fuel pressure

Gang, I could use a little help here.

I believe a buddy's engine driven fuel pump is failing and causing fuel pressure to fluctuate.

Why would it be worse at peak EGT vice well rich of peak EGT? And be worse means variable sound, feel, indicate, RPM change, etc. Frequency is about 2Hz.

BTW, this is on a Continental IO-520 in a Viking and turning on the electrically driven fuel pump to high-flow smooths everything out.

Thanks!

-Jim

Possible Vapor Issue

More than likely it?s not a pump failure, but a vapor problem on the inlet side of the pump. Fuel is a good heat sink, so the higher flow cools the pump thus keeps the vapor from forming on the inlet of the pump.

You need to check for pressure drop on the inlet of the pump; clogged filters, leaking shaft seals on boost pump, clogged vents, or leaking fuel caps on wings. A quick monitor of the temp on the pump is useful to determining if you have a problem. Avgas boils at around 130 F at sea level. The higher you go the lower temp the fuel boils at.

I'm no Continental FI expert, but on the Continental FI system the pump is the metering device, so if the engine runs OK at high power with the boost pump off, then I would be looking at other causes than the engine pump.

Don

Thanks Don, appreciate it. -Jim