knowledgeable peeps please....

Ted DuPuis said:
It can do that, too. Either way, your injectors should be cleaned first step. What also comes to mind is potentially other components in the fuel system.

I assume your plane has a mechanical fuel flow (pressure) gauge. What are you seeing at takeoff power? How does it compare to redline?
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I don't use any of those gauge thingies since my instructor told me to always look outside.

so I bring a safety pilot along with me every flight so they can look at those thingies and it's typically pretty stable between 20-25, usually right at 22 at idle and cruise. honestly I don't recall the # on takeoff, lemme see if I wrote that down anywhere.
 
eman1200 said:
I don't use any of those gauge thingies since my instructor told me to always look outside.

so I bring a safety pilot along with me every flight so they can look at those thingies and it's typically pretty stable between 20-25, usually right at 22 at idle and cruise. honestly I don't recall the # on takeoff, lemme see if I wrote that down anywhere.
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I'm curious what you have for a gauge then, and where it's measuring.

A fuel flow gauge should measure pressure at the fuel distributor, and read an output as a number in fuel flow (since the way these systems work is more pressure = more flow). The number at idle should be very low, near the bottom of the gauge, and the number at cruise should be very high, near the top. 20-25 GPH at takeoff sounds right, but saying 22 at idle and cruise doesn't make sense.

Now if your gauge measures pressure before it goes into the servo, that would make sense. But that means it won't tell you flow and thus you won't have the effect I described on my Aztec.

Similarly, if you have a digital fuel flow gauge that uses a transducer that actually measures flow, then that will give you... actual flow (assuming it's calibrated correctly).

Regardless, first step I'd take is cleaning the injectors. It's virtually free and can't hurt anything.
 
With a constant speed propeller you should be able to see max flow rate on a full power ground run up. The engine manual will tell you what that value should be. Which pattern did the other two injectors follow, the disrupted looking flow or the nice clean stream?

This is again considering you have a fuel flow gauge with a transducer inline.
 
Ted DuPuis said:
I'm curious what you have for a gauge then, and where it's measuring.

A fuel flow gauge should measure pressure at the fuel distributor, and read an output as a number in fuel flow (since the way these systems work is more pressure = more flow). The number at idle should be very low, near the bottom of the gauge, and the number at cruise should be very high, near the top. 20-25 GPH at takeoff sounds right, but saying 22 at idle and cruise doesn't make sense.

Now if your gauge measures pressure before it goes into the servo, that would make sense. But that means it won't tell you flow and thus you won't have the effect I described on my Aztec.

Similarly, if you have a digital fuel flow gauge that uses a transducer that actually measures flow, then that will give you... actual flow (assuming it's calibrated correctly).

Regardless, first step I'd take is cleaning the injectors. It's virtually free and can't hurt anything.
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this is the gauge, I'll check the #'s, maybe I'm wrong with the idle #'s.

IMG_1123.JPG
 
Grum.Man said:
....Which pattern did the other two injectors follow, the disrupted looking flow or the nice clean stream?...
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the others flowed like the first one in the vid. mechanic said he moved the bad nozzle around to the other lines and the erratic flow followed the nozzle.
 
I'm assuming a compression test has been done to check the health of the valves?
 
The fuel pressure gauge you showed (and the green arc that goes with it) makes me think that it shows the fuel pressure going into the servo, and not the fuel flow/pressure at the distributor. That fuel pressure that you see there should basically be constant at higher RPM or when the boost pump is on. With the boost pump off you should expect to see it lower at idle and higher at full power, although how much higher I can't recall.
 
@Ted DuPuis , Hoppes as in the gun cleaner? I don't believe we've ever cleaned the injectors, so I need to look into it.
 
Bill Jennings said:
@Ted DuPuis , Hoppes as in the gun cleaner? I don't believe we've ever cleaned the injectors, so I need to look into it.
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Correct. Stuff works great. Some use ultrasonic cleaners and those work well, too.
 
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My question is why they focused on the Mags before first checking all the lesser expensive possibilities (like most mechanics would). The symptoms pointed to spark or fuel, yet they got tunnel vision on the mags... Really sorry see you go through all of that, E....
 
FlySince9 said:
My question is why they focused on the Mags before first checking all the lesser expensive possibilities (like most mechanics would). The symptoms pointed to spark or fuel, yet they got tunnel vision on the mags... Really sorry see you go through all of that, E....
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they said they checked the nozzles. maybe they did, maybe they didn't, but the problem was intermittent so maybe they DID check but the prob wasn't there at the time. OR, you know, these guys suck.
 
Intermittent problems are challenging to troubleshoot. I'd suspect ignition before fuel every time, just based on experience, but, if you're going to start throwing money at it, rule out the lower cost possibilities first.
 
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