vapor lock

[al_roethlisberger]

... with the "vapor lock" one can clearly hear the pump trying to pump "vapor"....

 

al

[Guest wanie]

George: Sounds like it would work ! It looks like an interesting product.

Wanie

[Guest wanie]

Doc: I thought about the relay too but letting the bike sit and cool seemed to always cure the problem.

Wanie

[docc]

I get it ,Al. That makes sense since in normal operation the pump will stop whirring when the pressure comes up.

 

So, Wanie, listen for the pump because the relays will often work again after sitting for a little while.

 

Much luck and good riding, docc

[Paul Minnaert]

I don't get all the heat things, I located the fuel pump and filter under the tank, I don't like the look of the pump in front. All is pretty close to the 4V cilinders, but even a track day, 5x 20minutes, on the track doesn't give a problem. I've also seen posts about imploding tanks, that looks if the air doesn't come into the tank.

SO what happens exactly? Boiling fuel in the lines would be easyliy solved when you put on the contact, the fuel pump starts pumping fresh fuel around from tank, to pump and filter and back.

[al_roethlisberger]

It's hard to say exactly what happens Paul, as like most things of this type, it's hard to reproduce in a controlled environment. That's why it has been so frustrating for most people that have experienced it. Of course, even if a fix like a heat-shield is effective, it's hard to ever know if it really works... as one will just have to wait around for a whole season of riding to see if it never happens again

 

Not to make it sound like I don't want to describe the problem and it's symptoms ....but I have a long description in the FAQ section for both the similar but unrelated "tank suck" and "vapor lock" problems that might answer a few of your questions.

 

al

[Guest wanie]

Docc:

 

You're right, now that you mention it, I have listened to the pump and have heard it pumping air!

 

Wanie

[al_roethlisberger]

Here's an interesting observation while reading the "factory service manual" for the V11 Sport last night...

 

...in the fuel-injection section, they illustrate where the fuel-filter and pump are located. In the Service Manual, they show the PUMP up on TOP of the spine under the tank, and the FILTER down UNDER the frame... which is completely opposite of how I've seen most late-model V11 Sport/LeMans. And is of course is how my 2002 LeMans is, with the pump UNDER the frame.

 

This is interesting, as I had just been entertaining switching the location of the pump and filter to keep the pump and low-pressure side of the system cool.

 

I wonder why it flip-flopped.... did the factory guys just get confused? ...or was it a conscious design change?

 

al

[Guest David Viosca]

The suspected vapor-lock issues I have heard of seemed more prevalent on the 2000 V11 Sports, where one of the fuel-lines ran very close, and in some cases rested, upon one of the cylinders. The theory was that when the bike was shut off, without pressure, and no air/fuel-flow to cool the bike/fuel... the fuel would "boil" in that line. Upon trying to start the bike, the fuel-pump would attempt to pump "air"(fuel-vapor) instead of liquid-fuel, and hence the bike would not start.

 

The only on-the-spot fix was to let the bike sit for about 20-30 minutes and cool down. The long-term fix was to reroute and maybe shield the offending fuel-line.

 

On my 2002 LeMans, the fuel pump is not inside the tank, and is not above the left cylinder either. It is more accurately described as suspended below the frame, almost under the huge fuel-filter which is on top of the frame under the tank. The pump is "shielded" by a wrap of rubber, which I can only assume is to protect it from vibrations. It may provide some thermal protection, but who knows.

 

And the only fuel-lines that come near the heads seem far enough away to be OK. In the case of the fuel-supply from the tank, it passes within 2 or so inches of the head, but is covered with silver metal braiding. So, so far, it seems OK.

 

On the pressurized side of things, none of the hoses come close. note: The pressurized fuel-line *did* come within an inch of the right cylinder, but in light of my research into the vapor-lock reports, I thought it would be prudent to cut the length of this hose and shorten the loop, putting it far away from the head. BTW, this particular line was the pressurized fuel-return line to the tank, again on the right.

 

 

So far, knocking-on-wood, this arrangement hasn't proven to produce any vapor-lock, and yours is the first report I've heard on a new V11 LeMans.

 

But I would agree that building a quality heat-shield, perhaps from sheet aluminum, would be a good idea, if in fact the pump proved to be susceptible. In fact, if you fabricated a good solution, you could probably sell a few

 

But, taking care to check the routing of hoses should help. I'll keep an eye on mine when I ride it through the desert here in a month to Las Vegas. If it doesn't vapor-lock in the high-desert.... it never should!

 

The only other hose/cables that I've moved(other than some electrical re-routing) are the vent hose that used to go to my carbon-cannister(which is long-gone). I have it and the tip-over valve lashed to the frame now, so it always stays vertical. And that hose is a couple inches from the head, so I put a 3/8" 3-inch long heater-hose segment over it just for extra protection from melting. But I think that's overkill, and has no effect on issues like the vapor-lock. I also moved my enricher cable and tied it back from the right cylinder, as it was touching and starting to melt.

 

Just little nits I've found while working on various projects so far.

 

*thinking* I really need to re-route the pressurized fuel-supply that runs from left->right... the factory has it wedged under the air-box and the transmission... kinda tight, and that makes me nervous.

 

al

The suspected vapor-lock issues I have heard of seemed more prevalent on the 2000 V11 Sports, where one of the fuel-lines ran very close, and in some cases rested, upon one of the cylinders. The theory was that when the bike was shut off, without pressure, and no air/fuel-flow to cool the bike/fuel... the fuel would "boil" in that line. Upon trying to start the bike, the fuel-pump would attempt to pump "air"(fuel-vapor) instead of liquid-fuel, and hence the bike would not start.

