9-Series Carb Removal Without Affecting Sync?

Thanks!  I'll give that a shot!

Regards,

Craig

Craig E Maiman wrote:

Well, I am having an issue at start-up. Sometimes, when I crank it, it doesn't get above about 800rpm.  But, if you shut off the fuel pump when it's doing that, it will start, and then you can turn the fuel pump back on, and it's fine.

Dean says this is likely an issue with the float needle valve and I should do the float needle valve test in Section 73-00-10 of the heavy maintenance manual. I'm guessing that it probably just needs the cleaning of the 200 hr inspection.

Hi Craig -

If the carburettors are primed (have fuel) no further fuel is required to start and briefly run the engine, even in the absence of further fuel ie the boost/auxiliary pump should be off, when starting the engine.

A faulty float valve is likely to result in a flooded float chamber - symptoms may be; fuel exiting the breather tube, excessive smoke on start up, initial rough running, smell of fuel, nonstart.

In normal operation, the mechanical pump will supply sufficient fuel, for continued running, as soon as engine cranking commences - the boost pump should not be required for continued engine running (if it is you have a problem with fuel supply).

For the plugs to fire/spark & ignite the fuel, the engine will need a minimum of "225-250 engine rpm" (Roger Lee)

If your engine cold cranking speed is low you may have a weak battery - this could also explain why your engine starts, only when you turn of the boost pump.

In my training, all non essential electrical systems are off (including boost pump) before you press start, to minimise the energy demand on the battery (and to protect delicate system's)

I suggest that before going to a lot of trouble/expense, you review your first start of the day procedure:

Master on - all electrical systems off

Boost pump on - pump operating (OK)  fuel pressure acceptable (OK) - Pump off

Throttle - idle (do not open it even a little)

Choke - full on (not part way)

Ignition on both

Start - engine should start within about 3 revolutions. If not, stop & review procedure. Allow battery/start system to cool. If day is warm Choke off/reduce - try again.

Engine running - advance throttle (2200-2400 rpm) & gradually reduce choke (with practice you can do these two actions together)

Sean,

My plane is a low-wing and I think it requires a fuel pump to be running.  No pump running and the engine quits after a minute or so.  I don't think that is unexpected in my plane.

The battery is fine, so I don't think it's that.  When I do the 200hr inspection and cleaning of the carb, I suspect I'll find that cleaning the carb will fix my issue.

Craig - You have a fuel supply problem.

I have owned two 912ULS powerd, low wing, aircraft. Neither has required boost/auxiliary fuel pump to maintain fuel supply to the engine.

Your boost/auxiliary is there for emergencies (when main/mechanical pump fails in whole or part).

I only use my boost/aux on landing/take-off.

Hi Sean,

I’m pretty sure Craig is running a 914, no mechanical fuel pump hence the requirement for at least one electric fuel pump to be operational at all times.

Cheers.