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Fuel flow/pressure transducer


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Just now, FlyBoyM20J said:

Thanks, Skip - I've read about soaking in Hoppes in other threads (e.g., "Hoppes comes in a plastic bottle...so no worries about your plastic impeller"), but I'm not sure which Hoppes product to get at this point. 

Cliff

 

Hoppes #9

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8 minutes ago, jaylw314 said:

Yeah, sorry about all the peanut gallery comments, but sometimes we just don't know when to stop :) 

I really love the comments.  Large and medium Adel clamps and bolts and nuts and everything in the parts catalog to deal with securing SCAT ducts has now been ordered.  Also, smaller Adel clamps to get the JPI wires away from the magneto wires.  Going to need to do something with the Tanis wires, too.  The A&P who installed it didn't follow the manual's instructions about *not* bunching up excess wiring, so I think I'll need to get it trimmed to size and get the crimpers from Tanis and all that. 

 

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1 minute ago, FlyBoyM20J said:

Thanks, Skip - I've read about soaking in Hoppes in other threads (e.g., "Hoppes comes in a plastic bottle...so no worries about your plastic impeller"), but I'm not sure which Hoppes product to get at this point. 

Cliff

 

Cliff,

Hoppes No. 9 is a gun cleaning solvent. Find it wherever AK-47s are sold. Lycoming recommends it for cleaning fuel injector nozzles. 

Skip

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10 hours ago, FlyBoyM20J said:

I really love the comments.  Large and medium Adel clamps and bolts and nuts and everything in the parts catalog to deal with securing SCAT ducts has now been ordered.  Also, smaller Adel clamps to get the JPI wires away from the magneto wires.  Going to need to do something with the Tanis wires, too.  The A&P who installed it didn't follow the manual's instructions about *not* bunching up excess wiring, so I think I'll need to get it trimmed to size and get the crimpers from Tanis and all that. 

 

I’m clad you’re fixing up these minor things in your engine compartment. I find it really annoying when owners are having to fix things that other maintainers have done so wrong.

Keep up the good work!

Clarence

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  • 1 month later...

I finally got to take a look at the transducer.  It's a Floscan Model 201.  It has been sprayed with carb cleaner, soaked in Hoppes #9, and re-installed.  It seems to work well now.

My only question left is: is it a problem if the fire sleeve bundle actually touches the exhaust riser for C4?  It was previously clearing the surface of the riser by perhaps 1 mm (so probably was touching a lot due to vibration) with no damage - just soot.  But after re-assembly, it has less clearance and lightly touches the riser.

I should mention that there are 2 layers of fire sleeve here, adding at least 1/2" of barrier around the transducer.

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Touching the exhaust is not acceptable. Not only does it burn the firesleeve but it causes a cool spot on that red hot pipe and can crack it. Adel clamps over the intake tubes to the fuel hose, both forward and rear of the transducer.  Then put a clamp on heat shield on #4 exhaust. 

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I'd change the mounting a little bit. It looks like the transducer is just hanging from the fuel lines. This may allow it to vibrate which isn't particularly good for it. Also, it makes it hard to keep it away from the exhaust stack. Only one layer of firesleeve is normally used -- the second layer was probably added because the installer couldn't keep it away from the exhaust stack.

Below is a picture Byron's @jetdriven  installation. Note the use of stainless steel cable ties (won't cut through the firesleeve as safety wire might) and the adel clamps attaching the transducer to the intake tube.

Good luck with the solvent treatment. Mine worked for a few hours after I did it and then became intermittent again, so I replaced it. Maybe you'll have better luck.

IMG_2463.thumb.jpg.c5466f31f0c87ad4e3565f1ec0f4b96c.jpg.36b8d5c1d1afcdcd0c483919aee0cd2d.jpg

Skip

 

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Mine is horizontal...per the spec sheet, the wires need to come out of the top of it for venting purposes but they don't call for absolute level or anything.

I now have a lot of adel clamps so I'll get it away from the riser.  It always looked suspicious to me.  In the pics from a month ago, you can see that it didn't really have any clearance before I touched it. 

So many things about this engine setup are sketchy...sigh.

 

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See if I have this correctly...

Fire resistant polymer materials are best kept away from very hot surfaces....  they are a protectant, not a primary insulator for permanent mounting situation...

