flying on the fuel boost pump

[231LV]

OK...this am, I jumped in the plane to run over to my A&P (30 minute flight) to have him do a quick check of all lines for age/date stamp evaluation and replacement, if necessary. The engine grumbles and struggles to start...then starts but struggles to stay running...hmmm. Boost pump on and the engine smooths out...boost pump off, and the engine stumbles and dies. Fuel pressure drops to zero with the boost off. Pretty clear, my mechanical fuel pump has crapped out. I call my A&P to request an new pump be ordered which he agrees to do. My question to the group: do I risk flying the plane to the mechanic on the boost pump alone to replace the mechanical fuel pump or do I require him to drive to me with his tools (compensating him expenses, of course). I already know what I will do but wanted to get a sense from other Mooney drivers what they would do...

[Danb]

NOOOO

[epsalant]

Pay the money. I don't see any way around it. I really wanted once to fly with one mag to get the other one fixed. It's REALLY tempting, but it would be a REALLY dumb way to crash.

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[N6758N]

Borrow a friends plane and go pick the mechanic up!

[kortopates]

Seriously???
As for what others would do - I would hope most Mooney pilots would have reviewed their POH and realized that only Emergency procedures call for usage of the Boost pump and that even the High Boost pump is incapable of providing enough fuel to make full power.

Perhaps it would help if ever in a situation where you're wondering if it might be okay to push the limits is to just think how the newspaper headline will read if things don't go well and what all your peers will say or be thinking when the accident report comes out.


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[peevee]

Among other concerns don't risk your engine. What if it runs lean and detonates and damages it?

[231LV]

Yea....my answer, as well

[Bryan]

Could be fuel injector(s) clogged.  Saw a video recently of a Cirrus owner that stumbled upon the same issue while in-flight (only run smooth with fuel pump) and come to find out an injector on #6 cylinder was clogged.  A/P cleaned it out, re-installed, and engine ran like a top.

[OR75]

probably illegal to go with the boost pump

 

[ArtVandelay]

Could be fuel injector(s) clogged.  Saw a video recently of a Cirrus owner that stumbled upon the same issue while in-flight (only run smooth with fuel pump) and come to find out an injector on #6 cylinder was clogged.  A/P cleaned it out, re-installed, and engine ran like a top.

A six cylinder engine should run on 5 cylinders, it will be a bit rough but it should run. My 4 cylinder Lycoming has run on 3 and 2 cylinders, with just 2 I had to keep RPMs up to 1500 or it would die, but it ran smoother than when on 3.

[N201MKTurbo]

I have had this happen before after maintenance. It wasn't the fuel pump. Don't assume anything.

In my case it was a loose fuel line between boost pump and the mechanical pump. It was allowing air to be sucked into the fuel line so it couldn't suck any fuel. Turning on the boost pump pushes fuel past the leak (and some out the leak) to the mechanical fuel pump.

So what can go wrong with a mechanical fuel pump.

Broken spring would cause your problem with no other symptoms. So would the lift rod. If the diaphragm completely ruptured it would do it but you would get fuel running out the vent line with the boost pump running.

The first thing I would do is set the mixture to cutoff and the throttle to idle. Turn on the boost pump and look around the engine and boost pump for fuel leaking.

 

OOPS, I see you have a 231. Less failure modes on your fuel pump. Everything else still applies.

Edited April 6, 2017 by N201MKTurbo

[carusoam]

The biggest part of the challenge is...

1) you don't KNOW what the problem is.  You will be paying a mechanic to tell you.

2) it seems to be the pump, but could be a leaky line.

3) how long does it leak before it falls off, or leaks too much?

4) flying with an unknown mechanical issue is bad. If it happens in the air, land.  If it happens on the ground, seek help.

5) fuel pumps have some interesting ways of failing based on their design.  They have two diaphragms.  When one goes bad, it leaks fuel out the drain...while still operating....

6) planes don't come with a light on the instrument panel that says service engine soon. If they did, it would say service engine now.

7) if you take a plane with an unknown condition into the air, you can expect that it may fail at anytime. Resulting in an immediate off airport landing.  Or in five minutes, or in an hour...

8) problems with fuel systems can add the extra special side event.  Fire in the cowl mixed with an engine out.

9) If you can't tell what is wrong, seek professional help.

10) If this is related to the previous maintenance work.  Call and talk to the mechanic that did the work.  There is a good chance he knows what needs to be done and has the tools to do it.

11) do you know if your electric fuel pump is rated for continuous use? Some have limitations.

PP thoughts only, not a mechanic...

Best regards,

-a-

Edited April 6, 2017 by carusoam

[201er]

I'm very happy to have read this. Lots of things said that haven't crossed my mind.

