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Matt Dralle
Site Admin
Joined: 08 Nov 2005
Posts: 25203
Location: Livermore CA USA
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 Posted: Sun May 23, 2010 7:45 am Post subject: capacitive fuel probes (was: engine loping) |
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At 07:26 AM 5/23/2010 Sunday, you wrote:
| Quote: | All I have to do to be ready for my DAR inspection is to calibrate my capacitive fuel probes.
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Hi Tom,
Which capacitive fuel probes do you have? I have the Princeton units that GRT sells and haven't been able to even come close to getting them calibrated. Actually, they went through the calibration fine (5 set points), but the readings are completely erroneous. Sometimes they read full when the tanks are 1/2 empty. Sometimes they read empty when the tanks are full. Sometimes they read, well, whatever; usually not the actual amount of fuel. They are completely useless. I've talked with Princeton, and they've offered no suggestions.
I'm not sure what to do at this point. Replacing the senders will likely require removing the tanks which is no small job on the -7 and -8. Ack, this sucks. I sure wish I'd just used the S&W float senders from Van's now.
Matt Dralle
RV-8 #82880 N998RV
http://www.mattsrv8.com - Matt's RV-8 Construction Log
http://www.youtube.com/MattsRV8 - Matt's RV-8 HDTV YouTube Channel
Status: Phase 1 Test Flying
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sarg314(at)gmail.com
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| Posted: Sun May 23, 2010 12:31 pm Post subject: capacitive fuel probes (was: engine loping) |
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Matt:I have the Princeton probes and I too regret not going with the low-tech floats. Â The left tank is calibrated, I think. Â I have little experience with it yet. Â The right tank gave me the "short" signal on the 3 LEDs when I told it to calibrate empty. Â This afternoon I'm going to remove the drain valve because as I recall the end of the probe is bearing right on it. Â I can reach in with a screw driver or something and bend the probe up. Â If I am lucky that will clear the short. Â If not, I'll have to remove the tank and the probe. Â Todd at GRT told me that the outer tube can touch the tank, but the inner conductor should not. Â I'll let you know how it goes. I wish I had tested this stuff earlier.
On Sun, May 23, 2010 at 8:45 AM, Matt Dralle <dralle(at)matronics.com (dralle(at)matronics.com)> wrote:
| Quote: | --> RV-List message posted by: Matt Dralle <dralle(at)matronics.com (dralle(at)matronics.com)>
At 07:26 AM 5/23/2010 Â Sunday, you wrote:
>All I have to do to be ready for my DAR inspection is to calibrate my capacitive fuel probes.
<snip>
>--
>Tom Sargent
Hi Tom,
Which capacitive fuel probes do you have? Â I have the Princeton units that GRT sells and haven't been able to even come close to getting them calibrated. Â Actually, they went through the calibration fine (5 set points), but the readings are completely erroneous. Â Sometimes they read full when the tanks are 1/2 empty. Â Sometimes they read empty when the tanks are full. Â Sometimes they read, well, whatever; usually not the actual amount of fuel. Â They are completely useless. Â I've talked with Princeton, and they've offered no suggestions.
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Tom Sargent
[quote][b]
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sarg314(at)gmail.com
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| Posted: Sun May 23, 2010 3:15 pm Post subject: capacitive fuel probes (was: engine loping) |
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Matt:
My half-baked idea seems to have worked. I unscrewed the right tank drain valve, hooked a dental probe around the sensor tube and using a small screw driver pushed up, bending it up 1/8 or 1/4". I could see that the central conductor comes right to the end on that probe, so I guess it was in contact with the bottom of the tank. After that I was able to get a successful "empty" calibration point. It was too windy to taxi over to the pumps today (gusts over 36mph) so I'll try calibrating it later this week. I can't say yet if these probes will be flaky or not. I won't be surprised if there is some further issues with them.
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Tom Sargent
[quote][b]
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Matt Dralle
Site Admin
Joined: 08 Nov 2005
Posts: 25203
Location: Livermore CA USA
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| Posted: Sun May 23, 2010 4:14 pm Post subject: capacitive fuel probes (was: engine loping) |
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Hi Tom,
I'm really interested in your accuracy reports. Please post when you have some data. So far, mine are completely worthless. I'm thinking of recalibrating, but the first time I did the procedure went perfectly on both sides so I'm thinking that won't change anything.
Were your prebend by Princeton for the RV tanks? Kind of a "U" shape?
Matt
At 04:14 PM 5/23/2010 Sunday, you wrote:
| Quote: | Matt:
My half-baked idea seems to have worked. I unscrewed the right tank drain valve, hooked a dental probe around the sensor tube and using a small screw driver pushed up, bending it up 1/8 or 1/4". I could see that the central conductor comes right to the end on that probe, so I guess it was in contact with the bottom of the tank. After that I was able to get a successful "empty" calibration point. It was too windy to taxi over to the pumps today (gusts over 36mph) so I'll try calibrating it later this week. I can't say yet if these probes will be flaky or not. I won't be surprised if there is some further issues with them.
