Electrical Start problem - any suggestions?

[RobertP]

Hi All,

My F22A has the Lycoming 0235 115 HP engine. I have an intermitent fault which is annoying and gives the feel that one day probably at the worse time possible it will refuse to start.

When I switch the master switch up to the "on" position sometimes it refuses to give the "clunk" as the electrics engage and the starter light fails to illuminate. Switching it up and down several times then makes the starter light illuminate but then when you turn the ignition key the starter just "clunks" and the engine fails to turn over and the starter light goe's out and you have to start all over again.

It is similar to trying to start an engine with a battery which is to low on charge but I have recentley fitted a new heavy duty battery which improved things but on occasions the problem still persists, however this may be a clue as it may be charge related?

A friend told me that he had an identical problem with a F19 he used to fly and he was told it was a relay? any idea's if it could be the latter and if so where is it located in the engine bay and what does it look like?

Other times the ignition / battery / starter / spins the engine over and it starts at the first spin impressing all in sight!

[lfries]

Re: Electrical Start problem - any suggestions?

Just a thought. Have you checked to be sure that the full 12 volts are passing thru the master switch.

[Hank Jarrett]

Re: Electrical Start problem - any suggestions?

First thought on this since you just replaced the battery is the connections aren't tight on the battery or the main cables were damaged. Check the terminals for security and if the battery is accessible while cranking have someone check the battery voltage before and while cranking. There should be a movement of the volt meter as the starter load hits (MUCH more than just putting the master on). If you don't see a voltage drop the starter isn't pulling power from the battery. The BEST way to check is with an AMP meter, but those aren't as simple as just testing voltage at the terminals.
If the Volt test doesn't tell you anything, you can short across the starter terminals to check the switch (KNOW THE WIRING DIAGRAM BEFORE YOU DO THIS AND THE ENGINE CAN START!) IF the switch doesn't start the engine and shorting the terminals does, the switch is bad. You can also check a lot of wiring with some good wire and a couple of alligator clips. Parallel the wire you suspect and try starting again. If it works with the jumper and not without, you have a bad wire. AGAIN DON'T do these things unless you REALLY understand the wiring diagram. The engine could start when you make a connection!
Hank

[Larry Lyons]

Re: Electrical Start problem - any suggestions?

First impression here is a bad connection either at the Master or the battery. I see this all the time with our construction equipment. A relay might be the culprit but start with the connections, in my opinion anyway. Larry


PS: A digital volt meter is your friend here. Put the leads on each side of a connection and watch for a reading. A good connection will give you no voltage or very low numbers a bad connection will give something substantial and may in fact change with the application of power.

[Dick Smith]

Re: Electrical Start problem - any suggestions?

Here is an interesting link: This doesn't apply directly to a starting issue, but relates to the electrical system on an aircraft. Gives some good basic background.

http://www.nflite.com/ChargingSystem.html

It takes a while to read, but can be enlightening. Dick

[RobertP]

Re: Electrical Start problem - any suggestions?

Hi all,

Firstly Dick thank you for your very informative link, certainly some of the simple applications I can understand, all be it the more complicated aspects are beyond me but it does give an excellent steer on things. I am satisfied the problem is nothing to with the battery fitting as the problem was present and more prevelent before I fitted the new battery and the new battery has improved things greatly. This leads me to suspect that the problem is voltage related as the old battery was definetly defective and not holding a charge very well.

I have also checked the general wiring connections with the covers off and they seem ok with no obvious corrosion present etc. However I have not checked them with a meter so I have only done half the job I suppose!

Reading Dick's link I again suspect the master relay and a second issue which may be a total "red Herring" is that I am going through landing lights at an alarming rate (there is one in each wing in my aircraft ) on average they are lasting a maximum 10 hours flying time which is far less than I would expect, however I have been using them when I taxi at my airport as instructed when I learnt to fly so my use may well be greater than some.

I think the final answer ( apart from a good deal of testing work some of which quite frankly is beyond me ) is to hear from anyone who has a F series aircraft who has experienced a similar problem and what was the remedy as I can't imagine I am the only person to have experienced it particularly as it was present in a F19 a friend of mine flew and the problem was never rectified in that aircraft?

[Hank Jarrett]

Re: Electrical Start problem - any suggestions?

