Re: 1990 Grand Villa 6V92
Reply #10 –
I have been following this thread, but haven't commented because I know nothing about the 6V92.
Having said that, from what you say above, it appears that you have fuel flowing from the tank, through both filters, and through the primer pump. But you still can't build pressure at the injection pump inlet port.
On my Cummins engine, in the exact same scenario, the only item remaining in the fuel system that would prevent building pressure at the injection pump would be the "overflow valve". This is a spring loaded pressure relief valve that is installed in the fuel return line where it exits the injection pump. This valve regulates fuel pressure in the "low pressure" section of fuel line between the lift pump and the injection pump. On my engine, that pressure should normally run about 20psi at idle. If it was to get stuck open, say by some trash in the valve or a broken spring, then on my engine the fuel pressure at the injection pump inlet would never build, no matter how much I pumped on the primer hand pump.
Fuel System Science Project
I don't know if the 6V92 fuel system works like the Cummins. I'm just mentioning this valve because Pierce said (in Reply #1): "Our relief valve also had a crack so was letting air in". I assume from this that the 6V92 has a similar valve somewhere in the fuel delivery system. You didn't say anything about checking this component on your engine, so I thought it might be worth looking at.