Fuel injector problem

Aztec Driver

Aztec Driver

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Bryon
Anyone have any input on a recurring problem I have?

Fuel injected IO320
PA30
1966 Twin Comanche
#3 inboard left engine cylinder fuel injector keeps clogging solid shut, causing a rough engine.

I have cleaned it out, and the very next flight it clogs solid again. I find nothing in the feed line, and the injector is just a metered hole, and I cleaned it out thoroughly. It has now clogged three times in a row. My A&P is not well versed in fuel injection, so he doesn't have much input.
 
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How are you cleaning it? What is clogging it up? There is a special technique to cleaning an injector so it does not clog up with the things used to clean it.

Dan
 
We had a similar problem to this on a Cirrus SR22 at our airport.

It was tracked down to a failed fuel filter on the FBO truck. Fibers in the aircraft fuel tank were the "smoking gun".

That FBO is no longer in business.

I suggest you get the material removed analyzed.
 
Steve said:
We had a similar problem to this on a Cirrus SR22 at our airport.

It was tracked down to a failed fuel filter on the FBO truck. Fibers in the aircraft fuel tank were the "smoking gun".

That FBO is no longer in business.

I suggest you get the material removed analyzed.
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But only on the same out of 8 fuel injectors?
 
I clean mine with an ultrasound device I have access to, does a great job.

I would look closely at what the debris is, save it.
Then go looking upstream into all the lines, filters, tanks, sumps.
I think they can also carbon up from a misfire into the intake side which means an engine problem (incompletely closing i valve) but should have other symptoms.
 
Check the fitting in the flow divider that connects the injector line. This fitting, the line and the nozzle itself are the only things common only to that cylinder. I've seen deteriorated fittings cause this. Charlie Melot Zephyr Aircraft Engines
 
It was on the cylinder with the most direct routing from the splitter in line with the entering fuel line. Engine ran rough because only one cylinder was getting starved.

Aztec Driver said:
But only on the same out of 8 fuel injectors?
Click to expand...
 
Aztec Driver said:
Anyone have any input on a recurring problem I have?

Fuel injected IO320
PA30
1966 Twin Comanche
#3 inboard left engine cylinder fuel injector keeps clogging solid shut, causing a rough engine.

I have cleaned it out, and the very next flight it clogs solid again. I find nothing in the feed line, and the injector is just a metered hole, and I cleaned it out thoroughly. It has now clogged three times in a row. My A&P is not well versed in fuel injection, so he doesn't have much input.
Click to expand...

Well, first off, what is it? Considering it happens to the same cyl over and over, I would start in the spider and work my way out looking for damaged or degenerating material.
 
Cleaned the injector and tube again. Ran for three hours, going to the FlyBQ and on to OXB and it worked flawlessly. Hopefully, that will be the end of it.
 
Aztec Driver said:
Cleaned the injector and tube again. Ran for three hours, going to the FlyBQ and on to OXB and it worked flawlessly. Hopefully, that will be the end of it.
Click to expand...

You know the only way to know for sure is to find some IMC!:rofl:

Dan
 
Just from the sound of what you are experiencing it seems to be the flow divider. The metered fuel is delivered from the fuel control unit to a pressurized flow divider. This unit keeps metered fuel under pressure, divides fuel to the various cylinders at all engine speeds, and shuts off the individual nozzle lines when the control is placed in idle cutoff.

Metered fuel pressure enters the flow divider through a channel that permits fuel to pass through the inside diameter of the flow divider needle. At idle speed, the fuel pressure from the regulator must build up to overcome the spring force applied to the diaphragm and valve assembly. This moves the valve upward until fuel can pass out through the annulus of the valve to the fuel nozzle. Since the regulator meters and delivers a fixed amount of fuel to the flow divider, the valve will open only as far as necessary to pass this amount to the nozzles. At idle the opening required is very small; thus the fuel for the individual cylinders is divided at idle by the flow divider.

As fuel flow through the regulator is increased above idle requirements, fuel pressure builds up in the nozzle lines. This pressure fully opens the flow divider valve, and fuel distribution to the engine becomes a function of the discharge nozzles.

A fuel pressure gage, calibrated in pounds-per-hour fuel flow can be used as a fuel flow meter with the Bendix RSA injection system. This gage is connected to the flow divider and senses the pressure being applied to the discharge nozzle. This pressure is in direct proportion to fuel flow and indicates the engine power output and fuel consumption.

I would have your local FBO install a fuel pressure gage and check the system. I also would not use a wire to stick in the end of the fuel nozzle. Soak the injector in MEK for cleaning then us low pressure air to blow dry it.
 
Stache said:
I also would not use a wire to stick in the end of the fuel nozzle. Soak the injector in MEK for cleaning then us low pressure air to blow dry it.
Click to expand...


Agreed, a wire is likely to damage the injector. I've been told to use Hoppe's (gun cleaner) and that it works better than MEK but I know some mechanics use MEK. Another thing is to never use any kind of rag or paper towel on the injectors as you are too likely to snag some fibers which will lead to future problems.
 
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