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Fuel pressure sender broken, which replacement?

swisseagle

Well Known Member
Hello

Yesterday at run up, the fuel pressure alarm goes on ... to high fuel pressure. Ok, no flying.
I measured 65 Ohm with no pressure (unit removed).
Compared to the oil pressure sender, there I read about 6 Ohm with no pressure. So this unit is gone!
Ground of the case, the pressure manifold and the one for the engine are fine.

Type is a 0-80 PSI, single post, VDO, made in Germany. Hooked up to a Advanced 3400s EFIS/EM

On ACS I found many oil pressure senders that would fit, but no one mention fuel pressure!?:confused:

Can I just take an oil pressure sender of the correct range and it is fine for FUEL also?

Thanks a lot!
 

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No identification on old so you purchase same? What gauge does the sender feed? Most EFIS dictate sender by brand part number. No, I don’t think comparing to oil sender is a correct approach…. pressure range not in same range. Need more info to help. One time event, not sure replacing is right approach….several times high, maybe issue, but one time…check your wiring, especially ground.
 
A lot would depend on the device you’re using to actually read the pressure. If it’s not a simple mechanical gauge, it’s likely to be calibrated to that specific pressure sender. I replaced both of my Kavlico oil and fuel pressure senders due to the “service advisory” warning of their potential failure from a year or so ago. No big deal, but I did have to change the model number in the admin settings of my EFIS in order for them to correctly display the pressure readings on my EFIS.

FWIW, the replacements recommended by Kavlico, AFS, Garmin, and Dynon for both the “bad” fuel pressure and oil pressure senders was the same 0-150 PSI sensor. The original units were different model numbers and each had different pressure ranges, new ones are the same.
 
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Sender details

Can OP please post a picture of the old sender? Otherwise it's a bit hard to give good suggestions.

ACS listing for VDO senders states they must not be used in aircraft or in fuel systems. I suspect that this is a liability issue. The sender just measures pressure whether it's oil, air, water or fuel and it doesn't know if it's fitted to an airplane, car or tractor.
 
Just uploaded the picture of the broken sensor, see first post.

I would not like to replace it with a new style "chip-sensor", because then I have to rewire 5V supply to the sensor. So I'm looking for the same as it was, single post.

Grounding is fine, on the sensor case, on the pressure manifold and also on the engine.

Hooked up to a Advanced 3400s EFIS/EM
 
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FWIW, for my fuel and oil pressures, I have 2 identical Kavlico "fluid pressure sensors". They are not specifically labelled for fuel or oil.
Both rated 0-150 PSI. Both feed the EMS that feed the EFIS. Itself configured to display 0-150 PSI digital gauges.
If your setup is digital, I would say that the pressure range is not relevant (within what pressure you want to measure). Only that the EFIS is correctly configured.

If your setup is mechanical gauges, then yes, I would say that your pressure range should correspond to the actual gauge's range.
The brand of sensor should not be revelant...
 
I had the same thing happen to me this summer (AFS 4500). I bought one directly from Advanced. Fast service, and the correct sensor.
 
FWIW, for my fuel and oil pressures, I have 2 identical Kavlico "fluid pressure sensors". They are not specifically labelled for fuel or oil.
Both rated 0-150 PSI. Both feed the EMS that feed the EFIS. Itself configured to display 0-150 PSI digital gauges.
If your setup is digital, I would say that the pressure range is not relevant (within what pressure you want to measure). Only that the EFIS is correctly configured.

If your setup is mechanical gauges, then yes, I would say that your pressure range should correspond to the actual gauge's range.
The brand of sensor should not be revelant...

It varies from sensor to sensor. Prior to the recent safety advisory that required switching from the old Kavlico sensors to the new 150 psi ones for both oil and fuel, they were different sensors with different pressure ranges.

Any, OP mentioned that he didn't want to switch over to a system like the Kavlicos that required 5 volt power. I can understand that...is is a hassle.
 
