Engine won't start

[RobertE]

My mechanic will surely figure out why next week but this forum often comes up with the answer faster.

I've got a J model with th IO360 A3B6 engine. Yesterday after refueling it wouldn't start (I figured it was fuel percolation) but neither would it today. I've got fuel pressure and flow (disconnected one of the injector lines and filled a jar to be sure). So what do you think? Could a single failed mag do it? A bad impulse coupling? Something else?

[Skybrd]

Could it be flooded. If your mags p-leads are grounded, it won't start. I know you already know this but have you tried to start it with the mixture all the way out (if it was flooded). I doubt if you got bad fuel or had a valve stick causing the problem. Good luck and let us know when it's up and running. -- Darrell

[Mooneymite]

Fuel, Fire, Air.....

I'd check spark next, but that's just a wag.

[carusoam]

What was the OAT?

Did you prime the proper amount for the temp?

I often bump into this challenge while fearing flooding...

Best regards,

-a-

[jnisley]

My mechanic will surely figure out why next week but this forum often comes up with the answer faster.

I've got a J model with th IO360 A3B6 engine. Yesterday after refueling it wouldn't start (I figured it was fuel percolation) but neither would it today. I've got fuel pressure and flow (disconnected one of the injector lines and filled a jar to be sure). So what do you think? Could a single failed mag do it? A bad impulse coupling? Something else?

Several years ago one side of my starter switch failed in flight rendering one of the mags inoperative (don't remember if it was left or right mag) had I not done a mag check before shutdown and discovered it I would have had an unpleasant surprise the next time I would have tried to start it because it didn't even attempt to start.

[EDNR-Cruiser]

If your prop turns then it is at least not the starter or the Bendix drive...  If there is no fuel stain below the engine then it is not very likely that you drowned your engine in fuel either. Could be the magnets, the starter switch or just impatience with the engine... How long do you have your Mooney?

[ELT]

If you have the  "SHOWER OF SPARKS" one mag is turned off during start.  The problem can be switch, mag points, plead, multi vibrator or combination of these.  Had a similar problem ended up replacing ALL to fix the problem.  The mechanic ate many hours of trouble shooting.

Good luck

[Guest]

Should be pretty simple to isolate, FAST, fuel, air, spark, think.

You've proven the fuel delivery, the engine didn't likely stop breathing, all 4 cylinders likely didn't quit, all 8 spark plugs likely didn't quit, so it would suggest the magneto.

When you turn the engine over by hand you should hear the impulse coupling clicking. You can remove all plug wires and plugs, turning the propeller by hand while holding one wire at a time about 1/4-1/2" from the cylinder head you should see a spark out of each wire as the impulse fires the magneto, this should happen in the firing order, 1-3-2-4. Both wires for each cylinder should deliver a spark at the same time.

Depending on the vintage of your plane SI M20-59 may apply to the starter/magneto switch. This removed a grounding bar from the switch of early J models, allowing the right magneto to fire during starting.

Clarence

[bonal]

The mag that is tasked with starting has a separate set of points that are set at zero degrees or top dead center. Some times when the prop is turning through and you release the ignition to the both on your ignition switch the engine will fire. As long as you hold the starter on and the one mag is NG the engine will not start. I believe there were some other threads on this condition and I'm not sure if your J has the same system but I always look for spark as my first trouble shoot as long as the engine is cranking then fuel then compression.

Of course if I'm not mistaken you can at least verify your getting compression simply by pulling the prop through all 4 cylinders.

Good luck at least the weather is too crappy to fly this week.

[dcastor]

My high school engine repair teacher had a slightly different mnemonic... Fuel, compression and spark. It seems like it would star if there is fuel and while you haven't completely eliminated a lack of spark, I wonder if compression can be the problem. Of course that class was a single cylinder engine repair class so as I think about it, I'm guessing the engine would still start (albeit roughly) if one of the jugs didn't have compression.

[Piloto]

Sounds like a magneto problem. Easy to check.

 

Pull the #1 cylinder top and bottom spark plugs

Connect the plugs to the harness as before.

Rotate the prop until you find no compression resistance (CCW from your view).

Set the mag switch on BOTH.

