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Engine quit on takeoff roll


81X

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Hi gang.  On takeoff tonight after about 500 feet of ground roll, the airplane was making 36-37 inches MP and the engine just quit.  It felt like a mixture pull kind of wind down and not a abrupt mag-off type power down.  I Rolled off onto a taxiway and was able to get the airplane restarted without a ton of issue.  Pre-takeoff runup was normal, tanks weren't switched at all and tanks were sumped before flight.  The engine powered up and ran OK with a couple of full power runups.  I didn't fly it but after opening up the cowling, no smoking guns.  Any thoughts?   Fuel pump?  vapor lock (90F today and a 7 minute ground run)?  Gascolater/strainer?  I'm planning to take it in to the shop but would like to see if anyone has any must-check items.  M20k 231.  Sure glad it wasn't 10-60 seconds later!  

 

 

Edited by 81X
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I had exactly the same experience. Suspecting water in the tanks I drained the tanks on the taxiway and found no water. Decided to remove the drain valve and plenty of water drained down. What happens is that when the drain holes on the valve adapter plate get clogged the drain valve then drains from the top of the stem leaving water below. But when the plane accelerates this water is displaced toward the tank fuel pick up getting it sucked by the engine. You can clean the drain holes on the valve adapter plate or switch to the F391-72 drain valve as I did. The F391-72 has the drain holes just above the adapter plate, so it will not get clogged by debris on the bottom of the tank. It is the same valve used on the long range tanks. Also drain the gascolator for possible accumulated water. After replacing the drain valves never had the problem after 33 years. The drain holes on the adapter plate get clogged with old sealant peeling off, resealing oversight or fuel residue. 

José

Edited by Piloto
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81X,

Got any JPI data to share?

Something might be exposed there...

Have you been outside in the rain lately?  How old are your fuel cap seals?  Have they been inspected lately... two orings per cap... one small hidden one that is often forgotten ignored...

Loose wires on the ignition switch...?  Probably requires two bad wires for both magnetos...

How old are the mags?  Any OH history?

Blocked airflow to the engine?

Think in terms of....

  • Air
  • fuel
  • ignition

What got in the way of their delivery?

Then closer details like...

  • mixture
  • mags
  • Sparkplugs
  • Airfilter
  • fuelfilters and screens
  • blocked air vent to the fuel tanks...
  • turbo, hoses, controller...

The acceleration and water moving back toward the fuel pick-up is a strong possibility.  Try to capture what is in the tank looking for water...  don’t be in a rush to let it out on the ground without identifying that it is what was in there...

PP thoughts only. not a mechanic...

Best regards,

-a-

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I’m no expert, but why would you ever install the wrong drain valve which has its holes higher than designed?  You want your tanks to hold more water and debris?

I think you’re suffering from WD40 poisoning?

Clarence

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4 hours ago, M20Doc said:

I’m no expert, but why would you ever install the wrong drain valve which has its holes higher than designed?  You want your tanks to hold more water and debris?

I think you’re suffering from WD40 poisoning?

Clarence

Well, Jose’ states he hasn’t had an issue in 33 years and it’s the same valve used in the lr tanks. And he knows a thing or two about wet tanks!

Can his data points be considered valuable? Although empirically derived do they offer discrete information? I’m not an expert, just curious.

In any case I can see water may accumulate over time if tanks aren’t sampled or gascolator isn’t cleared but I certainly don’t think there should be any other “debris” in the tanks. 

I’m ready for a lesson: how do we clean these vlaves? I’ve never done it. I do carry a spare in the plane just in case one decides to get stuck open somewhere!

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Jose- I didn't even think of water as a possibility since I sumped and pulled the drain ring.  The way the engine smoothly lost power and shut down without spitting and sputtering feels like a strong contender for water.  Great point on how the water can collect with those plugs when there's crud in the bottom.  Did you remove the drain valves with the tanks full-ish or did you drain them down first?  

Carusoam- I'm headed back out tonight to download the 830 data.   After I restarted, nothing appeared out of the ordinary with ground ops CHT/EGT's but obviously wasn't in the best analytical state of mind.  

FWIW, I did wash the airplane about two weeks ago, but I've flown it for about 40 minutes on each tank since then, but I can't recall if I took off on the right tank for either flight.  It's been hangared before and after so the only water that could get in would be condensation and that washing water.  

 

 

Edited by 81X
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If you have not replaced both the inner and outer O-ring on both caps in the last year I would definitely do so.  I had neglected the new O-ring and was getting water when I washed or if left outside at a destination and it rained.  I went ahead and bought 10 inner and 10 outer which will do me 5 years.  

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3 minutes ago, Bartman said:

If you have not replaced both the inner and outer O-ring on both caps in the last year I would definitely do so.  I had neglected the new O-ring and was getting water when I washed or if left outside at a destination and it rained.  I went ahead and bought 10 inner and 10 outer which will do me 5 years.  

I think I recall some new material ones for sale in the Parts area of MS , were supposed to last longer than the stock ones

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Leakage through the cap is an issue.  The cap sits in a well so that when installed it is flush with the wing surface.  Water collects in the well when it rains, just looking for a chance to get into the tank.  If one of the O-rings is bad, that’s all it takes.  But there are lots of other possibilities.  Failing fuel pump?  Did you switch tanks right before takeoffs and perhaps not get the switch fully into a detent position? Failure in the spider?  Failure of the throttle linkage?