It is Best for cursory inspection to allow some visibility of the whole surface... if it is changing color, that is a hint to look closer... ignoring this hint doesn’t give any further clues of degradation or a failure...

Anything in contact with the hot pipe... isn’t going to be very good for the pipe either...

The two fittings on either end of the sensor have been know recently to have a leak... (in one case)

Where would I want that hidden leak to occur? At the fire wall or 1mm away from a hot exhaust pipe?

If I were trying to avoid hot start issues... I would keep fuel lines as far away from hot surfaces... especially have metal parts that really carry a bunch of heat energy after they have gotten hot...

want to loosen fittings... heat them up and cool them off often...

want to ruin a good sensor... let it get hotter than its rating...

want to gum up a sensor... allow it to boil off fuel inside of it...

See if you can find another example of somebody with a FF sensor there...?

That seems to defy a lot of  PP logic... :)

  • Tougher hot starts
  • Gummed up sensor
  • Some silicone rubbers are good up to 572°F What’s your EGT inside that thin exhaust pipe? Double?
  • wire and sensor temp degradation
  • Fuel leak
  • Extreme heat and cool cycles on sensor fittings... that may not be rated for this temp
  • Location of at least one hidden fuel leak... on MS.

 

PP thoughts only, not a mechanic... seriously consider confirmation of that mounting location... mine is running on the front of the firewall far away from any heat source...

The FF sensor can measure the same FF anywhere in the fuel line after the fuel selector switch... a straight horizontal run is best for the sensor accuracy. Away from the people and cabin makes some sense... Away from hot surfaces makes some sense... we have rubber hose connectors carrying fuel in the cabin... and many fittings related to the fuel selector near your feet...

Best regards,

-a-

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29 minutes ago, carusoam said:

See if I have this correctly...

Fire resistant polymer materials are best kept away from very hot surfaces....  they are a protectant, not a primary insulator for permanent mounting situation...

It is Best for cursory inspection to allow some visibility of the whole surface... if it is changing color, that is a hint to look closer... ignoring this hint doesn’t give any further clues of degradation or a failure...

Anything in contact with the hot pipe... isn’t going to be very good for the pipe either...

The two fittings on either end of the sensor have been know recently to have a leak... (in one case)

Where would I want that hidden leak to occur? At the fire wall or 1mm away from a hot exhaust pipe?

If I were trying to avoid hot start issues... I would keep fuel lines as far away from hot surfaces... especially have metal parts that really carry a bunch of heat energy after they have gotten hot...

want to loosen fittings... heat them up and cool them off often...

want to ruin a good sensor... let it get hotter than its rating...

want to gum up a sensor... allow it to boil off fuel inside of it...

See if you can find another example of somebody with a FF sensor there...?

That seems to defy a lot of  PP logic... :)

  • Tougher hot starts
  • Gummed up sensor
  • Some silicone rubbers are good up to 572°F What’s your EGT inside that thin exhaust pipe? Double?
  • wire and sensor temp degradation
  • Fuel leak
  • Extreme heat and cool cycles on sensor fittings... that may not be rated for this temp
  • Location of at least one hidden fuel leak... on MS.

 

PP thoughts only, not a mechanic... seriously consider confirmation of that mounting location... mine is running on the front of the firewall far away from any heat source...

The FF sensor can measure the same FF anywhere in the fuel line after the fuel selector switch... a straight horizontal run is best for the sensor accuracy. Away from the people and cabin makes some sense... Away from hot surfaces makes some sense... we have rubber hose connectors carrying fuel in the cabin... and many fittings related to the fuel selector near your feet...

Best regards,

-a-

You have all that correct.  This is a nutty bad location for the fuel line to run and probably even worse to have a bunch of fittings and a mechanical sensor.  I have no clue what motivated the original installer.  (Incidentally, the reason I created this thread was because I couldn't find the FF transducer...and I was not looking for such a device right next to an exhaust riser.)

I noticed that there was just a tiny bit of blue dye on the inner fire sleeve material when I took it off but nothing to indicate a real leak.  More like stuff from installation time.  That said, the fitting on the outflow was barely finger tight.  Yes, I could have loosened it by hand.  So the lack of a leak was just good timing in a game of Russian Roulette.

