Raptor05121 Posted November 16, 2015 Report Share Posted November 16, 2015 Starting my D/C: Master on Fuel pump on Mixture fill rich Throttle pump x2 Fuel pump off Starter engage. Fires on the second blade. Every time. 2 Quote Link to comment Share on other sites More sharing options...
DanM20C Posted November 16, 2015 Report Share Posted November 16, 2015 3 hours ago, Heloman said: Thank you to everyone for the responses; I'm going to check the ignition system as well but it sure seems I have a fuel problem. It sure is frustrating working on other people's airplanes when yours has a problem and you don't have time to deal with it! Does anyone know where the fuel pressure sensor is located, is it possible to read fuel pressure without fuel reaching the carb? I have the maintenance manual but I've been having a hard time getting a parts manual from the two MSCs I've asked. No, the fuel pressure line comes right off of the carb. It's directly inline with the fuel inlet, just on the other side of the carb. 1 Quote Link to comment Share on other sites More sharing options...
par Posted November 16, 2015 Report Share Posted November 16, 2015 3 hours ago, Shadrach said: If it works, it works. I think it's more leftover from the days of radial engines and the SOP of turning them through to ensure no cylinders were hydrolocked. I like your avatar. Is that you? When was it shot? Someone on here actually recommended it after my little fire incident last year. From then on, I figured why do everything I can to set myself up for success, especially when it doesn't take much time or cost me any money. That is me in the avatar. It was a good deal solo currency flight in the Quail MOA and pretty much a selfie fest. Miss those days! 3 Quote Link to comment Share on other sites More sharing options...
Raptor05121 Posted November 17, 2015 Report Share Posted November 17, 2015 Question of my Cherokee/152 days when starting with primer: I was taught hitting the accelerator pump without the engine turning just fills the induction with fuel, causing a risk to fire when fuel spills overboard. How much of a risk is this and/or is it true? Why did Mooney not provide us with a primer? Quote Link to comment Share on other sites More sharing options...
carusoam Posted November 17, 2015 Report Share Posted November 17, 2015 Alex, 1) priming is necessary to get fuel vapors into the engine when it is cold. 2) a priming system is helpful because you can pump more fuel while starting the engine without having the throttle go wide open. 3) a priming system adds mechanical complexity and failure points to the system. And probably overfills the intake equally well. 4) Everyone with a C has valid experience of how to properly start it in all conditions. 5) Pouring gas all over the front tire when it is 21°F outside.... If ignited, the flames will be several feet tall... 6) it is difficult to get a random ignition source close to fuel that is not evaporating. - when it is cold, it is dry. Dry makes static electricity a real danger... - pre-heating with an open flame type system also adds to the real danger of over priming. 7) the usual back fire through the carburator that then spreads around to the fuel on the front tire requires a more technical explanation. A usual backfire is of the scale that CFIs teach to keep turning the starter to suck up the excess fuel and flames. Followed by shut down and inspection. 8) If a couple of pumps is normal, stay with that plan. There are so many pre-heat systems available today, get one or build one. 9) pumping the throttle a dozen times when it's wicked cold out, is a CB ChE from N.E.'s idea of acceptable risk. If you like the science of fuels, look up vapor pressure of 100LL at various temps. The fuel companies will have a chart that will indicate how much fuel vapor will be generated at various temperatures. It takes a lot of fuel spread around to get a small amount of vapor. To get enough vapor to start the engine, you may accidently coat the front tire at 20°F. Don't do this. Build a CB Pre-heat device. Start using ordinary procedures. How does that sound? Best regards, -a- Quote Link to comment Share on other sites More sharing options...
