it's cavitating that means ya proly just got a bad pump- it's sucking air somewhere that may not be obvious to the naked eye.

easy way to test w/o a gauge: remove the thank, and remove the pump, and test the pump doing a submersion test using a 2ltr soda bottle (or similar) full of fuel with the top cut off. then note where it starts to suck air. it should get almost all of it out of your test container before it cavitates- an inch or so left in the bottom is ok (see above). then you know your pump is good but ya got a bad level sender (part of the pump module in almost cases soooo....)

if it dont do the above, then the pump is simply worn out and it is losing 'prime' when the fuel column gets low. . toss it and get a new one. i think the p# is 8000B0376. the aftermarket (Quantum- ebay) makes a "kit" that might work, replace evrything you can incl regulator and o-rings. OEM is big $$$, but it is complete, if you can find one. shop around. Motosport.com says the can still get one on B/O.

take a note: USE YOUR HEAD WHEN DOING THE ABOVE TYPE OF TEST. SPARKS + FUEL = U KNOW WHAT. IF IN DOUBT BE SAFE AND JUST BUY A NEW PUMP. Don't EVER dry run a pump and don't ever pump anything through it other than fuel or you will ruin it.

@pvduke thank for your analysis, honestly the dealer's words had not convinced me much, it seems to me impossible for a manufacturer that has been producing competition vehicles for years to put on the market a motorcycle that does not empty the reserve and goes off on the road with half a tank.

In the next few days I will disassemble the pump and do the suction test (without causing an atomic blast ) to see if the problem is what you hypothesized, it would actually explain everything...

About the rebuild of the pump... It's still a good idea, after all the bike have 12.000 km.
I searched on eBay and I found the Quantum kit, but with the indicated shipping time it would take all summer to get to me...

I've found two rebuild kits from Poland that could arrive to me in a week, the difference between the 2 kits is in the fuel pressure regulator (3.0 bar vs 3.5 bar)

Do you know the operating pressure of the original regulator?

Thanks,
tamb

sorry- no psi specs in my noodle. i'd suspect 30-40 ish psi before bypass if equipped..maybe a bit more but that's about it. these are low pressure systems. they aint doing 300 psi. i'd look for fluctuations in pressure as the column goes down. that means it's losing prime. that means something is cracked or leaking. replace as much as you can, get as many parts as you can. grab and go....hoard them, even if they might not be a the exact match. be deductive....that means replace this, oops, didnt work, try again, re-test, etc. start with the most logical point of failure part first, like PLASTIC crap on the suction side. ...if the tank is not out of spec, it's the delivery system. pure and simple. youll get it. stay with it, make notes so you can compare your failures/results. if you get frustrated- walk away for a while. we have all been through it. get some local help. make it scientific.

it sucks. but when it finally goes braaap? cuz it's a cool bike. make it happen. it's up to you.

sometimes the long road is the only one to home.

Regulator Specs- 3.5 bar

Note the pump itself is not rebuildable. You just replace it.
You could have crud/ethanol goop in the strainer on the suction or in the suction port itself. If you have ethanol residue it will be brown and look like corrosion. You can remove it with a soak in rubbing alcohol.

If there is a suction side restriction it will cause cavitation and loss of flow as others have said. But it will happen with a much higher fuel level than normal

Thank you @clydemule! I haven't had time to do the priming experiments yet, at the moment I'm using the bike at short distance.
Fortunately where I live there is a gas station every 5-10km

Thread update: I ordered the 3.5 bar kit from Poland (that comes only with the bottom sock filter), I bought a new fuel filter and yesterday I rebuilt the assembly, securing the pump with a couple of electrical ties in order to avoid slips.

I reassembled the pump in the tank and then I tested all...
- with 0.5 liter of fuel the motor doesn't start
- with 1 liter the pump can prime

I think the "zero level" is now between 0.5 and 1 liter, and it seems I gained 1 liter of fuel compared to the previous situation when the motor was dying with 2 liters in the tank.
This tank was designed by a complete idiot.