Looking for advice, guys. have a 180 hp A1A carburated engine. can't even get a spark by following Lyc. guidelines..crack throttle, no pumping. Will only start after numerous pumps. do I need primer installed, or is something a-miss? That pumping thing sounds dangerous..
Van's Air Force
Don't miss anything! Register now for full access to the definitive RV support community.
Lycoming A1A engines
- Thread starter flyguy44
- Start date
I have a primer system
I have a primer solenoid down stream of the aux pump feeding fuel directly into the cylinders through the restricted primer nipples silver soldered onto copper tubes with a butane torch (everything from Aircraft Spruce). When the engine is cold I press and hold the push-button switch for five full seconds before I engage the starter and it starts right up. When the engine is hot, as when I just landed to refuel, I use no primer whatsoever and it starts right up. If I do not prime it when it is cold, it will not start. If I prime it when it is hot it will not start. Until I hit on this combination for my O-360-A1A things were awkward with hit or miss results.
Bob Axsom
I have a primer solenoid down stream of the aux pump feeding fuel directly into the cylinders through the restricted primer nipples silver soldered onto copper tubes with a butane torch (everything from Aircraft Spruce). When the engine is cold I press and hold the push-button switch for five full seconds before I engage the starter and it starts right up. When the engine is hot, as when I just landed to refuel, I use no primer whatsoever and it starts right up. If I do not prime it when it is cold, it will not start. If I prime it when it is hot it will not start. Until I hit on this combination for my O-360-A1A things were awkward with hit or miss results.
Bob Axsom
garnt.piper
Well Known Member
No Primer
Hi, my a1a would start without any prime, just two full pumps of the throttle when cold (rely upon accelerator pump in carb). It was new from Van's and sat around for ten years before I started it on the 'plane. I'd have a real good look for induction leaks and check the magneto timing, if you haven't already. If it has been stored the gaskets on the inlet tubes dry and shrink, and internal components of Slick mags can time expire, even with no use. I had one fail in my test phase.
good luck.
Hi, my a1a would start without any prime, just two full pumps of the throttle when cold (rely upon accelerator pump in carb). It was new from Van's and sat around for ten years before I started it on the 'plane. I'd have a real good look for induction leaks and check the magneto timing, if you haven't already. If it has been stored the gaskets on the inlet tubes dry and shrink, and internal components of Slick mags can time expire, even with no use. I had one fail in my test phase.
good luck.
Mr. Fly guy
Have you checked if your mags are in good order, plug wire in the right place, P leads not grounding, as pointed out, the health of the engine?.. Ya gotta tell us all you did.
BTW, starting without priming a carburated engine, is not a wise thing to do. These engine have the most primitive carburators known to the internal combustion engine world (updrqaft), and priming with accelerator pump simply forms a nice pool of fuel in your filter. The engine spins with the hope that air mixture as it passes the pool, is enough to start the beast, but what ever mixture reaches the cylinders, is very lean. Lean condition can and will cause a backfire, and yes, make a torch out of your bird. It has happened numerous times. Do use a primer, be it electric or mechanical.
T88
Have you checked if your mags are in good order, plug wire in the right place, P leads not grounding, as pointed out, the health of the engine?.. Ya gotta tell us all you did.
BTW, starting without priming a carburated engine, is not a wise thing to do. These engine have the most primitive carburators known to the internal combustion engine world (updrqaft), and priming with accelerator pump simply forms a nice pool of fuel in your filter. The engine spins with the hope that air mixture as it passes the pool, is enough to start the beast, but what ever mixture reaches the cylinders, is very lean. Lean condition can and will cause a backfire, and yes, make a torch out of your bird. It has happened numerous times. Do use a primer, be it electric or mechanical.
T88
gmcjetpilot
Well Known Member
More info needed
In cold weather you need some kind of "prime" with a Carb engine. If you don't have a dedicated primer system (which blows raw fuel into the intake port area in a few of the cylinders) you can pump the throttle. The 360A1A has a carb with an accelerator pump, so it can be used to prime. It will blow raw fuel into the throat of the carb. The danger is fuel drips down into the airbox and in theory could be a fire hazard, if not done with some care. You can give it one or two shots with the throttle, wait 30 seconds (let it vaporize), than start. While cranking you may give it another throttle pump while cranking. Be sure after you pump the throttle, you set the throttle back to the slightly open/cracked position right away. Don't over do it because you can foul/flood the plugs.
