Cessna fuel sender and fuelsenders.com

arnoha

arnoha

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arnoha
My A&P tells me that a bad fuel sender is the cause of intermittent readings on my right hand tank in the 172 SP. Lovely. $610 for the factory part and $75 for the gasket. (How? How does a simple rubber gasket get to $75?) I balked at the price and he pointed out fuelsenders.com and this $350 rebuild:

http://www.fuelsenders.com/site/898219/product/S3852-2

He has no experience with the shop. Putting aside the awful website, does anyone have experience with Malkasian? Are the rebuilds they provide really a better part than the Cessna/Rochester garbage part?
 
arnoha said:
My A&P tells me that a bad fuel sender is the cause of intermittent readings on my right hand tank in the 172 SP. Lovely. $610 for the factory part and $75 for the gasket. (How? How does a simple rubber gasket get to $75?) I balked at the price and he pointed out fuelsenders.com and this $350 rebuild:

http://www.fuelsenders.com/site/898219/product/S3852-2

He has no experience with the shop. Putting aside the awful website, does anyone have experience with Malkasian? Are the rebuilds they provide really a better part than the Cessna/Rochester garbage part?
Click to expand...

A friend has two stewart warner senders that were repaired by him. They work great.
 
bnt83 said:
It doesn't look like they have a PMA replacement part for the 172SP.
Click to expand...

PMA or not, if the $12 gasket from McFarlane is the same as the one from Cessna, I sure as hell wouldn't be buying the $75 version.
 
bradg33 said:
PMA or not, if the $12 gasket from McFarlane is the same as the one from Cessna, I sure as hell wouldn't be buying the $75 version.
Click to expand...


The aftermarket parts supply is very limited for newer airplanes and why I wouldn't buy one. McFarlane makes just about every wear item for the CAR 3 (and early part 23) Certified Cessna at a fraction of the Cessna price.

Nor would I offer sender repair services for the prices already mentioned here.
 
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Dan Thomas said:
http://www.mcfarlane-aviation.com/Products/?CategoryID=162&ID=35994362&
Click to expand...

Don't think that applies to mine. Those are Stewart-Warner replacements and the SP apparently has Rochester. Interchangeable?

bnt83 said:
The aftermarket parts supply is very limited for newer airplanes and why I wouldn't buy one. McFarlane makes just about every wear item for the CAR 3 (and early part 23) Certified Cessna at a fraction of the Cessna price.

Nor would I offer sender repair services for the prices already mentioned here.
Click to expand...

Could you explain what you mean by that? I'm definitely learning about the tight supply, but how does that relate to not buying? (Also, I guarantee that my A&P won't install a non-PMA part. He's a stickler.) And what would be the reason for not pricing sender repair at $350? I really appreciate you chiming in with the vote of confidence for the repair shop. I think I'm going to pull the trigger on that this morning.

For reference, the plane is on leaseback, so everything is much stricter than what I could get away with on a personal airplane. When my contract is up in November, I'm definitely re-evaluating this boondoggle. It's averaging a $1200/month loss during its 7 months on the line and it's killing me. This month doesn't look like it's going to be any better.

EDIT: Found an error in my spreadsheet! $2K loss is actually closer to $1.2K.
 
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arnoha said:
It's averaging a $2000/month loss during its 7 months on the line and it's killing me. This month doesn't look like it's going to be any better.
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Jesus, losing $2k PER MONTH on a leaseback? I'd be evaluating my contract with a fine-tooth comb to figure out a way out of that mess.
 
arnoha said:
Don't think that applies to mine. Those are Stewart-Warner replacements and the SP apparently has Rochester. Interchangeable?



Could you explain what you mean by that? I'm definitely learning about the tight supply, but how does that relate to not buying? (Also, I guarantee that my A&P won't install a non-PMA part. He's a stickler.) And what would be the reason for not pricing sender repair at $350? I really appreciate you chiming in with the vote of confidence for the repair shop. I think I'm going to pull the trigger on that this morning.

For reference, the plane is on leaseback, so everything is much stricter than what I could get away with on a personal airplane. When my contract is up in November, I'm definitely re-evaluating this boondoggle. It's averaging a $2000/month loss during its 7 months on the line and it's killing me. This month doesn't look like it's going to be any better.
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The newer the airplane, the more likely you'll have to buy parts from the company that built the airplane = less competition


Example:

https://www.pennyanaero.com/Cessna-T-206-Stationair-Turbo-Lycoming-TIO-540-AJ1A-50.php
 
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bradg33 said:
Jesus, losing $2k PER MONTH on a leaseback? I'd be evaluating my contract with a fine-tooth comb to figure out a way out of that mess.
Click to expand...

