[fullkeel7]

Barry,

I've had on two different occasions, very similar symptoms you discribe, on two different boats. If I understand correctly, you found that you have no evidence of air at the main fuel filter (after bleeding)and when the system is free of air, the injector pump does it's job well. At least until air is again injected into the system. So...it sounds as if air is being introduced somewhere between the main filter and before or at the intake of the injector pump.

I think if the fuel lines are as old as you say, new ones are not a bad decision. While waiting for their arrival, I would break out the wrenches and check all line fittings between the main filter to, and including the inlet line fitting of the injector pump. It doesn't take much for air to be introduced into these fittings, so a physical check is needed to insure proper torque. If you find any of these fittings even slightly loose, back off the torque and retighten. This usually will insure any debris or maybe a small burr will be eliminated and no air can bypass. An old aircraft high pressure line trick.

After that procedure and if the same symptoms still ocur, another problem I've found, is the bleed pump. With age, sometimes the diaphram inside will develope a small pinhole and introduce air into the system. A good check is to get the air out as you have done, shut the engine down and check for good resistance when operating the bleed pump. If little resistance is felt, you may very well have a bad pump. Another easy way to find out is to pump this finger torturing device for about 30 seconds (quick pumps) and then try to start the engine. If the pump has a hole in the diaphram, the engine will start and then die in a few seconds.

The loose fitting scenario was a Yanmar 30gmf and the latter was a Perkins 4-108. Different engines, same principles and probably worth a try. Hope this helps and good luck.

Bob