Fuel injection problem

[a3holerman]

I have a good friend with a 185 on anfibs, TN IO-520 powered.
He called the other day and asked if I would come over and look at the plane as the engine is running rough. He told me he flew it a few days earlier and it just didn't seem to have the power it should and climbing out was only 200-300fpm. He has had a considerable amount of work done on it including a completely new new exhaust system and a new fuel pump; I believe it was the engine driven pump. The shop had a tough time getting the fuel adjustments correct; proper TO FF and idle. Finally it seemed to run fine for several months until lately.
We taxied out and indeed it was running somewhat rough at idle. Did a runup and it seemed the egts on the insight gauge were more uneven than normal with every other jug being higher than the other.
Mag check looked normal. On takeoff the MAP was up to 30 the Cessna FF gauge showed 29-30gph BUT the digital inline FF gauge was showing only 12-14gph and the rpm languished around 1900. It slowly began to come up but we aborted, obviously, and went back to the tiedown area. At shutdown with the idle at 600 I slowly leaned it out and it seemed to increase slightly then die.

The FBO now says they think its the fuel control unit.
The Cessna FF gauge I know is a pressure gauge and it was up in the normal range but the actual FF was way too low. I am not sure where the pressure is measured from but if its after the fuel control unit would that not indicate a blockage after the it and not necessary the fuel control unit?

The FBO where he had had the work done for the past several years lost their mechanic a month ago and I talked to the new one and he is not up to speed at all.


Does anybody have any idea on what this might be?

Tom

 

[mike mcs repair]

I have a good friend with a 185 on anfibs, TN IO-520 powered.
He called the other day and asked if I would come over and look at the plane as the engine is running rough. He told me he flew it a few days earlier and it just didn't seem to have the power it should and climbing out was only 200-300fpm. He has had a considerable amount of work done on it including a completely new new exhaust system and a new fuel pump; I believe it was the engine driven pump. The shop had a tough time getting the fuel adjustments correct; proper TO FF and idle. Finally it seemed to run fine for several months until lately.
We taxied out and indeed it was running somewhat rough at idle. Did a runup and it seemed the egts on the insight gauge were more uneven than normal with every other jug being higher than the other.
Mag check looked normal. On takeoff the MAP was up to 30 the Cessna FF gauge showed 29-30gph BUT the digital inline FF gauge was showing only 12-14gph and the rpm languished around 1900. It slowly began to come up but we aborted, obviously, and went back to the tiedown area. At shutdown with the idle at 600 I slowly leaned it out and it seemed to increase slightly then die.

The FBO now says they think its the fuel control unit.
The Cessna FF gauge I know is a pressure gauge and it was up in the normal range but the actual FF was way too low. I am not sure where the pressure is measured from but if its after the fuel control unit would that not indicate a blockage after the it and not necessary the fuel control unit?

The FBO where he had had the work done for the past several years lost their mechanic a month ago and I talked to the new one and he is not up to speed at all.


Does anybody have any idea on what this might be?

Tom

You said every other jug. Look for a intake tube off. Every other jug = one side of engine cylinders


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[mike mcs repair]

And it will NOT be the fuel control unit. That’s crazy

Most likely the hose on the Y on theHIT cylinders side. Or up front at the cross over. Also look for blown intake gaskets at cylinders, or broken intake tubes/ castings. It’s sucking extra air on hot side


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[mike mcs repair]

if none of the above fixes it... (unlikely)

then remove injector and hook them back up and flow them into cup with electric pump and see if they fill semi equally... but the likely hood of 3 of them on one side plugging up at same time is really remote....

air leaks are much more common

 

[a3holerman]

Mike,
Thank you so much for the advice.
The fact that the actual FF was so low made me think there must be a obstruction somewhere after the fuel control unit.

 

[mike mcs repair]

Mike,
Thank you so much for the advice.
The fact that the actual FF was so low made me think there must be a obstruction somewhere after the fuel control unit.

When you set pressure. You must do it in correct order. I don’t remember which first, high or low pressure we always set it to higher end of range, it would actually be over red line on takeoff

Are you getting full travel on fuel valve levers?

Have injector been cleaned lately?

Also if you have one cylinder with sticky intake valve(open) or cracked/broken/weak spring it will affect nearby cylinders.




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[mike mcs repair]

I think it measures fuel flow(pressure) from the divider on top of engine that goes to injectors, been years since i played with one....

 

[OLDCROWE]

I think it measures fuel flow(pressure) from the divider on top of engine that goes to injectors, been years since i played with one....

That's correct and they drip fuel out the drain/leak-check on the belly when they start going south.

