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Ignition relay repeated malfunction

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There is normal rotation of the engine fuel flow but no ignition.

After replacing ignition relay the engine start normally.

But after very few engine starts the ignition relay malfuction again and there is same problem.

The question is what causes the ignition relay malfuntion?

It is the exciter? the drip valve? the speed sensitive control? the harness? or something else?

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I would take the ignition relay from another engine and put it on the suspect engine. Put the new relay on the other engine. This will confirm whether it is the engine, or a problem with the new relays.

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we replace the exciter and during first flight we have for a few seconds secondary light ON and sparking.we replace speed sense control(65 switch open), make two engine starts everything was good.Also during the replacement of SSC we saw oil at the pad of ssc and a little leak of oil at the pad of accesory.the oil leak could make ssc malfuction and affect the ignition relay or we have ssc malfuction?

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If oil gets into the fly-weights it would most likely only affect the speed at which the switches operate; not the electrical functioning of the ignition system itself. At your next HSC, ISO or engine removal I would suggest replacing the speed switch garloc seal

You would only pull the ignition cb if you had continuous ignition after engine stabilized at LSGI or NGI

 

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If oil gets into the fly-weights it would most likely only affect the speed at which the switches operate; not the electrical functioning of the ignition system itself. At your next HSC, ISO or engine removal I would suggest replacing the speed switch garloc seal

 

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No i do not believe engine vibration to be the cause of the ignition system problem - that is a problem all on its own.

 

Having said that, i had an engine on the stand for vibration evaluation and found speed valve, speed switch, coordinator, gimbal assy all malfunctioning or worn out. A couple days after failing engine for out of limits vibration including turbine and RGB,  I canned the excitor box for another engine. Once it was removed and I could inspect it, I found the screws holding the internal mechanism in place to have vibrated out, leaving several holes in the casing.

 

Bottom line: vibration is NOT your friend

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