The not cold starting 912s
Posted: Fri Aug 07, 2009 3:12 pm
So here is our little saga of the hard cold starting 912s. Last year in August when I started Flying with Andy he complained of the 912s Starting hard in winter. It really was a problem and gut wrenching when you turn the key and the engine goes clang and kicks back against the starter. So I jump on the internet and look for causes. I find a document from rotax and they say - low power supply or possible too much gearbox free play. Andy gets it checked out by Gideon and the gearbox gets re-shimmed and magically the starting problem disappears - we are happy. Summer arrives and she flies some 300 hours till may this year. Comes the real cold - and there we go again clang.. So out comes Gidoen - gearbox gets re-shimmed again - couple of grand later seems ok for a few days - back to clang... I ask questions about battery and wiring - nope has been checked out and battery is replaced. Three weeks later- clang - another trip into the gearbox with no happiness. Gideon, Aviation engines and rainbow now decide - prop is too heavy(P-prop) - sprag clutch is stuffed and so the engine has to be lifted and the prop has to be changed. We not convinced - besides we work out this little trip looks like in excess of R30k.
Yesterday me and Andy flies to tedderfield after struggling to get her going and we notice the charge seems low - 13.2v - we think 13.8 should be more like it. Back at petit we make a couple of calls and Niren and Gideon thinks 13.2 is ok. Me and Andy don't think so. So off comes the cowling and we dive in there with a multimeter. I test the battery - 12.6 standing with nothing on - not bad - 12.7 or 12.8 would be better but seeing the charge rate is so low - not bad. Next port of call - see what the starter gets. With using the motor as a ground and checking during cranking the starter gets 10.1V - eish - not good. So we decide to double up the wiring to the starter and I look but can't find a decent engine earth so we bring one from the battery to the motor direct. Now under cranking the starter gets 11.2v. Much better. Charge is still low though. We go around the other side and test the voltage out of the rectifier and I use the rectifier's casing as earth - sure as heck 13.8 volt with the motor just above idle - shift the earth test point to the engine - 13.2V huh?. Look at the rectifier earth - iffy little wire - goes somewhere on the firewall to another iffy wire. We make up another decent earth - motor to rectifier. Immediatley the actual charge rate goes up to 13.6 on the system. We scratch some more and find another 0.1 volt drop over a fuse from between the rectifier to the connect point for the battery. We lay another fused wire and now we have close on 13.7v on the battery. Happiness. We let it idle a while to charge the battery.
This morning I get a very happy phone call - she starts first time - no kicking back and the charge is good.
Not what has us a little miffed is that between 2 AMO's and the engine agent they can't have found the wiring problems in over a year after Andy spent thousands on getting gearbox shims done. And he asked about wiring before. Anyway - she is still a magic little plane and the motor is good now that we have spent R50 on wiring it properly. If we have left it to them we would have spent a huge bundle and still got nowhere.
I have said it many times - 99% of electrical issues are earth related and there it was yet again. So gents - check those engine and rectifier earth wires out if she struggles to start and charges low. Have a good weekend
Yesterday me and Andy flies to tedderfield after struggling to get her going and we notice the charge seems low - 13.2v - we think 13.8 should be more like it. Back at petit we make a couple of calls and Niren and Gideon thinks 13.2 is ok. Me and Andy don't think so. So off comes the cowling and we dive in there with a multimeter. I test the battery - 12.6 standing with nothing on - not bad - 12.7 or 12.8 would be better but seeing the charge rate is so low - not bad. Next port of call - see what the starter gets. With using the motor as a ground and checking during cranking the starter gets 10.1V - eish - not good. So we decide to double up the wiring to the starter and I look but can't find a decent engine earth so we bring one from the battery to the motor direct. Now under cranking the starter gets 11.2v. Much better. Charge is still low though. We go around the other side and test the voltage out of the rectifier and I use the rectifier's casing as earth - sure as heck 13.8 volt with the motor just above idle - shift the earth test point to the engine - 13.2V huh?. Look at the rectifier earth - iffy little wire - goes somewhere on the firewall to another iffy wire. We make up another decent earth - motor to rectifier. Immediatley the actual charge rate goes up to 13.6 on the system. We scratch some more and find another 0.1 volt drop over a fuse from between the rectifier to the connect point for the battery. We lay another fused wire and now we have close on 13.7v on the battery. Happiness. We let it idle a while to charge the battery.
This morning I get a very happy phone call - she starts first time - no kicking back and the charge is good.
Not what has us a little miffed is that between 2 AMO's and the engine agent they can't have found the wiring problems in over a year after Andy spent thousands on getting gearbox shims done. And he asked about wiring before. Anyway - she is still a magic little plane and the motor is good now that we have spent R50 on wiring it properly. If we have left it to them we would have spent a huge bundle and still got nowhere.
I have said it many times - 99% of electrical issues are earth related and there it was yet again. So gents - check those engine and rectifier earth wires out if she struggles to start and charges low. Have a good weekend
