IMS 4.7 Tank - vacuum pump

After about 10,000 miles the vacuum pump that lifts fuel from the big wings has failed.  Kaput.  Bit the big one.    Almost stranded me out in the Big Bend area last year.   I finally got around to trouble shooting what the problem is.  I have verified that vacuum lines are all good.   I pull the fuel pump and positioned that fuel line so I could see if fuel was coming out of it or not.  No fuel being pumped.  So it is definitely a failed vacuum pump.  

Thought I would share this so anyone who has one of these tanks can keep an eye on that vacuum pump.  Not good to be depending upon that reserve and find the pump has gone out.  

On the new vacuum pump I may put a valve in the vacuum line so I can only turn on the pump when  I need to use the reserve fuel.  That way I might have a functioning pump when I need one.

The IMS tank is not providing any vacuum; the vacuum is coming from the WRR vacuum line: take a look at the IMS installation instructions on page 2 and page 3.

Oops. The "vacuum pump" failed. Thanks for catching that typo.

Can't quite follow what you consider "typo".

Your troubleshooting is not correct: there is no vacuum pump, either in the IMS tank or the bike; vacuum is created by the engine, and the IMS tank connects to one of the vacuum lines to lift fuel from the wings. If fuel is not being lifted from the wings, then the vacuum line has either been blocked, disconnected from the tank, or you connected the tank to the wrong vacuum line (the instructions I linked in my previous note make particular mention of this).

johnkol wrote:

Can't quite follow what you consider "typo".

Your troubleshooting is not correct: there is no vacuum pump, either in the IMS tank or the bike; vacuum is created by the engine, and the IMS tank connects to one of the vacuum lines to lift fuel from the wings. If fuel is not being lifted from the wings, then the vacuum line has either been blocked, disconnected from the tank, or you connected the tank to the wrong vacuum line (the instructions I linked in my previous note make particular mention of this).

Sorry. but there is a small pump inside the IMS tank driven by the motor's vacuum line that you connect. I called IMS today and ordered a replacement vacuum pump for the IMS 4.7 tank.

I am very confident in my trouble shooting.

My connection location to the motor's vacuum line is correct. Pulsing vacuum is happening in that line.

bsheet2 wrote:

johnkol wrote:

Can't quite follow what you consider "typo".

Your troubleshooting is not correct: there is no vacuum pump, either in the IMS tank or the bike; vacuum is created by the engine, and the IMS tank connects to one of the vacuum lines to lift fuel from the wings. If fuel is not being lifted from the wings, then the vacuum line has either been blocked, disconnected from the tank, or you connected the tank to the wrong vacuum line (the instructions I linked in my previous note make particular mention of this).

Sorry. but there is a small pump inside the IMS tank driven by the motor's vacuum line that you connect.  I called IMS today and ordered a replacement vacuum pump for the IMS 4.7 tank.  

I am very confident in my trouble shooting.    

My connection location to the motor's vacuum line is correct.  Pulsing vacuum is happening in that line.  

I have seen another report awhile back on the vacuum pump failing on either the IMS or Safari tank. I believe it is a relatively common pump that some bikes use. I know my 1995 VFR750 used one and it looked a lot like the one I saw in my 4.7 IMS tank - they do fail over time. If memory serves me correct it is a relatively small unit and if I was worried about it failing on a long trip I think I may opted to tape a spare to a side panel or something like that.

Not a bad idea to carry a spare.

bsheet2 wrote:

Sorry. but there is a small pump inside the IMS tank driven by the motor's vacuum line that you connect.

You mean the small metal box inside the tank? That is not a vacuum pump, it is a one-way valve that prevents fuel from dropping back into the wings during the neutral vacuum pulses.

How did you rationalise that this was a pump given that there is no power connection to the tank?

In any case, if that valve has indeed failed, that would be an interesting observation for all of us IMS tank owners.

johnkol wrote:

bsheet2 wrote:

Sorry. but there is a small pump inside the IMS tank driven by the motor's vacuum line that you connect.

