joepilot Posted January 25, 2017 Report Posted January 25, 2017 I've read other threads relating to this issue. '94J IO-360. 1550 TTSN. Full pwr TO at 1400' MSL, 55 degrees OAT, elec boost pump on, I'm getting 18.4 gph. BUT, at about 2000'-2500' MSL climbing out, the fuel flow (Shadin) will drop from 18.4 to 17-17.4 gph (1-1.4 gph) in about 5 seconds without me touching anything. All EGT's rise with fuel flow drop. Sometimes flow will rise back to 17.8 gph or so after a couple minutes, sometimes not. Fuel pressure rock steady at 25 psi. in almost all phases of flight. Press slightly higher w boost on. GPH drop occurs w either tank selected, and with elec boost pump on OR off. Turning boost on after the drop does NOT restore fuel flow. Happens with full tanks, or 1/4 tanks. Just OH'd fuel servo & have exact same results. Injectors recently cleaned. Fuel flow usually steady in cruise. WTF, over?? Thanks, -Joe N49GH Quote
joepilot Posted January 25, 2017 Author Report Posted January 25, 2017 I will add, it's never run better; except for the fuel flow fluctuation. Starts in a 1/2 blade turn, well balanced fuel flow/runs very smoothly LOP, inflight mag checks perfect, idles great at 700 rpm w throttle full aft and about 0 MAP, etc. I just don't want the fuel flow to "fluctuate" to 0 one day! Quote
Yetti Posted January 26, 2017 Report Posted January 26, 2017 I vote mechanical pump going south. On the ground Prime with elect fuel pump. When fuel cut off is closed. wait and see if it holds pressure. Quote
joepilot Posted January 26, 2017 Author Report Posted January 26, 2017 Thanks Yetti. Did this test. Holds pressure for a long time. Plus, when I get the drop in fuel flow during climb, turning the elec boost ON has zero effect on the fuel flow. The system doesn't seem to be lacking pressure. Quote
RobertGary1 Posted January 26, 2017 Report Posted January 26, 2017 At the risk of stating the obvious, fuel flow should decrease as atmospheric pressure drops. -RObert Quote
joepilot Posted January 26, 2017 Author Report Posted January 26, 2017 Thanks Robert. Problem is, mine drops exponentially. It's an immediate loss of 1-1.5 gph in a matter of seconds. Then sometimes rises back up while still climbing. 1 Quote
cnoe Posted January 26, 2017 Report Posted January 26, 2017 You got me to wondering so I checked my last 5 flights and see nothing so dramatic. My FF always jiggles around a bit but never shows a significant drop unless I instigate it (see graph below). Is there some chance your mixture cable isn't secured well or has excess slop? The answer you seek isn't really obvious. Sent from my iPad using Tapatalk Quote
M016576 Posted January 26, 2017 Report Posted January 26, 2017 (edited) 4 hours ago, joepilot said: I've read other threads relating to this issue. '94J IO-360. 1550 TTSN. Full pwr TO at 1400' MSL, 55 degrees OAT, elec boost pump on, I'm getting 18.4 gph. BUT, at about 2000'-2500' MSL climbing out, the fuel flow (Shadin) will drop from 18.4 to 17-17.4 gph (1-1.4 gph) in about 5 seconds without me touching anything. All EGT's rise with fuel flow drop. Sometimes flow will rise back to 17.8 gph or so after a couple minutes, sometimes not. Fuel pressure rock steady at 25 psi. in almost all phases of flight. Press slightly higher w boost on. GPH drop occurs w either tank selected, and with elec boost pump on OR off. Turning boost on after the drop does NOT restore fuel flow. Happens with full tanks, or 1/4 tanks. Just OH'd fuel servo & have exact same results. Injectors recently cleaned. Fuel flow usually steady in cruise. WTF, over?? Thanks, -Joe N49GH Fuel starting to vaporize in a line? Does the coincide with cylinder temps at all? Look to make sure all fuel lines that should be are shielded, maybe? its not an auto-leaning fuel pump, I take it? Edited January 26, 2017 by M016576 Quote
