Fuel Filter replacement, step by step

[soofle616]

By the pictures, the filter is upstream of the hi pressure pump. If it fails, it pumps 40-plus psi into a sealed tank vented to a canister (in most cases). I'm no physicist, but I do not understand how that would NOT increase pressure inside that tank and risk that fuel forcing it's way past the next weakest link.

But that's OK, I don't know everything. But I do know that if saving $40.00 on a one-time maintenance item of your exotic Italian motorbike by installing a cut-rate Chinese carburetor filter designed for 1950's tractors and 1960's automobiles is OK with you, who am I to tell you you're a fool?

And catastrophic failure, by my definition, is anything that might cause me to be stranded, or worse, stall my bike coming hot onto apex and potentially causing me to crash. Worse yet would be if it was my own damned fault for pinching a few pennies and installing a critical fuel delivery device that has no flippin' right to be on ANY EFI system on earth.

Go ask your aprilia mechanic if they would professionally install that filter for you.

If the filter is indeed upstream of the pump (i really don't care to look right now so lets assume you are right). Then a failure of the filter will have no effect on output pressure of the system. By the way, if the filter is upstream of the filter then it will never be subject to this imaginary dead head pressure you seem so concerned about so it wouldn't have failed due to pressure to begin with. But lets assume that by some magical happening the filter fails and by further magical happening that failure somehow causes things after the pump to see excessive pressure. You are still forgetting that the pump stops once the system reaches a certain pressure level. This is why the system pumps briefly when you first turn on the key then stops. It runs continuously while the engine is running because there is a consistent loss of pressure in the system (due to fuel being sprayed into the motor). So, if there was this kink in the return line, the system would pressurize as normal, then the pump would shut down.
As for why the pumping of fuel into the tank doesn't cause a pressure build up into the tank, think for a second about that. How is pumping fuel, from the tank, through hoses and a pump inside the tank, and back into the tank going to increase pressure in the NOT SEALED tank (you said yourself that it's vented so that makes it not sealed by any definition). All your doing is circulation the same volume of fluid into the same volume of space. Since i know your next argument will be that it's now pressurized the fluid I counter with this, NO IT HASN'T. The pump doesn't create pressure unless it has a restriction in front of it like the fuel pressure regulator. Don't believe me? Take the fuel line off your throttle bodies and stick it in a gas can. Now turn on the key. Notice how fuel flows out of the line in a steady stream without a great deal of force behind it? That's because the pump is not capable of moving fuel fast enough to create pressure unless something is in the system to slow the fuel down (regulator). So given a looped scenario resulting from the filter failure, the pump is simply going to circulate fuel inside the tank and not create pressure.

As for asking my aprilia tech if he would install the filter for me... I am my aprilia tech, he said yes

And PDXMille, Just to correct quickly, I do not work with EFI except on my own toys. I did years ago but I have since moved on to other things in my professional life.

[Motech]

If the filter is indeed upstream of the pump (i really don't care to look right now so lets assume you are right). Then a failure of the filter will have no effect on output pressure of the system. By the way, if the filter is upstream of the filter then it will never be subject to this imaginary dead head pressure you seem so concerned about so it wouldn't have failed due to pressure to begin with. But lets assume that by some magical happening the filter fails and by further magical happening that failure somehow causes things after the pump to see excessive pressure. You are still forgetting that the pump stops once the system reaches a certain pressure level. This is why the system pumps briefly when you first turn on the key then stops. It runs continuously while the engine is running because there is a consistent loss of pressure in the system (due to fuel being sprayed into the motor). So, if there was this kink in the return line, the system would pressurize as normal, then the pump would shut down.
As for why the pumping of fuel into the tank doesn't cause a pressure build up into the tank, think for a second about that. How is pumping fuel, from the tank, through hoses and a pump inside the tank, and back into the tank going to increase pressure in the NOT SEALED tank (you said yourself that it's vented so that makes it not sealed by any definition). All your doing is circulation the same volume of fluid into the same volume of space. Since i know your next argument will be that it's now pressurized the fluid I counter with this, NO IT HASN'T. The pump doesn't create pressure unless it has a restriction in front of it like the fuel pressure regulator. Don't believe me? Take the fuel line off your throttle bodies and stick it in a gas can. Now turn on the key. Notice how fuel flows out of the line in a steady stream without a great deal of force behind it? That's because the pump is not capable of moving fuel fast enough to create pressure unless something is in the system to slow the fuel down (regulator). So given a looped scenario resulting from the filter failure, the pump is simply going to circulate fuel inside the tank and not create pressure.

