1979 M20K GPH problem

[N231HZ]

Hello everyone!  This is my first post on MooneySpace.

 

I make routine trips from ATL to BTR.  A few weeks ago the motor coughed while climbing through 10,000.  I returned to airport to speak with my A&P, pull cowling, and look around.  We couldn't find anything so we did a long run-up and short maintenance flight (no problems).  Once again I departed, and once again climbing through 7500 the engine coughed.  I returned to airport and did another maintenance flight with my A&P.  This time we climbed to 7000 feet and shortly the engine coughed again.  We did mag check and isolated problem to right side mags.  We landed, changed all spark plugs and problem disappeared.  I decided to have him clean fuel injectors later that week.  Next flight my analog fuel flow gauge showed 6 GPH during climb (my JPI showed same).  It SLOWLY started climbing all way up to 50 GPH and then slowly worked its way down to 12 GPH and stayed there remaining flight.  On my trip home it did the exact same thing starting at 6 GPH all way to 50 GPH and then leveling off correctly.

 

Any thoughts?

 

Thanks!

[Bob_Belville]

Sounds like you have 2 problems.

 

• Did EGT confirm ff? If flows were really at the values you are seeing the EGT should have fluctuated with the flow. It seems very unlikely, impossible, that you were climbing @ 6 gph. And I seriously doubt that the system is capable of 50 gph. So you have a problem with the ff instrumentation.
• The rough running engine is probably unrelated and since you changed plugs that may have taken care of that issue. It certainly is possible that if you were running way too rich that the engine would complain as you got to a higher altitude. Most folks lean to maintain EGT about 200 ROP as they climb.

[chrisk]

What were your engine parameters when climbing?  I'm assuming 2600 rpm and 36 inches, maybe better (2700/40in)?  If so, I don't think there is any way the engine could do that at 6gph.  --And if it could, I don't think you would have been climbing.  And I also don't think 50gph is realistic, which is 2x what the fuel flow should be in a full power climb.  With that said, 12 Gph is in the normal range for a cruising 231, but again, it would help to know the rpm and mp and if it matches the POH.

 

As for the analogue gauge matching the JPI, look to see what is common.  It has to be there.  If the fuel system is the only thing in common, I would be concerned.....  Perhapse an obstruction?  I'm guessing something like a common sensor.

[N231HZ]

Bob, thanks for reply.  All other instrumentation was indicating normal temps (EGT/CHT).  I assumed the analog gauge and JPI were receiving information independently.  So it baffled me when both gauges were indicating incorrectly.  I assumed it was related to the removal/re-installation of fuel injectors.

[N231HZ]

chrisk.  I was climbing at 2600 RPM and 36".  All CHT temps were between 320-380.

 

Also, with the previous flight involving 2 RTB's due to engine problem I've been hyper senstive :- )

Most of my flying has been IFR ending with instrument approaches so the fuel flow really got my attention.  I'm hoping it's just in the instrumentation but the fact I just cleaned fuel injectors and the problem showed up makes me think it could be something else.

[Piloto]

I had similar problem with FF readings. Pulled out the FF transducer and flushed out with carburetor cleaner. Problem solved. The problem is due to fuel residue accumulated in the transducer.

 

José

[ArtVandelay]

•  It certainly is possible that if you were running way too rich that the engine would complain as you got to a higher altitude. Most folks lean to maintain EGT about 200 ROP as they climb.

 

I thought turbos didn't have this problem, they compensate for the lower air pressure at altitude??

 

You said you have a analog FF and JPI, and they both agreed...are they sharing the same fuel transducer....if not then it seems unlikely both transducers would fail exactly the same way.

 

Given these 2 problems, I would suspect a FF problem, since it would cause both the FF readings, and the engine problem. I would flush the fuel lines, do an IRAN on the gasolator, and check the age of your fuel hoses, hoses age from the inside out, if original, you might want to replace with new ones.

[N231HZ]

Thanks Jose.  I'll tell my A&P to do that.

[N231HZ]

teejayevans.  I always climb rich and lean once leveled off.  Never had any issues.  I was trained by one of the best!  I ferried Mooneys for 5 years for Don Maxwell at good'ole GGG.

[Marauder]

I had similar problem with FF readings. Pulled out the FF transducer and flushed out with carburetor cleaner. Problem solved. The problem is due to fuel residue accumulated in the transducer.

José

That was my thought as well but I am curious if they are both indeed sharing the same transducer.

[N231HZ]

^{That was my thought as well but I am curious if they are both indeed sharing the same transducer.}

 

^{Yeah it would be odd that both transducers errored simultaneously.}

[Marauder]

^{Yeah it would be odd that both transducers errored simultaneously.}

What year plane is this? It is possible that your fuel flow is a Shadin or Hoskins and those transducers could be shared with the JPI.

[jlunseth]

I also doubt it is a fuel flow problem, probably instrumentation. If it were fuel flow you would likely see a redline TIT at some point during a flow cycle like that.

[N231HZ]

Marauder, it's a 1979.  I'll have to look and see if it's a Shadin or Hoskins,

[Bob_Belville]

I also doubt it is a fuel flow problem, probably instrumentation. If it were fuel flow you would likely see a redline TIT at some point during a flow cycle like that.