 

[G280Driver]

http://victor-aviation.com/pdf/tech-docs/SID97-3E.pdf

PROCEDURES AND SPECIFICATIONS FOR ADJUSTMENT OF TELEDYNE CONTINENTAL MOTORS (TCM) CONTINUOUS FLOW FUEL INJECTION SYSTEMS.

Clean injectors first in Hoppe’s #9, gun cleaner. Soak overnight, ultrasonic cleaner if ya have one. Keep track of each injector as they can be different and ya don’t want to mix them up.

 

[8GCBC]

Don’t rule out an air induction issue (obstructions or leaks). Happens a lot.

Fatal example: Mechanics changed the fuel injection system completely out but, it was a delaminated induction hose.

http://www.kathrynsreport.com/2019/04/robinson-r44-raven-ii-n4046j-fatal.html

 

[OLDCROWE]

Next test see what it does with the prime pump on, should tell if you have a main pump issue.

 

[a3holerman]

The owner called me today and said the FBO had talked with the turbo company as it was a TN IO-520 and they said the suspected worn orings in the fuel control unit. It was removed and sent out for overhaul. Would not have been my call.
I will report back when it gets replaced.

 

[mike mcs repair]

The owner called me today and said the FBO had talked with the turbo company as it was a TN IO-520 and they said the suspected worn orings in the fuel control unit. It was removed and sent out for overhaul. Would not have been my call.
I will report back when it gets replaced.

Zero experience with turbo engines here....


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[wireweinie]

Not buying the fuel control as the problem. With every other EGT being off, there is a problem unique to one side only. Either a problem with fuel delivery to one side or an induction problem on one side. Remember that on a turbocharged engine, each injector has a shroud around it that has pressurized air in it from the turbo. If there is no/low air pressure here, the injectors won't work right.

Web

 

[behindpropellers]

I would ask what pressure the fuel flow was set at. If they cannot tell you, they did not set it up.

I'm sure, since it is a seaplane it is a PITA to get set up.

I could not find anybody to set up my 520. I ended up building a test rig and doing it all myself. Now I know that part of my engine system inside out.

Tim

 

[Grant]

An airplane almost killed me and had VERY Similar symptoms....

It ended up being the wrong engine driven fuel pump. It was when I was working for a company and I would occasionally fly the return to service flights after maintenance. In this case I had flown it earlier in the day and it had some rigging issues so they asked if I could fly it in the afternoon after they adjusted it. They also said they the fuel pump to address a service bulletin had just come in and they would do that at the same time. The time came to fly it and I did a run-up (1700RPM)and had no issues. Then I lined up on the runway and gave it to 'er. It stumbled for a split second and lumbered down the runway..... It was a new 172 on amphibs with darn near full fuel, and it turned out to be the hottest day of the year so I was not expecting it to leap for the clouds but once I got it off the ground I knew i was in for an interesting flight. It climbed by nothing more than the grace of God. I didn't dare touch anything because 20 foot/minute is better than nothing, and a wise person (Paul Fisher) once told me "If its climbing and somethings wrong dont F!#&k with it, just take what you can get". I eventually got it turned around and back to the airport and shut down. We re started and ran it up. At 1900 it shuttered and sputtered but smoothed out at 2000 but would not make any power and I don't think it ever went over 2200. Then we hit the boost pump and it ran like a scalded dog. We knew right then it was the wrong fuel pump.


At the end of the day, It was ordered incorrectly by the mechanic, it was installed without checking it by another mechanic, I (Pilot/Mechanic) ran it up according to the checklist (1700 RPM) and it checked out. When it stumbled on the take off roll, it was so fast because it passed through 1900 RPM so quickly. I did not pay attention and assumed it was just doggy performance from an already doggy airplane on a really hot day. It was a real example of lack of professionalism on all parts......

I do full static run-ups for any airplane coming out of maintenance now....And I assume everyone is trying to kill me.....



So, to add my 2 cents, check the fuel pump.


Sorry so long winded....

 

[skywagon8a]

I have a good friend with a 185 on anfibs, TN IO-520 powered......... and a new fuel pump; I believe it was the engine driven pump.
We taxied out and indeed it was running somewhat rough at idle. Did a runup and it seemed the egts on the insight gauge were more uneven than normal with every other jug being higher than the other.
Mag check looked normal. On takeoff the MAP was up to 30 the Cessna FF gauge showed 29-30gph BUT the digital inline FF gauge was showing only 12-14gph and the rpm languished around 1900. It slowly began to come up but we aborted, obviously, and went back to the tiedown area. At shutdown with the idle at 600 I slowly leaned it out and it seemed to increase slightly then die.