Raptor05121 Posted November 17, 2015 Report Share Posted November 17, 2015 I live in Florida, its rare for our winters to get near 40*F. Even then, hangars are +20*F above outside. Just curious how the accelerator pump squirted fuel downstream versus the primer being upstream being an increased fire risk, thanks. Quote Link to comment Share on other sites More sharing options...
bonal Posted November 17, 2015 Report Share Posted November 17, 2015 On November 16, 2015 at 04:26:40, Shadrach said: To those of you who are prop turners, can you expound on why you turn the prop? Everyone who uses this method appears to be turning the prop before priming, so it's not helping to distribute fuel. What does it do and why do you do it? I've flown a lot of carbureted airplanes, but I've never been told to do this. Cuzthat's how the big boys did back in WW1 it's the manly thing to do...freeing up the motor also let's me get off the compression that stopped the blade from last shut down. Has nothing to do with fueling the engine but definitely reduces initial load on the starter. Quote Link to comment Share on other sites More sharing options...
robert7467 Posted November 17, 2015 Report Share Posted November 17, 2015 Turn fuel pump on, pump 3 times and try starting while finessing the throttle. If you are still having issues, check the mags, plugs and also check the connections on the starter vibrator located below the avionics access panel. Quote Link to comment Share on other sites More sharing options...
Shadrach Posted November 17, 2015 Report Share Posted November 17, 2015 42 minutes ago, bonal said: Cuzthat's how the big boys did back in WW1 it's the manly thing to do...freeing up the motor also let's me get off the compression that stopped the blade from last shut down. Has nothing to do with fueling the engine but definitely reduces initial load on the starter. My sense is that folks do it because they like to feel an association with the former but if questioned about it's merits, feel compelled to do the latter which is to provide some alternate reasoning using anecdotal evidence to put forth some perceived benefit. I have no dog in the fight; you guys can pull your props all day long if you want to. I would say that my own anecdotal evidence tells me that any perceived notions about "saving" the starter are outweighed by the very real risk of a torn rotator cuff... 1 Quote Link to comment Share on other sites More sharing options...
DXB Posted November 17, 2015 Report Share Posted November 17, 2015 As far as the pulling the prop through technique, Orionfit posted a method and rationale for it last winter on a prior thread in response to my inquiry. I'm quoting our exchange here in case it helps. Honestly I don't know enough about the induction system to know if the mechanism is correct or not, but it seemed plausible and did seem to help. Of course preheating helps much more, and so I do that. Orionfit: "The C model in the cold without preheat can be tricky to start. I found that giving it 3-4 pumps then with everything shut down and the mags off pull the prop thru so you cycle thru all 4 cylinders. then I hop back in and fire everything back up. It may not stay running on the first attempt to start but if you pump the throttle another 3 times and try again it will usually stay running. my rule of thumb is if the cylinder temp is below 40 (temps below 40 the night before) expect trouble starting if you do not preheat, the colder the temp the harder it will be to start. what is happening is the cold cylinder walls are condensing the fuel keeping you from getting the optimum fuel air mix you need for starting. by leaving the fuel in the cylinder longer before attempting the start gives it more time to vaporize. just remember when you are doing this not to over crack your starter ( follow the duty cycle limits of the starter) and know that when you engine is cold sometimes it just wont start without preheating it first." Me: "Thanks Brian- I will try the trick with pulling the prop through next time temps are marginal. But wouldn't turning with the starter the first time accomplish the same thing to distribute fuel?" Orionfit: "when you crank with the starter you cycle thru the cylinders too fast and the fuel doesn't have time to vaporize, pulling thru by hand gives it the time it needs. I have tried pumping the throttle 3-4 times then spin the prop 3-4 turns with the starter, then waiting a minute but I have had less success with that and usually end up flooding the engine trying to get the right fuel air mix." Quote Link to comment Share on other sites More sharing options...
Andy95W Posted November 17, 2015 Report Share Posted November 17, 2015 4 hours ago, Raptor05121 said: Just curious how the accelerator pump squirted fuel downstream versus the primer being upstream being an increased fire risk, thanks. Basically, a primer (like on a Cessna 172/152) squirts fuel into the intake at the cylinders themselves. The accelerator pump from the carburetor shoots a stream of fuel straight up into the intake manifold- where it then drips straight back down, through the carburetor, and into the airbox that sits just below the carb. If the rubber tube isn't connected to the tube at the bottom of the airbox, the fuel pools at the bottom of the cowling with nowhere to go until it evaporates or catches on fire. Quote Link to comment Share on other sites More sharing options...