The older senders like in the picture are still available AS or other sources. The newer Kavlico are RATED at 150 meaning the case pressure is good for 150 psi, regardless of the range your service is and regardless if oil or fuel. . Generally , order a sender which has the range ( not rating) which best matches you're service ie.if fuel injected will be a 0 to 80 or maybe 100 psi. If carburated then you only need a 0 to 20 psi range. Most carburated never see more than 10 psi fuel pressure . And yes the EFIS or EIS will need to be set for the scale range you wish to display. Maybe that helps.
 
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Thank you all for your answers! At the moment I just replace with an VDO type. Then scheduling during winter to upgrade to the Kavlico senders. Must talk to Rob from AFS.
 
VDO sender failure is pretty common.

I lengthened to life on mine by isolating it from engine vibration on a short stub of flex hose.

I think the fuel injected engine and carbed engine has two different VDO models.

0 to 80 psi sounds like the fuel injected version.

JMHO
 
Simply call AFS and get a replacement. These have a life of about 300-400 hours. I’m on my third one.
 
The older senders like in the picture are still available AS or other sources. The newer Kavlico are RATED at 150 meaning the case pressure is good for 150 psi, regardless of the range your service is and regardless if oil or fuel. . Generally , order a sender which has the range ( not rating) which best matches you're service ie.if fuel injected will be a 0 to 80 or maybe 100 psi. If carburated then you only need a 0 to 20 psi range. Most carburated never see more than 10 psi fuel pressure . And yes the EFIS or EIS will need to be set for the scale range you wish to display. Maybe that helps.

If you're using Advanced Flight, Garmin, or Dynon with Kavlico 5 volt pressure sensors, the current recommended pressure sensor for both fuel and oil is the same one 103757-000, which is 0-150 pressure range.

https://www.steinair.com/product/sensor-oil-fluid-pressure/
 
VDO ranges

If you're using Advanced Flight, Garmin, or Dynon with Kavlico 5 volt pressure sensors, the current recommended pressure sensor for both fuel and oil is the same one 103757-000, which is 0-150 pressure range.

https://www.steinair.com/product/sensor-oil-fluid-pressure/

OP is using the VDO sensor which is a resistive type electro mechanical device. The correct range sender must be used otherwise the gauge or EMS will not read correctly. Many different VDO senders are available and typically the measurement range is 0-30 psi, 0-80 psi and 0-150 psi. The range is stamped on the hex nut that is at the base of the sensor.
Internally, the VDO sender has a diaphragm that is linked to a little wiper arm which moves across a resistor bridge. Over time the contact area wears due to movement and vibration. Resistance goes up and the gauge reads high and the only fix is to replace the sender.
 
OP is using the VDO sensor which is a resistive type electro mechanical device. The correct range sender must be used otherwise the gauge or EMS will not read correctly. Many different VDO senders are available and typically the measurement range is 0-30 psi, 0-80 psi and 0-150 psi. The range is stamped on the hex nut that is at the base of the sensor.
Internally, the VDO sender has a diaphragm that is linked to a little wiper arm which moves across a resistor bridge. Over time the contact area wears due to movement and vibration. Resistance goes up and the gauge reads high and the only fix is to replace the sender.

I'm aware. Actually, I was addressing Dennis' referral to the Kavlico sensors. My plane was built with the VDO's, being used with an AFS 4500. They were just too unreliable, the builder said, so he bit the bullet and re-wired the plane for the Kavlicos. I recently replaced mine for the upgraded version, not because they weren't working, but because of the relatively strident service advisory wherein they went so far as to mention the "F" word (fire).
 
My Kavlico has started reading oil pressures of over 100 psi at idle on start up (80F oil temp) and held a reading of 40 for over a minute after shut-down when I tried rebooting the EFIS.

In flight it gradually settled down to 90's - 80's - 70's in cruise and ended up at mid 60's which is where it normally reads. On the leg home it did the same except the startup pressure was about 102 and then gradually down to normal in cruise.

I guess this is the slow-death mode. it's a replacement Kavlico from Advanced Flight pursuant to their recommendation for replacement, and has about 70 hours on it. This frequency of failure (at $139 a pop) is disappointing to say the least. $2/hr just for sensor replacement is quite the engine operating expense, especially considering the EGT probes from AFS haven't been stellar either. 2 replacements so far...
 
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