Ragsf15e

For mine, the gmu-11 is in the tail just behind the battery/avionics rack. Others have it in the wing. My heading info is excellent, so there doesn’t seem to be a mag field issue in the tail. I think the -29 is on the avionics rack. typically temp probe should be under the wing (out of sun), and away from the engine. Theres a convenient inspection panel about 18” out and 10” back on the wing (underneath).

So you guys are saying there’s a tiny “breather” hole in this somewhere? (picture from Chief)

I knew my sender looked different… the page you added is from a 2008 manual. I have a newer sender. It’s $423 at Chief! Let’s hope it’s a loose fitting! Below is an updated manual with the sender I have:

I don’t think the 30psi is an issue. It was mid 20s before I replaced the mech fuel pump. The new pumps are notoriously strong and sit right at the 30psi limit. There’s a few threads on that. I agree that sender shows up in the manual, but I think I have a different one with a clip on connector and 3 wires which is almost exactly the same as the oil pressure transducer. Tough to tell in these pictures with an adel clamp around it. Maybe it is the one listed? But the wire connections are definitely through 1 clip.

So, it’s an actual fitting between the servo and the line going to the pressure gage? Like I could take a photo of that connection and we should see it?

Probably because you didn’t want to flood it! Im sure my mental model of this is not exactly right, but IF it’s a mechanical issue (ie air bubbles), I keep thinking that they must be coming in prior to the pump because the line after the pump is pressurized and it shouldn’t let air in. If anything, it would let fuel out. Before the pump though, I think anything is possible. After that video, I put it in ico and it held pressure for a long time. I wiggled the transducer and it’s wires with zero fluctuations.

So mine is steady with boost pump on, mixture ico. However, I think it was bouncing when I put the mixture forward and let it run fuel (but it was really quick because I didn’t want to flood it too bad). Video of pressure as BP comes on with mixture in middle position. https://photos.app.goo.gl/A9c5jKgQDLdTccHw8

Yeah, I gotta check and see if it fluctuates with just the electric pump. I’m not sure if it does. Also, if I run that pump for a minute or two won’t i flood the heck out of it? See this is why I need help, I’m only smart enough to be dangerous!

Agree, Im just having a hard time imagining the cowling off, engine running, mechanical gage in the engine compartment? Probably gonna be bouncing around just due to the engine running.

Here's mine on a similar time scale. It's right after start, but is relatively constant through the flight. It does gain in amplitude during takeoff, but settles back to this in the climb. Fuel Flow is about like this, but just barely more fluctuation when it's higher.

Gnx375 is another good option so you’ll have it all in one box.

What you describe sounds similar to mine, but mine is more than 2-3psi. More like 8psi. It hasn’t always done this. I’ll have to look closer with the pump on, engine off to see. Flow does fluctuate very little, like 0.1-0.2gph but I just figured that’s how they are since it’s tiny. I guess I’m going to have to find a mechanical transducer and test the pressure as I think I really need to eliminate the sender. Ill try to post a plot from my edm data. Maybe ours look similar? Is yours 1” recording?

Greg, thanks for looking for ways to help out. I’d love to see a basic new panel with say the GFC500 and G5s or G3Xs. With some options, something like: 1. Gfc500 with 2, 3 or 4 servos (3 options) 2. G5s x 2 3. G3x 7”, g5 backup 4. g3x 10”, g5 backup 5. G3x 10”, eis, g5 backup obviously there are lots of other factors to consider (GPS, comm, transponder) that complicate the panel and installation, but those are the different levels of upgrade that go through my mind when I consider my old AP failing permanently.

That seems like exactly where the connection is for my JPI Sender. There’s a line off the back of the servo routed under 1/3 cylinders to the sender on the firewall. Sounds like it might already have a built in restrictor? How do you go about troubleshooting these kinds of things? I definitely appreciate all your guys inputs. I’m just trying to build a plan before attacking it with tools…. Also I think I have as much chance of messing with something that isn’t broken while searching blindly for the problem.

That is something Ive thought about. Currently no snubber on that line, but I do have them on MP and Oil Pressure. I would put one on there, but it started in the middle of a flight, so I might just be covering up a real problem. I’m definitely not against having a snubber, just don’t want to hide something else…

Thanks guys, that is definitely helpful. I would really like a way to check the sender (without buying a new one), so I’ll talk to jpi about that. I feel like it’s hard to narrow down the problem which could be: 1. Wiring for the JPI or EMI from somewhere else. 2. Sender. 3. Mechanical. I feel like I need to narrow that down to 1 area before really attacking it.

IO-360, A1A: I need some help troubleshooting my fuel pressure. My IA is busy with other stuff and not interested in chasing this. I don’t mind getting my hands dirty, but I only know enough to get myself in trouble… Fuel flow fluctuates pretty much all the time but more noticeably in full power than in idle. In idle it’s not really that big a deal, say 28-30psi. In full power, it bounces 22-30 randomly but pretty constant. I have a jpi-930. Jpi says it’s probably not the sender as that’s not how they die but it could be emi from something else or it’s real. It didn’t use to fluctuate like this. I searched my flight logs and found where it started last year, in cruise in the middle of a flight. Before that it was very steady. Several things I know/have done- this year at annual (2 weeks ago) my IA cleaned/checked the gascolator and the servo fuel screen. He said they both looked perfect. The fluctuation happens no matter which tank I select. Electric boost pump makes no difference. Mechanical boost pump was replaced 2 years ago because it was leaking oil. Engine runs good but it’s a 1998 OH with 1200 hours. I have a Surefly and a standard mag, both P leads seem reasonably shielded. How can I check the sender without buying a new one? Should I go through all the fuel fittings and “put a wrench” on them to make sure they’re tight? I can’t see any leaks and it was just inspected at annual? How do I find out what is causing this and how to narrow it down? Id prefer to be out in front of an issue instead of waiting for the engine to stumble on takeoff or worse…

You should try it with ap engaged in altitude hold. I bet you get both annunciations. Now that I think of it, when you activate the roll esp by rolling outside the limits, you don’t get a caution or annunciation either, just nudges back toward level flight. I bet they just put that text in the wrong section… i bet it’s supposed to show what the AP will do when engaged and in a low speed condition.

Yeah that seems like it needs fixed. Do you get voice and visual airspeed alerts with the AP engaged? AP Engaged: The g1000 Meridian I fly makes both the voice and visual alerts you describe while pitching down to avoid stall. It would definitely be a surprise without the warnings. Actually, if the AP is engaged, the min airspeed caution comes on early, before the pitch down (say 10kts above) so that you have time to correct.

It all depends on what you need though. Engine and avionics are generally other companies (not Mooney). I once needed a new trim tube and it could only be made by Mooney. It’s the airframe specific stuff that could be worrisome.

Me neither. I was thinking they were for an autopilot but he doesn’t have one…

Looks nice! Your attitude is good and your wallet is lighter. Makes the airplane fly even faster!

Mine was in annual 2 weeks ago and there were 2 Cirrus sitting in the back of the shop waiting on parts. The IA said they have been there several weeks. But you’re right, at least they have a path forward. What do you need specifically, maybe someone here can help?

Well that’s the issue… the parts manual calls for #8, but many have been replaced with 10s as the tinnerman nuts are enlarged over the years. I just bought all new 8s and new 8 tinnerman nuts, so I’m going to replace that whole mess next time I take off that forward panel. One note, the parts manual calls for (at least for my ‘68F), “round head #8” screws but the truss head ones seem more like the ones that are in there.

Try @Alan Fox for used one…