Had a problem starting today

[Todd Cullen]

I went on a short cross country to Cape Girardeau today....haven’t flown in a few days and wanted to go for lunch and to get some time in at a towered airport and a few practice approached in my new to me Mooney as I’m finishing up my IFR work...

Starting up went perfect as usual...5 second of boost pump and then mixture to lean and increase to rich as it begins to start..   anyway the problem was after I tried to start at Cape after lunch...maybe 35-50 minutes I absolutely could not get the machine started.  First I tried a normal hot start first...no boost pump, mixture lean, throttle cracked.  Then I tried a little boost pump and still no dice.  Talked to one of my instructors and he had me give it more fuel via boost pump with throttle and mixture fully open...this had fuel running out underneath the plane. 

 

Anyway i go inside the FBOs hangar and their mechanic is nice enough to help...he says it was really flooded and maybe vapor locked and helped start it by cranking more than I ever would with the throttle open and mixture out...

 

what should I have done...I’ve hot started this money 5/7 Times with no Issues but this was a big pain...

[aggiepilot04]

Don Maxwell has a great video on YouTube for hot starting the IO360.  Hot starts were a breeze in my J model following those procedures.

[aggiepilot04]

 

[Guest]

200HP Lycoming engines don’t usually need any fuel with a hot start.  I would have cracked the throttle (some say leave it where it was at shut down) start cranking and slowly advance the mixture as it starts.

Clarence

[thomas1142]

This same issue plagued me like crazy; nice start when cold, maybe a bit long in cranking, but nice start. Once I shut down for an hour or so for lunch, or even at the fuel pump (with a little conversation) I could not start it for the life of me. It would finally start hours latter. I finally had maintenance look at it and found two items that impacted the issue. One was the timing was so messed up that the mechanic was supprized that it even started at all. The second item was related to the first, the mag “distributer cap” was so loose it was hard to set the timing. Finally had to have both mags rebuilt. Now the starts happen on one or two blades. Fantastic.

[Todd Cullen]

Hit starts haven’t been that tough...something happened when it sat for 30-45 minutes...it had to be cranked A LOT...I wouldn’t have cranked it as Muchas the mechanic did...but he did that after I flooded it...so I’m confused...

[bradp]

The DMax video above works if you shut down and restart almost immediately - like picking up a passenger.  

If you stop for lunch and gas for 45 min you will be vapor locked. That hot start procedure will be a different one.  Assume you have not enough fuel in the cylinder to fire, vapor locked lines, and a hot engine that won’t want to start too rich like a cold start.  Really the worst possible combination.  

 

First - Try whatever hot start typically works for you (I leave throttle open mixture open no boost pump for 12 seconds, close mixture, throttle to 1/2 inch instead of 1/4 inch and crank).

 

If you can’t get it started using your typical hot start and you haven’t given any gas- add a touch - like less than one second - of gas - just a little squirt.  Or if you’re cranking crack the mixture a little and almost immediately close it.  Once it catches slowly add in mixture until its running.  If it starts to die after you had it running for a few seconds there’s too much fuel or there’s gas in the lines.   You can add a bit of air (throttle) or pull the mixture to lean on the ground.  If it dies in a too much fuel state at least you learned something - you had too much fuel.  

 

If that doesn’t work intentionally flood it.  Just do a normal “cold” start to move the vapor out of the fuel lines and use at least half throttle.  Each plane has a flooded sweet spot throttle position.  Mine is about half open.  Just be ready with the three handed shuffle.  

 

 

[jetdriven]

You can do the 1000 RPM no touch technique to start an engine sitting for 30 minutes or 45 minutes or whatever. The difference between a restart within a couple minutes and 30 minutes is the fuel lines are hot and the fuel is all vapor locked. It will fire then die. The electric boost pump will fix the vapor lock. Do your normal startup but when you shove the mixture forward, put on the boost pump for 20 seconds. Use that time to go to 1200-1400 rpm and blow that hot air from the cowl. Watch the fuel pressure when you turn off the pump. 

[bradp]

2 minutes ago, jetdriven said:

You can do the 1000 RPM no touch technique to start an engine sitting for 30 minutes or 45 minutes or whatever. The difference between a restart within a couple minutes and 30 minutes is the fuel lines are hot and the fuel is all vapor locked. It will fire then die. The electric boost pump will fix the vapor lock. Do your normal startup but when you shove the mixture forward, put on the boost pump for 20 seconds. Use that time to go to 1200-1400 rpm and blow that hot air from the cowl. Watch the fuel pressure when you turn off the pump. 

 

Byron is right here.  You can put your boost pump on to drive out bubbles.  I’ll occasionally use his technique of running the boost while / just after hot starting - it helps with the vapor lock.   If it’s misfiring while taxiing on a really hot day after a hot start I know that’s vapor in the fuel lines and will run the electric boost for a bit until it clears up.  