Rotate the prop half a turn back CW (from your view)

Look at the plugs and rotate the prop CCW until you hear a click from the mags

When the mags click a spark should be visible on either plug.

 

If no spark is visible the retard on the mag is not working. This problem is only noticeable during engine start. It will not show up during a run up mag check. 

 

Good luck

 

José

[Wakeup]

Jos'e...how do you know so much? I am always impressed by how much you and other mooniacs know about airplanes. I feel so clueless. Troy

[N201MKTurbo]

If you do what Jose says, pull all the top plugs so you don't have any compression. Spinning the prop with live mags is dangerous!

[bonal]

Very dangerous! Question about posting. How do you take someone's post and attach it to a new reply?

[Hank]

Very dangerous! Question about posting. How do you take someone's post and attach it to a new reply?

Very easy. Use the blue "Quote" button in the bottom right corner of the post.

You can use "Multiquote" to attach several posts to your reply, and can type stuff between them if you want to.

BUT if you're using Tapatalk, I can't help you, and it's probably different.

[bonal]

Very easy. Use the blue "Quote" button in the bottom right corner of the post.

You can use "Multiquote" to attach several posts to your reply, and can type stuff between them if you want to.

BUT if you're using Tapatalk, I can't help you, and it's probably different.

Check and see

Thanks Hank

[Piloto]

If you do what Jose says, pull all the top plugs so you don't have any compression. Spinning the prop with live mags is dangerous!

 

Not a bad advice. But now you have to identify cylinder #1 compression prop position. 

Insert one plug on cylinder #1 and a finger on the other plug hole.

Rotate the prop until you feel pressure. This will be the prop position for the spark to occur when the mag clicks.

 

José

[Piloto]

Jos'e...how do you know so much? I am always impressed by how much you and other mooniacs know about airplanes. I feel so clueless. Troy

 

An old airplane and age will teach you a lot.

 

José 

[DAVIDWH]

First we were talking about starting an engine then we have morphed to putting a "Finger in the other plug hole.

 

Now I am totally lost. If my wife catches reading this porn, there will really be problems.

 

Must turn off for now and have my morning coffee before this post goes any deeper.

[Marauder]

First we were talking about starting an engine then we have morphed to putting a "Finger in the other plug hole.

Now I am totally lost. If my wife catches reading this porn, there will really be problems.

Must turn off for now and have my morning coffee before this post goes any deeper.

Or are you going to seek out the wife and ask her to help relieve your tension?

[Bartman]

I once had a flight with high EGT on all 4 cylinders and after shutdown the plane would crank, but would not start. At the time I didn't understand why. The mechanic easily diagnosed a bad dual magneto and I decided to do an exchange....not cheap. I later learned the engine starts on one mag, then runs on two. I then realized why my EGT was high on all 4 cylinders on the last flight and refused to start after shutdown because I was flying on a single mag and didn't realize it. And yes, I did do a mag check before takeoff so it occurred during the flight.

[Jerry 5TJ]

Here in northern California it has been wet the past few days, but dry for most of the past 6 months, so perhaps the novel presence of water is a factor: 

• Any chance you've got water shorting out something electrical in the ignition area?                          
• Or perhaps water got into the fuel system when you tanked up last week and now your injectors are squirting pure H₂O?  (You filled a jar with the liquid from an injector so I presume you'd have noticed clear versus light blue.)   

[RobertE]

Here in northern California it has been wet the past few days, but dry for most of the past 6 months, so perhaps the novel presence of water is a factor: 

• Any chance you've got water shorting out something electrical in the ignition area?                          
• Or perhaps water got into the fuel system when you tanked up last week and now your injectors are squirting pure H₂O?  (You filled a jar with the liquid from an injector so I presume you'd have noticed clear versus light blue.)   

No water in the system. I sumped it and, besides, what emerged from the injector was pure fuel. I'll let you know at it was once ie learn.

[RobertE]

OK. The verdict is in. A dead left mag. Dead. That's the one used at start up. Funny, but I was having a little trouble starting the engine for the preceding couple of weeks, thinking it was something else. So apparently the aircraft does speak to you. I just wasn't listening.

[jetdriven]

I got 50$ it is a slick mag. For some reason, slick impulse mags are failing pretty regularly.