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Here's some graphical food for thought.  The top two graphs below aren't in sync, but all of the peaks and dropoffs coincide, although the RPM appears to drop off 1-2 seconds before anything else which makes sense to me  Nothing out of the ordinary for EGT's.  Unfortunately I don't have fuel flow on the 830.  

 

I also loosened the sump drains and *unfortunately* no water came out of either tank.  Anybody suspect the engine driven fuel pump?  After reading a little more about the spider, it seems that low fuel pressure could have caused the spider to shut off the fuel flow.  Thoughts on this?  

I didn't switch tanks before takeoff this time, and ironically I normally do this, but the R tank was the fullest, so that's where it stayed for start, runup and attempted takeoff; it was definitely in the detent.  Subsequent full power runups and taxi seemed normal but with low-ish oil pressure (oil was getting hot) and throttle action was normal.  

 

 

 

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On the topic of fuel pumps...

The K has two...

  • electrical
  • mechanical

Both should be on for Take-off.  Depending on which engine set-up you have...  the electric pump operation may be automated.

PP thoughts only. Not a mechanic...

Best regards,

-a-

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Anything noticeable regarding the turbo?

any oil coming out the exhaust pipe, hose come disconnected from the intake, or maintenance done on the control system?

A sudden turbo failure would drop the MP from the usual mid 30s down to the NA High 20s.

Briefly, The fuel ratio may be un burnable....

I expect that you may want to take a closer look at turbo health issues as well...

PP thoughts only. Not a mechanic...

Best regards,

-a-

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11 hours ago, 81X said:

Jose- I didn't even think of water as a possibility since I sumped and pulled the drain ring.  The way the engine smoothly lost power and shut down without spitting and sputtering feels like a strong contender for water.  Great point on how the water can collect with those plugs when there's crud in the bottom.  Did you remove the drain valves with the tanks full-ish or did you drain them down first?  

Carusoam- I'm headed back out tonight to download the 830 data.   After I restarted, nothing appeared out of the ordinary with ground ops CHT/EGT's but obviously wasn't in the best analytical state of mind.  

FWIW, I did wash the airplane about two weeks ago, but I've flown it for about 40 minutes on each tank since then, but I can't recall if I took off on the right tank for either flight.  It's been hangared before and after so the only water that could get in would be condensation and that washing water.  

 

 

I removed the drain valves with the tanks full after taxing off the runway with the momentum to the taxiway. There was no engine sputtering and fuel pressure was normal. If you are parking your plane outside I would recommend that occasionally remove the drain valve and check for water if using the F391-53S drain valve. No need to remove it for F391-72 drain valve.

José

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Some more color on this issue- I performed about 12 high speed taxis.  Issue reproduced the first couple of taxis.  Third time around, the engine stayed alive but was surging from 38"mp to about 33, and it seemed to need more throttle than usual.  Fourth time around and now we're getting somewhere, I ran the high speed with the low boost on.  fuel flow seemed a little low but the surging was gone.  it seemed to almost hold 36 as per normal.  

Throughout all of this, the fuel flow seemed too low- about 18-19GPH whereas it's normally about 23 GPH at 36".  

So, I suspect it's the mechanical pump is going (or has gone) bad.  It's going in to the shop tomorrow to find out for sure, I'll report back to hopefully help someone out in the future.  

Related, who runs their M20K's with the low boost on for TO and landing?  The POH says not to, but this experience gives me pause during those critical phases of flight.  

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No, the electric pump should be off during the takeoff.  I have a line in my checklist to make sure it is.  I have not tried it, but likely it would make the mixture very rich.

The OPs problem looks like a fuel starvation event, whatever the cause was.  Possible something went in the turbo to drop the MP, but it looks more like the engine was dying and therefore no exhaust to operate the turbo.

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Great additional details 81X!

do you have a mechanical background to go with that?

Fortunately the problem isn't intermittant...

You have FF data from experience.  You can also get FF settings from the right documents... TCDS?

Point your mechanic in that direction quickly to find out what is causing the low FF...

Review your entire thread with them... all pertinent info...

Also for the electric FP... See if the pump is supposed to come on automatically... the Continental IO550 has a FT switch that activates the electric pump...  flipping another switch may change something regarding flow...

I believe The IO550 operates the electric pump at Hi boost.  Enough to supply full fuel even without the mechanical pump... this is a design criteria that prevents what you are seeing if the mechanical pump has failed...

Even in my old M20C... FP on for T/O solely because mechanical pumps fail...

Also Check and see if you can see anything funny going on around the mechanical FP... drive parts worn or leaks...

PP thoughts only, not a mechanic...

Best regards,

-a-

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Good afternoon, Paul! :)

 

Not even automatic electric pump back-up, Paul?

(To me) There is something funny about not having an electric pump as the back-up...

The diaphragms just are not robust enough...

Best regards,

-a-

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Thanks :-) it is afternoon on this side of the planet. 

See now you've got me wondering. There probably is some automatic backup at work here otherwise you'd expect to have the boost pump on the checklist.  When I get back to the same hemisphere as my Mooney and it's POH, I'll see what it says.

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Fuel pumps on TCM engines installed in Mooney airframes are rotary vane type, fuel pumps on most Lycoming engines are diaphragm type, a few Lycomings use rotary vane pumps.

If the airframe boost pump regulator is set up correctly, turning the pump on to the “low” setting should have no effect on engine idle mixture as long as the engine fuel system is also set correctly per SID97-3G and the airframe maintenance manual.

Clarence

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