The landing lights burning out fast may not be a red Herring. Bulb filaments burn out faster when the voltage drops which causes a current rise (high voltage will also burn out a filament. but there is a limit to how much voltage a battery can produce). If you have a volt meter on the alternator, and it isn't indicating high voltage (which would mean you have a bad voltage regulator) you could have a bad wire with high resistance. That high resistance wire would cause a voltage drop that would cause the hard starting and could cause the bulbs to fail too.
Got to have a disclaimer here. Like in the prop mounting discussion, I'm NOT an electrical engineer either. I have just burned up my share of electric motors because of bad wires dropping voltage and raising amperage. If bulbs do the same thing you may need to start checking wire sections with that digital volt meter.
Hank

I know, some of you guys just HATE that cheap Chinese junk at Harbor Freight, but their $3.95 Digital Volt meter is great. I have several.

[Larry Lyons]

Re: Electrical Start problem - any suggestions?

You are right Hank, we have meters from under $10 to over $600, they all work great and for this sort of testing the cheapo's work just fine. Larry

[Garry Crookham]

Re: Electrical Start problem - any suggestions?

RobertP:

Looking over the write-up of your electric system problems a couple of things seem to stand out.
First, should the starter light illuminate when the master switch is turned on? The starter light in all the airplanes I'm involved with only illuminate when the starter is cranking...the purpose of the light is to warn the pilot if the starter continues to crank after the engine starts.
Second, if you fail to hear a clunk (the master relay engaging) when the master switch is turned on, there is probably a basic problem, such as an intermittent master switch, master relay, or wiring to the switch or relay.
An easy way to troubleshoot the problem would be to unhook the starter relay from the circuit and verify the master relay is transferring when the master switch is turned on. It is possible that the starter relay might be hanging in the "on" position at times (explaining why the starter light illuminates), loading the electrical system down, but I would expect the starter to try to turn the engine if that were happening.
I'll try to post a picture of a typical master relay and starter relay.
If you have a wiring diagram of your F-22 you might post it here and we could probably better analyze the problem.

Good luck.

Garry Crookham
N5112M
Tulsa, Ok

[RobertP]

Re: Electrical Start problem - any suggestions?

Gary / all,

Thanks for your advice it certainly gives me a very good start.

The master switch illuminates the red ignition light when the switch is flicked up to the "on " position.

When the switch is switched up to the "on" position and the ignition light fails to illuminate the ignition is totally dead ie when the ignition key is turned to the "start" position.

The red ignition light goe's out immeadiately when the ignition switch is turned to the "start" position and the engine goes to turn over but "kicks out" immeadiately then the light goe's out again and you have to flick the master switch up and down five or six times before the red light illuminates again which is accompanied by the reassuring "Clunk" from the electrics which accompanies the illumination and you start all over again turning the ignition switch to the "start" position.

I hope all this makes sense as it is the best way I can explain it!

I still fancy the master relay myself so will probably try that first as and when I can recreate the problem. If that fails to solve it I will move on to those other suggestions I feel capable of trying.

The problem gives the impression that it should be easy to sort out but so far it has baffled brains a good deal better than mine! I will report back when it is solved.

[Hank Jarrett]

Re: Electrical Start problem - any suggestions?

Time for the volt ohm meter again! You should be able to test to see if the relay is closing when you change the switch positions. If it isn't, you should be able to jumper the relay (MAKE SURE YOU JUMP THE RIGHT POLES!!!!) and bypass the relay. If that works you know for sure it was the relay that was bad. Two tests, both showing the relay was not working and that the system did work when you bypassed it.
This should be a pretty simple test if you have someone around who has wired up a starter relay before (and a fairly dangerous one if you start running cables to the wrong terminals!).
Hank

[RobertP]

Re: Electrical Start problem - any suggestions?

Hank,

Thanks for the advice and will give it a try.

[RobertP]

Re: Electrical Start problem - any suggestions?

Hi Guys,

Relay replaced and this seems to have done the trick and she is starting like a dream now! thanks again for all your imput.

[jdoran]

Re: Electrical Start problem - any suggestions?

For those of you that don't know, watch out when buying a solenoid switch like one Gary showed the picture of.

Those things all look the same on the outside, but the coil that energizes the relay may be connected in many different ways internally. Many airplane batteries (and lots of other stuff)drain due to this.

If you are interested, go to Cole Hersee website and look at the schematics that they show for these solenoids. Some are frame grounded, some require a separate ground wire, some have one end of the coil connected internally to the BAT post.

I attached one example schematic.

Also, they come in continuous duty rating, and intermittent duty rating. The master switch requires continuous (because it stays on all the time), the starter relay maybe not so.