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Scott,
You did a FINE job!!! Glad everyone is safe and on the ground. Always been instructed, do your diag on the ground if at all possible. Again, Great Job! :) |
I had the same problem.
....And it turned out to be blocked and partially blocked nozzles in the spray bar of the TBI (throttle body injection). The Mogas is what caused that. All the testing on the ground would not replicate the problem, it was only after T/O when the RPM got up that it would play up. The high EGT's to me indicated a lean mixture, so I pulled the TBI off and discovered the blocked and partially blocked nozzles. Stale mogas was gumming them up. I have found if the plane sits for three weeks or more (and weather can cause that), the nozzles in the TBI are partially blocked.
I have overcome the mogas problem by adding a fuel stabilizer to the fuel and now it doesn't congeal in the nozzles. Lawn mower shops and marine outboard motor shops use the stabilizer for the same reason. Bob |
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You can check the injector quickly to rule it out. Unscrew the fitting connecting the stainless injector line to the nozzle. Use a 7/16" deep socket to remove the nozzle assembly from the head. There's an insert in the nozzle that will fall out if you turn it upside down, so be careful. Once you have the nozzle out in your hand, drop the insert out, and peer through both parts (nozzle and insert). If there's something clogging it, you'll see the offending particle. Upon reassembly, there is a preferred orientation of the injector in the head. An "A" stamped on one flat of the nozzle should be down, which is the preferred orientation, but torque governs. 60 in-lb for nozzle into head, 25-50 (do not exceed 50!) for tube fitting to nozzle. More info here: http://www.precisionairmotive.com/Pu...s/25-020_a.pdf For what it's worth, I had all nozzles off, did flow tests, etc, eventually changed nozzles, lines, flow divider, plugs, wires, etc. before finally sucking it up and doing the wobble test and valve ream. |
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Water
I'd check for water in your tanks.
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+1
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I was not there, so do not know exactly how mission critical it was to get on the ground ASAP.
The airline folk here might comment, but sometimes rushing to get on the deck can actually increase the dangers quite a lot. So before you beat up Kahuna, think carefully about this. The engine was still running and capable of climbing, stay in the circuit area, and do a bit of troubleshooting and don't panic. Troubleshooting on the ground may not reveal the problem, and may just bite you on the next take off at a worse time. Think about that for a few minutes. What you want to do is do a ROP mag check, and a LOP mag check, one with MAP reduced and a few variables, all logged on your EMS, then land and study the data carefully. You would not believe what I have found in the air that can never be found on the ground. But you do have to play a cautious line here and know what you are looking at in real time. One of the reasons I preach education all the time. The same argument as running a tank dry. Overhead that airfield there is never a reason to panic. This is no way a criticism of the OP, but more data could have been collected with more safety that will be apparent on the next take off. Seems that the valve matter is quite common in some engines so maybe a precautionary ream would be a good idea. |
I had the issue as Lars, same people told me it can't be the Valve, but it was. It's worth checking.
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;) CJ |
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If this was a second take off, you could have had a fleeting vapor lock, especially with a heat soaked top end. I would take on some 100LL and go out for a flight test. |
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