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Kavlico fuel pressure sensor D180 capacitor

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BigJohn

Well Known Member
Kavlico fuel pressure sensor capacitor

Tried to get all the good search arguments in the title! Two weeks ago installed the Kavlico sensor to replace the original, which was beginning to give flaky readings. Worked fine for a couple of weeks. Then yesterday the needle was jumping between zero and max reading, with frantic high fuel pressure alarms going off. Searched the forum, read about the necessity for placing a 330 mf capacitor across the sensor output and ground. Installed the cap today after confirming with Dynon tech support. Actually installed a 470 mf as that is what they had at the Radio Shack Aviation Store. Problem solved!

My recommendation to anyone replacing the sensor with the Kavlico unit - save yourself double work, install the capacitor from the get-go.
 
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When I installed the Kavlico a few months ago, I followed Petie's suggestion and installed the capacitor. Also ran 3 wires from the back of the Dynon to the Kavlico, thus, bypasiing the Van's passthru/un-necessary control panel. Works great!!
 
Kavlico sensor needs a capacitor to kill noise

Bringing this thread to the top again since reading several recent posts about low or erratic fuel pressure indications. If you have the Kavlico sensor, it is prone to noisey readings unless you add a capacitor across the output. My erratic reading problem was solved more than a year ago by this suggestion from one of the guys at Dynon. I had nearly forgotten about this issue until this week when I ran into it again on a customer's airplane.
 
If I'm not mistaken, there are three leads from the Kavlico. Which leads should the capacitor go across? Also, please confirm that "mf" means millifarad, not microfarad.
 
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John,
I have the Skyview and the pressure varies quite a bit. Is it appropriate to add the capacitor to it?

Mitch
 
kritsher said:
If I'm not mistaken, there are three leads from the Kavlico. Which leads should the capacitor go across? Also, please confirm that "mf" means millifarad, not microfarad.
Click to expand...

Black lead is ground. Red lead is power. green lead is output to the Dynon. Small electrolytic capacitor goes from green to black. Positive side on green, negative on black. 330 or 470 microfarad, voltage rating around 25 volts. About the size of a pencil eraser.
 
Mitch757 said:
John,
I have the Skyview and the pressure varies quite a bit. Is it appropriate to add the capacitor to it?

Mitch
Click to expand...

I believe so, if you have the Kavlico sensor. But check with Dynon support first. Be aware, as of Wednesday not all the Dynon guys knew about this fix. The first guy I got Wednesday didn't know about this. I called back later, this time the rep did know about the fix, and said he would make sure all the other support reps did.

Apparently not all installations of the Kavlico sensor have the noise problem, don't know why. But I have now seen it personally in two 12's, and have heard of more. IMHO, the capacitor should be routinely installed to prevent problems later.
 
Purple ring

One more thing. While working on the Kavlico sensor you may want to remove the little purple sealing ring that slips over the connector. It has been known to cause false readings when changing altitude in some cases.
 
Make sure you observe the positive and negative on the electrolytic caps. In my Heathkit days I soldered one in backwards and it went off like a firecracker!
 
Cap to what color wires

I'm just installing my fuel pressure sensor. Can the capacitor be installed at the wiring splices on fire wall. If so, what color wire to what color wire (and which lead on capacitor to what color wires��

Edit: Sorry...should have read all posts...thanks BigJohn.
 
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Phantom30 said:
Where can you buy the capacitors.....help
Click to expand...

Easiest is Radio Shack, if your local store is still open. Otherwise there are online sources. Mouser is one. These little caps are cheap, and shipping will cost more than the cap! Exact capacitance is not critical. Dynon recommended 330, local RS had only 470, worked fine.

As far as where to install, I soldered mine into leads coming out of sensor. Insulate with shrink wrap.

Yes be careful of polarity. Hooked up wrong they make dandy little firecrackers!
 
BigJohn said:
Easiest is Radio Shack, if your local store is still open. Otherwise there are online sources. Mouser is one. These little caps are cheap, and shipping will cost more than the cap! Exact capacitance is not critical. Dynon recommended 330, local RS had only 470, worked fine.

As far as where to install, I soldered mine into leads coming out of sensor. Insulate with shrink wrap.

Yes be careful of polarity. Hooked up wrong they make dandy little firecrackers!
Click to expand...

Yup....that and a LiFi battery up front; and I'd have a real firecracker!
 
I'm going to try this on my RV8 / G3X system that is experiencing FP problems - my thread is located in the Glass Cockpit section, will post the link below. I'm still a bit unclear where to install the capacitor. The Kavilco sensor has a harness that snaps into the sensor. I've soldered the harness wires to a shielded 3-conductor cable that connects to the EIS. Would a good place to install the cap be where the harness wires are soldered to the shielded cable, or should I strip a section of the harness wires closer to the sensor?

