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Fuel Flow transducer problem


gsxrpilot

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TSIO360MB and JPI EDM900

I had the fuel flow transducer replaced almost exactly 1 year ago by Arapaho Aero here in Denver. The symptoms at that time were no FF readout on the JPI or sometimes it would fluctuate up and down while in cruise and then drop to zero again. 

Now here I am a year later and I'm having the same symptoms. I was hoping this would have lasted more than a year ;). I've read @kortopates comments on the subject and had a very close look at the install. Fire sleeve is intact, in the proper location, and looks new. There is no blue staining anywhere to indicate a leak. The wires all look good and aren't chafed anywhere I could see. The plug/connector looks new, tight, correct, as well. 

We opened it all up, disconnected the fuel lines and blew through the transducer gently. It immediately registered on the JPI as expected. We put it all back together and started it up. Same thing, erratic FF readings on the JPI.

So should I just replace the transducer again? I'm thinking of replacing it with the FT-60 "red cube". Has anyone put one of those on a 252? And thanks in advance...

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Paul, is your Transducer mounted on a bracket above and the front of cyl #5 just behind the fuel pump versus just free standing on the hose able to move around? If so it might be suffering from vibration in flight affecting its longevity. These should last decades. The only other thing I can think of is our engines don't have a fuel filter after the gascolator nor in the pump - not till the screen in the fuel divider - so we're a bit more vulnerable to debris from the tank. But I've never had a problem with the transducer, just the divider screen getting dirty.

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30 minutes ago, kortopates said:

Paul, is your Transducer mounted on a bracket above and the front of cyl #5 just behind the fuel pump versus just free standing on the hose able to move around? If so it might be suffering from vibration in flight affecting its longevity. These should last decades. The only other thing I can think of is our engines don't have a fuel filter after the gascolator nor in the pump - not till the screen in the fuel divider - so we're a bit more vulnerable to debris from the tank. But I've never had a problem with the transducer, just the divider screen getting dirty.

Mine is mounted on a bracket above and near the front of #5. In fact, it's wedged hard up against the inboard most fins on #5 with the fire sleeve wedged tightly between the transducer and the fin on #5. I'm sure the vibration must be unbelievable with it up against the cylinder. Should be be left free standing on the hose?

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Paddle wheel sensors are pretty robust, but...

Heat, vibration, leaks (air often leaks in), dirty sensor, and sharp corners in the entry/exit tubing are the enemy...

Heat, if vapor bubbles occur... the bubbles may get stuck and occupy space that the fuel used to use... typically the FF numbers will increase with this issue...

Vibration... probably interferes with vanes motion... the vanes try to self centered to some extent... fuel isn’t a very good lubricant... the vanes might be crashing into the case and coming to a halt...(?) pure conjecture on my part...

Corners... plumbing angles before and after cause turbulent flow in the tube... 

Optical sensor... The red cube uses an optical sensor, not sure what the others are using... it may be experiencing something interfering with the sensor...

Wondering if all these variations allow the vanes to contact the case more often... the vanes May be wearing at an increased rate...

 

Probably Best to remove, and send some cleaner through it... (check with the sensor OEM... for their recommendation....)

Cleaning procedures are often supplied by the sensor people... often mentions things like don’t use compressed air...
 

PP thoughts only, it’s been a while since I studied the red cube... lots of conjecture...
 

Best regards,

-a-

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Mine is mounted on a bracket above and near the front of #5. In fact, it's wedged hard up against the inboard most fins on #5 with the fire sleeve wedged tightly between the transducer and the fin on #5. I'm sure the vibration must be unbelievable with it up against the cylinder. Should be be left free standing on the hose?

It shouldn’t be actually touching the cylinder fins but should be enough inboard of the fins to clear them. If I remember right the supporting bracket is mounted to a clamp on an induction tube and can be moved around accordingly. It also needs to be clear of the upper cowling where it joins the lower cowling. But the bracket is needed to fix and stabilize its position.


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Mine is doing the same thing. Replaced it for the second time also. Along with my amp meter that continually reads -1 connected or not. I am done with JPI. Bought top of the line EDM900 paid good money I worked very hard to earn and got junk. Was told by their technician I had it installed wrong. My guess after removing my sensor again and bench testing it is that the hall effect sensor is of a cheaper design. I can make the sensor read differently just by tilting. And maintaining consistent regulated flow. I am going to the red cube and will try that when I have time. I am just not sure the sensor is all to blame I wonder if the head unit is not regulating voltage correctly to the sensor and I have not tested that. I honestly get so mad I just leave it alone cause I really don't want to know the answer.

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28 minutes ago, Dream to fly said:

Mine is doing the same thing. Replaced it for the second time also. Along with my amp meter that continually reads -1 connected or not. I am done with JPI. Bought top of the line EDM900 paid good money I worked very hard to earn and got junk. Was told by their technician I had it installed wrong. My guess after removing my sensor again and bench testing it is that the hall effect sensor is of a cheaper design. I can make the sensor read differently just by tilting. And maintaining consistent regulated flow. I am going to the red cube and will try that when I have time. I am just not sure the sensor is all to blame I wonder if the head unit is not regulating voltage correctly to the sensor and I have not tested that. I honestly get so mad I just leave it alone cause I really don't want to know the answer.

In my case, the JPI transducer is exactly the same part number as the original equipment transducer from Mooney. I'm going to try moving the location of the transducer to reduce vibration. JD is sending me a couple of used ones today. We'll see how that works.

