Hard starting PA-28 140

Hard starting PA-28 140

I am having trouble getting my PA-28 140 started.  Just completed an annual and had ignition wires changed, also discovered some water in one of the tanks.  The aircraft had set for 8 months prior to the annual.  My A&P is stumped.

Anyone have a recommendation?

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Re: Hard starting PA-28 140

Mike,

I'm not a mechanic, but there could be many causes here.  First, check the ignition system:  Are the spark plugs okay?  Are the spark plug wires and connections okay?  Are the mags timed and operating correctly?  Does the airplane have aluminum cables instead of copper?  (the original aluminum ones don't conduct as well and the starter might not rotate very fast - they can be replaced with copper).  Are the battery connections corroded?  What condition is the battery?  What condition is the ignition switch and connections and is it working properly?

Then, is the carburetor functioning correctly?  Is it gummed up (could happen if car gas has been used)? Have you gotten all of the water out of the system?  Are the primer tubes clear and working and does the primer work correctly?  Are you using it? I've got a very well cared for 140 and have never had a problem starting it. It would seem to me that a qualified mechanic should be able to troubleshoot the problem(s).  Good luck!

Gary

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Re: Hard starting PA-28 140

Mike,

Probably the most often overlooked of the Items Gary listed is the primer system, more specifically the nozzles themselves. sometimes the orifice tube will be missing and all the shot goes to that single cylinder but most of the time the tubes will be plugged. If You have a set of small numbered drill bits and an ultrasonic cleaner they can be cleaned relatively easily but they aren't extremely expensive to replace either. Like Gary, I also wonder why Your mechanic can't diagnose the problem.

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Re: Hard starting PA-28 140

I would first check how long it has been since the points have been checked/reset in the magneto's. Most mags get finiky if this is not checked every 500 hrs or so, this is based on the fact that the ignition timing is set up correctly.

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Re: Hard starting PA-28 140

Mike Elder Wrote:
-------------------------------------------------------
> I am having trouble getting my PA-28 140 started.
> Just completed an annual and had ignition wires
> changed, also discovered some water in one of the
> tanks.  The aircraft had set for 8 months prior to
> the annual.  My A&P is stumped.
>
> Anyone have a recommendation?

What do you mean by "it's hard starting". What are you doing when you try and start it, how is the plane/engine acting ??

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Re: Hard starting PA-28 140

As Dave suggested not a lot of info to go on.

As with any engine it is usually one or a combination of 3 things.

Fuel
Spark
Compression

If you have the all of the above then it is - Houston we have lift off!

Frank L
Cherokee 140

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Re: Hard starting PA-28 140

How many pumps are you using for your prime?  I've watched 140 owners use only 2 or 3 pumps and crank for 2 minutes to get it started.  I always use 5 pumps on a cold engine for both my Cherokee's engine and the O-360 in my homebuilt and both planes start up in 2 or 3 blades.  I've talked to other Cherokee owners who think they'll flood the engine out with 5 pumps but I've never had a problem with it in 30 years as a pilot.  FWIW....

Ken

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Re: Hard starting PA-28 140

Hi,

I had the same problem but priming the engine 4-5 times did it.

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Re: Hard starting PA-28 140

Agreed, same thing here, 4-5 times and the engine starts right up.

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Re: Hard starting PA-28 140

I am a new owner of a 1980 Warrior II and need advise on how many times to prime.  I agree 4 to 6 primes on a cold engine works well but I am getting conflicting advise on priming a hot engine.  Starting a hot engine has become a problem and I am being told not to use prime.  Any advise?
Thanks in advance,
Dennis

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Re: Hard starting PA-28 140

I prime my Cherokee 140 3 to 4 times. The number depends on how well the first prime pulled. If I rush the first prime I dont get much fuel.
The 2nd one does as well as the 3rd etc.  Rushing the primer process will deliver less fuel.  Pausing to make sure the primer fills on the pull out is important. If you are not getting consistent resistance after the pause then the primer could be in need of some attention.  If I get a good first pull on the primer I will then only prime 2 more times.  If I dont then I go 3 more times.
Dont know if 5 would be any different or not because I have never done it. Too much prime is not good on the cylinders.
After testing what works best for your airplane is more important than what others do.

