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GTCP85-180L APU does not attain combustion


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Hello guys. GTCP85-180L does not fire. It does not go beyond 20% rpm and there is no combustion. We have replaced FCU, oil pressure switch, oil sequencing switch, centrifugal switch, igniter plug, exciter yet no combustion. It just rolls but never achieves combustion. Any help please.

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11 hours ago, pjvr99 said:

you didnt mention replacing aux start relay and fuel holding relay. try that. also

try replacing 110% overspeed solenoid on back of apu.

 

back to ignitor: can you hear it firing?

We replaced both the aux start relay and the fuel holding relay. We also replaced the centrifugal speed switch (110% overspeed switch). We heard the ignite firing. We even saw the spark before installing it back into the combustion chamber. During one of the attempts, the APU rpm rose to 32% and got stagnated. The combustion chamber was also hot indicating some combustion. However,  the APU couldn't self sustain its operations. We have replaced virtually every component from FCU to oil pump to atomizer. We are however not sure of the integrity of the ignite as we do not have a new one in store. We have placed order for new ignitors for further troubleshooting. Thank you all for your contribution. I think we all can learn one or two things from this experience after we might have succeeded. Meanwhile,  kindly keep your suggestions coming.

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ok. sounds like you got the important bits. when you started

troubleshooting, did you set cracking 57 - 63psi? did you 

remove the control air line from fuel cluster while setting

cracking pressure? Have you changed the acceleration/load

control thermostat?

 

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10 hours ago, Shola said:

Model of the APU is GTCP80-180L. Part Number of the APU is 381116-1-7. Thanks a lot. 

Ok was just curious. Gonna go out on a limb here because we had something similar 

last year. Try replacing flexible oil hoses to and from the oil tank, and make sure the

rigid lines and the tank are clean and free of contaminants

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4 minutes ago, pjvr99 said:

Ok was just curious. Gonna go out on a limb here because we had something similar 

last year. Try replacing flexible oil hoses to and from the oil tank, and make sure the

rigid lines and the tank are clean and free of contaminants

Thanks buddy. We will try this suggestion and let you know the outcome. 

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