[KLRDMD]

13 hours ago, Todd Cullen said:

The problem was after I tried to start at Cape after lunch...maybe 35-50 minutes I absolutely could not get the machine started.  First I tried a normal hot start first...no boost pump, mixture lean, throttle cracked.  Then I tried a little boost pump and still no dice.  Talked to one of my instructors and he had me give it more fuel via boost pump with throttle and mixture fully open...this had fuel running out underneath the plane. Anyway i go inside the FBOs hangar and their mechanic is nice enough to help...he says it was really flooded and maybe vapor locked and helped start it by cranking more than I ever would with the throttle open and mixture out.. what should I have done...I’ve hot started this money 5/7 Times with no Issues but this was a big pain...

Assuming the ignition system is good, fuel system good and the engine is getting air (three things necessary for combustion; spark, fuel and air), a general rule of thumb for almost any piston GA airplane when an engine isn't starting as anticipated:

Lycoming: has too much fuel

Continental: doesn't have enough fuel

[ArtVandelay]

Assuming the ignition system is good, fuel system good and the engine is getting air (three things necessary for combustion; spark, fuel and air), a general rule of thumb for almost any piston GA airplane when an engine isn't starting as anticipated:
Lycoming: has too much fuel
Continental: doesn't have enough fuel

Explain how a Lycoming can have too much fuel when you just shut it down by pulling the mixture and starving it of fuel?

[PaulM]

If this was a one time event, then consider it an anomaly.     I started having re-starting problems in my Bravo (Lycoming)   I could do the initial start by the book, but after taxing over for fuel the post re-fuel restart  (not really hot) might take 30-40 seconds of cranking, hitting the boost, etc.   (after years of Dave's 1000RPM no touch warm/hot starts of mixture off, crank, cough, start, mixture smoothly to rich).  I had the shop clean the plugs and check the mag timing.. seemed to help, and then it didn't.    In the end it was the left mag points. (loose)  The run up check was fine, but they weren't getting in the right position during the start.   Probably needed the right mag to start (comes back on line when you release the key).

So,  if you haven't had problems in the past, don't discount that it could be a starter mag problem.. 

[aggiepilot04]

31 minutes ago, teejayevans said:

Explain how a Lycoming can have too much fuel when you just shut it down by pulling the mixture and starving it of fuel?

Watch the Dmax video that I attached.  He explains it in detail.

[INA201]

I do the throttle full open and mixture off approach and when it fires I quickly switch the throttle back and mixture open.  D Max's approach may be worth a go.

[jetdriven]

7 hours ago, teejayevans said:

Explain how a Lycoming can have too much fuel when you just shut it down by pulling the mixture and starving it of fuel?

Because about 5 feet of fuel line plus about 5 feet of fuel injector lines all get super hot and start to boil and the pressure pushes all that fuel into the cylinders. That’s what you hear gurgling and sizzling when pushing the airplane back into the hanger it’s the fuel being pushed out of the fuel lines into the cylinder heads. Its self flooding.  But those fuel lines are now boilled off and dry. Hence the vapor lock. 

[ArtVandelay]

Because about 5 feet of fuel line plus about 5 feet of fuel injector lines all get super hot and start to boil and the pressure pushes all that fuel into the cylinders. That’s what you hear gurgling and sizzling when pushing the airplane back into the hanger it’s the fuel being pushed out of the fuel lines into the cylinder heads. Its self flooding.  But those fuel lines are now boilled off and dry. Hence the vapor lock. 

Ok, but cars don’t do this? It would be nice to have engines that weren’t designed before color TV was invented. This is why when in doubt I do the full throttle, mixture for 10+ seconds, clears the fuel lines, then do hot start.

[MB65E]

Pushing the mixture fwd for several seconds prior to cranking usually moves the air and fuel around enough to clear the lines. You'll notice a fuel P change just sitting there with out running the fuel pump. It's helped me a bunch and prevents running the fuel pump to purge the lines and flooding it. 

-Matt

[Todd Cullen]

Mb65E...just move the mixture full rich for how long?   I’m sure I had a vapor lock... 

 

 

[MB65E]

About 5-6 seconds. Almost like you would priming, but no boost pump. Then back to ico. It just vents the upper lines and makes the air/fuel in the lines stabilize. 

Its kind of an in between hot start procedure. Not adding fuel with the pump, but also doing somthing more than nothing. 

-Matt

[EricJ]

14 hours ago, teejayevans said:

Ok, but cars don’t do this? It would be nice to have engines that weren’t designed before color TV was invented. This is why when in doubt I do the full throttle, mixture for 10+ seconds, clears the fuel lines, then do hot start.

Aircraft injectors are always "on" or open.   There aren't many failure modes other than getting clogged with something.   Modern automotive injectors are electrically controlled by the engine computer, and turned on and off every intake stroke to meter the amount of fuel fed to the cylinder.   An automotive engine won't flood through an injector unless the injector is failed "on", which is rare.