al_roethlisberger Posted January 17, 2003 Posted January 17, 2003 Moto Guzzi V11 Sport/LeMans "Vapor Lock" and "Tank Suck" FAQ ****************************************************** Introduction: ---------------- Many owners of 2000-2002 V11 Sports and LeMans have complained of an issue often characterized as "vapor lock." This condition is often described as having just parked the motorcycle after a longish ride in a hot and sometimes high-altitude environment, then finding that when coming back to start the bike within approximately 30 minutes, that the fuel pump "whirrs" as if never pressurizing... as if "pumping vapor, " and the bike will not start. If the bike starts at all, it runs very poorly, stumbling, and ultimately stalling. However, if given another 20 to 30 minutes to cool off, the bike will start without incident. As is common with many conditions of this type, the problem has proven nearly impossible to replicate on command by dealers and service centers, although several have diligently attempted to do so. However, this condition, while uncommon as measured against a total percentage of V11 Sport/LeMans owners, is genuine and inconvenient. Moto Guzzi North America and in Italy apparently also do not have an official opinion on this issue as of January, 2003. However, one has to wonder why all 2003+ V11 Sports and LeMans will have an in-tank fuel-pump. This modification could have only come at significant expense and engineering effort on the part of Moto Guzzi, so we can only assume that Moto Guzzi is aware of the issue and this new pump location is partly to address this problem. Hopefully, all 2003+ bikes with the new integrated fuel-pump will not experience this issue going foward. However, the exact cause of this condition continues to be debated. Depending on the motorcycle and circumstances, several different issues can be at fault that present similar symptoms. These include: - The infamous "tank suck" (non-vertical alignment of the tip-over valve) - Faulty electronic pet-cocks on early V11 Sports - Faulty relays - Poor EFI pressure regulation But, it is believed by many that the "classic vapor lock" scenario is actually heat related based on apparently correlated evidence and symptoms experienced by riders unfortunate enough to suffer through this issue. In almost every case, the owners have reported parking the bike after a hot ride, experiencing the scenario described, but then finding that the bike will start reliably once given additional time to cool. In this scenario, the obvious culprits seem to be the fuel-supply line and fuel-pump which reside closely above the left cylinder on V11's. In some cases, it has been found that the fuel-line actually rested upon the cylinder upon delivery from the factory. With this in mind, many have surmised that heat radiating from the left cylinder has soaked into the pump and/or line, vaporizing the fuel, making it nigh impossible to properly pressurize the EFI. However, after attempting to start and pressurize the system and/or letting the bike cool over time, the fuel has an opportunity to condense, and allow for a normal start. While there is not currently any certain solution or conclusion for this issue, several discussions have been evolving, and some suggestions for "heat shielding" for the fuel line and pump have been considered. Unfortunately, at this time there are no aftermarket kits available providing any shielding for the pump and line. As more information can be gathered, perhaps sometime in the near future the exact condition and cause of this problem can be identified. Until then, owners will have to simply be aware that when this condition exhibits itself, the only solution is to provide time, allowing the engine to cool. One other option is to find heat-shielding from an auto-parts supply for the line, and potentially build one from aluminum for the pump. However, no one has done so with any measureable results as far as this Forum is aware. UPDATE (01/27/03) ----------------------- It has been discovered that some late 2002 V11 LeMans(and perhaps Sports) have had their fuel-pumps relocated as delivered from the factory in front of the oil-cooler, aligned perpendicular(horizontal) to the frame, with the fuel-filter relocated as well. As mentioned, all 2003 bikes are to be delivered with their fuel pump integral to the fuel tank, but perhaps this was an interim solution to address the heat-related "vapor lock" issue until the new system was delivered in 2003 models. If one has this unusual setup, the "vapor lock" issue may be less likely. UPDATE (11/18/03) ----------------------- After some testing, it seems verified that relocating the fuel-pump above the spine can significantly reduce the temperatures of the pump and low-pressure fuel-supply line, and reduce if not eliminate this condition. This of course requires removal of the air-box, and replumbing and shielding the lines. More information can be found in the two "fuel pump relocation" and "vapor lock" threads listed below. Additionally, often related or confused with this condition is the oft-reported "tank suck" phenomenon common to V11 bikes with the plastic fuel tank. This condition is exhibited also by poor starting, idle, and performance very similar to the "vapor lock" issue. However the cause is well documented, and easily rectified. To verify "tank suck", one merely needs to open their fuel-cap, and if upon doing so one hears a "whoosh" of air being sucked into the tank AND/OR one notices deformity of the plastic fuel tank before or after relieving the pressure differential, "tank suck" is the culprit. Fortunately, again, the cause is well-known... the one-way tip-over valve under the fuel tank is not oriented vertically and should be stabilized to a vertical member of the motorcycle. For emissions equipped bikes these days, the fuel-cap no longer vents to the atmosphere. Instead, intake vaccuum is used to "suck" the gasoline vapors from the tank into a charcoal recovery system, which is then fed back into the intake for clean burning. Additionally, your overflow hose has a one way valve, called a tip-over valve. If this valve becomes oriented "non vertically" it seals off, not allowing the tank to breath. Because this hose and valve typically hang free, if the hose is moved and orients the valve incorrectly, the tank will seal... and contraction of the internal fumes and/or vaccuum from the intake will cause the "tank suck" condition. Fortunately, it's an easy fix... just attach the tip-over valve to a vertical member of the frame or other mostly secure item under the tank with a nylon wire-tie, and all will be fine. Or like some folks, you can simply remove the valve altogether. The disadvantage there of course is if the bike falls over, without the valve, you may dump fuel on the motor and ground, which can be a "bad thing" Other solutions include removing the entire emissions systems from the motorcycle, and removing or piercing the rubber venting plug in the fuel-cap. However, depending on the modification, there can be some risk of fuel spillage in a tip-over, and venting fuel fumes where undesired. As always, YMMV. Listed below are URLs and contact information for general information and several online discussions. Information: --------------- Guzzitech - Electronic Petcock Malfunction V11 Forum Topics: ---------------------- Fuel Pump Relocation Thread Vapor Lock Link to Jason Tucker's "vapor lock" Online Survey Pinging and Vapor Lock - Dealer experience with these issues Engine Hot = Start Problems - Fuel injection pump is not working Tank Suck
Ryland3210 Posted March 26, 2008 Posted March 26, 2008 UPDATE March 25, 2008: The tipover valve must to be oriented vertically, but also right side up. If upside down, even if vertical, it will not prevent the vacuum from forming in the tank. For pictures of the layout, see the following post: http://www.v11lemans.com/forums/index.php?...st&p=132990 FAQ Administrative Contact: ---------------------------------- Please feel free to contact this FAQ's administrator via Forum Private Message to submit new information or suggest corrections. Ryland3210
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