Water in Fuel Lines, Pumps, Servo - what have you had to do to rectify?

[IdahoMooneyPilot]

First - a warning:  I have an M20J, with O&N bladders from about 20 years ago, with the old Shaw Aero fuel caps.  My new (now former) A&P last year decided to do me a "favor" and replaced the O-Rings on my fuel caps.  Thing is, he didn't do any research.  It turns out that Shaw made about 50 different styles, and the ones I had were exceedingly rare (I doubt they installed 50 of them), with no documentation available today - - so inevitably the A&P put in the wrong O-rings, just as winter was coming on.  Three months, parked on a slight slope, and 12 inches of wet snow later, I ended up with about a pint of water in each tank, which successfully hid in the bladders when I (religiously) sumped tanks and gascolator, only finding a trace of water from each at that time.  Fifteen minutes later, the engine quit just as I was throttling up for takeoff - and that's when the bulk of the water manifest at the sumps and in the gascolator.  This led to water contamination in the fuel injection servo, which I didn't realize was significant until operational problems with the servo this fall, after six months and 25 hours of flight.  Fuel servo is now out for overhaul, and was found with water & rust inside upon opening.  BTW: The fuel caps were immediately replaced six months ago with Griggs' (nee O&N) new cap & flange assemblies out of England, and they are wonderful!  Not a drop of water.

 

Now, my question:  Have any of you had experience with this kind of thing?  Did you find that the fuel pumps (engine & electric boost) also had water contamination issues, or were they fine?  After 25 hours of flight, my gut feel is that any water in the pumps has probably been cleared - but I am not certain, and no two A&P's concur on what corrective action, if any, is needed regarding the pumps.  I'm not too worried about from the fuel tanks up to the gascolator, as the gascolator is designed to trap out small amounts of water.  I'm confident the fuel tanks & lines are clear of water up to the gascolator.  But what about the pumps?  Do they trap water the same way as the fuel injection servo?

[N201MKTurbo]

The pumps are not an issue. Fuel will flush out any water. As far as the servo is concerned, the best thing you can do is go fly the airplane as soon as possible after the water incident. I think there are some pressure sense aeras where the fuel doesn't circulate, so if water got in there it would tend to stay there. On the flip side, the fuel should keep the water from getting in there in the first place. I have a paper RSA service manual at the hangar. I will have to look at it.

I've never tried it, but it should work, if you connected the fuel input line to 30 PSI of compressed air, and set the servo to full throttle and rich mixture, it should blow any fuel and water out of the servo. If you didn't want to blow it into your cylinders, unhook the hose going to your spider and catch what comes out.

[IdahoMooneyPilot]

N201MKTurbo:  Thanks for your input.  I note that after about 25 hours of flight (when the servo started misbehaving badly), on opening, the shop did find water trapped against the diaphragm, which is a low spot in the assembly.  The water had not flushed out, but sat in there corroding springs, filters, etc.  Fortunately no sealing surfaces had yet been compromised, so the unit is repairable and is being overhauled.

[EricJ]

2 hours ago, IdahoMooneyPilot said:

N201MKTurbo:  Thanks for your input.  I note that after about 25 hours of flight (when the servo started misbehaving badly), on opening, the shop did find water trapped against the diaphragm, which is a low spot in the assembly.  The water had not flushed out, but sat in there corroding springs, filters, etc.  Fortunately no sealing surfaces had yet been compromised, so the unit is repairable and is being overhauled.

At a seminar I attended the Precision Airmotive guy said that this is mostly a Mooney thing, where the servos can get trapped water and there's a water line evident across the diaphragms after disassembly.   I got the old parts back from when mine was overhauled and it definitely had that, and had failed in flight, presumably due to the "grit" that the overhauler said was in it.   I think Mooneys get this because they sometimes operate with the ram air door open in rain or somehow otherwise get water in through the ram tubes.    If it was an issue with water contaminated fuel, it'd likely be more prevalent in other aircraft as well.

