Read this one already? Go to page 2

Words of Wisdom

October 29, 2007

Topic #1

Buying used diesel engines:

We buy and sell used diesel powered equipment. In order to not get screwed a few basic tests need to be done when looking at any used equipment. Generator sets are one of  the easiest machines to check out. First you need to make sure to bring or have on hand the correct battery, fuel, spare wires, jumper cables, hoses etc. If the unit has a built in tank make sure it has fuel and the fuel does not stink like old paint. Look the unit over. Make sure the brand of engine and generator are known and easily identifiable. Make sure the unit was not made during the stone age. For generators the ONAN is a good example. Anything that says MAGNECITER needs to be in a museum. The newer brushless ONANS with VR21 are a better choice. They used different brand diesels through the years from Allis Chalmers (good but obsolete), Deere, Cummins, British Ford. Lets look at the Deere. The Deere 4-219 was used through the late 70s for 20-30kw machines. The first thing to do is check the fluid levels and quality. No oil in the antifreeze and no gray lube oil. Once this looks good then you can try turning it over. A hand turn is recommended but not always necessary. Attach a good 12v battery and if equipped with a standard ONAN panel move the switch from off to manual. The engine should crank. If no smoke is evident and it does not start then time to prime. From either a remote tank or the base tank hand pump the primer after loosening the prime ports on the primary, secondary filters and injection pump. The Deeres used mostly Roosa-Master injection pumps which may or may not have prime ports. After you see clean fuel at each port, close them and crack open the injector lines at each injector. Crank again until fuel squirts out of those lines. If none is seen check for 12v at the fuel solenoid on top of the RM injection pump. If no 12v evident attach a hot jumper. Try again and if fuel squirts close the lines. The engine should fire without the need for ether unless the ambient temp is below 50F. If you see lots of white smoke try spraying ether on a rag placing the rag over the air cleaner. Never use ether without seeing unburned diesel out the exhaust. Ether only increases the volatility of the fuel and does not replace fuel. If you get the tell tale knocking sound then you are doing damage. The engine should start like it is a warm summer day not as if it is going to explode! Run the engine for 30 seconds and shut off. When you checked the antifreeze you should have closed the cap and squeezed a hose. Squeezing tells if the cap is sealing. After that short run open the cap to see if there is any pressure in the cooling system. If there is then the head gasket or head is damaged. NEXT! If it passes then start it again and check the output of the generator end. Before running a genset one caution. Make sure the electrical system is completely disconnected from by a breaker or from any permanent wiring. If unwired make sure there are no bare output wires. Determine safe test points for a multimeter before running. Once you test the end for output then application of a known load is a good idea. Allow the engine to warm up. Any smoke on startup should be gone in 3-5 minutes no load. Read the smoke: white is cold combustion possibly low compression; gray is overfueling and cold combustion; black is overfueling from overloading or during spool up; blue is either lube oil (smell) or dirty worn injectors. The best way of testing an engine is under load. If a load is available apply it in increments until the engine reaches operation temp. A good tool to have is a IR non contact thermometer. These can be used to read the overall condition of the engine. For example point it toward the outlets of each cylinder on the exhaust manifold. A diesel no load may get to 200F in a few minutes and upwards of 600F under load. See smoke and a cold cylinder? Suspect bad injector, rings, or valves. Engine block running cold? Possible no or bad thermostat. Get the picture.

    Loading a genset: We used resistance heaters either air or water. You need a voltmeter, clamp type or built in amp meter, cycle meter. With a single phase set apply loads in 25% increments and note the engines response. With a full rated load check the gen end for correct voltage and cycles. Cycles are a factor of speed. The engine with a mechanical governor should be 61-62hz no load and 58-60hz fully loaded. Watch the engine for leaks and blow by out the breather.

Watch this column for the next topic. Check out my listings on eBay seller "cusdn" for new and used gensets.