The FBO now says they think its the fuel control unit.
The Cessna FF gauge I know is a pressure gauge and it was up in the normal range but the actual FF was way too low. I am not sure where the pressure is measured from but if its after the fuel control unit would that not indicate a blockage after the it and not necessary the fuel control unit?

The FBO where he had had the work done for the past several years lost their mechanic a month ago and I talked to the new one and he is not up to speed at all.


Does anybody have any idea on what this might be?

Tom

if none of the above fixes it... (unlikely)

then remove injector and hook them back up and flow them into cup with electric pump and see if they fill semi equally... but the likely hood of 3 of them on one side plugging up at same time is really remote....

air leaks are much more common

Tom, Is this a manual or automatic waistgate? Manual would keep the turbo out of the condition.
Turbo engines require a pressurized fuel pump. I assume it has the correct one since it operated normally for a period of time?
With normal fuel pressure and low fuel flow, I suspect blockage in the fuel nozzles. The pressure connection is at the flow divider direct to the gauge. The fuel flow is the amount of fuel flowing through the lines. You have the pressure but not the flow. Divider or nozzles. First step is to remove the nozzles from the engine, then with them connected to their plumbing place them each into a small jar. With the mixture full rich run the electric fuel pump for a few seconds. Look in the jars, do they have the same fuel level? If not, are the low ones on the same side of the engine or not? All on the same side it could be something in the flow divider blocking the flow. Otherwise, dirty nozzles.

 

[a3holerman]

Again thank you all for the suggestions.
Pete, Yes that is what I thought, fuel pressure/Fuel flow Cessna gauge did indeed read slightly above 30 but as reported earlier the Digital FF gauge was around 15-17 GPH. Looked up the FF diagram and did see the pressure was taken from the flow divider. Must be a blockage on one side of the divider. me thinks. Its an TN setup so it is an automatic waste gate. They did sent the fuel control unit out for overhaul as there was an AD the needed to be complied with when running it with a TN engine although it worked fine for a couple of years.
Behind propellers , I did the same thing on my 185, built a set of gauges and the IA and myself set it up per the manual. Problem is the pressure could be correct but the actual FF can be way off as in this case.

 

[skywagon8a]

Tom, For what its worth. I installed permanently a JPI slimline fuel pressure gauge T'd in where the Continental manual shows the test installation in my 185 so that I can read both fuel pressures on every take off. Saves all that monkey motion to run the test. I never liked the idea of running the engine at full power on the ground without the cowl on.

 

[a3holerman]

I agree,
I had the FF digital gauge tuned after several tanks of gas so I knew it was accurate on my plane. The full power setting was done using that gauge. AS I recall the two did correlate very close on the 185 with the problem in the past when it was running well.

 

[a3holerman]

Well, here is the followup on the issue.

The shop did remove the fuel metering unit and send it in for overhaul. I had talked to the shop and explained that I was sure the issue was not in the unit and why with the available information we had observed during the runup.
It came back a week later and was installed. Guess what.......made no difference at all. Talked to the shop again and asked/told them to open up the fuel manifold valve on top of the engine and check for contamination. They said they could not do that, it would have to be sent out for overhaul. They said they were not allowed to open that up. BS. Off it cam along with all the lines, the injectors, the fuel pump which keep in mind was producing around 32gph pressure on the Cessna gauge. It was all put back on the other day and the owner and I did a runup and a full power run; everything was back to normal. There was no fuel leaks so we went flying. All was normal. If it was my plane I would have been livid, well actually I was, but kept it to myself as the owner is a good friend and didn't want to spoil the enjoyment he had flying that day.
T

 

[skywagon8a]

Tom, Ask the maintenance persons to look at the piece of plastic in their wallet. Specifically after the IX where it says MECHANIC. Then tell them to turn it over under XII where it says RATINGS. Ask them if the word POWERPLANT is there. That is their authorization to look at the flow divider.
I gather these "mechanics" work at the big facility at the BIG airport nearby?

me·chan·ic
noun

• 1.
  a person who repairs and maintains machinery.

 

[OLDCROWE]

How many hours on the engine pump, mine (IO520-D) showed good pressure/flow but was stumbling after landing when I would give it throttle to taxi to the point I had to hit the electric prime switch to keep it running. Turned into habit until I was getting my flow divider rebuilt (it was dribbling out the vent) and I mentioned it to the fuel metering shop in Tulsa and he said 'bring me the engine driven pump, next time its beginning to fail" and sure enough that was it, but unfortunately mine wasn't rebuildable...

 

[a3holerman]

Pete,
I know its sad that a well known shop near me has come to this.
Oldcrow, actually the repair shop said the pump was OK but did rehab it anyway.