As for asking my aprilia tech if he would install the filter for me... I am my aprilia tech, he said yes

And PDXMille, Just to correct quickly, I do not work with EFI except on my own toys. I did years ago but I have since moved on to other things in my professional life.

You are absolutely right. I meant "downstream" when I wrote "upstream". My bad. I'll also confess to physical ignorance when I suggested deadhead fuel delivery in the tank could do damage that might cause fuel leakage. I simply am not smart enough to make that contention, and I could be wrong.

On your own contentions though...

The pump does not stop running when pressure reaches a certain point. The fuel pressure regulator is calibrated to return the excess pressure to the tank, hence the return line with the famed crappy QD connector.

Deadhead pressure is a common industry term for the pump's unregulated pressure, typically 2-3 times higher than the regulated pressure. A pump must have the capacity to deliver the same amount of fuel at speeds as it does at idle. With much more fuel required under loads, 36 psi could not be maintained if that were the pumps max output pressure. Don't believe me? Pinch off the return hose on your bike and eliminate the return path. Go ahead. That pump will put out at least 80 psi guaranteed, more likely over 100. Or try your own challenge: Disconnect the supply line at the TB, THEN crank it over with that return line blocked off and see how far your fuel stream flies. Go ahead. And take pics, post them up here.

Furthermore, pressure regulators on a couple other manufacturers (same principle as ours) are sometimes known to fail and block the return path, causing deadhead pressure at all points downstream from the pump. These vehicles have locked or threaded line connections on EFI filters that can withstand that pressure, so the fuel blows by the injectors when they're opened and severely floods the engine, with documented cases of hydro-lock in the affected cylinder(s), and extreme cases causing bent connecting rods. You really think that Chinese filter and 15 cent hose clamps can handle pressure that can overpower a modern fuel injector?

I'm done here. The info is clear as a west coast sky in this thread. Stick with the right part for the job and ride with confidence, or try and be clever and save a few bucks on a totally wrong part and risk the consequence of your own ignorance.

There seems good reason you "used to be" an EFI tech.

[deefred]

Yes, the pump runs continuously except for ignition ON from OFF as the ECU gives the command to prime the system for a few seconds and then stops.
As long as the pressure is higher than 3 bar the fuel pressure regulator will shunt the fuel back to the tank via the return line but the fuel pump will run continously.

Disconnecting the return line and then prime the system is a good way to check if the pressure to the fuel regulator is more than 3 bars.
If no flow out of the return hose the pressure is less than 3 bars.

I have done this myself (don´t smoke and at your own risk) and there is only a steady slow flow of fuel coming out. No high pressure to be scared of as it is after the fuel pressure regulator

[pdxmille]

Weeeeell, gents, installed the gas cap on the "new" tank. I then installed the fuel pump/filter into the gas tank. I first liberally smeared Locktite 518 on the o-ring and around the fuel pump base plate outside the o-ring. I also used lock washers on the 8 bolts that hold the pump assembly to the tank. Tightened down the 8 bolts, which made the perfect amount of 518 ooze out from between the fuel pump assembly base plate and the tank itself. Hooked up the fuel feed and return line, mounted the tank on the bike, filled her with 3 gallons of petrol and looked for leaks....none seen.

turned the ignition on 4 times to prime the pump. Again, checked thoroughly for any leaks...none found

turned the ignition on, then started the bike. It started on the first try.

And guess what? the bike DIDN'T EXPLODE! lol!!

Ran the bike up to operating temperature, constantly checking for leaks....none to be found....

turned the bike off, let her sit and cool down, checking for leaks, again, there were none....

About 15 minutes later, turned on the ignition, which primed the pump, checked for leaks....none....started the bike, let her warm up, again, no leaks, idled smoothly....geared up, put the bike in gear, then went for a ride....