carusoam Posted January 26, 2017 Report Posted January 26, 2017 (edited) Joe, nicely asked question! Well supported with all the details that usually get asked. A well asked question draws well supported replies. Go CNOE! Summarizing what I think I saw in the thread so far... It seems at this point many of the normal operations are occurring as expected... other people don't experience the same challenge. A good reason to continue looking for the cause... I am noticing a couple of related ideas pointing towards the FF gauge. Bubbles in the line either air or vapor. Bubbles have a way of mixing up the FF data. Some bubbles may appear and cause trouble. Sometimes they get passed through, and the problem goes with them. A change in mixture would be obvious if the knob is turning with vibration, mark the knob with something. Or tighten the thingy(?). Mixture changes usually go one way randomly. It would be unlikely to drift one way and the come exactly back to the same spot. Are there any automatic enrichening devices with this engine? (The carb gets the extra jet, the IO550 gets an automatic fuel pump) The FF is dependent on... - Throttle (& altitude) - Mixture - mechanical fuel Pump (diaphragms leak allowing air in and fuel out to some extent) check the pump drains. - electric FP, same caution regarding diaphragms... - air can leak in from the fuel selector valve switch. - when it is hot enough fuel vapors can for bubbles. - How does the FI system detect altitude/air density/air flow for metering fuel? Something could be going awry with this metering device...? got any recorded flight data from a JPI that you can share? PP thoughts about the information supplied by the community only. I am not a mechanic. Best regards, -a- Edited January 26, 2017 by carusoam 1 Quote
joepilot Posted January 26, 2017 Author Report Posted January 26, 2017 The pumps are not leaking any fuel. It's not a gauge prob as I am getting corresponding EGT rise w drop in ff. I don't believe it's fuel vaporizing in the lines, as it really doesn't do it in cruise or at low fuel flow settings. The mixture knob is not moving & the linkage is tight. But it definitely could be air getting in at the fuel selector valve I guess. I tried to eliminate the fuel servo by overhauling it, which primarily does the fuel metering, etc. Sorry no data. JPI but nobody knows where the data port is located. Thanks! 1 Quote
carusoam Posted January 26, 2017 Report Posted January 26, 2017 (edited) Somebody detailed how to check for leaks regarding the fuel selector. I just don't recall enough detail to find the thread. We have a guy... The used JPI guy that can probably help you get the socket, rs232 wire, and USB converter to make the data download really easy. The socket looks like a small headphone jack. No music coming out of that spot... Best regards, -a- see if this is helpful... https://mooneyspace.com/search/?&q=Leaky fuel selector valve Edited January 26, 2017 by carusoam Quote
cnoe Posted January 26, 2017 Report Posted January 26, 2017 Excellent query by Anthony (possible air intrusion), but it's at a consistent altitude/pressure? This one's a real page turner. Sent from my iPad using Tapatalk Quote
merrja Posted January 26, 2017 Report Posted January 26, 2017 Had the same problem after my recent rebuild. They replaced the fuel pump which fixed it. In speaking with the Lycoming rep at Oshkosh, he told me that they had been having a lot of problems with the fuel pumps being made for them Quote
joepilot Posted January 26, 2017 Author Report Posted January 26, 2017 It would seem obvious to suspect the fuel pump. But wouldn't turning on the electric boost restore the fuel flow if the engine pump's output was low? In my case, elec pump does not change the fuel flow. 1 Quote
cnoe Posted January 26, 2017 Report Posted January 26, 2017 It would seem obvious to suspect the fuel pump. But wouldn't turning on the electric boost restore the fuel flow if the engine pump's output was low? In my case, elec pump does not change the fuel flow. FYI, my engine-driven manual pump outperforms my Dukes electric pump. The electric still holds pressure in the middle of the green arc but the mechanical is at the top. Don't rule out an oddly-performing mechanical pump. Sent from my iPad using Tapatalk Quote
