Only hitting on 5 or 6 cyls after sitting long time. Change IP?

[914turboford]

I just fired a motor that has been sitting for a few years. It is a 6.2 (DB2 mechanical pump) with 6.5 injectors, turbo and serpentine setup. I think it is only firing on 5 or 6 cyls. There is no fuel coming out of the driver's side front injector when the line is cracked open while running. I'm assuming that is the case on the turbo side as well, but I've only checked the one that is easy to get to. Should I run the engine for a while and hope that the IP starts to pump fuel to all the inectors? Or, should I just change the IP?
Brian

[DmaxMaverick]

It's probably air-locked on a couple cylinders. If a part has failed, it's more likely injector(s) than the pump. The pump is pretty predictable. If it pumps to one injector, it will pump to all. Over time, injectors can bleed down, which replaces the fuel in the system with air. If you aren't running the engine under load (higher fuel rate), it can take a lot of running to clear it up. If the lift pump and supply system isn't healthy (leak free with no obstructions), it may never clear up until it is.

[914turboford]

It's probably air-locked on a couple cylinders. If a part has failed, it's more likely injector(s) than the pump. The pump is pretty predictable. If it pumps to one injector, it will pump to all. Over time, injectors can bleed down, which replaces the fuel in the system with air. If you aren't running the engine under load (higher fuel rate), it can take a lot of running to clear it up. If the lift pump and supply system isn't healthy (leak free with no obstructions), it may never clear up until it is.

The electric 6.5 lift pump seems to be working very well. I ran it with the air bleed on the filter open and it made quite a fountain. Would you elaborate on


If it pumps to one injector, it will pump to all.?

Is there only one piston or something? I've ran it for about a minute with that one injector fitting cracked and no fuel came out.

Also, what would air locked mean? Air in the IP or air in the injector lines?

[DmaxMaverick]

The high pressure pistons in the pump are shared by all cylinders, according to the pump rotor timing (it's an axial pump). Unlike an inline pump, which has individual pistons for each cylinder. DS4/DB2: S=electronic; B=mechanical; #=piston numbers. There is also a DB4 marine pump.

If it's been sitting for a long time, some of the injectors could be sticky, or stuck. It takes time, heat cycles and fuel to free them up. If an injector is stuck, it may not pass fuel well, or well enough. Relatively, the fuel injector lines are quite large, compared to the volume of fuel that gets pushed through them. If a line is dry, it can take quite some time to fill it up. As long as there is an air space in the line(s), the injector won't pop (or pop properly), and will delay (retard) injector event when it does. Fuel injector cleaning additives can help speed the process.

In any case, fuel should start to flow from all the injectors after some running. It may still miss for a while, and this could be due to other reasons, too. Stuck valves or rings will reduce cylinder compression, often to the point the fuel won't combust.