Bike ran smoothly, runs nice....no problems at all.....

drove around for 15 minutes, parked the bike, and again, checked for leaks....again...none....

Soooooo, as of now, my new tank works great, the new fuel filter works fine, and there are no leaks....if the bike does leak around the fuel filter baseplate, I will let you guys know....

it was a fun project even though it was necessary....

[ghostrider71]

I think u should probably go check it ONE MORE TIME!

Seriously - lock washer???
I can't decide if this is pure GENIUS or just plain old trouble!??

Wouldn't that put more torque-load on the already weak bolt receptacles??
(Lack of better descriptor)

Seriously - opinions needed on this...and no offense intended -PDX!

Assume you used STAINLESS locks, yes??? ;-p


Gr

[pdxmille]

yes, stainless lock washers, and remember, these bolts are seriously only a little above hand tight, they are nowhere near weakening the bolt receptacles. I even used an 8mm socket on a screwdriver type driver and only then did them hand tight. I think the spec is like 8 nm? And with these bolts not being very tight at all, I cant help but think the vibration inherent in a big twin would looosen up these bolts over time. I thought, huh, its either locktite to prevent loosening or lock washers....why not lockwashers?

I went for another ride later in the day, made two stops at different places, checked for leaks...none.

went out and polished the "new" tank some more tonight, checked for leaks again....none.

I am optimistic at this point

[soofle616]

If the bolts were tightened to spec, the use of lock washers or not will have no effect on the load imparted on the bolt holes. The torque applied to the bolts determines tensile load so no matter what you put in there it will be the same. If the bolts were overtightened in an attempt to actually collapse the washers then yes, there would be more tensile load but otherwise it's 6 of one, half dozen of the other. PDX, if you're worried about vibrations lossening things over time I would suggest using a toothed washer instead of a standard split ring lock washer. It requires less clamping force before it starts to do it's job since it creates more friction (and therefore more resistance to backing out) under less load.

Top row, middle three in the picture.

[ghostrider71]

Good INfo - thanks Soofle.

PDX - were you able to "snap" the lock washers inline with that little torque on the Fuel Pump Bolts???

I'm trying to remember the EXACT value, but you're right -- not much more than 5-8 lb/ft on each.
Many guys reporting subsequent stripping from being hamfisted with these little guys....

I'm STILL vasilating over the clamps -- damn you guys for making me doubt myself!!

gr

[pdxmille]

yes, the washers snap with very little torque, they're tiny washers! lol!

yes, I was very aware and very careful knowing that those inserts would'nt take much to become stripped out, hence I didn't use a socket wrench to tighten them, I just used a socket on a socket "screwdriver" so I could'nt possibly strip them...

Day 2 update...still no leaks and I put 50 miles on her today...she's running great!

[pdxmille]

day 6...

no leaks, looking good!

still runs great!

[Motech]

Little nervous eh? Don't blame you.

[pdxmille]

Little nervous eh? Don't blame you.

Not nervous at all!! as you will see by my posts, I'm keeping EVERYONE posted to prove YOU WERE SO VERY WRONG ON THIS TOPIC.

btw, bike is running fantastic, no leaks....

[ghostrider71]

So, I went with PDX's suggestion of using SS lock-washers on the pump retaining bolts WITH a LIBERAL amount of anerorbic gasket Sealant slathered under the rubber o-ring AND on top of the o-ring.
WHOA! --I'm not taking any chances--

I actually used Permatex Anaerobic gasket Maker/Sealant -- found it at a local auto parts store for abt $6 1oz. Expensive yes, but not as bad as the Loctite 518.
I guess we'll SEE if it works properly -- but i have it on good authority from another member that it's 100%.

Tank isn't installed yet - but i too, will report back any issues I may have in the future.
I did NOT replace my inner fuel hoses: they were in good shape.
Here's to HOPING my Oetiker clamps hold-up inside the tank!!


gr

[soofle616]

Those oetikers look properly cinched so you should be just fine.

[pdxmille]

Yeah Nate, they look fine, I myself might have made them a little tighter, but then again, I dont use those clamps...and thats exactly how much sealant squeezed out from around my fuel pump baseplate when i tightened her up....lookin good brother!