The contract has an out...selling the plane is an allowed out. Not sure I'm quite ready for that yet, but I'm getting really close. Leaseback has not treated me well.

Side note: looks like the DG is going out. TC and AI also wore out in the last couple months. Yay! Another AMU down the drain...
 
arnoha said:
The contract has an out...selling the plane is an allowed out. Not sure I'm quite ready for that yet, but I'm getting really close. Leaseback has not treated me well.

Side note: looks like the DG is going out. TC and AI also wore out in the last couple months. Yay! Another AMU down the drain...
Click to expand...

Sell the airplane to another LLC you control...
 
Yeah, leaseback seemed like a really good way to loose money when I contemplated one. Good luck with the senders.
 
bnt83 said:
The aftermarket parts supply is very limited for newer airplanes and why I wouldn't buy one. McFarlane makes just about every wear item for the CAR 3 (and early part 23) Certified Cessna at a fraction of the Cessna price.
Click to expand...

A newer airplane needs a lot less repairing/replacing than an old one. We spend a lot of time fixing old airplanes here, while the newer ones need little work. Seats and rails, for instance, are a big, bad deal in the old models, while the new ones are so robust that they never give any trouble. McFarlane has parts like control cables for the newer stuff, too.

A buyer of an old airplane can end up spending as much, once the snags are fixed, as he would have if he'd bought a ten- or fifteen-year-old model. And the old airplane is still old and worth considerably less. Too many old airplanes have been owned by folks who can barely afford them and the maintenance has been shorted accordingly, leading to nasty surprises for the unwary buyer.
 
Sounds to me like the shop is fixing whatever the renters write up, which may or may not really need help. What do most renters know about wear & tear on an airplane? What is normal and what isn't...

I've seen Cessna T41s that I would never have guessed actually fly.
 
Dan Thomas said:
A newer airplane needs a lot less repairing/replacing than an old one. We spend a lot of time fixing old airplanes here, while the newer ones need little work. Seats and rails, for instance, are a big, bad deal in the old models, while the new ones are so robust that they never give any trouble. McFarlane has parts like control cables for the newer stuff, too.

A buyer of an old airplane can end up spending as much, once the snags are fixed, as he would have if he'd bought a ten- or fifteen-year-old model. And the old airplane is still old and worth considerably less. Too many old airplanes have been owned by folks who can barely afford them and the maintenance has been shorted accordingly, leading to nasty surprises for the unwary buyer.
Click to expand...


How much is the insurance premium difference on a rental between 172SP worth $120k+ vs a 172M worth $45k?
 
Insurance for my 172, with a hull value of $140K, is $571 per month. I don't know, off-hand, how much is liability and how much is hull.
 
I would expect the problem to be corrosion where the float wiper arm moves over the windings of the potentiometer. If the windings are accessible after the sensors are removed, try cleaning them with a pencil eraser or some other fine abrasive.
 
bnt83 said:
Sounds to me like the shop is fixing whatever the renters write up, which may or may not really need help. What do most renters know about wear & tear on an airplane? What is normal and what isn't...

I've seen Cessna T41s that I would never have guessed actually fly.
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They're not. There are definitely items I am not fixing. Door springs are broken, seatback rake doesn't work, MFD is flagged. Other things I've learned is that you do not mess with the right seat. If the CFI doesn't like the plane, it won't fly. You can see the whole sorrid history of what has happened at http://n194sp.aero/squawks if you like.
 
Graueradler said:
I would expect the problem to be corrosion where the float wiper arm moves over the windings of the potentiometer. If the windings are accessible after the sensors are removed, try cleaning them with a pencil eraser or some other fine abrasive.
Click to expand...

My understanding is that this is a film deposition style pot and the failure is abrasion of the film. More abrasion isn't likely to help.
 
Graueradler said:
I would expect the problem to be corrosion where the float wiper arm moves over the windings of the potentiometer. If the windings are accessible after the sensors are removed, try cleaning them with a pencil eraser or some other fine abrasive.
Click to expand...

Big If,,,, they are not.
Every one that I've taken apart were worn out either the slide or the windings are worn beyond recovery.
 