I will see about getting my A&P to relocate this thing entirely but in the mean time, I will clean all this up and use Adel clamps to get it down and away from the exhaust riser.  There's a good chance that this sensor has been abused beyond salvage...I'll find that out once I fly a bit.  All I know at this point is that the setup doesn't leak and that the Shadin computer now reads fuel flow.

Cliff

 

 

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pulling the wire down the fire sleeve and out the end of it will eventually tear up the wires going into the FF sensor.  (instead of poking a hole in the fire sleeve and fishing the wires out per the drawings).   thats what happened to both sides of my friend's PA30 twin comanche Those things are also way over 300$ each, now, as well.

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1 minute ago, jetdriven said:

pulling the wire down the fire sleeve and out the end of it will eventually tear up the wires going into the FF sensor.  (instead of poking a hole in the fire sleeve and fishing the wires out per the drawings).   thats what happened to both sides of my friend's PA30 twin comanche Those things are also way over 300$ each, now, as well.

Good point.  Well, this thing has been in this configuration, wires bent, inches away from this exhaust riser for at least 20 years and perhaps 1500 hours of flight...so this is one more bit of luck.

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Great details, and Pics, Cliff...

You are in a good starting position of knowing what good FF looks like... some installations with elbows near the fitting never work quite right.  Causing all kinds of do-overs because it seems like the sensor isn’t working... when it is the installation...

See if you can find another J to copy...

Skip often supplies great photo details... @PT20J  but in this case above... i’m Not sure if I even see the exhaust pipes in the pic... :)

Best regards,

-a-

 

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15 minutes ago, carusoam said:

Great details, and Pics, Cliff...

You are in a good starting position of knowing what good FF looks like... some installations with elbows near the fitting never work quite right.  Causing all kinds of do-overs because it seems like the sensor isn’t working... when it is the installation...

See if you can find another J to copy...

Skip often supplies great photo details... @PT20J  but in this case above... i’m Not sure if I even see the exhaust pipes in the pic... :)

Best regards,

-a-

 

It may not be clear form the picture of the transducer, but the blue inflow NPT fitting is itself a 45 degree elbow.  This installation may have been misguided in more ways than one.

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This is actually the location where Mooney mounted the transducer in factory installations except that Mooney used a bracket mounted to the top of the sump. Mooney mounts the transducer with wires coming out the bottom. I asked Mooney service and several MSCs and none have heard of a problem with that mounting. I’m still trying to figure out why my new transducer reads nearly 10% high with a +/- 2% variation using the specified K-factor. I suspect electrical interference, but it might be the mounting. So, I would stick with the wires out the top as Floscan specifies. 

Mooney used a straight fitting on the output and a 45 on the input side. Fittings shouldn’t be blue (aluminum). The transducer case is aluminum and aluminum fittings can cause the threads to fret when you tighten them. Use steel fittings instead.  Floscan says not to use any pipe lube/sealant on the fittings, but NPT fittings frequently seep if you don’t ( the source of your blue stains). Use fuel lube or a fuel proof pipe joint compound on the male threads and just don’t get any on the last two threads. You really don’t want a fuel leak next to the exhaust. 

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8 minutes ago, PT20J said:

This is actually the location where Mooney mounted the transducer in factory installations except that Mooney used a bracket mounted to the top of the sump. Mooney mounts the transducer with wires coming out the bottom. I asked Mooney service and several MSCs and none have heard of a problem with that mounting. I’m still trying to figure out why my new transducer reads nearly 10% high with a +/- 2% variation using the specified K-factor. I suspect electrical interference, but it might be the mounting. So, I would stick with the wires out the top as Floscan specifies. 

Mooney used a straight fitting on the output and a 45 on the input side. Fittings shouldn’t be blue (aluminum). The transducer case is aluminum and aluminum fittings can cause the threads to fret when you tighten them. Use steel fittings instead.  Floscan says not to use any pipe lube/sealant on the fittings, but NPT fittings frequently seep if you don’t ( the source of your blue stains). Use fuel lube or a fuel proof pipe joint compound on the male threads and just don’t get any on the last two threads. You really don’t want a fuel leak next to the exhaust. 

