[jbstok]

Did the smoke test successfully yesterday and everything worked but the fuel pressure sender. I know it's wired correctly but reads 0 psi all the time, even with the engine running. I've sent it back to Dynon (at my expense) to have it tested and replaced if it is indeed bad.

The folks at Dynon told me that this Kavilco 50 psi sender is supposed to read 4 psi with nothing running. That is the lowest reading it is supposed to have, ever. To have it be accurate on the low end would have required a big expensive change to the D-180 itself, so they chose to live with it. The more I think about it, the more that bugs me. Why would you use a sender that you know is not going to work right? By right, I mean causing a reading of zero when there is no pressure present. Surely there is a sender out there that will work the right way? Does this bother anyone else? Is anyone using a fuel pressure sender on a D-180 that is gives an accurate reading on the low end?

 

[Dynon]

You can always use the mechanical VDO senders that we used for years. They read zero when they are at zero. At least the first time you use them. Eventually, with all the shaking, baking, and what have you, they eventually read whatever they feel like Also, they're not all that accurate, especially at low pressures. They can give you a false sense of security.

We upgraded to the Kavlicos because they are more reliable, but yes, without hardware changes in the D100 series products, they read a bit off zero when at zero. We don't know of any affordable, reliable sender that won't have this issue. This issue doesn't exist on SkyView since it was designed with the senders in mind.

The reality is that your fuel pressure should be >20PSI. If it reads 4 are you going to do anything different than when it reads 0? You're going to keep flying, hope the engine is still running and land ASAP. It's so far out of bounds that it isn't an issue. Kind of like the fact that if your pressure gets up to 56 PSI we'll only say 50 PSI since the sender maxes out.

Seriously, if you prefer an older style mechanical sender, then we can send you one of those back instead.

 

[jbstok]

Apparently I didn't understand that there is fuel pressure, then there is fuel pressure. My existing gauge seems to have come out of the same Mooney that the engine came out of. It takes the fuel pressure from the spider, but according to some, that's not really fuel pressure, it is some sort of differential pressure and requires a gauge made to measure that. It yields very low numbers, in the 3 to 5 psi. range when idling, and not a lot more during cruise. When I tried to hook the Kavilco up the same way, it just flat didn't work. I moved the the Kavilco to a new pressure line I tee'd off behind the mechanical fuel pump, and that reads the sort of numbers you describe, 20 lbs. on up. The other thing that was making me crazy after I got the Kavilco back was that when I hooked it up on the new line, it still read zero, same as it did before I sent it back, when there was no pressure on the line. I checked the wiring, I checked the voltages, I called out there a couple of times all to no good end. Then I actually put air pressure on the sender on the sender and lo and behold, it read pressure! I took pressure off and it read zero. Not 4 psi, not 3.4, but zero. I hooked everything back up, turned on the boost pump and bingo, I have pressure! After sitting for a while, like overnight, when I first turn the D-180 on, it reads zero. I don't know why, it just does. It seems to be reading normally in flight as well. I'm declaring victory and going flying.

.........JB