I've only done two - from a Cherokee. The potentiometer windings were totally exposed. Cleaning the surface of the wires where the wiper makes contact completely fixed one and greatly improved the other.

From an engineering standpoint, I have always wondered about the wisdom of having moving electrical contacts exposed in the atmosphere of a fuel tank. Sometimes they are submerged, sometimes not. When it is working correctly, the wiper must make contact with the next wire turn before it breaks contact with the last one. It doesn't always work correctly or this thread wouldn't exist.
 
Graueradler said:
I've only done two - from a Cherokee. The potentiometer windings were totally exposed. Cleaning the surface of the wires where the wiper makes contact completely fixed one and greatly improved the other.

From an engineering standpoint, I have always wondered about the wisdom of having moving electrical contacts exposed in the atmosphere of a fuel tank. Sometimes they are submerged, sometimes not. When it is working correctly, the wiper must make contact with the next wire turn before it breaks contact with the last one. It doesn't always work correctly or this thread wouldn't exist.
Click to expand...
all it is, is a very low voltage seeking a ground. ground is always made in varying degrees, thus no spark.
 
Graueradler said:
I've only done two - from a Cherokee. The potentiometer windings were totally exposed. Cleaning the surface of the wires where the wiper makes contact completely fixed one and greatly improved the other.

From an engineering standpoint, I have always wondered about the wisdom of having moving electrical contacts exposed in the atmosphere of a fuel tank. Sometimes they are submerged, sometimes not. When it is working correctly, the wiper must make contact with the next wire turn before it breaks contact with the last one. It doesn't always work correctly or this thread wouldn't exist.
Click to expand...

Yeah, I don't get it. Why are fuel senders for aircraft such crap? It's an easier environment than a car. The fuel is more consistent and no ethanol to worry about. There isn't the constant vibration and jostling of bouncing down the road. They should last longer than automotive ones, which operate on basically the same principle. But they don't; they fail frequently. What gives?

Tom-D said:
Do the upgrade,

http://www.aircraftspruce.com/catalog/eppages/skysportfuelsys.php?clickkey=3407530

ask for a safety upgrade on the 337 requesting approval to use this equipment.
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Too expensive. $400 for the two tanks, plus the massive labor for redoing the whole system and panel. And the extra cost for the 337. And now I'm non-standard. And I'd lose the gallons markings. And I lose a panel position. Granted, it's a much better, more reliable solution, but it doesn't make sense here. I'd guess $2000 vs. $500. Maybe if I hadn't found fuelsenders.com.

Tom-D said:
all it is, is a very low voltage seeking a ground. ground is always made in varying degrees, thus no spark.
Click to expand...

Tom, I think he was referencing corrosion and wear, not the possibility of explosion. Clearly, that does not happen in normal operation. Though...in a crash, wonder if that ever plays a role in a post-crash fire.
 
arnoha said:
Yeah, I don't get it. Why are fuel senders for aircraft such crap? It's an easier environment than a car. The fuel is more consistent and no ethanol to worry about. There isn't the constant vibration and jostling of bouncing down the road. They should last longer than automotive ones, which operate on basically the same principle. But they don't; they fail frequently. What gives?



Too expensive. $400 for the two tanks, plus the massive labor for redoing the whole system and panel. And the extra cost for the 337. And now I'm non-standard. And I'd lose the gallons markings. And I lose a panel position. Granted, it's a much better, more reliable solution, but it doesn't make sense here. I'd guess $2000 vs. $500. Maybe if I hadn't found fuelsenders.com.



Tom, I think he was referencing corrosion and wear, not the possibility of explosion. Clearly, that does not happen in normal operation. Though...in a crash, wonder if that ever plays a role in a post-crash fire.
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Actually it's $240.00 per a/c, and 1 hour labor to instal, so can I be your mechanic? I'll do the whole thing in including the 337 for a grand.

I have the cover letter saved as a PDF, and the 337 block #8 saved also, I fill them out, print and send to FSDO, they come back approved in 3 working days.
Many owners aren't too cheap to make the improvement to their fuel system.
 
Tom-D said:
Actually it's $240.00 per a/c, and 1 hour labor to instal, so can I be your mechanic? I'll do the whole thing in including the 337 for a grand.

