Fuel pump going bad?

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deaston

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Dan
The facts:

Well maintained 182S. Flying in Texas afternoon heat. ~3 hr flight. Enroute climb from 6500' to 8500'. Engine loses power and starts coughing and sputtering. Trim for best glide and point toward airport. Enrichen - no effect. Lean - no effect. Throttle in, more sputtering. Throttle out, less sputtering but still rough and no power. Switch tanks - no effect. Aux fuel pump on - bingo! Plane roars back to life. Later turned off fuel pump and engine continued to run fine.

Of course, now I'm on the edge of my seat so the slightest creak, groan, bump, etc makes me think it's going to start up again. Passengers were pretty quiet too. Decided to press on while monitoring everything very closely. Finished flight without incident.

Talked to home mechanic. Said likely fuel pump. Took a local mechanic for a run up. Multiple full run ups. Laps around the pattern. No problem. Said it sounded fine and he would make the flight home.

In climb out, same problem. Immediately hit the fuel pump and engine back to normal. Shut it off a little while later and plane made the 3 hour return without further incident.

Mechanic planned to replace fuel pump.

Everything I've read says engine-driven fuel pump failure is very rare. I'm seem to lucky that way...

Still, the heat and the fact that it cleared up and only happened during climbs makes me wonder about vapor/fuel boiling in the lines. Is that just an old wives tail?

So the questions:
- fuel pump or vapor in lines?
- was I foolish to continue the flight and make the return?
 
Cannot find a Fuel System schematic for a 182S, but agree it sounds like vapor lock to me. This isn't a Mogas approved aircraft is it, by any chance?
 
Vapor lock is very rare in gravity-feed systems. Almost impossible. You need heat and a much-reduced pressure on the fuel, below atmospheric pressure at least. The injected 182 has its engine pump on the back of the engine, and since it's a lot lower than the tanks, gravity keeps a small positive pressure on the fuel. The boost pump is under the floor beneath the copilot's feet.

Has this AD been addressed?

http://www.airweb.faa.gov/Regulator...5ace4def86257547005dcd89/$FILE/2009-02-03.pdf
 
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Dan Thomas said:
Vapor lock is very rare in gravity-feed systems. Almost impossible. You need heat and a much-reduced pressure on the fuel, below atmospheric pressure at least. The injected 182 has its engine pump on the back of the engine, and since it's a lot lower than the tanks, gravity keeps a small positive pressure on the fuel. The boost pump is under the floor beneath the copilot's feet.

Has this AD been addressed?

http://www.airweb.faa.gov/Regulator...5ace4def86257547005dcd89/$FILE/2009-02-03.pdf
Click to expand...

Am I looking at the right link? That appears to be for an IO360. This is IO540.

Edit: I see now that it is all Lycoming IO series. I'll ask mechanic.
 
I'm a student in just the first phases of learning to fly (4 hours total flying time, many hours studying) so please understand I don't think I know anything, but wouldn't the electric (aux) fuel pump be the first thing to try? Or at least as I understand it, in our club all checklists say to turn on the aux fuel pump before switching tanks?

What is your plan if it happens again? I was thinking that if there is a next time, and you did nothing except turn on the aux fuel pump, would that then point back to the main fuel pump starting to have problems, or if it was vapor lock would turning on he aux possibly correct that (meaning you still wouldn't be sure if it was VL or the main pump?)
 
You turn on the aux pump in a Warrior to shorten the correction time if you screw up and switch to an empty tank or the OFF position or leave it between detents. A 182S has a "both" position on the fuel selector, and you use it almost all the time. The aux pump is used as a primer. Earlier (carbed) 182s have no aux pumps at all. They are gravity driven and not needed.

177RGs are prone to vapor lock (though usually in the context of warm starts on the ground), and the aux pump helps there by forcing liquid fuel into the lines.
 
LongRoadBob said:
wouldn't the electric (aux) fuel pump be the first thing to try? Or at least as I understand it, in our club all checklists say to turn on the aux fuel pump before switching tanks?

What is your plan if it happens again?
Click to expand...

What plane are your training in? I was taught that if you lose an engine at altitude (what I thought was happening), you trim for best glide, then point yourself at a suitable landing site. Then you start troubleshooting (I let ATC know I was having issues while I was trimming in case I needed help and so they knew I might be maneuvering unexpectedly).

On the troubleshooting end, it very much felt like a fuel issue, so I tried related controls (fuel selector, mixture, throttle, then fuel pump). In the 182S POH, the only time it calls for "normal" use of fuel pump is priming before start. There are some references to using it to resolve vapor issues, but that's only in the detailed system description of the fuel pump. That's probably why it was the last thing I tried. The second time it happened, it was the first thing I tried since I was expecting it.

In the POH, I see that it calls for this order (Best Glide, Fuel Selector, AUX FUEL PUMP, Mixture, Magnetos). So I didn't get the order quite right. Thankfully I had plenty of time and none of those things takes long to execute.

