The fuel won’t get pumped up
I have a Nanni Diesel 4.150HE engine that has a small pump on the side with a hand lever for priming. I have pumped the lever several hundred times over the course of an hour without any fuel arriving at the main filter. I don’t fill the pre-filter (water separator) with fuel before fitting as the fuel would leak out the bottom before the bowl is tightened. I also don’t fill the main fuel filter because I prefer to have clean fuel filling it via the pre-filter. However, I was tempted to fill it with the fuel from the old filter to cut down the number of times I’m pumping away on the priming lever. Can you help?
QThere’s one position in every two engine revs that will render a mechanical liftpump all-but inoperative. Engines tend to stop in only one or two positions, so if yours is stopping in that position, operating the priming lever won’t deliver much fuel. You can tell if this is the case because the lever will operate with very little resistance.
First, try turning the engine over one complete
Aturn and re-trying the lever with a bleed screw open. Also, pumping like fury will have little effect, it requires long slow strokes.
If that’s not the problem then either air is leaking in between the tank and liftpump or the pump is faulty. Turn the fuel tap off and disconnect the fuel pump outlet. Spin the engine on the starter while catching the fuel delivered. You should get at least half an egg cup per ‘squirt’. If it is less, then either the pump is faulty or there is a blockage between the tank and pump. Try blowing back down the pipe into the tank.
Next disconnect the inlet pipe on the pump and put your finger over the inlet. Spin the engine on the starter for a few revolutions. Pause 30 seconds and take your finger off. The pump should have held a vacuum. Do the same for the outlet but this time it should have held pressure. If it fails on either count, the liftpump is faulty. It might be cheaper to leave the faulty pump in place and fit an electrical liftpump fed from the ignition switch. Facit is one readily available make.
If the fuel pump is okay, look for air leaks. The Beta version of your engine is self-bleeding, so if you combine a small suction from the elements in the injector pump with the fuel head in the tank, the engine might bleed sufficient air back into the tank to allow it to run.
Don’t fill the new filters with fuel from the old filter, but it will help the bleeding immensely if you do fill it. Buy a small amount of fuel from a filling station.