Fuel pressure, running hot?

[JayMatt]

Flying home yesterday, my fuel gauge decided to ping past max pressure during climb out. Didn't notice any change in the motor and assumed it was the fuel gauge. Motor seemed to be running a little hotter than normal but I've never done long flights in the dead heat of summer so I had no way of knowing one way or the other. I Gauge were in the green and I assumed Mooney made those ranges green for a reason. 

As far as the fuel pressure goes, I've had it go wonky before and it seems to bounce around. Maybe it's a faulty gauge or dirty injectors? any ideas? Is this hot for summer flying? I does 2600 and 23 or 24mp can't remember but it was book 75% power at 4k. Thought I detected slight roughness but wasn't sure. I think my prop needs an overhaul to be fair. 

Opinions? 

These old gauges all that accurate and reliable? 

[Fly Boomer]

1 hour ago, JayMatt said:

Flying home yesterday, my fuel gauge decided to ping past max pressure during climb out. Didn't notice any change in the motor and assumed it was the fuel gauge. Motor seemed to be running a little hotter than normal but I've never done long flights in the dead heat of summer so I had no way of knowing one way or the other. I Gauge were in the green and I assumed Mooney made those ranges green for a reason. 

Does your FUEL PRESS gauge lay over to the right like that when everything is off?

[JayMatt]

Just now, Fly Boomer said:

Does your FUEL PRESS gauge lay over to the right like that when everything is off?

no, it came back down in decent and landing. It's done something wonky before but when I talked to my mechanic about it I couldn't get it to do it again and thought maybe it was dirty injectors or something to that extent. I'd also done a little research and some people said things to that extent. Just hoping there's some experience on here with weird stuff like that. 

Oddly enough it jumps up when I cut the throttle most the time and slow down and then it settles back down. I'll be sorting it out with my mechanic again just digging around on here for experience 

[ArtVandelay]

I think it’s an indication problem, bad connection or probe.
And no, they’re not reliable or accurate in my experience, which is why I replaced them with an modern engine monitor.
Do you think your cylinder temperature is 475° and your oil pressure is just above 60?

[JayMatt]

4 minutes ago, ArtVandelay said:

Do you think your cylinder temperature is 475°

I don't think it's 475 as that would be the tip of the green but maybe that's 400 to 425? I don't know if that's bad or not? According to Mike Busch you should run at 350 and I at least know I'm over that, but it's near impossible to know with this gauge. And I don't know that I agree with him either on his whole red box lean of peak. I was 75% power anyway so it shouldn't matter.  

Here is my theory. Maybe not the cleanest gas on my last fill up even though I did sump my tanks. Some dirty injectors leads to uneven rich lean mixtures and that led to the high fuel pressure read out and the warmer operating temperatures? What was it yesterday afternoon, 95 outside? My exhaust gas temperatures were around 700c which I thought were pretty good. Or maybe this is where everyone else runs on temps and I don't know what 6 hours flying does in the middle of a hot summer day. 

[PT20J]

The 475 on the CHT gauge is the redline.

A clogged injector should cause the engine to run rough. Perhaps your mechanic is confusing this with the case where clogged injectors can cause fuel flow anomalies with pressure type fuel flow gauges that plumb off the GAGE port on the flow divider. You don't have that.

Fuel pressure sometimes varies due to vapor forming in the lines but it does not seem to affect the fuel injection system.

According to the Service Manual, the pressure gauges read full scale when the wire between the sender and the gauge is disconnected or open. I'd check the wiring first. Next most likely is the sender.

[A64Pilot]

Disregarding the fuel pressure thing, I believe your running WAY too hot, I mean really, really hot at least compared to my J, assuming this was cruise and not a long climb, but too hot even in a climb for me.

Oil pressure barely in the green and that hot is concerning, my oil temp never even gets to midway, but then my cylinder head temp I keep at the F mark too.

I assume cowl flaps were fully open? If so then you need to run way richer or lower power and WAY leaner, if they weren’t fully open, then open them, nothing wrong with full open cowl flaps in cruise if that’s what it takes.

Someone else will chime in and say so long as your in the green your fine, and technically they are right, but it’s my opinion that running one that hot significantly shortens it’s life, whatever my opinion is worth.

Back to fuel pressure, I believe it’s an indicating problem, but your mechanic can easily tell by temporarily installing a cheap pressure gauge and seeing.

Check it engine off with the boost pump, if it pegs out it’s very unlikely both your pumps have failed to high pressure. If it’s normal with boost pressure but pegs out when you start the engine, then it’s possible it really is high pressure.

