Unstable fuel pressure

[Browncbr1]

I was flying last weekend and opened ram air during a climb to 9000...  It just wouldn't run as smooth and I chalked it up to intake turbulence caused by the ram air.  It missed a few times so I closed the ram air.  But then I started to realize it may have been that I had WOT rather than pulling it back until it just starts to drop MP.   

This weekend, I climbed to 10k and setup cruise and never touched the ram air.  It started missing again, so I pulled throttle back until MP just started to drop then eased it back it to get what I lost.    It seemed to eliminate the missing.  During the process, I noticed the fuel pressure wasn't very stable so I took the video.  After the video, I turned on the boost pump for a bit, then turned it off.  It seemed to help it run smoother the rest of the flight, but that is likely not causation.    Any ideas or advice?  I usually lean to peak. 

IMG_1350.MOV

[kortopates]

No engine monitor data?

[Browncbr1]

Brain farted and forgot to pull data before leaving airport.  But I was watching normalized egts closely and there was never any indication on screen.  

[kortopates]

Any missing would show in the EGT's and we should see CHT corroborate it as well.


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[jetdriven]

If it gets worse with altitude it can be either a failing mechanical fuel pump or fuel starting to form vapor on the pump inlet line from the firewall. Insulating that like with extra fire sleeve did it for me 

[Browncbr1]

5 hours ago, jetdriven said:

If it gets worse with altitude it can be either a failing mechanical fuel pump or fuel starting to form vapor on the pump inlet line from the firewall. Insulating that like with extra fire sleeve did it for me 

This kind of makes sense because my FF was fluctuating up and down as much as .5 gph and does seem to happen at higher altitude

[Joe Larussa]

16 hours ago, Browncbr1 said:

This kind of makes sense because my FF was fluctuating up and down as much as .5 gph and does seem to happen at higher altitude

Let me know what you find. Except for the missing mine does the same thing.

[Joe Larussa]

On 2/20/2017 at 6:33 PM, Browncbr1 said:

I was flying last weekend and opened ram air during a climb to 9000...  It just wouldn't run as smooth and I chalked it up to intake turbulence caused by the ram air.  It missed a few times so I closed the ram air.  But then I started to realize it may have been that I had WOT rather than pulling it back until it just starts to drop MP.   

This weekend, I climbed to 10k and setup cruise and never touched the ram air.  It started missing again, so I pulled throttle back until MP just started to drop then eased it back it to get what I lost.    It seemed to eliminate the missing.  During the process, I noticed the fuel pressure wasn't very stable so I took the video.  After the video, I turned on the boost pump for a bit, then turned it off.  It seemed to help it run smoother the rest of the flight, but that is likely not causation.    Any ideas or advice?  I usually lean to peak. 

IMG_1350.MOV

Having trouble viewing the video.

[FloridaMan]

I had a surging with the ram air open years ago. Eventually it evolved into a hard miss on a takeoff roll that I then aborted. Turns out I had a clogged injector. No engine monitor back then so I can't say, but I'd be curious to see your EGTs when you had the miss and I would recommend diagnosing it before flying again. 

[Browncbr1]

I'm going out to the field tomorrow to look at things and will bring the data back with me.  I was obsessively watching normalized EGTs enroute and did not see anything more than about a 10 degreeF variance on cylinders which is normal.  I saw gradual CHT variances of about 10 degrees, but attributed that to flying into warmer lower pressure air.   stay tuned!

 

[Browncbr1]

After reviewing JPI data, there is no real story there other than FF going up and down .3-.5 gph continuously.   It is possible that my #1 plugs need cleaning, but the rise on left mag check there was not insane.  Just a little higher.   I think over the past 8 months, my left mag has retarded slightly.   

I found some light dye staining on the fire sleeve around the FF transducer fitting.  I tightened up the fitting and hope that will solve.  

[Joe Larussa]

2 hours ago, Browncbr1 said:

After reviewing JPI data, there is no real story there other than FF going up and down .3-.5 gph continuously.   It is possible that my #1 plugs need cleaning, but the rise on left mag check there was not insane.  Just a little higher.   I think over the past 8 months, my left mag has retarded slightly.   

I found some light dye staining on the fire sleeve around the FF transducer fitting.  I tightened up the fitting and hope that will solve.  

I cleaned my fuel flow transducer and found that my fuel pressure is now more consistent. I then put extra fire sleeve on my fuel line going from firewall to fuel pump yesterday. I took it up to 8500 and fuel pressure was way better but flow still runs up and down. Not sure what this means but if I play with the mixer a bit there are spots where the flow is way more consistent.

[Ressum]

You may want to check the fuel servo it could be that it is getting gunked up so that the actual airflow through it and what it meters the fuel at don't fully line up thus having to play with the mixture to smooth it out.

