Fuel related issue on rear engine

[n86121]

The electrical one is fueling the engine, meaning the mechanical one is not.

Mine is turbo, so the fuel adjusts with both altitude and RPM.

My famous drain problem was fuel leaking past the inside of the fuel pump,
back UP the turbo/throttle pressure sense line that goes to throttle body,
into all the intakes.

All said, sounds like a dead mechanical fuel pump.
Prepare for a $1,000 or so OH.

[YankeeClipper]

Yeah, I figured that the rear pump was failed.

But why does the electric pump appear to flood the engine? Or at least it acts like it does--again, I have to turn it on and off with the just the right rhythm to keep the engine going. I would think that a fuel pressure regulator would take care of any excess pressure that the electric pump provides, so that I don't have to turn it back off to keep the engine running.

[wslade2]

I likewise had failed pump(s) issues. This is my learned understanding: there is an orifice (not a regulator per se) built into mechanical pump. In fact, after new engine pump installed, part of check out process is checking fuel pressure and adjusting orifice on it if necessary, with the bleed orifice being the "regulator" of fuel pressure. It appears the electric boost pump on high provides flow for 75% power (not idle) "blowing through" a failed engine driven pump via a bypass valve in the event of a failure. At idle, high boost electric pump is thus flooding the engine providing flow for 75% power (bypassing the "regulating orifice") rather than only providing the fraction of that fuel flow necessary sitting on the ground.

check this out:

http://www.kellyaerospace.com/articl...inuousFlow.pdf

[YankeeClipper]

Thanks for that. Lot's of information in there. I notice however that it does show a separate fuel pressure regulator, but it doesn't say this applies in its entirety to the 360.

With regard to the situation that made me wonder about all of this:

Since posting, my IA says that persistence has gotten him to the point where "something worked itself out" and the engine runs fine, but idles a bit rough. I've long since conclude that nothing works itself out in cars, computers, or relationships--and I'm inclined to carry that mindset forward into aviation. Off the pump goes to QAA for replacement/overhaul.

[frank.oconnor19]

Have you contacted Continental? I have found that their technicians can really help.

[YankeeClipper]

Was not aware they were able to offer help. We're pretty confident that rear pump is not trustworthy at this point, so we're sending it out regardless. But no guarantee that all will go well after replacement, so I'll definitely keep that in mind.

Thanks for the tip.

[wslade2]

you might find this AvWeb article interesting (this is focused on the 360 engine whereas the prior takes in all manner of injected continentals):


https://www.avweb.com/ownership/cont...uel-injection/