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Tom Sargent
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Matt Dralle
RV-8 #82880 N998RV
http://www.mattsrv8.com - Matt's RV-8 Construction Log
http://www.youtube.com/MattsRV8 - Matt's RV-8 HDTV YouTube Channel
Status: Phase 1 Test Flying
| | - The Matronics RV-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?RV-List |
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Matt Dralle
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dan.pat.b(at)gmail.com
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| Posted: Sun May 23, 2010 4:50 pm Post subject: capacitive fuel probes (was: engine loping) |
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Matt:The best advice I can give anyone contemplating capacitive fuel sending units is: "Don't do it - stick with the resistive, float units." I bought my capacitive sending units from Vans along with the wing kit, and the Princeton converters from GRT. It's a useless combination. I've lost track of how many times I've drained my fuel tanks and recalibrated the converters. (What was it Einstein said?
"Insanity is doing the same thing, over and over again, expecting different results.") Right now they tell me the left tank is empty when it has 12 - 14 gallons in it; the right tank is a bit more accurate but not much. I've spent time on the phone with Sandy and Todd at GRT; they try to be helpful but nothing has worked. The only alternative seems to be to pull the tanks and install float units; and I have no illusions as to what's involved, a real pain in the butt. Thank God the totalizer is spot on accurate.
Dan
RV-7A - N307TB
145 hours since first flight on Aug 4, 2009
On Sun, May 23, 2010 at 8:13 PM, Matt Dralle <dralle(at)matronics.com (dralle(at)matronics.com)> wrote:
[quote]--> RV-List message posted by: Matt Dralle <dralle(at)matronics.com (dralle(at)matronics.com)>
Hi Tom,
I'm really interested in your accuracy reports. Please post when you have some data. So far, mine are completely worthless. I'm thinking of recalibrating, but the first time I did the procedure went perfectly on both sides so I'm thinking that won't change anything.
Were your prebend by Princeton for the RV tanks? Kind of a "U" shape?
Matt
At 04:14 PM 5/23/2010 Sunday, you wrote:
>Matt:
| Quote: | My half-baked idea seems to have worked. I unscrewed the right tank drain valve, hooked a dental probe around the sensor tube and using a small screw driver pushed up, bending it up 1/8 or 1/4". I could see that the central conductor comes right to the end on that probe, so I guess it was in contact with the bottom of the tank. After that I was able to get a successful "empty" calibration point. It was too windy to taxi over to the pumps today (gusts over 36mph) so I'll try calibrating it later this week. I can't say yet if these probes will be flaky or not. I won't be surprised if there is some further issues with them.
>
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>--
>Tom Sargent
Matt Dralle
RV-8 #82880 N998RV
http://www.mattsrv8.com - Matt's RV-8 Construction Log
http://www.youtube.com/MattsRV8 - Matt's RV-8 HDTV YouTube Channel
Status: Phase 1 Test Flying
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sarg314(at)gmail.com
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| Posted: Sun May 23, 2010 6:20 pm Post subject: capacitive fuel probes (was: engine loping) |
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Matt:
Mine were pre-bent for the 6A. Maybe that makes a difference, I don't know.  Your experience and Dan's leaves me expecting lots of problems. I'll keep the list appraised of my results.
| Quote: | | Quote: | Hi Tom,
I'm really interested in your accuracy reports. Â Please post when you have some data. Â So far, mine are completely worthless. Â I'm thinking of recalibrating, but the first time I did the procedure went perfectly on both sides so I'm thinking that won't change anything.
Were your prebend by Princeton for the RV tanks? Â Kind of a "U" shape?
Matt
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Tom Sargent
[quote][b]
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sarg314(at)gmail.com
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| Posted: Mon May 31, 2010 3:06 pm Post subject: capacitive fuel probes (was: engine loping) |
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Matt:
FYI I calibrated my right tank Princeton fuel level sensor. I should mention that mine are the 2 set-point models. I doubt that makes much difference since that is probably just a software issue. At any rate both sensors seem to be working. The right one never shows more than 3/4 full, the left gets up to about 7/8. But they are repeatable. I'm not flying yet, so I haven't run the tanks down to see how it behaves. I did drain about 5 gal out of each tank (I don't want to do first flight with completely full tanks), but that didn't bring the level down far enough to register any change. The 6A tanks are 19 gallons, so they still each have at least 14 gallons in them which probably still has the probes completely submerged.
On Sun, May 23, 2010 at 7:17 PM, thomas sargent <sarg314(at)gmail.com (sarg314(at)gmail.com)> wrote:
| Quote: | Matt:
Mine were pre-bent for the 6A. Maybe that makes a difference, I don't know.  Your experience and Dan's leaves me expecting lots of problems. I'll keep the list appraised of my results.
| Quote: | | Quote: | Hi Tom,
I'm really interested in your accuracy reports. Â Please post when you have some data. Â So far, mine are completely worthless. Â I'm thinking of recalibrating, but the first time I did the procedure went perfectly on both sides so I'm thinking that won't change anything.
Were your prebend by Princeton for the RV tanks? Â Kind of a "U" shape?
Matt
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--
Tom Sargent
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--
Tom Sargent
[quote][b]
| | - The Matronics RV-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?RV-List |
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