02-05-2026, 05:03 AM
Not an MGL expert and there's a lot of things that could be wrong but it sounds like you get a clean enough signal for the fuel tech display? Is the ground wire from the MGL going direct to the engine block and not being shared with other loads? Double check the dipswitch setting for high frequency filtering. Make sure the tach signal wire is routed safely away from spark plug, fuel injector and alternator wires to reduce possible interference. The ~1k ohm pull-up resistor that you used between pins 6 and 14 wired in parallel, try replacing it.
Other than the obvious (inspect for chaffing/corrosion, poor connections, etc..), I'm not sure what else to suggest. Mine's worked great from the start. Is it also possible you have a short occurring intermittently somewhere unrelated that is being picked up by the tach? If nothing suggested works, then I'd say it's time to take the cowlings off and hang test with new wire & fresh connections.
Other than the obvious (inspect for chaffing/corrosion, poor connections, etc..), I'm not sure what else to suggest. Mine's worked great from the start. Is it also possible you have a short occurring intermittently somewhere unrelated that is being picked up by the tach? If nothing suggested works, then I'd say it's time to take the cowlings off and hang test with new wire & fresh connections.