That said, I had had a lot of water contamination issues in the fuel before my servo failed.   The reasons were similar to yours, that it had been left out in the rain a lot before I purchased it and got water in the tanks.   The fuel cap o-rings were disintegrating and weren't keeping the water out.

[IdahoMooneyPilot]

EricJ:  I appreciate your quick feedback, and that you've had direct experience with this issue.  Thank you!

May I ask about your fuel pumps after your servo problem?  Did either fuel pump:

1) have to be cleaned / overhauled / replaced?,

2) have problems or show evidence of trapped water causing damage?, or

3) no problems to date with either of the fuel pumps (no failures or no re-contamination of the fuel injections servo)?

 

[EricJ]

18 hours ago, IdahoMooneyPilot said:

EricJ:  I appreciate your quick feedback, and that you've had direct experience with this issue.  Thank you!

May I ask about your fuel pumps after your servo problem?  Did either fuel pump:

1) have to be cleaned / overhauled / replaced?,

No.   Overhauling the servo cured the last of the issues.   Maxwells put in a new boost pump just before I picked up the airplane, but it was old.

18 hours ago, IdahoMooneyPilot said:

2) have problems or show evidence of trapped water causing damage?, or

The only evidence of water damage was on the diaphragms that were removed from the servo at overhaul.   Everything else has been fine.   

18 hours ago, IdahoMooneyPilot said:

3) no problems to date with either of the fuel pumps (no failures or no re-contamination of the fuel injections servo)?

 

No more problems.   It's been seven years and about a thousand hours since then, so there doesn't appear to be anything lurking.

FWIW, about a month prior to the final servo failure that led to the overhaul we cleaned a bunch of rusty-looking crap out of the finger filter in the servo.   I've no idea what that was.   I've not seen anything like it since.

[IdahoMooneyPilot]

EricJ:  Wonderful information!!  Thank you for sharing it.

From what I heard from the servo overhaul shop, the screens are plain steel - and so they rust.  I also understand that the boost pump is a vane-type pump with a steel sleeve that the vanes ride on; perhaps with ingress of water (which then sits for a while, depending...) that steel sleeve rusts a bit.  I have had one party recommend rebuilding or replacing the boost pump as it may fail (and yes - mine is old too - I think it is an old Dukes, but haven't looked...).

Thanks again!!

[Bartman]

@IdahoMooneyPilot

If you have concerns about water in the system, add some 99% Isopropyl Alcohol. IPA absorbs water, but you don't want the stuff you get at CVS which is 70% IPA, you want the 99% stuff.  I think I got some from Aircraft Spruce years ago. The POH for my J gives specifics on amount and/or concentration.  Add to the tanks and go fly.

[Fly Boomer]

On 1/3/2025 at 11:42 AM, IdahoMooneyPilot said:

perhaps with ingress of water

https://www.amazon.com/gp/product/B08HX5VCYJ

[IdahoMooneyPilot]

Bartman & Fly Boomer:  Thank you both for the IPA info & Amazon lead.  I actually have 99% IPA; I will scour my POH for that information, as well as touching base with Griggs (nee O&N) regarding the bladders to see if they are compatible with IPA.  And to your point - yes, 70% IPA is 30% water - it won't solubilize much additional water (if any), and might actually drop its water when added to 100LL. 

I had wondered about doing something like that - it's nice to hear confirmation from others!

 

[Fly Boomer]

8 minutes ago, IdahoMooneyPilot said:

Bartman & Fly Boomer:  Thank you both for the IPA info & Amazon lead.  I actually have 99% IPA; I will scour my POH for that information, as well as touching base with Griggs (nee O&N) regarding the bladders to see if they are compatible with IPA.  And to your point - yes, 70% IPA is 30% water - it won't solubilize much additional water (if any), and might actually drop its water when added to 100LL. 

I had wondered about doing something like that - it's nice to hear confirmation from others!

 

Try Section II - Limitations.

[IdahoMooneyPilot]

Fly Boomer:  Thanks for the direction - will do!