CA

http://www.vansairforce.com/community/showthread.php?t=131269
 
You can solder it in wherever convenient, but reading the other thread I dont think it is going to help your problem.
 
Another Kavlico problem

Hi,

Please can anyone offer suggestions as to next steps? Here's the background...

1. After 250 hours I suddenly started getting intermittent high fuel pressure warnings. I have a D180 with the original VDO sensor.

2. I replaced the VDO with a Kavlico 15 psi unit. As documented elsewhere I tapped the MAP 5v supply for the red wire, I connected the original VDO earth to the black wire, and the original VDO signal to the green wire. I installed a 330uf 50v capacitor between the green and black cables. I reconfigured the Dynon from sensor=1 to sensor=6. The Dynon software has been updated to a version that supports the Kavlico.

3. With the engine off, I get zero psi. The Dynon instructions said I should get 1.2 psi.

4. With the engine on, I get low fuel pressure warnings with readings varying between 0.9 and 1.2 psi, regardless of the engine power setting (I tried from idle to full static rpm). The engine sounds OK at all power settings.

5. If I disconnect the earth, I get about 19 psi, and if I select an alternate earthing point on the airframe the reading goes back to zero. So the sensor seems to be earthed.

6. I can see 5v at the splice to the MAP sensor cable.

7. With the electric fuel pump running and the engine off I get 4 litres (a gallon) per hour flow, so the return line appears not to be blocked.

Any clues...Keith
 
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kritsher said:
If I'm not mistaken, there are three leads from the Kavlico. Which leads should the capacitor go across? Also, please confirm that "mf" means millifarad, not microfarad.
Click to expand...

"mf" = micro farad, confusingly enough, as is "uf" ... clearly, the second is preferred.

A milli-farad is a huge capacitance value; 470 milli-farad cap would be the size of a brick.
 
I'm not sure if it can cause your problem, but did you observe the polarity convention on the capacitor? I think I mentioned that in my Heathkit hobby days I set one off like a firecracker by reversing the polarity on an electrolytic capacitor.
 
Capacitor wiring

Thanks, but yes. Positive to green. So no firecracker.

Cheers...Keith
 
Keith,
Measure the voltage between the green wire and black wires without fuel pumps running, then measure again with the electric pump running.
According to Dynon Support Forum, "At 2.3 PSI, a voltage of about 2.3V is close to what we'd expect".

Per my calculations, a water column 63.5" high equals 2.3 psi and a gasoline column 86" high also equals 2.3 psi.
 
You may have a bad capacitor. Try putting an ohm meter across it and see if it is passing current. A good capacitor will read 0 ohms initially and approach infinity as it charges.
 
In order to eliminate the capacitor as the culprit, just disconnect it. Then run the electric pump and if still zero readings its not the capacitor that is bad. Suggest leaving the capacitor out of the circuit until you find the real source of the problem. Simplifies trouble shooting. The capacitor is just to smooth out the output of the sensor to eliminate erratic readings.
 
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Progress...

After much investigation it turns out that the fuel sensor supplied had the correct Dynon part number on the packet and the accompanying paperwork, but the Kavlico part inside the packet did not have the equivalent Kavlico part number. So although externally it looked the same, it was built to a different spec.

I await a replacement part in the hope that this will fix my problem.

Thanks for your diagnostic help, which eventually pointed me to the sensor itself rather than the wiring, or the Dynon config.

Cheers...Keith
 
Capacitor

Okay...... I am replacing my original fuel pressure sensor 42100 that feeds my Advanced Flight Systems ACS 2002 EMS. I believe Dynon and AFS have merged. The sensor AFS sold me to replace the original fuel pressure sensor is a Kavlico 41201. Has anyone installed this Kavlico 41201 with their AFS EMS?
And if so, did you install the capacitor?

My fuel pressure is erratic ( with the original sensor) and never goes to 0 when shut down...stays around 2.7 or higher.

It also reads 9.0 plus!!! sometimes on climb out, etc. With of course the aural and visual warnings.
As always, found good info on VAF.

RV-7A o-360

LL
 
Fuel sensor install

In addition to the above post,.......senior moment, I forgot to ask if anyone had a simple way to put a "known pressure" on the sensor to enter the data settings on the EMS. I have the Vans sensor manifold setup.

THX

LL
 
A water column can be used to obtain a known pressure.
Do a Google search for "water column to psi"
The first hit is an online converter.
A water column 11.5 feet high gives 5 psi.
A water column might be impractical for higher pressures.
 
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