If that had not resolved it, next to try was mags, but then I was running out of options and planned to nurse it in to a nearby runway or glide it in if I lost the engine completely.
 
This plane is trying to tell you something, I would not go with vapor lock or any other might be type problem. You need to find out why it did what it did fuel system crud blockage, failing pump, whatever, or someday the Aux pump wont get the power back.
 
brien23 said:
This plane is trying to tell you something, I would not go with vapor lock or any other might be type problem. You need to find out why it did what it did fuel system crud blockage, failing pump, whatever, or someday the Aux pump wont get the power back.
Click to expand...

I agree. I wouldnt fly it again until I had the entire fuel system gone over and found out what it is that the boost pump "clears up." For awhile.
 
brien23 said:
This plane is trying to tell you something, I would not go with vapor lock or any other might be type problem. You need to find out why it did what it did fuel system crud blockage, failing pump, whatever, or someday the Aux pump wont get the power back.
Click to expand...

Amen. Both the owner and the mechanic, both of whom have exponentially more experience than I do, think symptoms point to engine-driven fuel pump going out. Mechanic was planning to replace fuel pump yesterday (I haven't talked to him yet to confirm). My concern is that the problem is intermittent and therefore diagnosis is not definitive. But I don't like guessing on airplane repairs, and everything I have read says see pump failures before engine TBO are extremely rare. Perhaps there are tests that can be performed on the fuel pump to confirm it is going bad, but the fact is that it ran for the majority of 6 hours of flight with only a few minutes exhibiting a noticeable problem. I'm not an A&P, but that doesn't seem like a failure mode of a pump. I would expect it to gradually lose pressure/pumping power or fail all at once and permanently. But again, I'm not a mechanic. Hence the question here.
 
deaston said:
Amen. Both the owner and the mechanic, both of whom have exponentially more experience than I do, think symptoms point to engine-driven fuel pump going out. Mechanic was planning to replace fuel pump yesterday (I haven't talked to him yet to confirm). My concern is that the problem is intermittent and therefore diagnosis is not definitive. But I don't like guessing on airplane repairs, and everything I have read says see pump failures before engine TBO are extremely rare. Perhaps there are tests that can be performed on the fuel pump to confirm it is going bad, but the fact is that it ran for the majority of 6 hours of flight with only a few minutes exhibiting a noticeable problem. I'm not an A&P, but that doesn't seem like a failure mode of a pump. I would expect it to gradually lose pressure/pumping power or fail all at once and permanently. But again, I'm not a mechanic. Hence the question here.
Click to expand...

Do you have a fuel pressure gauge? Did you happen to notice what it read during these events?

This is always one of my fears, I watch mine pretty closely because I'm assuming (hopefully correctly) that any fuel related issue will present itself on the gauge prior to the fan stopping.
 
Were you on th same tank both times it happened?
Anyone have A clue why it would stumble in climb but run fine in level flight?
Angle causing a fuel port issue or aerating the fuel somehow.


Seems odd it started in climb only and didn't return in level flight after th aux pump "fixed it"

Could be a coincidence.
 
deaston said:
What plane are your training in? I was taught that if you lose an engine at altitude (what I thought was happening), you trim for best glide, then point yourself at a suitable landing site. Then you start troubleshooting (I let ATC know I was having issues while I was trimming in case I needed help and so they knew I might be maneuvering unexpectedly).

On the troubleshooting end, it very much felt like a fuel issue, so I tried related controls (fuel selector, mixture, throttle, then fuel pump). In the 182S POH, the only time it calls for "normal" use of fuel pump is priming before start. There are some references to using it to resolve vapor issues, but that's only in the detailed system description of the fuel pump. That's probably why it was the last thing I tried. The second time it happened, it was the first thing I tried since I was expecting it.

In the POH, I see that it calls for this order (Best Glide, plan a landing site, Fuel Selector, AUX FUEL PUMP, Mixture, Magnetos). So I didn't get the order quite right. Thankfully I had plenty of time and none of those things takes long to execute.

If that had not resolved it, next to try was mags, but then I was running out of options and planned to nurse it in to a nearby runway or glide it in if I lost the engine completely.
Click to expand...

PA-28-161 Piper warrior II now (just went over from an Aquila) but again, I wasn't even second guessing you at all, just very curious as the problem you had interests me a lot. Of course too, I haven't checked but what you say sounds right, best glide first, but in both of the planes I have (very minimal) experience with they both recommend aux fuel before switching tanks. I see that this is not an issue (I learned something) when you can choose both tanks.

What I'm really interested in is that question I had. Just for arguments sake, say after best glide, and planning for landing, you had turned on the aux fuel there would be two possible outcomes, either it helped or it didn't. If it did, would that nail down the problem pointing to what you thought (engine fuel pump is getting faults) or would the cause still be open (vapor lock, which some say isn't likely, or clogged fuel lines, etc.?)