You mean the small metal box inside the tank? That is not a vacuum pump, it is a one-way valve that prevents fuel from dropping back into the wings during the neutral vacuum pulses.

How did you rationalise that this was a pump given that there is no power connection to the tank?

In any case, if that valve has indeed failed, that would be an interesting observation for all of us IMS tank owners.

That is what is being referred to as a pump.  My VFR750 service manual called it a fuel pump as well.

It uses the vacuum pulses from the engine to drive the pump in the manner you describe.  Ever see an air diaphragm pump in action?  Basically the same thing but in reverse.

A pump does not need to be powered by electricity only. Compressed air and vacuum can provide a source of power as well.

https://www.everestpartssupplies.com/products/new-universal-vacuum-fuel-pump-stv-utv-farm-motorcycle-mikuni-single-outlet?utm_medium=cpc&utm_source=googlepla&variant=1036406169&gclid=CjwKEAiAlZDFBRCKncm67qihiHwSJABtoNIgtEmkg4AQeszS_g7zyJ4jwv_9dYUSKPckdR9Kq6ksRxoCEarw_wcB

rsteiger wrote:

A pump does not need to be powered by electricity only.

That is true; if the device was being powered by mechanical means (e.g., via a motor and axle), then the word "pump" would be apposite.

But in this case the vacuum is already provided by the engine; the device only smooths the pulses.

Let me make an analogy that I'm sure you'll understand: the generator (aka alternator) in our bikes produces alternating current, which is analogous to the positive/neutral pulses of the vacuum line. This AC is then fed into a device that smooths the up-and-down transitions of the AC, and produces DC: a constant current that powers all the electrical accessories. This device is analogous to the device in the tank that smooths the vacuum pulses.

The electrical device that provides this smoothing is not called a generator, although this is where the DC comes from; it is instead called a rectifier.

By analogy, why would you call the device in the tank a "vacuum pump"? "Rectifier" would be a more appropriate term, but absent that, "valve" is a more to-the-point term (because that's how the vacuum rectification is being performed -- through a one-way valve).

Anyway, enough with the semantics, it is interesting to learn that this component can fail too.

johnkol wrote:

rsteiger wrote:

A pump does not need to be powered by electricity only.

That is true; if the device was being powered by mechanical means (e.g., via a motor and axle), then the word "pump" would be apposite.

But in this case the vacuum is already provided by the engine; the device only smooths the pulses.

Let me make an analogy that I'm sure you'll understand: the generator (aka alternator) in our bikes produces alternating current, which is analogous to the positive/neutral pulses of the vacuum line. This AC is then fed into a device that smooths the up-and-down transitions of the AC, and produces DC: a constant current that powers all the electrical accessories. This device is analogous to the device in the tank that smooths the vacuum pulses.

The electrical device that provides this smoothing is not called a generator, although this is where the DC comes from; it is instead called a rectifier.

By analogy, why would you call the device in the tank a "vacuum pump"? "Rectifier" would be a more appropriate term, but absent that, "valve" is a more to-the-point term (because that's how the vacuum rectification is being performed -- through a one-way valve).

Anyway, enough with the semantics, it is interesting to learn that this component can fail too.

Very in depth discussion and I am glad I read that when I was having a beer last night.

I think the reason they are know as pumps is if you look at what is happening on the fuel side of the device. Basically you have a pumping action due to the vacuum pulses that lifts the fuel from the bottom of the tank. Those vacuum pulses function like the little hand transfer hand pump I have when I don't care to suck on a line full of gas to transfer fuel. Basically it is a little rubber ball you squeeze which provides the motive power and check valves in the line assure that the fuel only moves in one direction.

I think the reason why these vacuum pumps or rectifiers fail comes down to two things. Either dirt gets in the check valve and basically renders it in operative or the rubber diaphragm degrades over time (could be quite fast if the source the wrong material when it comes to being exposed to fuel).