But it still leaves me wondering, is it risky or is it impossible to make this flight? When it comes to flight on one mag, it would certainly be risky and certainly undesirable to do but in a dire situation I think it can be done. What is the physical case when it comes to the fuel pump? Not opinion if it's a good decision or not but just if it can be done?

[carusoam]

Mike,

1) if your fuel pressure is good.

2) if your fuel flow is good.

3) your engine won't know where the flow and pressure came from.  It just knows it is getting fuel properly.

4) this can all be good on the ground. But won't be so accurate with a change of attitude.  Really important If you fly an M20C.  Very low FP to work with.

5) We can probably simplify it and call you a test pilot.  Because that is what you would be doing. There isn't a procedure that says this is OK.

6) when you look back on it, you will probably say that wasn't a good idea.

7) just because you can, doesn't mean you should.  Because my mom said so... 

8) what will be the effect of mixture control, will it work? Or does the restriction overload the single pump.

9) Some Mooney's require two pumps operating for T/O.  Doing it on one pump probably doesn't provide the designed max FF.  In this case CHTs are going to get pretty hot.

 

other goofy things like this come to mind...

1) departing on one mag. Side effect: valve burning, exhaust system burning... not enough power to climb

2) departing without rpm control. Side effect: it is very easy to overspeed the engine. Controlling rpm using the throttle will not produce full power.

3) departing with a bad plug.  Side effect: arcing in the mag

These are indications you are already having a bad day.  Experimenting with these kind of ideas is better when you are single. And definitely better before having kids. It can get worse.

This stuff is bad enough when it occurs in flight.  It makes less sense to do this without at least consulting somebody that knows. This way you can confirm what the problem is. And see what else may be wrong.  Fuel leak, oil leak, exhaust leak...Things that come to mind.

withoutout know what is wrong. You would be unknowing of how bad it can really be.

Private Pilot ideas only. Not recommending flying when something is not in AW condition. The risk of damaging things is too high.

Always consider what is off the end of the runway. Like wide open fields or city streets and houses.

Hows that?

Best regards,

-a-

Edited April 7, 2017 by carusoam

[thinwing]

9 hours ago, 231LV said:

OK...this am, I jumped in the plane to run over to my A&P (30 minute flight) to have him do a quick check of all lines for age/date stamp evaluation and replacement, if necessary. The engine grumbles and struggles to start...then starts but struggles to stay running...hmmm. Boost pump on and the engine smooths out...boost pump off, and the engine stumbles and dies. Fuel pressure drops to zero with the boost off. Pretty clear, my mechanical fuel pump has crapped out. I call my A&P to request an new pump be ordered which he agrees to do. My question to the group: do I risk flying the plane to the mechanic on the boost pump alone to replace the mechanical fuel pump or do I require him to drive to me with his tools (compensating him expenses, of course). I already know what I will do but wanted to get a sense from other Mooney drivers what they would do...

I couldn't think of a worse place to have an engine failure ,low power event than taking off from Sedona AZ...is that we're your based?Even posing this question with a known difficiency like a fuel pump issue tells me you are not longed for this earth!

[epsalant]

I couldn't think of a worse place to have an engine failure ,low power event than taking off from Sedona AZ...is that we're your based?Even posing this question with a known difficiency like a fuel pump issue tells me you are not longed for this earth!

I respectfully disagee. I think there are a lot of good reasons for posting questions, even when the answer is "obvious". I would not criticize the poster. I have learned a lot from this discussion. Initially my answer was going to be that it would be perfectly safe to taxi this airplane but in no way would I take off. After reading some of the very insightful answers, I'm not even certain that I would taxi with this condition. I appreciate the question and the answers. They may help me next time I have a questionable condition discovered on the ground (e.g. inop landing light).

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[jlunseth]

I am sorry to do this, but now that you have put the pre-flight condition of the aircraft on a public website there is no way you can make that flight without a ferry permit.  The aircraft is not airworthy and there is a very public record of it.  Even if you make the flight successfully (without a permit), the chances are pretty good that someone is watching this thread, and all that is needed now, for an enforcement proceeding, is for there to be evidence that the aircraft went into the air.  I would not try to fly it nor recommend to anyone that they should, but that said, people do try to get away with things under the radar.  This is not under the radar at all.  Besides, we generally like each other on this forum and we have actually lost people from the forum to in-air accidents.  We would just as soon not lose another please.

I also have a 231.  I have had to replace the boost pump so they do fail.  And there is only one, despite a "high" and "low" setting, those are only settings for the one pump.  You have no backup.

