Help! My engine wont start.

rph142 · #1 02-19-2016, 10:54 PM

After a two month hiatus from aviation I finally got out to the airport and attempted to start my plane. I performed the normal startup procedures for my engine only to crank and crank until my battery was dead. I then charged the battery and tried again the following day - same result. The engine has two bendix mags and a new battery. I don't believe fuel is an issue because I could smell it in the filter air box. Ironically, I just ordered the 500 hour inspection kits for my mags as they are due for inspection. The engine had been slow/difficult to start before my two month hiatus and now it simply wont start. Could the impulse coupler have failed? Mag coils? Timing issues? I'm only starting to research magnetos so any thoughts and opinions will help.

Thanks!

tim2542 · #2 02-20-2016, 04:51 AM

Remember you most likely have only one mag with an impulse, so the other is not participating while cranking, so it could very well be a magneto problem. You should hear the mag snap as you turn the prop by hand in direction of operation. (Mag off of course)
You can disconnect the p lead from the impulse mag and see if it starts (don't disconnect the non impulse mag or you might break your starter), if it starts you have a problem with the switch or p lead.
It's not likely the timing changed while sitting.
Otherwise you don't say if you have a carb or fuel injection so it's hard to suggest fuel related issues.
Tim Andres

Petedfl12 · #3 02-20-2016, 05:43 AM

Check your mag capacitors.
Pete
RV6A

RV6_flyer · #4 02-20-2016, 06:21 AM

Lycoming publishes SSP-475 Reciprocating Engine Trouble Shooting Guide and you can download it from their website.

Back to basics, you need fuel, ignition, and compression occurring at the correct time. Hard to troubleshoot over the internet without being there. Use the troubleshooting guide step by step to eliminate items.

lr172 · #5 02-20-2016, 08:09 AM

Clean and gap the plugs. My speculation is the slowly worsening starting performance was due to deposits build up on the plugs or an increased gap due to erosion. Either one makes starting more difficult in optimum fuel air conditions. Once you flood it, you would have a much harder time getting them to fire with authority.

Try cleaning and gapping the plugs and try again. This is far more likely cause than a mag part failing overnight. You can focus on just the four plugs connected to your impulse mag, as those four do the work during starting.

FYI, I am not suggesting that you don't have bigger issues with the Mag or wires, but it is usually best to start your troubleshooting with the most likely suspects and work backwards to the less likely; especially when the former are easy and cheap.

EDIT: you should also pull a plug to be sure that you are flooding it. Depending upon your starting technique, there are other ways to get gas smells in the carb. If you are carb'ed, I hope that you don't pump the throttle while the engine is not running. Many do it and it dumps raw fuel into the FAB and this is NOT considered a flooded state, only an accident waiting to happen.

Larry

rph142 · #6 02-20-2016, 08:45 PM

I should've mentioned its running an AFP-FM150 injection. My plan is to start with the plugs then 500 hour mag inspections. I'll let everyone know what I find. Thanks for the help.

FLY6 · #7 02-21-2016, 06:35 AM

Could be a long shot but check your ground wires. I saw where a guy couldn't get his plane to start. Only after I saw smoke coming from an oil line did he think to check his ground. This was a new build and he left the paint on the engine when he applied the ground wire. Maybe yours is loose or has some corrosion.

Good luck

Low Pass · #8 02-21-2016, 06:41 AM

If you have to ask an internet discussion board, you should seek out an A&P.

N427EF · #9 02-21-2016, 09:41 AM

You have been getting very good advice in this forum, except for this.

Quote:

If you have to ask an internet discussion board, you should seek out an A&P.

jabarr · #10 02-21-2016, 10:24 AM

I believe most if not all Bendix mags have retard points used for starting as opposed to impulse couplings. I'd be looking for issues with the Slick Start unit or (whatever external device you have installed). Do you hear an audible click when turning engine over by hand? If not, you probably don't have impulse couplings but retard points instead.