New engine will not start after already been started

[Dick Denenny]

Alright Mooney friends need help. Just had a new rebuild from Western Airways put in my '66 M20E. I had a lot done and more money than I ever expected. New prop etc. Also had a SureFly installed. The engine will start immediately when it is completely cold. If I run it even ten minutes or more and then try to start it will not take. With my other engine I had no problem learning a sequence that let me start it no matter how hot it was. I tried every veriable I can and the only one the works is to completely flood the engine and then crank the hell out of it with no mixture and full throttle and I'm going to ruin my Sky-Tech. Any input. Could the timing be off or what? Wrong plugs? Thanks in advance. Dick

 

[PT20J]

Perhaps the idle mixture might be set too lean? 

[Fritz1]

If you have impulse coupling the sky tech may spin the warm engine fast enough for the impulse coupling not to engage, try slick start mag booster, there may be another problem, but the slick start may fire the hot engine regardless 

[Pinecone]

I would contact SureFly.

 

[Z W]

If the flooded start procedure is working (mixture full lean, throttle full forward), then I would suspect your engine is getting flooded somehow as you try to restart.  In many engines, after a short shutdown, you can just put the mixture back in, turn the mags on, and crank to restart, and any boost pump or priming activity before that or along the way will flood the engine, requiring the use of the flooded start procedure.

I'm not familiar enough with the E engine to recommend a hot start procedure for it, but I bet if you post here what you're trying to do that isn't working, you'll get some suggestions. 

[Echo]

Sorry you are experiencing the failure to fire off after a quick re-start.  I have the same problem with my 65 E Model.  I feel confident that my issue is to MUCH fuel vs. NOT ENOUGH on the re-start.  My home drome fuel is over a dollar a gallon (self serve) higher than a short flight so NOT having consistent re-start capability after a shut down is a major bummer.  There are so many different "techniques" that I find the information confusing.  I wish there was one definitive procedure for this situation (I don't believe mine to be vapor lock), but I have NOT yet found it for my plane.  I am just avoiding a quick re-start as much as possible.  

[Echo]

3 hours ago, Z W said:

If the flooded start procedure is working (mixture full lean, throttle full forward), then I would suspect your engine is getting flooded somehow as you try to restart.  In many engines, after a short shutdown, you can just put the mixture back in, turn the mags on, and crank to restart, and any boost pump or priming activity before that or along the way will flood the engine, requiring the use of the flooded start procedure.

I'm not familiar enough with the E engine to recommend a hot start procedure for it, but I bet if you post here what you're trying to do that isn't working, you'll get some suggestions. 

I will give this technique a try.  

[Shadrach]

If it starts using the the flood procedure, then it is making spark. That does not mean it is making spark at the right time.  You can check idle mixture next time you shut it down by leaning slowly idle rpm. You should see a rise of 25-50RPM as the mixture hits best power on the way to idle cut off. I think this is likely ignition related and would focus on the starting mag (Surefly).

[Z W]

2 hours ago, Echo said:

I will give this technique a try.  

The theory here is this: You had a perfectly running engine at shutdown.  For shutdown, all you did is move the mixture to idle.  There's still gas in the lines, primed and ready to enter the cylinders.  The throttle is already cracked and set to idle speed.  If you put the mixture back to full rich and crank, you're returning the engine just back to how it was a few moments before when it was running happily.  It should re-start.

This works only on short turns, such as refueling or loading or unloading passengers.  If the plane sits for longer (30+ minutes) the fuel in the lines may vaporize from engine heat (vapor lock), drain back to the tank, or drain or evaporate out of the carb.  Then you have to either re-prime, flush the lines with cool fuel from the tanks, or something else to return the cylinders to the proper fuel/air mixture to run.  But after a quick turn, I will typically just crank first and see if it fires.  If it doesn't, then you know it's safe to add more fuel without flooding the engine.

[Shadrach]

22 minutes ago, Z W said:

The theory here is this: You had a perfectly running engine at shutdown.  For shutdown, all you did is move the mixture to idle.  There's still gas in the lines, primed and ready to enter the cylinders.  The throttle is already cracked and set to idle speed.  If you put the mixture back to full rich and crank, you're returning the engine just back to how it was a few moments before when it was running happily.  It should re-start.

This works only on short turns, such as refueling or loading or unloading passengers.  If the plane sits for longer (30+ minutes) the fuel in the lines may vaporize from engine heat (vapor lock), drain back to the tank, or drain or evaporate out of the carb.  Then you have to either re-prime, flush the lines with cool fuel from the tanks, or something else to return the cylinders to the proper fuel/air mixture to run.  But after a quick turn, I will typically just crank first and see if it fires.  If it doesn't, then you know it's safe to add more fuel without flooding the engine.

I’m being a touch pedantic, but the theory actually counts on the fact that the fuel in the lines will boil out and “pre prime” the intake manifold with fuel almost immediately.  You can hear the fuel bubbling, hissing and moving through the lines almost immediately after shutdown. If the plane sits for too long, the fuel vapor that has boiled into the intake manifold dissipates and you are left with no prime and little to no fuel in the injector lines. This is no problem of course as you can just add more using any number methods discussed here multiple times over the last few decades.