If I didn't know that the NPT fittings are anodized blue, I'd be up all night worrying that they had turned the color from all the leaks...but there really also isn't much on the interior of the fire sleeve (thank goodness).

I don't have much faith in this particular sensor and I'm not going to change the fittings on it now.  I'll secure it well away from the exhaust riser with Adel clamps tomorrow morning and then see how far off the K factor appears to be.

When this was operating last year, it read ~1.7x what was actually consumed.  That is, per my notes for a 1.2 hour flight with 2 approaches and a hold (much LOP), the Shadin indicated 16.5 gallons consumed but it took only 9.6 to top it back off to where it was before the flight.

Not sure how to adjust the K factor to compensate for this but before I get into that, I'll want to see what the new ratio is now that it's cleaned and operating again.

Cliff

 

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The fire-sleeve was touching the exhaust probably because too long a hose was ordered (most of us naturally prefer to add a few inches !!! rather than face the embarrassment of ending up short :D)    ... and kinks are not acceptable !

It can be a trial and error - expensive if you have to reorder a hose -  

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6 minutes ago, OR75 said:

 

The fire-sleeve was touching the exhaust probably because too long a hose was ordered (most of us naturally prefer to add a few inches !!! rather than face the embarrassment of ending up short :D)    ... and kinks are not acceptable !

It can be a trial and error - expensive if you have to reorder a hose -  

I bet...I'm not sure how much freedom I will have to get this thing down low like in @jetdriven 's beautiful install (missing exhaust risers as @carusoam noted, so can't determine clearance easily, though it must be worlds better than mine).  But if the hose is so long that the assembly ended up too far out to the side, perhaps I have the latitude to redirect it down and away instead.

The longer term plan (read: this summer) is to get FF module added to my EDM-700, and for that, I need a reliable transducer and a good installation.

So, this is going to be temporary unless this turns out to be a super-stable sensor once relocated away from the riser and once the K-factor is adjusted in the Shadin computer.

If I have to replace the transducer, I will work with my mechanic to re-route the fuel lines to locate the transducer near the firewall like others have done.  This will require some new hoses. 

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I am not sure what you mean by locating the transducer near the firewall. The install manual states that the transducer has to be between the fuel pump and the injector. This is from what i recall when i did my FS450 install.    

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If you follow the JPI instructions the only place for that transducer is between the fuel pump in the fuel injector servo inlet. Which puts it behind the number 4 exhaust riser. I have previously posted all of the 124J fuel hoses part numbers.  It’s two hoses there. Mine work perfectly. It’s about 1 inch of clearance. Less than the 2 inches suggested to be optimal but good enough when you put the aircraft spruce heat shield on the number 4  exhaust pipe

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+1 on Following the install instructions...

Technically it is a bit odd to put it in that environment...

When there are some less hazardous places to locate it...

The instructions may have been based on various things including aftermarket costs...

Technically the sensor won’t know where it is compared to the mechanical fuel pump.... the flow will be the same from the tank selector to the fuel divider... it is insensitive to the FuelP...

The newer planes that came from the factory with a FF gauge has the sensor mounted across the fire wall... a bit cooler, and further away from hot things if it decides to leak...

PP thoughts only, not a mechanic...

Best regards,

-a-

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OR75 is correct - I looked at what it would take to move the FF transducer closer to the sump and lower down on the intake tubes.  It seems that the fuel hose connecting the output of the FF transducer to the servo is simply too long. 

I was able to add some Adel clamps and get about 3/4" of clearance from the C4 riser but I would like to get this done properly.  These are all nice, certified fire hoses but I think I'd be more comfortable replacing them.  If I can make out the "Cure Date" on the metal band on the hose that that is so long it's forcing the FF transducer towards the exhaust, I believe it is 2004. 

The hose on the other side going to the FP transducer has been resting on the C1 intake tube forever and has a dent in the fireproof material at that point.  I think something else should be done there, too.

Anyone have a picture of how that side of things should be done, too? 

@jetdriven I see that you have posted about 124J hoses a lot over time and I'll start by researching what you've written already.

And when you suggest a heat shield, are you talking about one of these?

https://www.aircraftspruce.com/catalog/eppages/clamponHeatShield.php

Thanks,

Cliff

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