There are few things more simple that a diesel engine, but if you start out on the wrong foot you may quickly grow intimidated by diesel power.
Nothing is simpler, and few things are more efficient, reliable, or live longer. You need clean dry fuel, decent compression, and the engine should run. There are a few simple things people trip over all the time and it shakes their confidence. The following is not a complete guide by any means, but these are typical things people new to diesels trip over.
What generally happens is they lose focus of the simplicity and they widen their search for the cause and become even more frustrated, this is exactly the wrong approach. Stay focused on the basics, that’s all there is on a diesel.
First things first. I have seen a lot of engines come right out of the box with a frozen fuel rack. On some engines, this is easy to spot because the linkage is external, and you can disconnect the linkage and then grab hold of the rack itself and prove it is free or frozen. An example of this type engine would be the Lister 6/1 and clones. A typical example of other engines where it is not so obvious there’s a problem is the Yanmar air cooled clones, most Chinese horizontals, in fact the majority of small diesels often have the connections between the governor and fuel rack inside the engine case out of the elements. If you look carefully, there’s often a little door you can remove and watch the linkage. In other cases, you might need to remove the injection pump, but you will know there is often a slot and a ball that need be aligned when the pump is reassembled. In a number of the Chinese horizontals, there’s a bolt in the side cover that can be removed and you can push on the linkage to prove it’s free.
Removing all the tension from the governor adjustment is typically the thing to do before you remove the pump.
Once you decide the rack is frozen, understand that applying a lot of pressure to the rack itself could break something. It is best that you understand how the basic helix plunger works, and how a frozen plunger will prevent the fuel rack from moving. It is not wise to try and free the rack, it is your goal to free the plunger which is keeping the rack from moving.
I don’t know all the reasons plungers stick in brand new engines, but I do know that the fuel can not be left in the engine when it is shipped, and fuel displaces air which might allow minute amounts of oxidation and cause the plunger to stick. This is a high percision part…. simple yes, but highly precision and close tolerances just the same. The trick is to understand which way the plunger travels, try and get some of your favorite penetrate like WD40 into the plunger and barrel. then with the delivery valve removed, and loose parts off.. look for a piece of hard wood to lay on top of an anvil or other dead surface. bring down the pump body hard on this surface and let the kinetic energy free the plunger. In the most stubborn cases, drop the pump in a small can of diesel fuel overnight. Heating the pump up to about 150F might help too, but usually two or three serious smacks onto the hardwood will free the plunger. once you get the rack to move even .001″, you work it back and forth and keep applying penetrate. Once free, you’ll likely never see this problem again as long as you keep clean and dry fuel in the pump.
Again.. frozen pumps are over looked by people new to small diesels and it can cause a LOT of frustration. I know one person who literally burned out a starter trying to start a small diesel that had a frozen plunger in the injection pump. Once you understand just how basic the system is and what to look for first, and how similar all small diesels are, your confidence will grow. Spend your time understanding how something works instead of trying different things to make it work.
If you have a manual start engine you can hear the very distinct ‘clink’ as the injector pops off and sprays fuel into the combustion chamber. If you don’t hear this, there is room to suspect a fuel problem.
Fuel problems in brand new engines with brand new owners are often traced to the improper bleeding of air from the fuel system. This is a frustration for the beginner , but easily understood if you put a little effort into studying the system. you start by assuring that the air vent to your fuel tank is open, next you go to the outlet side of the fuel filter, or on the top of same you’ll finds a vent, open it and let the air escape from the lines and filter, next, move onto the injection pump and remove the high pressure line that goes to the injector. Under this fitting is another nut that holds the fuel delivery valve, remove it and watch for a spring on top. make sure the decompressor is on, turn the engine flywheel slowly until fuel gushes from the top, put the fuel delivery valve back in place. Yes rags are nice to place and making sure all parts are clean before you disassemble anything it important.
Now it’s onto the high pressure side, replace the high pressure line on the injection pump, making sure you understand that you need not use two hands! Many HP lines are ruined by over tightening, it need be tight enough not to leak, too tight cracks the metal, and the line leaks until replaced.
With the injector end loose, and the throttle open, check that that the decompressor is still on, and turn the engine over until you see fuel coming out the injector end of the high pressure line. Now keep turning over the engine, and slowly tighten the HP line at the injector. You should hear a very distinct ‘clink’ sound.
Another problem for the new owner and some not so new owner is to try and fire the engine and not get any ignition at all. After studying the problem, you determine it’s cranking a little too easy. Take off the air intake and the exhaust of you can, put an ear to either side and listen for the “hiss” as the piston comes up. A common problem is a piece of carbon lodged between the valve and valve seat. This is a common problem see in the Lister 6/1, and of course it can be seen more often in engines running a percentage of waste or poorer quality fuels. Simply put the engine on top dead center and tapp on top of the rocker arm directly over the valve stem. Every time I’ve been faced with is problem, I’ve had the engine running with a few taps. I try and find a piece of clean wood, but on one occasion it was a clean field rock that fit in my hand nicely.
I have a CD that has a PDF file on it that shows the typical pumps and how to take them apart and put them back together again. there are small parts in here, and a wise person will lay out an old sheet or similiar to work on. Remember, when you take a pump apart, you need work as if you were in a clean room.
All the best,