Andy95W Posted November 17, 2015 Report Share Posted November 17, 2015 1 hour ago, DXB said: "when you crank with the starter you cycle thru the cylinders too fast and the fuel doesn't have time to vaporize, pulling thru by hand gives it the time it needs. But unless the engine fires on the very first compression stroke of the very first cylinder that was "preloaded" with fuel vapor, wouldn't the rotation of the engine by the starter push all of the fuel/air mixture out of the cylinders before it ever saw an ignition cycle? Sorry, I'm still having a hard time seeing the necessity of pulling the prop through by hand unless 1.) you want to feel like a B-17 crew chief, or 2.) want a rotator cuff injury like Ross said. 1 Quote Link to comment Share on other sites More sharing options...
bonal Posted November 17, 2015 Report Share Posted November 17, 2015 We all have our little quirks that work best for us. Another thing I do while pulling the prop through is giving myself a better look at my spinner and the hub to blade without having to bend down and look up checking for cracks or oil I am also inspecting the generator belt . And I know this may sound crazy but I listen to and feel what's happening and if I hear or feel something not right or normal. As for starting procedure knowledge I have gained from this very site hot or cold my engine starts so easy every time. I would love to be a crew chief on a 17 Quote Link to comment Share on other sites More sharing options...
Oscar Avalle Posted November 17, 2015 Report Share Posted November 17, 2015 I had a similar problem when I bought my M20C. She was very hard to start once the temperature went below 40s. What I did was to install a Slick Start unit. That helped, but what really makes a difference is preheating the engine. Then you use the electrical fuel pump, throttle twice or three times wait and start. 2 Quote Link to comment Share on other sites More sharing options...
Shadrach Posted November 17, 2015 Report Share Posted November 17, 2015 Indeed the challenge is getting a combustable mixture into the cylinder when temps are so low that the fuel is at its lease volatile. I am sure that preheating helps. Preheating the whole plane would be better as I am sure that a carb warmed to 80° isn't going to stay that way for long when it's filled with 15° gas. 'Tis a dilemma that a primer circuit would have helped to alleviate. That being said, I get why folks prime and then hand prop, though I don't think it superior to using the starter and certainly a $hitty way to discover a bad P lead. I would never touch a prop on an engine that's been primed unless I was trying to start it by hand, something I'd be loath to do on our airplanes for several reasons (prop indexing is less than optimal to say the least). There is potential for a lot of not so good stuff to happen. Does anyone ever just bump the prop a few blades with the starter while pumping the throttle and then pause 15-20 sec? It seems like that would be just as likely to prime the engine as standing in the cold potentially risking your fingers...or worse. It would be bad enough to have your fingers torn off on a warm day...it would really sting in sub freezing temps. 2 Quote Link to comment Share on other sites More sharing options...
carusoam Posted November 17, 2015 Report Share Posted November 17, 2015 Way too many ways to find out you are only human... Making errors or simply forgetting the keys are in the ignition are likely. The compression is so strong on our engines, it requires strength, balance and being really close to the prop. If you lose your balance, you become one with the prop. Watching somebody hand prop a Cub, you can see how weird the idea of hand propping a Mooney engine is. I would like to report that there is a benefit to rotating the prop by hand, I just haven't found one. Best regards, -a- 1 Quote Link to comment Share on other sites More sharing options...
par Posted November 17, 2015 Report Share Posted November 17, 2015 4 hours ago, Oscar Avalle said: I had a similar problem when I bought my M20C. She was very hard to start once the temperature went below 40s. What I did was to install a Slick Start unit. That helped, but what really makes a difference is preheating the engine. Then you use the electrical fuel pump, throttle twice or three times wait and start. Yes, preheating is absolutely key. However, it doesn't have to be something expensive or elaborate. If you have a hangar with electricity, simply stuffing two 100watt bulbs in the cowlings will keep the oil temp right around 50 degrees even if the outside temperature is freezing. I did this the entire winter last year and never had an issue starting. 2 Quote Link to comment Share on other sites More sharing options...
