Mine hung up in the 50’s a couple times too. What finally solved it was a new ecu. But, before you buy one, try some of these things. It might be a signal issue between the ecu and receiver. So, replace the male-male servo lead. Could be a signal issue between the ECU and the engine, so replace Ethernet cable. The plugs get old. Reset the engine back to factory settings. This is found under STATISTICS #27. Set to YES, then cycle the battery power switches. Then do an R/C Thottle reset and relearn throttle parameters. Try a start. If no success, Go to LIMITS #32 and make sure that the voltage is set 9.9 V. Then go to AUTOSTART #43 and set to Max 40 seconds. Try a start. If no, then you may have to start buying components, like an ECU, fuel pump, starter, or valve. Try the other stuff first because it is the free trouble shooting items.