Yeah, I think he meant ff sensor, not the actual fuel flow. The engine performance certainly confirms that the actual fuel flow is not what the fuel flow indicators are reading. And that both indicators are wrong in lock step would indicate that they share the same sensor.

[N231HZ]

I just spoke with Don Maxwell.  He suggests the transducers piggy back and share.  He thinks maxing the K-factor and checking hoses for debris may solve issue.  He also suggested to check the connectors at sensor.  The connectors get brittle over time and sometimes get broken or damaged.  He said there are 3 wires going into a connector located on the pilot's side top left corner which cause a lot FF instrumentation problems.  He said to check and replace these if necessary.  I'll post an update soon.

[Marauder]

I just spoke with Don Maxwell. He suggests the transducers piggy back and share. He thinks maxing the K-factor and checking hoses for debris may solve issue. He also suggested to check the connectors at sensor. The connectors get brittle over time and sometimes get broken or damaged. He said there are 3 wires going into a connector located on the pilot's side top left corner which cause a lot FF instrumentation problems. He said to check and replace these if necessary. I'll post an update soon.

That makes sense. My JPI and EI share the same transducer as well.

[Bob_Belville]

You guys with redundancies are just begging for conflicting info. Next thing you know somebody here will be opting for an extra engine.

 

When I added the JPI930 I sold DrBill the 450. Yesterday I finally pulled the old OAT out of the side window. I was tired of trying to decide which one was "right" between it at the 930. Fixed that sucker.  

[Marauder]

You guys with redundancies are just begging for conflicting info. Next thing you know somebody here will be opting for an extra engine.

 

When I added the JPI930 I sold DrBill the 450. Yesterday I finally pulled the old OAT out of the side window. I was tired of trying to decide which one was "right" between it at the 930. Fixed that sucker.  

 

Actually most of my redundant equipment matches fairly closely. In some cases I have a tie breaker I have OAT on the JPI, on the Aspen and the mechanical one stuck in the side window. My JPI manifold pressure and RPM readings agree with their corresponding EI counterparts. And the total fuel used matches on the EI FP-5, JPI and the mechanical fuel gauges (as accurate as they can be). I got to get that fuel flow in the GTN to start working again and then I could have some more tie breakers.

[N231HZ]

^{Bob I'm just flying the hand I was dealt from previous owner (lol).   At the end of year I'm adding G500 with MVP 50.  I'm actually a minimalist and want to clear the extra junk off my panel.    With that being said I'll have a few instruments coming up for sale.}

 

^{I went to hangar on lunch break and as Don predicted the wire harness was damaged to connector and the knife splices connecting wires were elcheapo.  Going to replace them with high quality ones and hopefully resolve problem.}

[chrisk]

You guys with redundancies are just begging for conflicting info. Next thing you know somebody here will be opting for an extra engine.

 

When I added the JPI930 I sold DrBill the 450. Yesterday I finally pulled the old OAT out of the side window. I was tired of trying to decide which one was "right" between it at the 930. Fixed that sucker.  

 

You should try having multiple altimeters!  In a manor of speaking, I have 3.  An Aspen, my old altimeter, and my transponder.   The Aspen and the old altimeter are rarely exactly the same.  

 

So one day, I get a scolding from ATC claiming I am a few hundred feet low.  I ask for confirmation on the barometric pressure.  It matches. My transponder matches ATCs number.  My other two altimeters are within 25 feet of each other and right at altitude (14,000).  And setting one of them to 29.92 matches ATCs number.  I told ATC I was on altitude and never heard anymore about it.    I assume ATC was using the wrong pressure?  --Sometimes redundancy is nice.

[Marauder]

You should try having multiple altimeters! In a manor of speaking, I have 3. An Aspen, my old altimeter, and my transponder. The Aspen and the old altimeter are rarely exactly the same.

So one day, I get a scolding from ATC claiming I am a few hundred feet low. I ask for confirmation on the barometric pressure. It matches. My transponder matches ATCs number. My other two altimeters are within 25 feet of each other and right at altitude (14,000). And setting one of them to 29.92 matches ATCs number. I told ATC I was on altitude and never heard anymore about it. I assume ATC was using the wrong pressure? --Sometimes redundancy is nice.

I think some ATC facilities are off a bit. Take a look at FlightAware and you can see this happen.

[N231HZ]

Mystery solved!  It was a faulty wire going through harness into back of JPI.  I installed new G430W, radio stack and transponder.  The installer ran wires over the edge of bare metal.  It rubbed the wire and caused a short and loosened the wire from JPI.  My avionics guy said when he installs the G500 and MVP-50 he will clean up all the garbage from previous avionics shop.  Hopefully no more issues!

[Bob_Belville]

You should try having multiple altimeters!  In a manor of speaking, I have 3.  An Aspen, my old altimeter, and my transponder.   The Aspen and the old altimeter are rarely exactly the same.  

 

So one day, I get a scolding from ATC claiming I am a few hundred feet low.  I ask for confirmation on the barometric pressure.  It matches. My transponder matches ATCs number.  My other two altimeters are within 25 feet of each other and right at altitude (14,000).  And setting one of them to 29.92 matches ATCs number.  I told ATC I was on altitude and never heard anymore about it.    I assume ATC was using the wrong pressure?  --Sometimes redundancy is nice.

Actually, I have the same 3 altimeter reading. And think it is a good thing. There's also a GPS altitude which is a number based on geometry and does not adjust for atmos press.