I have the cover letter saved as a PDF, and the 337 block #8 saved also, I fill them out, print and send to FSDO, they come back approved in 3 working days.
Many owners aren't too cheap to make the improvement to their fuel system.
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I'm not sure I understand. The kit you linked is about $190 per tank. I can't reuse the gauges, as the Cessna's pot system isn't 0-5V like this one. I don't see how it can be done in an hour. And there's two tanks, so $240 total does not compute. What am I missing?

I'm not sure why you took my response to your post personally. I explained why it doesn't make sense in this application. I didn't think it was a bad suggestion nor did I say anything like that. You often have great advice, but tossing an insult at the end makes it hard to take seriously.
 
arnoha said:
I'm not sure I understand. The kit you linked is about $190 per tank. I can't reuse the gauges, as the Cessna's pot system isn't 0-5V like this one. I don't see how it can be done in an hour. And there's two tanks, so $240 total does not compute. What am I missing?

I'm not sure why you took my response to your post personally. I explained why it doesn't make sense in this application. I didn't think it was a bad suggestion nor did I say anything like that. You often have great advice, but tossing an insult at the end makes it hard to take seriously.
Click to expand...
2" X 6" probes are 170 a set.
I found out a long time ago, the only thing in aviation that is cheap is owners.

and a 337 doesn't cost anything.your post just struck me as you were trying to cheap it out.
 
Tom-D said:
all it is, is a very low voltage seeking a ground. ground is always made in varying degrees, thus no spark.
Click to expand...

They do make sparks, when they're faiilng and contact is making and breaking. The secret is the ratio of fuel to air in the tank; it's way too rich to burn. Gasoline is combustible at ratios between 8:1 air to fuel, by weight (8:1 is rich) and 18:1 (lean). The mix in the tank's airspace is richer than 8:1.

There's danger when the tank is emptied. The fuel evaporates and what little is left can result in an explosive mixture. I'm much more careful around a recently-drained tank than a full one.

Cars have the same fuel senders in them, and newer cars also have electic fuel pumps in the tank, too. That pump sometimes uses an open-frame motor with a commutator and brushes, and it's submerged most of the time. Fuel right in the motor. When the fuel is low, those brushes and commutator are making sparks, quite safely. The pump can't completely drain the tank, so the mix stays too rich to burn.
 
Tom-D said:
2" X 6" probes are 170 a set.
I found out a long time ago, the only thing in aviation that is cheap is owners.

and a 337 doesn't cost anything.your post just struck me as you were trying to cheap it out.
Click to expand...

OK. You were computing only the cost of the probes. You forget, I need a pair of gauges as well, as the current combination gauge won't work. Or a converter, if such exists. And that means panel work, which isn't cheap.

A 337 is free to you, because you're an A&P. It is not free to me. Having non-standard gauges and non-standard senders is also not free, as it impacts both the rental volume and resale value of the aircraft. Yes, a capacitive solution is a better technical solution, no one is questioning that. But it isn't necessarily the better solution to my problem.

Here's the way the math works out for this choice:

1. Replace the sender with Cessna parts: $1000. Do this again in 10 years. Baseline resale.
2. Replace the sender with rebuilt parts: $500. Do this again in 15 years. No change to resale.
3. Replace the sender with capacitive parts: $2000. Never replace anything. Resale declines, rental volume declines.

The math is really easy. Option 1 makes no sense at all. Option 2 costs me $100/year assuming I keep the aircraft 5 years. Option 3 costs me $400+ per year on the same assumption. If you take out the resale piece, option 3 doesn't pay back for 60 years. I'll be dead. Which option would you pick?
 
arnoha said:
A 337 is free to you, because you're an A&P. It is not free to me.
Click to expand...
what stops you from filling out the 337 and sending it in for approval?
 
arnoha said:
OK. You were computing only the cost of the probes. You forget, I need a pair of gauges as well, as the current combination gauge won't work. Or a converter, if such exists. And that means panel work, which isn't cheap.

A 337 is free to you, because you're an A&P. It is not free to me. Having non-standard gauges and non-standard senders is also not free, as it impacts both the rental volume and resale value of the aircraft. Yes, a capacitive solution is a better technical solution, no one is questioning that. But it isn't necessarily the better solution to my problem.

Here's the way the math works out for this choice:

1. Replace the sender with Cessna parts: $1000. Do this again in 10 years. Baseline resale.
2. Replace the sender with rebuilt parts: $500. Do this again in 15 years. No change to resale.
3. Replace the sender with capacitive parts: $2000. Never replace anything. Resale declines, rental volume declines.