 

The only on-the-spot fix was to let the bike sit for about 20-30 minutes and cool down. The long-term fix was to reroute and maybe shield the offending fuel-line.

 

This did not work for me on one occasion I waited an hour,while napping,under a tree.

 

And the only fuel-lines that come near the heads seem far enough away to be OK. In the case of the fuel-supply from the tank, it passes within 2 or so inches of the head, but is covered with silver metal braiding. So, so far, it seems OK.

 

Very well covered post about the vapor lock I experienced in Colorado.

 

While disconnecting the braded fuel line to bleed the vapor out I noticed it touches the engine block and also forms a bend downward which I think could act like a P-trap which helps to block the vapor from escaping upward back into the tank. I will re-route this line to address this issue. If it is the pump this will not fix the problem.

However, I suspect the fuel line. Has anyone re-routed the line and still has the problem? FWIW I had the problem occur on onother occasion in the Texas heat not at alltitude. I have plenty of room to move the pump upward and back as my airbox is removed. I hesitate to do this because it might cause more of a problem not being below the petcock, e.g. fuel would tend to run out of the pump causing it to loose prime.

TIA, later,

 

David

[al_roethlisberger]

Actually, this is true of all the V11 Sport

varieties(LeMans, Scura, etc) where the fuel supply

line is probably the main culprit as it often runs

very close to, or actually touches, the left cylinder.

 

After a "hot run" and parking the bike, the line gets

heat-soaked and the fuel vaporizes. At least that's

the theory. This has been the case from the original

models up through 2003 where the fuel-pump went in the

tank.

 

MG is apparently aware of the issue though, and since

2000 has moved the pump location at least 3 times that

I am aware of on the Sports before finally resorting

to putting the pump in the tank. This may or may not

be the blessing it appears to be, depending on the

reliability of the pump, and the space it consumes.

We will only have to see over time how well it holds

up. But I often laugh to myself wondering what

engineering "intern" was assigned the task of fixing

this issue, as the problem and resolution seem very

obvious to me.

 

I suspect putting the new pump in the tank will solve

the majority(if not all) of the "vapor lock" problems,

although I think MG could have relocated the pump any

number of other imaginative locations much earlier in

the model's lifetime.

 

The three "relocations" that I am aware of have been:

 

1) If you take a look at the original service manual

for the V11 Sport, the fuel pump is located on top of

the spine, where the filter typically is on

later(pre-2003) bikes today. This seems to have been

really short-lived, which seems obvious if the fuel is

being vaporized and the bubble is flowing up to the

pump = bad.

 

2) The pump and filter were swapped, with the pump

now located slung under the spine, but now very close

to the left cylinder. This may have helped to some

degree, but I think the main issue of the supply line

being too hot was not addressed, ergo the problem

still extant.

 

3) Sometime in 2002, and seemingly to show up on the

Tennis first, the pump was once again moved, this time

"out front" of the engine/frame, perpendicular to the

frame, mounted right above the oil-cooler.

 

Many of us believe this final move was a stop-gap

until the 2003 in-tank solution was ready to go.

Whether moving the pump "out front" helped with the

Vapor Lock or not, is unknown.

 

 

However, in my opinion, the primary culprit was still

the fuel supply line running closely(or touching) the

left cylinder, and since it had no heat-shielding(the

metal braiding is not heat-shield, just abrasion

resistance) was susceptible. Even in the case where

the pump was "out front", many fuel lines were still

resting on the cylinder.

 

The easiest fix to me is if one can simply move the

supply line away from the head, and shield it, I

believe(unsubstantiated) that this will help quite a

bit. The reason I can't verify the efficacy of this

technique is the very nature of the problem. The only

100% way I will know if my heat-shielding and

relocation will help(as detailed on www.v11lemans.com)

is in a failure mode(it happens again). Otherwise

since this is such an intermittent and

hard-to-reproduce problem, if it never seems to happen

again, I can only assume that my modification worked.

*sigh*

 

But so far I feel pretty confident as I rode the bike

in very hot weather the other week, and while I had

other problems(unrelated... ah hem...) I didn't have

the Vapor Lock rear it's head after repeated stops.

But who knows yet. I'm not ready to declare victory.

 

 

The only real sure-fire solution would seem to get a

2003 tank/pump and retrofit it. That would be a very

pricey option though.

 

al

[al_roethlisberger]

Here's something else interesting... in spirit at least:

 

Buell Accessory Thermostatically Controlled Fan

 

It's a bit pricey, and I'm sure one could go down to the local electronics superstore(like Fry's here in the States) and put it together for a lot less. But if one lived in a very hot environment, and at altitude... and was concerned about heating problems... something like this could be a useful accessory to keep air moving under the tank/spine.

 

al

[callison]

I did nearly 3000 miles last week on the V11 Sport TT in temperatures in the 100˚F rnage and altitudes to 8511 ' and nary a sign of vapor lock. These bikes seem to have a tremendous lattitude in how they respond to the environment.

[al_roethlisberger]

I'm hoping my various modifications are as successful.

 

[dlaing]

If anyone knows the dimension of the hose going from the tank to the fuel pump, could you post the inner diameter?

Thanks in advance.

And if you know a source for an aircraft or military grade of the hose, that would also be helpful.

[Gio]

I believe this to be approximately 7/16" (am still looking for a source myself - nearest I have found so far is 3/8")

 

Gio