Cold weather will cause harder starting in general due to low crank speed if the battery is weak, oil is thick or starter is weak.
As far as starting problems in general, not related to priming, you left out way to much. Has it had a history of easy/hard starting? We can guess, but the basics are you need compression, gas / air mixture (in the right proportion) and spark (strong and at the time). You can run those items down one at a time; it could be a little of many items, such as: clean the plugs, check timing, fuel quantity/pressure/quality and compression check. George
flyguy44, lots of missing info and some basics to check. Sounds like it starts but it hard to start? Is the a new thing? Was it easy now all of sudden hard to start? It also sounds like you are not priming at ALL?flyguy44 said:
In cold weather you need some kind of "prime" with a Carb engine. If you don't have a dedicated primer system (which blows raw fuel into the intake port area in a few of the cylinders) you can pump the throttle. The 360A1A has a carb with an accelerator pump, so it can be used to prime. It will blow raw fuel into the throat of the carb. The danger is fuel drips down into the airbox and in theory could be a fire hazard, if not done with some care. You can give it one or two shots with the throttle, wait 30 seconds (let it vaporize), than start. While cranking you may give it another throttle pump while cranking. Be sure after you pump the throttle, you set the throttle back to the slightly open/cracked position right away. Don't over do it because you can foul/flood the plugs.
Cold weather will cause harder starting in general due to low crank speed if the battery is weak, oil is thick or starter is weak.
As far as starting problems in general, not related to priming, you left out way to much. Has it had a history of easy/hard starting? We can guess, but the basics are you need compression, gas / air mixture (in the right proportion) and spark (strong and at the time). You can run those items down one at a time; it could be a little of many items, such as: clean the plugs, check timing, fuel quantity/pressure/quality and compression check. George
Last edited:
Try pumping the throttle three or four times while cranking with the starter, during the starting sequence. This tends to get the fuel into the cylinders better then pumping the throttle before engaging the starter.
Good Luck,
Mahlon
"The opinions and information provided in this and all of my posts are hopefully helpful to you. Please use the information provided responsibly and at you own risk."
Good Luck,
Mahlon
"The opinions and information provided in this and all of my posts are hopefully helpful to you. Please use the information provided responsibly and at you own risk."
A1A starting probs.
Thx for the ideas, guys. As to further info, 1 yr. old engine w/ 160 hrs. has always started fine when cold w/ 5 pumps before turning key (so says prev. owner, and its worked for me for 2 mos.) Last several flts. its crapping out on me and taking forever to start. wonder what to look for...it runs great once it starts.
Thx for the ideas, guys. As to further info, 1 yr. old engine w/ 160 hrs. has always started fine when cold w/ 5 pumps before turning key (so says prev. owner, and its worked for me for 2 mos.) Last several flts. its crapping out on me and taking forever to start. wonder what to look for...it runs great once it starts.
gmcjetpilot
Well Known Member
Too much of a good thing
Lycoming article, priming cold weather
Go down about 14 paragraphs to number of pumps on the primer. Lots of GOOD INFO that may help.
5 PUMPS of what, primer or throttle? I think 5 is a little overkill. If you are using the throttle, that's a lot of raw fuel in your filter. If you have a vans airbox you should have a little drain hole. That hole will allow fuel to drip into the cowl and down to the ground. At best a waste at worse you can wash the filter in fuel (can't be good) and potentially have a fire hazard. Even if you are doing this 5 PUMPS with a primer pump (less of a fire hazard), you are washing lots of fuel into the cylinders which can dilute the oil film and cause wear, not to mention flooding and fouling of the plugs.
Try just two throttle PUMPS before cranking and a couple while cranking like Mahlon suggested in very cold weather. Since it's a new problem, I would look into what Mel suggest with the MAG. Good Luck. G
Here is what Lycoming says about cold weather starting and number of prime pumps (not throttle).flyguy44 said:
Lycoming article, priming cold weather
Go down about 14 paragraphs to number of pumps on the primer. Lots of GOOD INFO that may help.
5 PUMPS of what, primer or throttle? I think 5 is a little overkill. If you are using the throttle, that's a lot of raw fuel in your filter. If you have a vans airbox you should have a little drain hole. That hole will allow fuel to drip into the cowl and down to the ground. At best a waste at worse you can wash the filter in fuel (can't be good) and potentially have a fire hazard. Even if you are doing this 5 PUMPS with a primer pump (less of a fire hazard), you are washing lots of fuel into the cylinders which can dilute the oil film and cause wear, not to mention flooding and fouling of the plugs.
