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O-360 Dies w/ Facet pump on Low power

Redbud40

Well Known Member
Soooo O- 360 , MA 4-5 carb ,dual p mags. Some time ago I was taxiing out and turned Facet electric pump on and realized the engine started to stumble and turned pump off. I only use pump when I notice low fuel press.
During a touch and go I had turned pump on for 0.5 press. I forgot to turn off once press came up and on the roll out waiting to stabilize the engine died. Rut Roh.

I remembered the situation of low power from before and turned pump off used a flooded engine start procedure ( mixture cutoff) and engine fired back up.

Next day I did some testing. Cold engine pump on 4.0 psi. Start procedure, engine won’t start. Turn pump off. Start procedure, engine starts. While engine running at idle , turn pump on, engine dies.... Flooded engine start procedure, engine starts. Run to 1000 RPM , pump on engine runs.

So, engine seems to flood at low power setting or no power ( starting) with the Facet pump on.

Engine/ Carb experts. What say you. Thanks
Red
 
I'm no expert, but the first thing I would check is the float and float valve in the carburetor. From your description, it sounds like the 4.0 psi is forcing too much fuel through the carb. The float valve should prevent that.

YMMV, as always.
 
I'm no expert, but the first thing I would check is the float and float valve in the carburetor. From your description, it sounds like the 4.0 psi is forcing too much fuel through the carb. The float valve should prevent that.

YMMV, as always.

Agree, time to get the carb overhauled. I recommend carb OH at least every 10 yrs.
 
Took carb to experts in Justin. Float and needle seat replaced and cleaned up. Put back on plane and still have the symptoms. Maybe I’m thinking a problem where there isn’t one? Operational you don’t use Facet boost pump except at higher power settings. However if you forget and leave it on ( like I did on roll out) the engine I don’t think should die because of too much fuel.
5.0 fuel pressure output on gauge with pump on, engine not running.
Experts ?.

One solution I heard. Just don’t turn on at low power settings.
 
Sounds like there is a problem with the carb, should be able to run the Facet continually without any impact on how the engine runs.
 
Anyone know of a Facet pump going bad on the high side? ie for some reason it starts putting out way more than 5 psi?
 
Anyone know of a Facet pump going bad on the high side? ie for some reason it starts putting out way more than 5 psi?

Yes, pumps can fail high and often do. My first step in addressing this is replacing that pump. Pump on=bad, pump off=good means replace the pump! In normal situations, it should be putting out about the same pressure as the mechanical pump. Assuming the mech pump is working well, a carb should not be an issue.

FYI, overfilling the bowl is just as often a failing float as it is a bad needle/seat. Hopefully your guy checkef for that while in there.

Larry
 
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If the electic pump is indeed overpowering the carb float/needle/seat then one easy test is to turn on the pump (engine off) and watch for fuel to overflow the carb. Should take no more than 30 seconds to see fuel coming out of a drain or airbox. If this happens, there's your sign.
 
5 PSI ?

Why isn't 5 PSI always 5 PSI ? If the float handles 5 PSI from mechanical pump and the Facet shows 5 when on, how is the Facet to blame ?

Not disagreeing with parts substitution to move forward, but 5 PSI is 5PSI.
 
Numerous times I have dealt with carbs that weren't right after overhaul, some requiring multiple trips back. You will have to take the carb back to the shop and have the float level checked. The best way is to actually do it on the airplane with a clear hose attached to the bowl fitting.
 
Sounds like it is running TOO rich.(see last par below). Is the pump really the issue? Or is there something internal to the carb. What is the fuel pressure?

Sorry my Rocket Surgeon and Brain Engineer hats are in the cleaners so I have no scientific wild A guesses.

Please let us know what you did to solve it. "The over power float" I don't fully get since that would close the main jet, unless you float is not "float-ee" any more, i.e., sinking. It may be some leak internally and the extra fuel pressure is enriching the mixture to the point of rough running.

You could be fouling the plugs due to a too rich condition (see last par.) and the boost pump at idle is just pushing you past that tipping point. The Carb should not change mixture to any significant degree with variation in fuel pressure within the limits of normal fuel pressure.

DO YOU AGGRESSIVELY LEAN FOR TAXI??? You should, we all should lean aggressively on the ground. No need to be full rich during taxi.
 
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Why isn't 5 PSI always 5 PSI ? If the float handles 5 PSI from mechanical pump and the Facet shows 5 when on, how is the Facet to blame ?

Not disagreeing with parts substitution to move forward, but 5 PSI is 5PSI.

agree. If the mech pump is working properly it is also putting out 4-5 PSI at low RPMs. Therefore, either the mech pump is underperforming and there is a carb problem only seen on the elec pump (due to the higher pressure differential) or the elec pump is putting out too much pressure and pushing past the needle / seat.

Larry
 
Update. Problem is not fuel related. It is electrical interaction with the p mags. I did the low rpm mag internal generator check on both mags. Recorded the numbers. Then did a similar check with power on the mags but turned the boost pump on the reduced power from a high power setting. Did this on both , L and R. The engine dies almost exactly the same RPM as the self generating Mag low RPM number. With both on it dies at the lower of the two numbers.

For some reason the boost pump on switch activation ( I believe ) is cutting power to the PMags , if I am below self generating power setting engine dies, if I’m above those numbers engine runs.

The fact it is the boost pump may completely coincidental. ( ie engine related). IOW whatever this problem is, it might be similar if it was say the landing light switch.

Good news I have a new carburetor, Bad news not sure where this abnormal could be coming from. 1st step going to check the connections on PMag power and ground , boost pump power and ground. After that ????
 
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