Also I have a question that I may have "learned" but forgot, or not, but in an airplane with all systems working correctly, is there any bump in fuel pressure when the engine fuel pump is working correctly and you turn on the aux pump? I'd love to know. I haven't noticed it in the pre takeoff, but may not have paid enough attention. Like I said, I have four flight hours, I'm nobody to listen to about piloting.
 
In my BE35S (many years ago) turning on the aux fuel pump with engine running would cause a very slight increase in fuel pressure.
 
Twice in your description you stated that the problem occurred on takeoff and climb out. This is when your engine is drawing its maximum fuel quantity. On the Piper Saratoga IO-540 I flew, the fuel flow would approach 30 gallons/hour at wide open throttle/full rich.

Now if your fuel pump has a small tear in its diaphragm it could well have a reduced fuel flow capability, apparent only at wide open throttle. See if your A&P can dissect the removed pump to confirm the diagnosis.

-Skip
 
ChemGuy said:
Were you on th same tank both times it happened?
Anyone have A clue why it would stumble in climb but run fine in level flight?
Angle causing a fuel port issue or aerating the fuel somehow.


Seems odd it started in climb only and didn't return in level flight after th aux pump "fixed it"

Could be a coincidence.
Click to expand...

Can't say for sure on same tank or not, but changing tanks did NOT resolve the problem (at least not immediately). Turning Aux fuel pump on DID resolve it immediately both times. The first time it was after some fiddling. The second time I hit the fuel pump first and engine immediately went back to normal. Also note that while both times it happened during a climb, there were other times where it climbed just fine without the aux pump on.
 
that is a very common failure mode of engine driven pumps. they get weak and cannot move the amount of fuel needed at wide open throttle. how many hours are on the pump ( not that new pumps don't fail).

bob
 
LongRoadBob said:
I wasn't even second guessing you at all
Click to expand...

I didn't take it that way at all. I'm happy to have my actions scrutinized. Thats one of the ways I learn and the reason why I posted all the detail.

Regarding the root cause, I'm still not convinced that it was the fuel pump. It was extremely hot - hottest ambient temps I've flown in. The oil temperature was still in the green, but about 225F, which is much hotter than I'm used to seeing. Also, I was climbing meaning that air pressure is dropping. That seems like good combination to have fuel suddenly start boiling. That said, I can't seem to find much about 182s having this problem. Seems like most information is about 210s and 172s on MOGAS.

A couple of other key points:

I've noticed that when I land (and plane is obviously hot) the engine tends to run rough at idle, sometimes seeming like it might even die. This seems exacerbated on fields at high altitude (home is almost sea level). I have thought at times that it was my inexperience in figuring out how to lean the engine on landing (how do you set the mixture for an engine that is at low power and you a descending because you are landing? I've head some leave it alone from start of descent and others say full rich...). After the first experience of power loss in flight, when we landed, engine was again rough at idle. I kicked on fuel pump and engine idled much smoother. But it doesn't do this when engine is not hot (i.e. start up and taxing for takeoff). Always at the end of the flight.

Last weekend, I was departing on a hot (but not as hot) day. It was barely perceptible, but engine "burbled" on takeoff roll just before liftoff. I aborted, taxied back, did a full power run-up. Everything normal. Completed the flight and the return without any other incident.

Lastly, yes, when engine pump is running normally, aux fuel pump slightly enrichens mixture in my plane (according to POH and my ear). In reading up on this, it sounds like the auxiliary and boost pump configurations vary from plane to plane, and you need to pay attention to YOUR POH to see appropriate opporation. In some cases, running the electric fuel pump in certain phases of flight can apparently flood and kill the engine! So as always, read the manual!
 
unsafervguy said:
that is a very common failure mode of engine driven pumps. they get weak and cannot move the amount of fuel needed at wide open throttle. how many hours are on the pump ( not that new pumps don't fail).

bob
Click to expand...

Interesting. I can't say for certain that both times were at full throttle. The POH says top of the green OR WOT, whichever is less, for enroute climb. It could have been full throttle in both cases, but there were plenty of other instances where I had WOT and it did not exhibit this behavior.
 
LongRoadBob said:
Also I have a question that I may have "learned" but forgot, or not, but in an airplane with all systems working correctly, is there any bump in fuel pressure when the engine fuel pump is working correctly and you turn on the aux pump? I'd love to know. I haven't noticed it in the pre takeoff, but may not have paid enough attention. Like I said, I have four flight hours, I'm nobody to listen to about piloting.
Click to expand...

Only if the pressure is below the regulated value. Otherwise the regulator will modify it.

You might see this at idle. Definitely engine-off (which is where you're supposed to check it per the checklist). Not necessarily in cruise.
 
it doesnt have to be WOT, ive seen it do it at cruise also. if you have a fuel pressure gauge, you will see a drop in pressure and the pressure will go back up when the aux pump is turned on. sometimes it will stay up and sometimes the pressure will fall when the aux is turned off. my bet is the pump is going bad.
bob
 
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