[A64Pilot]

Just as a reference this is where mine normally runs, oil pressure is a little higher now because I shimmed the relief valve, you can tell by fuel flow that I’m much lower power than you were, but even full throttle if I fully open the cowl flaps and keep it rich it doesn’t get much if any hotter, but I rarely do that as yes I’m hauling Butt, but burning, no wasting large amounts of fuel.

700C isn’t hot I don’t think, mine usually peaks right at 800C, I think your cowl flaps weren’t fully open?

The old gauges can be validated but they are usually pretty close, we really don’t need extreme accuracy, just keep things in the middle of the green and you will be fine, these engines have flown just fine for decades with those old gauges.

On edit some will say you MUST have a monitor, it’s just not safe to not have one.

I disagree, I think your fine without one, sure they are nice I’ve had several, best one was an MVP-50, and they are good for trouble shooting, but do you have to have one? I don’t think so.

But, but I cant determine my Gami spread without one, you just must know your Gami spread ! I can run honestly 100C LOP smoothly which is way leaner than I ever need to be, so why do I care what my Gami spread is? Only thing that matters is is it smooth.

 

Edited July 25, 2023 by A64Pilot

[PT20J]

The green range on oil temp is 150 to 245, so this looks like about 221 deg F. My J runs around 196 deg F @ 65% power, peak EGT, WOT, 2500 rpm

The green range on the CHT is 300 - 475, so this looks like about 440 deg F. My J runs around 360-380 deg F @ 65% power, peak EGT, WOT, 2500 rpm

The IO-360 will start to show lower oil pressure and increased oil temp when the oil level gets below 5 qts.

From the vintage of the gauges you have an early J which probably has the flat left cowl flap. This should probably be set to have a half inch or so gap when closed for better cooling.

The baffle seal condition makes a big difference.

Slower airspeeds and higher OAT increase CHTs. 

 

 

[A64Pilot]

9 hours ago, PT20J said:

 

The IO-360 will start to show lower oil pressure and increased oil temp when the oil level gets below 5 qts.

 

 

 @PT20J I have noticed that too, but can’t come up with a reason why, oil temp does not increase mine runs about 180 at 6 or 5 qts, but pressure is lower at 5.

Logically I could see lower volume means higher temps and higher temps means decreased viscosity and lower pressure, but temp stays the same?

I think temp is actually higher, but where we measure it isn’t.

You have a theory that explains it?

[PT20J]

6 hours ago, A64Pilot said:

 @PT20J I have noticed that too, but can’t come up with a reason why, oil temp does not increase mine runs about 180 at 6 or 5 qts, but pressure is lower at 5.

Logically I could see lower volume means higher temps and higher temps means decreased viscosity and lower pressure, but temp stays the same?

I think temp is actually higher, but where we measure it isn’t.

You have a theory that explains it?

The temperature of a substance will increase as it is heated and decrease as it is cooled. The amount of temperature rise will depend on the quantity of substance and the amount of heat transferred. In the case of the oil, the oil is heated by the engine and cooled by the oil cooler. When the amount of heat added and removed are in balance the temperature will remain constant. However, if the amount of oil is decreased, the the same amount of heat will cause a greater temperature rise. 

[JayMatt]

16 hours ago, PT20J said:

The green range on oil temp is 150 to 245, so this looks like about 221 deg F. My J runs around 196 deg F @ 65% power, peak EGT, WOT, 2500 rpm

The green range on the CHT is 300 - 475, so this looks like about 440 deg F. My J runs around 360-380 deg F @ 65% power, peak EGT, WOT, 2500 rpm

The IO-360 will start to show lower oil pressure and increased oil temp when the oil level gets below 5 qts.

From the vintage of the gauges you have an early J which probably has the flat left cowl flap. This should probably be set to have a half inch or so gap when closed for better cooling.

The baffle seal condition makes a big difference.

Slower airspeeds and higher OAT increase CHTs. 

 

 

I was at 75% power but thank you for the numbers. I was trying to figure out where people were running at normally. I know this was a long flight at roughly 3 hours. It also ran a bit cooler up north in Kentucky. I just suspected it wasn't normally to run hotter in Texas even if it was hot outside. very odd thing to me is the exhaust gas being lower than most everyone else but the cylinder head being higher than most... 

I wasn't running with cowl flaps open either. Not at level flight.

I also wasn't all that lean, not compared to normal. This is why I think something may have been going on with the fuel system. It ran fine to the first airport and cooler but we stopped for a half hour and took off again. If there any tips to stopping and hot start that can prevent issues? Maybe relieve pressure on the fuel system by pushing mixture back in after we have it shut off? Don't really know but I plan to do some test runs and see if I'm getting the same issue. 

We'll see what mechanic says too. 

