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RV Doctor ColumnRV Doctor #351 Dear RV Doctor, in an earlier issue of RV View you answered a question about vapor lock with the suggestion of adding a second electronic fuel pump among other remedies. Recently I bought an older (1993) Ford 350 Frontier Flyer. The main difference is that it is fuel-injected but I believe it, too, is vapor locking. Some people I have spoken to were surprised it is fuel-injected and said that they had never heard of a fuel-injected motorhome vapor locking. Can vapor lock occur in a fuel-injected engine and if so, do the remedies you suggested in the earlier article apply? If not any ideas on what it may be? It is definitely a temperature related issue because after it cools down it will run fine. Dallas Drewry, (Salt Lake City, UT)
Yes Dallas, vapor lock can occur when using an in-tank high pressure pump to deliver fuel to the engine. It is my belief there are at least three possibilities that may cause the problem you are experiencing. First, Ford had a recall on in-tank fuel pumps and pressure regulators for 1990-93 model year vehicles. It is possible that your in-tank fuel pump or pressure regulator may be a faulty component. Others agree with me that you should focus on the pressure regulator first, because if it fails it would not allow fuel to return properly to the fuel tank. This could cause the vapor lock problem because it would literally boil any stagnate or stationary fuel before it gets to the injector. Have an engine mechanic confirm that the pressure regulator is within factory specifications. Second, as mentioned above, the in-tank fuel pump itself may be the problem. That in-tank pump is of a type that is highly susceptible to damage from contamination. As the pump begins to wear, its output becomes weaker. If the pump is weak, the vehicle will lose power after the pump has warmed up. Again, have a technician confirm that the output pressure of the pump is within factory specs, especially after the engine has warmed up. And thirdly, the final possibility is that the fuel lines may be heated beyond design parameters. This typically happens when the fuel lines and exhaust manifold follow each other too closely along the frame rail. This could be the result of a faulty catalytic converter or it could be the result of ill-placed or missing heat shields in that area. For more specific information regarding the specs for your chassis, I recommend you contact Transfer Flow Inc., in my opinion the premier authority on all things relating to RV fuel containers. Feel free to contact Bill Gaines at: bgaines@transferflow.com or give them a call at 800-442-0056.
Dear Gary, first of all I enjoy reading your articles. Now, I have a problem with my gasoline Onan generator. My generator surges during idle. The voltage checks out at 110-115 volts AC during idle or load. I've cleaned the carburetor, replaced the fuel filter, and replaced both spark plugs, all to no avail. Can you please help me with the carburetor and governor adjustments? It's an Onan 4000-watt Genset, Emerald Plus. Michael Cheatham, (Clinton, SC)
Well Michael, it certainly sounds like the governor is out of adjustment; basically hunting around for the proper frequency. At no-load (idle), the frequency should measure around 62 or 63-hertz. Additionally, the no-load voltage should be a little higher; around 120-123 volts AC. Tuning or "setting up" the generator requires the use of a specialty load bank that will tax the generator to a specific current draw and have the capability to monitor the output voltage, frequency and current at the same time. They can't be tuned by ear. On your particular generator there are three separate carburetor adjustments and three governor adjustments and they must monitored and adjusted simultaneously. The load bank is the preferred method. In fact it's my opinion that using a load bank is the only method. Not all RV service techs, let alone RVers, realize that every mechanical action performed on the carburetor and governor will have a direct electrical response. Therefore, the only way to adjust the RV generator (properly) is to make such adjustments while monitoring the output voltage and the electrical frequency, while applying a known load in incremental steps. Oh, it can be done from a "ballpark" perspective, but you'd just be guessing and running the risk of harming a myriad of 120-volt AC loads in the coach. Unfortunately, the generator set-up procedures are too in-depth to fit within the confines of this column, but I do have a possible solution in the form of a training video I developed for professional RV service technicians. If you would be interested in knowing exactly what takes place during a professional generator set-up, "RV Generator Tune-Up/Set-Up Procedures" will show you each step in the process. Send a self-addressed, stamped, long envelope to the column and I'd be happy to send you an order form. If not, I would recommend you find a properly equipped RV generator shop for those finite tweakings that are necessary. Call first to be sure they indeed have a load bank.
Dear RV Doc, I am going to go look at a used 24-foot travel trailer that had the roof replaced back in 1998. It has sat in an RV park its entire life. My concern is about roofing standards. Hopefully, it wasn't re-roofed with tar and gravel, which might be fine if parked permanently, but wouldn't be appreciated by those behind you if you're towing it. Is there a roofing standard for travel trailers? What should I look for/ask to ensure that the roof is okay for towing it? Thanks, Larry Niemoeller (somewhere in the US)
Larry, RV roofing surfaces vary in construction. Some are comprised of sheet metal over wooden or metal rafters, (soft roof construction), bonded fiberglass laminated with Styrofoam insulation and a plywood or luan ceiling panel inside, (solid roof construction), or an EPDM rubber sheeting or the fabric-like TPO material, both of which is glued to a plywood substrate secured to either wooden or metal rafters or a solid sandwiched roof. There are pros and cons to each type of construction technique. The main point is that the roof be leak-proof. The solid roof construction is considered better in those instances when storage pods or heavy air conditioners are installed. They are generally more expensive to produce and they do weigh more. The soft roof construction technique is less costly, but in my opinion, more prone to roof leaks since it will be more flexible, providing movement during travel. When items flex and wrack back and forth, screws and other fasteners have a tendency to loosen. The same thing can happen with temperature swings. Frequent inspections should be made on RVs with a soft roof. Obviously, if the roof has been replaced with anything other than the above, it would not be recommended for towing. Let's hope they didn't tar and gravel it! If you are unsure as to the condition of the roof, have an experienced RV technician perform a complete inspection including a leak test. The roof of the RV is obviously of utmost importance.
Dear RV Doctor, we cannot get the water to come to the sink in our camper with the equipped hand pump. It was working fine not that long ago. What could be the problem? We keep trying and trying but the hand pump will not bring water to the sink. And yes the water tank is full. Kris Tienhaara, (Laurium, MI)
Kris, it's quite likely there is an air leak somewhere in the hand pump itself or in the hose between it and the tank. Check the hose carefully for any splits or holes. Some simple hand pumps were not usually constructed under the strictest of tolerances and it may simply be faulty. Though replacement hand pumps are readily available at any Camping World store, it may be time to upgrade to an automatic 12-volt demand pump, even for a single sink configuration in a truck camper. It would depend on how much time you actually spend in the RV and if you have the space to install it.
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