[mike_elliott]

19 hours ago, 231LV said:

OK...this am, I jumped in the plane to run over to my A&P (30 minute flight) to have him do a quick check of all lines for age/date stamp evaluation and replacement, if necessary. The engine grumbles and struggles to start...then starts but struggles to stay running...hmmm. Boost pump on and the engine smooths out...boost pump off, and the engine stumbles and dies. Fuel pressure drops to zero with the boost off. Pretty clear, my mechanical fuel pump has crapped out. I call my A&P to request an new pump be ordered which he agrees to do. My question to the group: do I risk flying the plane to the mechanic on the boost pump alone to replace the mechanical fuel pump or do I require him to drive to me with his tools (compensating him expenses, of course). I already know what I will do but wanted to get a sense from other Mooney drivers what they would do...

Wow,.,,which is cheaper? Paying the MX to come to you or an ambulance ride and a month or 2 in the hospital? Is it cheap to buy a burial plot in Sedona now days? Always ask yourself "What is the worst that can happen?"

[Danb]

these type of threads are of good use, It's a good learning tool, not whether to fly but the mechanical issues if one did. Being a mechanical incompetent I learn a great deal reading many of the threads  on the forum. It is a lot better than the one's where we lose a pilot.

[epsalant]

Would a 201 fly on the boost pump alone? It is my understanding that some aircraft, e.g. the Cirrus SR22, have a boost pump only to prevent vapor lock. But they will not supply sufficient fuel to maintain level flight.

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[231LV]

As the OP, I already said what I planned to do but wanted to hear thoughts from others....I appreciate ALL the thoughts and opinions expressed. I have 1300 hours in this airplane. As soon as I realized I had a fuel pump failure, I knew the airplane was grounded, unairworthy, unable to fly. There was NO WAY I was going to make any flight and I am fully prepared to bring my mechanic to me.....for those who think I would have made such a flight, thanks for your gentle "corrections" and concerns. I appreciate that there are people willing to say what needs to be said, irregardless of hurt feelings....this forum is great for gathering information and opinions. Maybe, a lower time pilot reading these posts would have considered a flight in similar circumstances and is now all the wiser. If so, it is worth putting this out there!!

[thinwing]

Ok,I am glad to hear you have accumulated 1300 hrs of experience in your 231... that certainly speaks to some maturity and ability.But your last paragraph poses a very foolish question,and in a forum  we don't know what you are actually thinking...so some really experienced pilots such as Kortopates,jlunseth,mike Elliott and myself naturally reacted and answered in a very direct way that this action shouldn't even be considered!My concern was some lower experience pilots reading this forum would have a mechanical issue somewhere very inconvenient (like a lonely gravel strip Baja,north west territory or AK)and actually consider a takeoff when things got unpleasant cause they couldn't call for help or didn't have food or water.Last year we had a speaker at our Sherriff Squadron meeting who survived a 172 crash in very remote mountains southern Idaho.The pilot was a nonistrument rated flying his wife and daughter for a reunion from Lodi calif to mountain home ID.The pilot was a senior fire fighter in my town and used to making life and death decisions,but the flight starts out badly with a dead battery..weather forecasts were for deterating conditions with high winds and mountain obscuration,and due to the battery issue they launched late and barely made Susanville scudrunning.After refueling and waiting 3 more hours for the weather to clear they discover the battery again wouldn't hold charge...but a friendly fbo guy handprops them and off they go again.They are forced to scudrun but they put down on a very lonely strip at sod house nv .This very level headed guy now has to listen to his daughter whine a bit about no place to sleep,get warm and gee we are only 120 miles from our destination.He also worried about his battery condition...how long will it hold charge...he sees a big glory hole in the direction of mountain home and launchs again...this time ,though he's not so lucky and impacts a ridge near silver city ID.They survive and due to a ringing cell phone back in the tail of the Cessna are able to get a call out to local sheriffs dept 40 miles away.In the hospital ,everybody is praising his great airmanship in putting down successfully,but no he is honest in saying I almost killed my family,I had so many chances to abort this flight but refused to believe mechanical issues could screw a trip up I had planned for weeks!

[Piloto]

Electric fuel pumps wear with use so their pumping capacity gets reduced. It may have enough power to sustain cruise flight but takeoff fuel flow demand is twice. This could lead to an engine failure during takeoff.

José

[FBCK]

I'm told there are all kinds of bodies in shallow graves out in the desert.

[231LV]

As a follow-up to this original post, I had my fuel pump replaced today and problem solved. As a For What Its Worth note...this is the second time I have had work done on my fuel system (the first was to thoroughly clean it out a few years back). In both instances, the mechanic used the book to set fuel flow...in both instances, the book flow is a bit low and the mechanics had to dial up the fuel flow. If you are running a turbo in your Mooney with an intercooler, the correct fuel flow is about 21 gph...the book seems to have it set at 18 gph(based on pressure) which causes CHT's to climb very quickly. Of course, your own plane may be slightly different.