I think I know the answer to this, but thought I would check with more experienced heads on this forum.

Getting some hands-on experience with diesel engines. My Bukh 10 HP was starting and running nicely, but was due a change to the oil and fuel filter, so I pumped out the old oil (engine and gearbox), replaced it with new (to the right grades), and replaced the fuel filter. There is an awkwardly placed fuel bleed screw that I loosened and tightened again when it drizzled some diesel fuel into the bilge.

Afterwards, the engine started up, but after about a minute, chugged to a slow halt. I went to the servo to get some more diesel, filled the tank, turned the bleed screw again, started it up and, after a couple of minutes it chugged to a halt again. After one or two more attempts, and a few revs, it got going and stayed going, running smoothly.

I think the problem was air bubbles in the fuel line. Turning it on and off a few times seemed to be enough to knock the bubbles through the engine, so that it was drawing fuel smoothly from the tank.

Is there a cleverer way to purge the air bubbles? I'm thinking of an air valve or some such on a high point in the fuel line. However, the tank is higher than the engine. Also, the fuel line also has a water separator between the tank and engine, so I will need to investigate that further.

A few of us have installed a bulb primer into the fuel line to purge air easier and save time. Works a treat in my yanmar. It does sound like air in the line and mine used to do exactly the same after a change.

Yes, sounds like air in the fuel Archie. I put a small electric primer pump on my boat, wonderful. Ramona gave
me the details if you want to go that way. Go on Search and look for Primer Bulb by Samsturdy, and look at Ramona's
comment towards the end of the thread. It works a treat.

I have a bulb primer as well but I also just crack the bleed screws when the engine is first fired up to get rid of any air.

I've been tempted, when I got sick of working the lift pump lever, to crack the bleeder, lift the decompressors, close the CW valve, pull the stop button, and then crank the motor till the bubbles stopped. I assume it would work pretty quickly. It would be pretty easy on the battery due to no compression.

Bit it might be a bad idea - I just can't see why - what did I miss?

Cheers, Graeme

UPDATE, the engine chugs along nicely now. It must have been air in the fuel pipes.