Shadrach Posted November 18, 2015 Report Share Posted November 18, 2015 3 hours ago, par said: Yes, preheating is absolutely key. However, it doesn't have to be something expensive or elaborate. If you have a hangar with electricity, simply stuffing two 100watt bulbs in the cowlings will keep the oil temp right around 50 degrees even if the outside temperature is freezing. I did this the entire winter last year and never had an issue starting. Those brutal VA Beach winters are a real bitch! Quote Link to comment Share on other sites More sharing options...
par Posted November 18, 2015 Report Share Posted November 18, 2015 13 minutes ago, Shadrach said: Those brutal VA Beach winters are a real bitch! Snow and ice the last two winters....cold enough for a californian. Quote Link to comment Share on other sites More sharing options...
Shadrach Posted November 18, 2015 Report Share Posted November 18, 2015 11 minutes ago, par said: Snow and ice the last two winters....cold enough for a californian. No doubt. That being said, I've spent more than a few nights in the Sierra at altitude in single digits trying to remind myself that late season backpacking is fun. Quote Link to comment Share on other sites More sharing options...
DXB Posted November 18, 2015 Report Share Posted November 18, 2015 In case some folks want to see the "pulling the prop through for cold starts" topic beaten to death further, there's this thread: http://www.pilotsofamerica.com/forum/showthread.php?t=68455 Apparently there are some C172s from the 1970s for which the POH actually recommends pulling the prop through before cold temperature starts. It goes so far as to recommend turning it backwards for added safety related to p lead grounding. Perhaps this is where the practice made its jump from WWII bombers to modern GA practice? Quote Link to comment Share on other sites More sharing options...
Heloman Posted November 18, 2015 Author Report Share Posted November 18, 2015 I had a little time this morning so I sprayed a little fuel up the airbox; it started right up, and ran perfect. After shut down, I verified again no amount of pumping could cause any fuel drips from the airbox, so carbs being repaired. Thanks again for all the help, and the unrelated yet interesting information! 1 Quote Link to comment Share on other sites More sharing options...
rbridges Posted November 18, 2015 Report Share Posted November 18, 2015 22 hours ago, par said: Yes, preheating is absolutely key. However, it doesn't have to be something expensive or elaborate. If you have a hangar with electricity, simply stuffing two 100watt bulbs in the cowlings will keep the oil temp right around 50 degrees even if the outside temperature is freezing. I did this the entire winter last year and never had an issue starting. I've got a shop light with a 60w bulb. Someone had previously mentioned putting a blanket on the cowl to insulate it. Even with just a 60w bulb, it will keep it around 40 degrees or so according to the engine monitor. 1 Quote Link to comment Share on other sites More sharing options...
DXB Posted November 18, 2015 Report Share Posted November 18, 2015 37 minutes ago, Heloman said: I had a little time this morning so I sprayed a little fuel up the airbox; it started right up, and ran perfect. After shut down, I verified again no amount of pumping could cause any fuel drips from the airbox, so carbs being repaired. Thanks again for all the help, and the unrelated yet interesting information! This is interesting. Just curious, if the accelerator pump is not working, does it also hesitate or stumble when opening the throttle? One would expect this I think? 1 Quote Link to comment Share on other sites More sharing options...
par Posted November 18, 2015 Report Share Posted November 18, 2015 39 minutes ago, rbridges said: I've got a shop light with a 60w bulb. Someone had previously mentioned putting a blanket on the cowl to insulate it. Even with just a 60w bulb, it will keep it around 40 degrees or so according to the engine monitor. Yep...forgot to mention I do that as well. Its a good cheap solution for my cheap airplane. Quote Link to comment Share on other sites More sharing options...
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