 

[PT20J]

1 hour ago, JayMatt said:

I also wasn't all that lean, not compared to normal.

The highest CHT will occur about 50 deg F ROP. 

[JayMatt]

https://www.aopa.org/news-and-media/all-news/2021/october/pilot/savvy-maintenance-hot-heads

 

According to this article, running 420f is not unrealistic for a lycoming motor and my A&P confirmed this. It was an extremely hot day when we flew. He also thinks it's mostly likely the pressure gauge that is faulty because I wouldn't have made power or I would have detected engine roughness which I didn't have a problem with either. That being said, we'll test the fuel system anyway and use RTV silicone to make sure we are getting all the airflow that we want. We can mess with the baffling some if need be. I'll tinker with all these things and see if I can get better results in a few test flights.

I've never had this issue before but I've never flow cross country on the hottest days of the year in the middle of the day. 

[Fly Boomer]

9 hours ago, JayMatt said:

https://www.aopa.org/news-and-media/all-news/2021/october/pilot/savvy-maintenance-hot-heads

 

According to this article, running 420f is not unrealistic for a lycoming motor and my A&P confirmed this. It was an extremely hot day when we flew. He also thinks it's mostly likely the pressure gauge that is faulty because I wouldn't have made power or I would have detected engine roughness which I didn't have a problem with either. That being said, we'll test the fuel system anyway and use RTV silicone to make sure we are getting all the airflow that we want. We can mess with the baffling some if need be. I'll tinker with all these things and see if I can get better results in a few test flights.

I've never had this issue before but I've never flow cross country on the hottest days of the year in the middle of the day. 

Mike Busch says 380 for Continental and 400 for Lycoming.  Higher temp=shorter life.

[A64Pilot]

10 hours ago, JayMatt said:

https://www.aopa.org/news-and-media/all-news/2021/october/pilot/savvy-maintenance-hot-heads

 

According to this article, running 420f is not unrealistic for a lycoming motor and my A&P confirmed this. It was an extremely hot day when we flew. He also thinks it's mostly likely the pressure gauge that is faulty because I wouldn't have made power or I would have detected engine roughness which I didn't have a problem with either. That being said, we'll test the fuel system anyway and use RTV silicone to make sure we are getting all the airflow that we want. We can mess with the baffling some if need be. I'll tinker with all these things and see if I can get better results in a few test flights.

I've never had this issue before but I've never flow cross country on the hottest days of the year in the middle of the day. 

What position were the cowl flaps in?

[JayMatt]

14 hours ago, A64Pilot said:

What position were the cowl flaps in?

closed. I wasn't too sure if the heat was bad or not at the time, It's green and there was nothing in the manual. It wasn't for a long time that it was that high so it's not a big deal, we flew into cooler areas and some rain not long after but I still want to make sure I don't have issues somewhere in the future. I'm taking measures to get the temps down a little more and to get some better equipment to monitor CHT's more closely. The Oil pressure and and Temp were also fine along with the EGT's per everything I've come across. I've heard people say those may have been off but I've seen plenty of source information showing everyone runs right there also regardless where they say they are running. Fuel pressure is likely a faulty ground from further digging around and looking at the engine last night. We'll also have it tested out next week and go from there. Like I said it's time for a JPI so I don't have to worry about the analog sticks.  

[A64Pilot]

On 7/25/2023 at 2:11 PM, PT20J said:

The temperature of a substance will increase as it is heated and decrease as it is cooled. The amount of temperature rise will depend on the quantity of substance and the amount of heat transferred. In the case of the oil, the oil is heated by the engine and cooled by the oil cooler. When the amount of heat added and removed are in balance the temperature will remain constant. However, if the amount of oil is decreased, the the same amount of heat will cause a greater temperature rise. 

Sure, but my temp gauge remains constant even at 5 qts, but pressure does drop a little as you say. I’d completely understand lower pressure if it was coincident with higher temp, but don’t understand no change in temp with a pressure drop.

My temp gauge does work, it does increase in an extended climb

[PT20J]

9 minutes ago, A64Pilot said:

Sure, but my temp gauge remains constant even at 5 qts, but pressure does drop a little as you say. I’d completely understand lower pressure if it was coincident with higher temp, but don’t understand no change in temp with a pressure drop.

My temp gauge does work, it does increase in an extended climb

What I noticed was that at 4 qts I got a temperature rise and a pressure drop. I haven’t seen a change in either pressure or temperature at 5 qts.