 

[ArtVandelay]

After reviewing JPI data, there is no real story there other than FF going up and down .3-.5 gph continuously.   It is possible that my #1 plugs need cleaning, but the rise on left mag check there was not insane.  Just a little higher.   I think over the past 8 months, my left mag has retarded slightly.   
I found some light dye staining on the fire sleeve around the FF transducer fitting.  I tightened up the fitting and hope that will solve.  

I had a leak coming from my boost pump, just sent it off, this is what I was seeing, will see if it improves after overhaul:

[Browncbr1]

9 hours ago, Joe Larussa said:

I cleaned my fuel flow transducer and found that my fuel pressure is now more consistent. I then put extra fire sleeve on my fuel line going from firewall to fuel pump yesterday. I took it up to 8500 and fuel pressure was way better but flow still runs up and down. Not sure what this means but if I play with the mixer a bit there are spots where the flow is way more consistent.

How did you clean it?  

My transducer only has about 150 hours on it. 

[Joe Larussa]

17 minutes ago, Browncbr1 said:

How did you clean it?  

My transducer only has about 150 hours on it. 

I spoke with the tech guy at JPI. He said to spray WD40 and back flush the transducer. Honestly I used carb cleaner instead. 

[Browncbr1]

I got a chance to get out for a short local flight after having tightened up the fitting last week.  FF was solid at 3000 ft.  I didn't have time to take it up to 8 or 10k.. 

Before starting, I thought I would check the mechanical fuel pump by boosting pressure and holding mixture to cut off to see if it would hold.   It very slowly lost pressure. maybe at a rate of about 5psi per 30-60 seconds..  can anyone tell me if it actually should be able to hold pressure no mater the time lapse?  This mechanical fuel pump is going on 20 years old... 

[Joe Larussa]

1 hour ago, Browncbr1 said:

I got a chance to get out for a short local flight after having tightened up the fitting last week.  FF was solid at 3000 ft.  I didn't have time to take it up to 8 or 10k.. 

Before starting, I thought I would check the mechanical fuel pump by boosting pressure and holding mixture to cut off to see if it would hold.   It very slowly lost pressure. maybe at a rate of about 5psi per 30-60 seconds..  can anyone tell me if it actually should be able to hold pressure no mater the time lapse?  This mechanical fuel pump is going on 20 years old... 

That seems a bit quick compared to mine. I might see 1lb in an hour. If I come the following day

I still have pressure.

[Browncbr1]

14 minutes ago, Joe Larussa said:

That seems a bit quick compared to mine. I might see 1lb in an hour. If I come the following day

I still have pressure.

yea, this is definitely not doing that..i can see the needle slowly move, but it slows down after a couple of minutes..   i'll go ahead and order up a rebuilt pump...  pump cost isn't too bad, but looks like a bear to replace...

[Joe Larussa]

4 minutes ago, Browncbr1 said:

yea, this is definitely not doing that..i can see the needle slowly move, but it slows down after a couple of minutes..   i'll go ahead and order up a rebuilt pump...  pump cost isn't too bad, but looks like a bear to replace...

You are right they are a xxxxx to replace. Not my money but a new pump isn't that expensive and

if you went through all that trouble and you got a jacked rebuilt you would not be a happy man.

Ask me how I know. LOL

[Browncbr1]

3 hours ago, Joe Larussa said:

You are right they are a xxxxx to replace. Not my money but a new pump isn't that expensive and

if you went through all that trouble and you got a jacked rebuilt you would not be a happy man.

Ask me how I know. LOL

Dang it.  Is this another story similar to Kelley overhauled slick mags?    I see tempest rebuilt and lycoming rebuilt...   Am I better to send my pump to a specialist rather than do a core swap?   I don't understand the need to buy new if it's just rubber seals that go bad.  

[Joe Larussa]

1 hour ago, Browncbr1 said:

Dang it.  Is this another story similar to Kelley overhauled slick mags?    I see tempest rebuilt and lycoming rebuilt...   Am I better to send my pump to a specialist rather than do a core swap?   I don't understand the need to buy new if it's just rubber seals that go bad.  

I'm hip to what your saying. I once went through three rebuilt carbs on a 172. Almost killed me. I finally told them I wanted  a brand new carb sent direct from the factory. Problem solved! Shoot we had to remove the mags to get the Mooney pump back in. 

[Joe Larussa]

Looks like new they run about 349.00

[Browncbr1]

12 hours ago, Joe Larussa said:

Looks like new they run about 349.00

where are you seeing that price?   I need LW15473 (IO-360 high pressure) and spruce shows it for $576 new or $273 for "overhauled"

Is AF15473 the tempest part number for LW15473?  I found a new tempest made pump for $309... I trust tempest plugs and oil filters... is there any improvement over the lycoming fuel pump that tempest made?

[Browncbr1]

found the answer... AF15473 is the exact replacement for LW15473, but made by tempest.. i ordered a new one instead of overhauled.. 

This experience has made me fully appreciate that I have a continuous duty electric fuel pump on board!..