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@gsxrpilot I read somewhere they get crapped up with dye in the fuel and can be cleaned out (somehow). I’ve seen fuel that is heavily dyed which could cause that issue, maybe. Always best to correct the problem rather than throwing parts at it..... Heat and vibration can’t be good either. 

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I recently replaced an FT60 with a JPI flowscan. I had a EI FP-5L with the FT60 and had nothing but problems. I had it cleaned twice and it would work fine for awhile and then would randomly read zero and come back up again. I upgraded my edm700 to a 730 and replaced it with a flowscan and have had zero issues since, but its only been about 30 hours of flying since it was replaced.

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5 minutes ago, N201MKTurbo said:

When mine was behaving badly, I took it off, capped both ends after filling it with hoppes #9 and let it sit over night. It has been working fine ever sense.

Curious what flushed out

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40 minutes ago, N201MKTurbo said:

When mine was behaving badly, I took it off, capped both ends after filling it with hoppes #9 and let it sit over night. It has been working fine ever sense.

I'll try that...

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As you can see from my posting above, I had all sorts of weird symptoms. I went around and around with JPI, including buying and installing a new transducer, which still did not fix it. After confirming that it was the display head (temporarily replaced it with a JPI loaner), I sent my FS450 display and they found a bad connector/board. It was replaced and it works like a charm. And JPI confirmed my “old” transducer was fine (and the unit had been in my airplane for 25 years/3000 hours!)

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Update to this issue.

We replaced the transducer with a used (working when removed) transducer. They are both exactly the same model/part (flowscan 201) 

The replacement seems to be working correctly, but the K factor is WAY off. The previous K factor was something like 29.54. I haven't done a two hour flight and measured the fuel used, as recommended by JPI when adjusting the fuel flow. But on takeoff, the FF on the EDM-900 was reading 74.9 gph. Obviously that is incorrect. I changed the K factor twice and it seems like I'm close on the expected take-off fuel flow. I realize this is not the proper way to determine the actual fuel flow. But I'm just trying to get it in the ball park. Now my K factor is set to something like 83.54. That seems a bit off the chart so to speak. But now my full power fuel flow is in the mid 20's gph range.

Question... is a K factor in this range normal? Or is there something completely wrong with our install, config, etc?

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if the transducer is running slow, it usually means it is dirty. If it runs fast it is either electrical noise giving false pulses or air in the fuel line.

Air in the fuel line can come from any fuel line connection, the selector or gascolator. It can also be cavitation bubbles caused by sharp bends just before the sensor.

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there are 2 or 2 different Floscan 201 trandsducer K-factor ranges.  some are 28K ish, some are 24. some are different than that.   the EI red cube is 80k something as well.,  the color of the plastic cap where the wires comes out tells you which model it is.  Also, usually the k factor is engraved, stamped, or ink stamped on the unit. but yes, if you dont know the K-factor, set it to where the takeoff FF is close, then burn off 30-40 gallons, and use some math to determine fuel actually used vs fuel it thinks it used, and hone in from there.

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  • 2 weeks later...

I replaced my JPI transducer yesterday with a new unit from JPI and have zero fuel flow priming the engine...get fuel pressure but 0 fuel flow. Have verified continuity through the flat connector.  Expecting now I have to trace wiring back to unit and/or re-seat the unit. :mellow:

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Have had the Red Cube for many years now. It must be mounted away from the engine since it's highly prone to failure due to vibration (learned that after 2 replacements in four years).  The accuracy can't be beat. Each time I fuel up to the same point in the neck, the gallons used displayed on the JPI is within ounces of what I refilled with.

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I have messed with my factory-installed Floscan 201B connected to a Shadin Miniflo-L on my '94 J more than makes sense. Here is all I know:

1. The original transducer was intermittent when I purchased the airplane. I tried soaking it in Hoppes No. 9 and this fixed it -- for about a month -- after which I replaced it.

2. The K-factor marked on the original 201B was 29.0. The new one (purchased directly from JPI that now owns Floscan) came with a calibration tag marked 28.989. The Shadin K-factor  was set at 33.06. I'm pretty sure this is the way the Mooney factory set it because it was metal stamped on the foil label on the unit. I set it to 28.99 and the fuel flow was way off. I confirmed that the Shadin was good by swapping with a borrowed unit. The results were identical.

3. With the new transducer and the Shadin K-factor set to 33.06, I get fuel burns that vary from correct (compared to the pump meter) to 3.5% low over many tanks of gas. I'm going to adjust the K-factor to center the error, but it's a pain on the Shadin because it cannot be done entirely from the front panel -- it requires removing the unit to set a dip switch.

4. Mooney's installation violates Floscan recommendations: It is mounted upside down and it has an elbow directly attached to the transducer inlet. I corrected both of these issues by making a new mounting bracket in the same location as the original. None of these changes made any difference in the fuel burn variability.

So, even though these transducers are specified as being accurate to half a percent on the flow bench at 16.0 gph, I cannot get mine to read accurately at my typical 8.5-9.5 gph unless I adjust the K-factor to be much different than the transducer K-factor and then the variation is within +/- 2% which may be within the measurement error of topping off the tanks.

Attached are some Floscan docs of interest. It would appear that a 201A would be a better match for my fuel flow, but I ordered a 201B because that's what Mooney originally used.

Skip

FloScan Instrument Co. Inc_.pdf

Series_200_FlowTransducer_Installation_Comments_201_052_00E.pdf

 

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