The math is really easy. Option 1 makes no sense at all. Option 2 costs me $100/year assuming I keep the aircraft 5 years. Option 3 costs me $400+ per year on the same assumption. If you take out the resale piece, option 3 doesn't pay back for 60 years. I'll be dead. Which option would you pick?
Click to expand...

Again, you are think costs, trying to take the cheapest way out.
What makes you think a set of standard senders will last 15 years. ( they were crap the day they were made)
What is the cost of a safe and reliable aircraft worth to you?
 
Tom-D said:
what stops you from filling out the 337 and sending it in for approval?
Click to expand...

I've no idea what to do with it. Same as my taxes...I can fill it out myself, but it's not a good use of my time. And I will not get everything right, because I'm not an expert. You are an expert and that makes it easy for you. Ask me how to get 100K QPS out of a service; this I can do easily. But I bet that would be a challenge for you. The 337 form is the worst kind of form. It has a large block for freeform text. I've got no framework to work with.

Tom-D said:
Again, you are think costs, trying to take the cheapest way out.
What makes you think a set of standard senders will last 15 years. ( they were crap the day they were made)
What is the cost of a safe and reliable aircraft worth to you?
Click to expand...

It's a fuel gauge. It won't make the plane fall out of the sky. And the failure modes for the gauge are very rarely sudden. They give warning...as mine is right now. It's intermittent and still very easy to interpret. If it weren't a leaseback, I wouldn't even be considering replacing it. But it will fail the 100-hour so not fixing it will suspend rentals. It's a long way from a safety issue.

And the longevity? My aircraft is a 2003. This is the first replacement of the sender. 13 years...it's not much time for the part to last, but it matches my estimate.

There are better uses for the $1500 than fuel senders. Looking at the airplane, a 406MHz ELT would be a better spend of $1500. But even better than that would be dropping it into my 2 year old's college fund. That's something that I know will make him happier and safer.

I know you have a lot of money and that these are not serious considerations in your world. But $1500 makes a difference in mine. I'm not complaining; I'm doing great. I own a mfing plane! :D But the money is hardly an infinite resource.
 
Dan Thomas said:
They do make sparks, when they're faiilng and contact is making and breaking. The secret is the ratio of fuel to air in the tank; it's way too rich to burn. Gasoline is combustible at ratios between 8:1 air to fuel, by weight (8:1 is rich) and 18:1 (lean). The mix in the tank's airspace is richer than 8:1.

There's danger when the tank is emptied. The fuel evaporates and what little is left can result in an explosive mixture. I'm much more careful around a recently-drained tank than a full one.

Cars have the same fuel senders in them, and newer cars also have electic fuel pumps in the tank, too. That pump sometimes uses an open-frame motor with a commutator and brushes, and it's submerged most of the time. Fuel right in the motor. When the fuel is low, those brushes and commutator are making sparks, quite safely. The pump can't completely drain the tank, so the mix stays too rich to burn.
Click to expand...
If your premise was true we'd see tanks blow up way more than we do.
next you have one disconnected, try reading the voltage at the connection to the transmitter
 
Tom-D said:
If your premise was true we'd see tanks blow up way more than we do.
next you have one disconnected, try reading the voltage at the connection to the transmitter
Click to expand...

There is voltage there. It doesn't matter which way the electrons flow. There is current flow there, and that's all that's necessary to make a spark. Tanks don't blow up because the conditions aren't right for it.

I have a textbook here somewhere that discusses it. Besides that, there are plenty of references online that speak of lower and upper explosion limits. This is one of them:

https://work.alberta.ca/documents/WHS-PUB-FEX004.pdf
 
Per the above link, between 1.3% and 8% gasoline vapor/air mixture the mixture is explosive. That means that 93.3 % of the possible concentration range is not explosive but 6.7% is explosive.

Numbers edited per Tim's comment. Thanks
 
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Well, pulled the trigger on fuelsenders.com and $350 for the rebuild. 1 year warranty on film-type pots, 2-year on wire-type pots. Even after that, he's charging only $100 for repair on one of his own rebuilds. $10 for the gasket vs. $75 from Cessna. Only downside is that he has nearly zero inventory, so it's a 5-day turn-around. Wish it were an exchange instead, but I'll take what I can get.

I'll update on how things go.
 
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