Try just two throttle PUMPS before cranking and a couple while cranking like Mahlon suggested in very cold weather. Since it's a new problem, I would look into what Mel suggest with the MAG. Good Luck. G
Last edited:
Try to confirm that the accelerator pump on the carb was working correctly and pumping adequate fuel when the throttle is moved. If it is taking 5-6 pumps to get the fuel you should get in 2 pumps, then maybe that could be your problem.
Good Luck,
Mahlon
"The opinions and information provided in this and all of my posts are hopefully helpful to you. Please use the information provided responsibly and at you own risk."
Good Luck,
Mahlon
"The opinions and information provided in this and all of my posts are hopefully helpful to you. Please use the information provided responsibly and at you own risk."
Starts
Mr. Flyguy.
Five pumps is a bit over kill unless it's 10 below outside. If your last fiights were getting "worse", you may have other issues to address. Most Lycs use the left mag for starting, although some are equiped with dual impluse. It's unllikely that one is even dead and virtually impossible to loose both, if dual equiped.
You described the"last flights", that the engine wasn't running normally, then indeed there are other issues. Starting with the easiest, check the spark plugs for fouling, if they are wet, there are even more issues. Plug wires if aged will weaken spark. The magnetos themselves can have weakening condensors, worn or pitted points, or improper gap.
On the issue of priming, any 2 or 4 cycle piston engine requires more fuel for starting than when running. This is due to temperatures of the engine itself/ As OAT drops, so is more fuel required. On a typical Floriday day, at 80 to 90 deg, one shot is enough, but when I lived in the windy city, at -10, five or so was not abnormal. In no case should you use the pump for starting. It will invite a fire.
A cold engine requiring fuel, if not enough of it is used for starting, will constitute a lean mixture. Lean mixture will back fire. An air filter with raw fuel in it is ripe for fires. Lycs are outfited with primers for that reason, as are Contis, Franklins and other carburated engines.
It was not unusual for early Cubs and similar hand propping ACs to "flood" the carb with just enough fuel so that vapor made its way to the cylinder. Hand propping would also allow this due to the "slow" movement of the engine. These engine had slower timing than most Lycs have, 18 to 22 deg vs 25 for most Lycs. and less likely to back fire, though they occasionally did.
Having witnessed starting a lean engine (cold) go up in flames on more than one occasion, it's best that primers rather than accelerator pumps be used for cold starts, Always remember that a cold engine is lean. and lean is ripe for backfire. More importantly, correct your problem.
T88
Mr. Flyguy.
Five pumps is a bit over kill unless it's 10 below outside. If your last fiights were getting "worse", you may have other issues to address. Most Lycs use the left mag for starting, although some are equiped with dual impluse. It's unllikely that one is even dead and virtually impossible to loose both, if dual equiped.
You described the"last flights", that the engine wasn't running normally, then indeed there are other issues. Starting with the easiest, check the spark plugs for fouling, if they are wet, there are even more issues. Plug wires if aged will weaken spark. The magnetos themselves can have weakening condensors, worn or pitted points, or improper gap.
On the issue of priming, any 2 or 4 cycle piston engine requires more fuel for starting than when running. This is due to temperatures of the engine itself/ As OAT drops, so is more fuel required. On a typical Floriday day, at 80 to 90 deg, one shot is enough, but when I lived in the windy city, at -10, five or so was not abnormal. In no case should you use the pump for starting. It will invite a fire.
A cold engine requiring fuel, if not enough of it is used for starting, will constitute a lean mixture. Lean mixture will back fire. An air filter with raw fuel in it is ripe for fires. Lycs are outfited with primers for that reason, as are Contis, Franklins and other carburated engines.
It was not unusual for early Cubs and similar hand propping ACs to "flood" the carb with just enough fuel so that vapor made its way to the cylinder. Hand propping would also allow this due to the "slow" movement of the engine. These engine had slower timing than most Lycs have, 18 to 22 deg vs 25 for most Lycs. and less likely to back fire, though they occasionally did.
Having witnessed starting a lean engine (cold) go up in flames on more than one occasion, it's best that primers rather than accelerator pumps be used for cold starts, Always remember that a cold engine is lean. and lean is ripe for backfire. More importantly, correct your problem.
T88
