What causes vapor lock?
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4th Gear
Joined: Jun 2006
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From: Albuquerque, NM
What causes vapor lock?
I have 2004 FLHRI that has vapor locked twice. I was told told that it can occur after putting cold gas in a hot bike and then shutting it down before the gas can get warmed up. This is what occured the first time it happened but not next second. The second time, I went for a short ride, shut it down and the next morning, it just wouldn't start.
Solution: remove air cleaner, put hand over the intake to cut of the air, hit the starter and it fires up rather quickly. Reassemble the intake and go riding.
Like I said , it has only happpened twice in the 2 years that I have owned the bike so it is not a big problem. I am just curious as to what is really going on here. Any insight is appreciated.
e¿e
[IMG]local://upfiles/14410/90F1E5D056734178A6EB2A56E2C84BB0.jpg[/IMG]
Solution: remove air cleaner, put hand over the intake to cut of the air, hit the starter and it fires up rather quickly. Reassemble the intake and go riding.
Like I said , it has only happpened twice in the 2 years that I have owned the bike so it is not a big problem. I am just curious as to what is really going on here. Any insight is appreciated.
e¿e
[IMG]local://upfiles/14410/90F1E5D056734178A6EB2A56E2C84BB0.jpg[/IMG]
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From:
RE: What causes vapor lock?
On old cars vapor lock was the result of a gas line being to close to the exhaust pipe or manifold.
causing the fuel to change from a liquid to a gas before it got to the carb, it was normal for this
to happen on very hot summer days, the fix would be to move or wrap your fuel line with
aluminum foil,
I don't think this is your problem. keep us posted.
Hog202
causing the fuel to change from a liquid to a gas before it got to the carb, it was normal for this
to happen on very hot summer days, the fix would be to move or wrap your fuel line with
aluminum foil,
I don't think this is your problem. keep us posted.
Hog202
Seasoned HDF Member
Joined: Dec 2005
Posts: 5,464
Likes: 624
RE: What causes vapor lock?
What makes you think it is vapor lock that is causing this problem? I don't think it is a common problem, especially on bikes because the gas line is so short. I would be willing to bet there is a problem with your vent hose. If you bike is carb'd, it could be your petcock as well? Is it clean and flowing freely?
Thread Starter
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4th Gear
Joined: Jun 2006
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From: Albuquerque, NM
RE: What causes vapor lock?
Hog, I agree with you that this is probably not the problem. The pipes and gas line are stock and in their factory locations.
Zed, as far as this being a vapor lock, I am only repeating what the 2 HD mechanics told me. Could be like going to the doctor. If they don't know what you've got, that have to call it something. One of them had seen this happen only once before. I really don't care what they call it since they took a half hour to diagnose it and it didn't cost me anything but a little riding time.(Thanks Billy and Zee) Also, the bike has EFI and has been well maintained.
In both instances, the bike was parked for 10-12 hours before trying to start it. The first time was in 2005 in Sturgis, this time it was this weekend in Phoenix. So, if this only happens once every 20 months, it is not a big deal. It is just something that shouldn't happen (I think).
Thanks for the input.
Scott
e¿e
Zed, as far as this being a vapor lock, I am only repeating what the 2 HD mechanics told me. Could be like going to the doctor. If they don't know what you've got, that have to call it something. One of them had seen this happen only once before. I really don't care what they call it since they took a half hour to diagnose it and it didn't cost me anything but a little riding time.(Thanks Billy and Zee) Also, the bike has EFI and has been well maintained.
In both instances, the bike was parked for 10-12 hours before trying to start it. The first time was in 2005 in Sturgis, this time it was this weekend in Phoenix. So, if this only happens once every 20 months, it is not a big deal. It is just something that shouldn't happen (I think).
Thanks for the input.
Scott
e¿e
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RE: What causes vapor lock?
Is it carb or fuelly.
VERY RARE for fuelly to do it. As it is under constant pressure. Not much chance
for a vapor to occur.
Vapor locking is just that; a vapor in the line.
fuel lines too close to hot spots on engines will tend to "boil" thus causing
a bubble in the line. sometimes the fuel can not get past this bubble, thus the lock.
Putting fuel in the tank will NOT cause this. As it is caused by hot, not cold fuel.
It will normally happen after a hot ride at slow speeds through town, where the lines
don't have enough air flow. It can also sometimes occur in the carb itself.
First thing I would do if carb, is change the filter and make sure the petcock isn't partially clogged. Then insulate the lines with a fuel line wrap.
If a fuelly same thing, check the pump pressure when cold and thoroughly warmed up.
Replace the filter. Also check the pressure regulator. If weak it is not holding enough pressure up against the injectors. They can fail hot or cold.
the older bikes don't like ethanol and we are seeing more of that in the gas today.
Ethanol in hot climates doesn't produce the spark front like good old gas does, so less power, and I understand it is prone to vaporizing also (but can't confirm this).
Also have your fuel / air/ timing checked by a quality shop.
VERY RARE for fuelly to do it. As it is under constant pressure. Not much chance
for a vapor to occur.
Vapor locking is just that; a vapor in the line.
fuel lines too close to hot spots on engines will tend to "boil" thus causing
a bubble in the line. sometimes the fuel can not get past this bubble, thus the lock.
Putting fuel in the tank will NOT cause this. As it is caused by hot, not cold fuel.
It will normally happen after a hot ride at slow speeds through town, where the lines
don't have enough air flow. It can also sometimes occur in the carb itself.
First thing I would do if carb, is change the filter and make sure the petcock isn't partially clogged. Then insulate the lines with a fuel line wrap.
If a fuelly same thing, check the pump pressure when cold and thoroughly warmed up.
Replace the filter. Also check the pressure regulator. If weak it is not holding enough pressure up against the injectors. They can fail hot or cold.
the older bikes don't like ethanol and we are seeing more of that in the gas today.
Ethanol in hot climates doesn't produce the spark front like good old gas does, so less power, and I understand it is prone to vaporizing also (but can't confirm this).
Also have your fuel / air/ timing checked by a quality shop.
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RE: What causes vapor lock?
I would be inclined to think that it may be a problem with temperature sensor not reading correctly on cold startup. I do not where you are or what the temp's might be but by closing off the intake you are in a sense using a "choke" to enrichen the mixture for startup. It may be tough to find if the problem is that intermittent. I aree that the vapor lock is VERY unlickley. See if this seems to occur more so on cold mournings or not also-it may help to narrow it down.
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Grand HDF Member
Joined: Feb 2005
Posts: 4,307
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From: Twin Cities Minnesota
RE: What causes vapor lock?
To really simplyfy it....vapor lock occurs when fuel boils. Gas with corn in it boils very quickly at a lower temp than corn free fuel...injected bikes under higher pressure don't normally have this problem. Corn free gas also have far less problem with vapor lock. We can thank the politicans for corn in our gas.[&:]
Stellar HDF Member
Joined: Sep 2006
Posts: 3,236
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From: lancaster, pa
RE: What causes vapor lock?
I had a Bike mech at an indy tell me that was happening all the time during last summers heat wave. But I do not believe him. (gas vaperizing in the lines)