[A64Pilot]

7 hours ago, JayMatt said:

closed. I wasn't too sure if the heat was bad or not at the time, It's green and there was nothing in the manual. It wasn't for a long time that it was that high so it's not a big deal, we flew into cooler areas and some rain not long after but I still want to make sure I don't have issues somewhere in the future. I'm taking measures to get the temps down a little more and to get some better equipment to monitor CHT's more closely. The Oil pressure and and Temp were also fine along with the EGT's per everything I've come across. I've heard people say those may have been off but I've seen plenty of source information showing everyone runs right there also regardless where they say they are running. Fuel pressure is likely a faulty ground from further digging around and looking at the engine last night. We'll also have it tested out next week and go from there. Like I said it's time for a JPI so I don't have to worry about the analog sticks.  

I figured it had to be closed.

In hot Wx even at lower power than you were running I’ll put them in trail, I define that as pull the cable until pressure relaxes, the point where the cable is relaxed, it takes pressure to open or close it.

On the ground my aircraft won’t have this trail feel, only in flight, and if you land with them in trail you’ll see that even though the cable is about half way out, the flaps are only an inch or so open, so in trail they are only open about an inch, many seem to think this reduces drag and increases airspeed, I won’t argue that it doesn’t but I bet the slight increased power from a cooler running engine may be where the increased speed comes from, but it doesn’t matter, what does is that opening the flaps to trail cools the engine and costs you no speed loss, heck you may even gain a kt or two

In my opinion as a pilot we should adjust the cowl flaps as necessary to keep the temps in the middle of the green if possible, if I’m at higher power say 75% on a hot day it may take full open to stay in the middle of the green. If it’s stupid hot and even that won’t keep it in the middle, then I’ll back off on power and run LOP, that will lower cyl head temp significantly, so much so that putting them in trail will keep it in the middle.

Lycoming has said in a few publications that for maximum engine longevity to fly at 65% or less power, which is another reason I fly at lower power, plus I’m old and Retired, I just don’t need to worry about a few minutes longer that it takes to get there.

But I’m convinced that flying towards the higher end of the green does over hundreds of hours reduce the engine life, it’s allowed of course so it’s up to you 

[A64Pilot]

3 minutes ago, PT20J said:

What I noticed was that at 4 qts I got a temperature rise and a pressure drop. I haven’t seen a change in either pressure or temperature at 5 qts.

Mine will drop a little, it’s not much and if I’m honest that’s what tells me to add a quart, yes I do check level before flight, I even open the fuel caps and check level visually.

I’ve not let it get to four yet, any above 6 though I may as well pour on the ground 

Edited July 27, 2023 by A64Pilot

[A64Pilot]

You can do the JPI sure it doesn’t hurt of course, and they are great for troubleshooting, but to quote my old fixed wing test pilot mentor, “close is good enough” meaning that your fine with factory instrumentation.

What I have seen more times than I can count is people with engine monitors get into analysis paralysis and start chasing “problems” that aren’t really problems now that they have all of this data.

My MVP-50 displayed 14 temperatures for instance, factory instruments I believe 2 temps.

Just don’t get wrapped around the axle chasing different cyl head temps and buying nozzles to get your Gami spread down etc, when it was running just fine before the fancy analyzer

 

Edited July 27, 2023 by A64Pilot

[PT20J]

5 minutes ago, A64Pilot said:

Mine will drop a little, it’s not much and if I’m honest that’s what tells me to add a quart, yes I do check level before flight, I even open the fuel caps and check level visually.

I’ve not let it get to four yet, any above 6 though I may as well pour on the ground 

I think they are all a bit unique. The old engine was burning a qt every 2 hrs and that’s how it got down to 4 once. The rebuilt one doesn’t change its use rate noticeably if I keep it between five and six compared to keeping it between six and seven. It did improve from 1 qt every 9-10 hours to 1 in 12 when I switched to X/C 20 w50 from straight 100. 

[A64Pilot]

Yes they are all different, usually though oil consumption is less with straight 50 than with multi vis.

My IO-540W1A5D that I overhauled with 1900 or so hours on it that burned a quart every few hours I expected to get it down to 1 at every ten or so, but with new  Millenium Cylinders and perfect gapped rings it’s oil consumption was exactly the same. I really shouldn’t have overhauled that engine

I honestly don’t track consumption, when it gets down to 5 I add one

Edited July 27, 2023 by A64Pilot

[firelog1101]

Same fuel gauge on my J has been wonky aswell with the engine running normally, will be getting checked on annual. I suspect the gauges just aren't very reliable. I would agree however that your Temps are higher than what I run.  I am usually full cowl flaps to cruise altitude then full close. Temps are good unless low altitude high engine settings.  Over 400 to me would be concerning. Climb out whe away from obstacles around 120 to 130mph, more effecient for time to destination and better airflow.