carusoam Posted January 26, 2017 Report Posted January 26, 2017 I think CNOE and I are on the same page... The two pumps are in series, in line with each other. One pump will make it easier for the other pump to do its job. In real life, it would be difficult to tell which one is working or not, or at what %... if you have a fuel pressure gauge, you should see a change in pressure when one pump is on and slightly more when both are on. The pressure isn't very much, so a few psi may be the difference. (M20C logic, but the C uses a lot less fuel pressure). Expect... FF is regulated / metered by the FI system working with the pressure that is being delivered. The system is amazing at how it compensates for so many variables mechanically. Best regards, -a- 1 Quote
M016576 Posted January 26, 2017 Report Posted January 26, 2017 1 hour ago, joepilot said: The pumps are not leaking any fuel. It's not a gauge prob as I am getting corresponding EGT rise w drop in ff. I don't believe it's fuel vaporizing in the lines, as it really doesn't do it in cruise or at low fuel flow settings. The mixture knob is not moving & the linkage is tight. But it definitely could be air getting in at the fuel selector valve I guess. I tried to eliminate the fuel servo by overhauling it, which primarily does the fuel metering, etc. Sorry no data. JPI but nobody knows where the data port is located. Thanks! The reason why fuel might only vaporize in the lines during climb is due to reduced airflow through the cowling. It's a more common issue with bonanzas with the io-550's than mooneys with the io-360... but maybe that could be the issue. Are you seeing cht's above 380, or oil temps over 200? If so, see if a lower climb angle (higher ias), or opening the cowl flaps to full helps. Quote
joepilot Posted January 26, 2017 Author Report Posted January 26, 2017 My shop, via speaking with Lycoming & Bendix, are talking about running a pressure test on the pumps. I guess we'll go ahead with that, thanks. I highly doubt fuel's vaporizing. Cool OAT & my plane runs cool; <330 CHT & <180 oil temp in climb in winter @ 105 KIAS. Quote
Browncbr1 Posted January 26, 2017 Report Posted January 26, 2017 I am based at 1000' msl and usually see GHP in the 17s but it changes with DA and as you climb. Are you certain this is a new phenomenon with your engine? You can check to make sure your pumps aren't leaking by setting mixture to cut off and running electric pump to build up pressure to max value. Then, turn off. It should hold pressure. If pressure drops off, then you have a leak somewhere. I check this before hot starts, as its needed in order to clear the lines of vapor anyway. Quote
Yetti Posted January 26, 2017 Report Posted January 26, 2017 Where is your FF transducer installed? There was a picture of one installed between the divider and servo that seemed to not be in accordance with instructions. Also if the transducer is getting close to the exhaust.... So check the fuel lines from mech pump to the injectors. Take pictures while you are there. Could also be a FF transducer that is gumming up. Quote
Brian Scranton Posted January 26, 2017 Report Posted January 26, 2017 By chance, does your AOA change? My FF/FP changes as I nose over a bit... Quote
joepilot Posted January 30, 2017 Author Report Posted January 30, 2017 This is what I'm seeing. Climbing out of 2000' MSL, full everything, boost pump still on. Fuel flow (left side of display) quickly drops from 18.1 gph to 17.6 gph. Only 1/2 gph this time, but sometimes >1 gph. Corresponding rise in all EGT's. Stabilizes there, usually, then slowly reduces with altitude, as per usual. I'm beginning to think I'm over analyzing this phenomenon. IMG_8211.MOV Quote
joepilot Posted January 30, 2017 Author Report Posted January 30, 2017 On a related note, anybody know what kind of port this is? I've asked everyone. It's presumably for the JPI 700. Quote
carusoam Posted January 30, 2017 Report Posted January 30, 2017 (edited) Looks like it. needs a widely available rs232 to USB converter for laptop use. probably has the 1/8th(?) to rs232 plug / cable in the pockets of the plane. That's where I keep mine anyway... i bought the converter to work with my KLN90B and it just works with the JPI.... jpi sells the cable if you need one. See if our MS /JPI guy has one too. Best regards, -a- Edited January 30, 2017 by carusoam Quote
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