Dukes Fuel Pump Drip

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Steve
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Re: Dukes Fuel Pump Drip

Post by Steve »

I agree with Keith - based on the symptoms you report and the steps you have taken so far, it sounds like an ignition problem to me. FWIW...

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RMarkSampson
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Re: Dukes Fuel Pump Drip

Post by RMarkSampson »

Six months ago, I went through a period of hard starts. Went through all the usual suspects of fuel and spark - no joy. Turned out to be the Magnetos. Six months before I had them serviced IRAN (inspect, replace as necessary) - so it was the last thing I thought would be causing problems starting. Especially since once started the engine ran fine.

However the problems was definitely the Magnetos - they essentially filled with oil. When I removed them from the plane - the one was dripping oil out of the front end (the one that hooked up to the shower of sparks). The mag shop could not validate a magneto problem and did not admit to forgetting any gaskets or seals. They did clean them up for free - so I was happy with them standing behind their work. Anyway besides seals not working right, the other possibility of getting oil in the mags is from "positive crankcase pressure" - i.e. when the breather tube does not vent properly. If the air-oil separator is slow to drain, it could potentially fill up with oil and cause the engine crankcase pressure to rise.
So before starting the engine with the cleaned up mags, I removed the air-oil separator and dunked into cleaning solvent. My air-oil separator is a sealed unit so I could not see inside, but after the solvent bath it was definitely free from any blockage.

Bottom line - cleaning the oil out of the mags and cleaning the air-oil separator cured my hard starting problems - she now cranks up without issue.
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Re: Dukes Fuel Pump Drip

Post by thefoxx »

Thanks for the reply - thats all good information! I'll mention that to my shop regarding cleaning out the air/oil separator as a precaution.

Well, we just sent the mags away for the 500hr check/rebuild (whatever they do) in an effort to eliminate that as a cause as well.

Once the replaced mags were installed, the engine fired up right away and ran just great - immediate restarts after run up performed great as well with no hesitation! We thought mystery was solved! We were all pretty happy, but then the next morning (yesterday) after it sat overnight - I try to start, and nothing. Just cranking, cranking, cranking - trying every combination I could think of (flooded starts, normal starts) and didn't even get a pop. This is the mystery - after it sits overnight, is when it seems to regress into non-starting. Keep in mind, before the fuel pump was replaced due to dripping, I never encountered hard starts at all. The only thing we did was replace the fuel pump with the rebuilt Aeromotors, and these problems have cropped up.

RMarkSampson: What is the sound of your electric pump? I know it's real tough to describe a sound, but on high speed, it sounds almost like a sump pump that is running out of water and sucking air (gurgle-ating!) Is this the normal sound? It is definitely a different sound than the Dukes pump.

Some little gremlin is bouncing around in that engine compartment - we just have to capture it!
RMarkSampson wrote:Six months ago, I went through a period of hard starts. Went through all the usual suspects of fuel and spark - no joy. Turned out to be the Magnetos. Six months before I had them serviced IRAN (inspect, replace as necessary) - so it was the last thing I thought would be causing problems starting. Especially since once started the engine ran fine.

However the problems was definitely the Magnetos - they essentially filled with oil. When I removed them from the plane - the one was dripping oil out of the front end (the one that hooked up to the shower of sparks). The mag shop could not validate a magneto problem and did not admit to forgetting any gaskets or seals. They did clean them up for free - so I was happy with them standing behind their work. Anyway besides seals not working right, the other possibility of getting oil in the mags is from "positive crankcase pressure" - i.e. when the breather tube does not vent properly. If the air-oil separator is slow to drain, it could potentially fill up with oil and cause the engine crankcase pressure to rise.
So before starting the engine with the cleaned up mags, I removed the air-oil separator and dunked into cleaning solvent. My air-oil separator is a sealed unit so I could not see inside, but after the solvent bath it was definitely free from any blockage.

Bottom line - cleaning the oil out of the mags and cleaning the air-oil separator cured my hard starting problems - she now cranks up without issue.
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Re: Dukes Fuel Pump Drip

Post by RMarkSampson »

I can definitely hear the electric Dukes pump on low and high. Not sure how to describe the sound. I have an EDM-900 engine monitor and I would just cite that the fuel pressure gauge shows a solid ~3 PSI on its low setting. Not sure about the high setting as I never really paid attention to that during the short amount of fuel priming I do.

During my Duke's pump problem, my A&P and I checked to see if it was pushing fuel. We unhooked the fuel lines at each injector, put a Ziploc bag around each line and confirmed it was pushing fuel. Might want to do that one at a time vice all four together.
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