Getting the right throttle advance has helped my starting also. I do my best to have the engine start at 1000 RPM.  I then lean immediately to clear the cylinders and make it run smooth.

If I go for a Hamburger which usually takes and hour to 1 1/2 hours I do not prime. If I stop for Gas I do not prime. I do advance the throttle more after I have stopped for food or gas and as soon as it starts which is almost immediately I pull the throttle and reduce the RPM's.

In addition to the above I also have the Sky Tec Starter and copper cables.  Both improved how fast it spins.

Frank L
Cherokee 140

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Re: Hard starting PA-28 140

Hi,

For my cherokee 140, if I prime it once during a hot start it starts right up. Too much priming when the engine is hot will definately flood the engine.

One thing that I did after I bought my plane it was to experiement different ways.

I allways thought that 4-5 priming an engine when it was cold too much but that exactly what the engine needed.

For hot starts the same thing, I tried different ways, no fuel pump, open the throttle 1/2 way, the only way that the engine fires right up is when I prime it one time.

keep trying different ways.

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Re: Hard starting PA-28 140

Hi,

Just recently purchase a 140 and on the way down for delivery from a family friend, he had to replace the starter solenoid because they were having hard times starting it. They thought it was the battery, and after realizing it wasn't that replaced the starter solenoid. That was the magic ticket, and everything has been fine since. So just a possibility.

Sara

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Re: Hard starting PA-28 140

Been following the priming recommendations and in the summer months work great...  Strange thing though when temp drops to around 40 to 35 degrees F.... nothing seems to work...  Checked timing, plugs, and gas all ok as per my mechanic ... any other ideas.

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Re: Hard starting PA-28 140

That is a little peculiar but here's more or less the list of things to check, if it doesn't start, one of these items has probably been overlooked. Since the problem seams temperature related, my first guess is as long as the engine is in sound mechanical shape (Compression, cam lift and timing etc.), and the starter is cranking the engine with adequate speed, the problem probably lies with the fuel delivery/primer system or procedure.

Aux pump on during prime/good fuel pressure?

Verify all primer nozzles are clear but not broken? (Nobody wants to do this but it's an easy job. Nozzles plug with time and need cleared every 5-10 years. If one breaks off, that cylinder floods and the others get nothing during prime)

Verify pump fills when plunger is extended and empties when compressed?
(it really shouldn't need any more than 4-5 shots if the primer system is clear and operating correctly)

Is throttle positioned to yield an engine speed of approx 1000 RPM shortly after it starts? (just off the idle stop but little more)

Ignition switch in correct position for start and correctly wired? (Usually set to start on the left mag only)

Has your mech checked your impulse coupling?

If you're positive everything mentioned on this thread has been checked, it's hard to imagine why there is still a problem but if it comes down to it, try this (It's a variant of the hot start procedure and will only work if your plane has separate mag switch and start button).
Everything as above except an extra shot or two of prime and mag switch off. Push starter button and let engine rotate approx. twice before turning mag switch to "left" mag. Keep starter engaged as you turn mag switch to "left", when (if?) engine starts to fire, leave starter engaged until after you have switched mags to "Both" and engine is running strongly on it's own.

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Re: Hard starting PA-28 140

Thanks.  Dave. Will try a fender the-gsm this morning as temp is 35  will let you know. Lee

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Re: Hard starting PA-28 140

Assuming things are mechaniclly correct in the engine; ie. clean air filter, clear spark plugs, tight sealed carb, properly timed and working mags, charged battery and good starter...

Plunger Primer
I find the plunger primer works great with around 3-4 pulls for most temps and 5-6 for cold temps.  Maybe only 2 for a warm engine.  When using the plunger primer, pull it out slowly, letting it fill with fuel, then push it in sharply.  This will atomize the fuel the best.  Pulling out too sharply will put less fuel and more air into the cylinders.  Begin cranking ASAP after priming to take advantage of the atomized fuel now in the cylinders.  Know how many cylinders are being primed.  I've seen all variations from 1 cylinder to all cylinders.  Count the skinny lines going to the cylinders.  The fewer lines, the fewer plunges you will need.

Carburetor Accelerator Pumps
Because of a very effective accelerator pump, many instructors teach not to use the plunger primer.  I'm pretty sure all carbureted Cherokee's carbs are equipped with an accelerator pump.  This feature is designed to give the engine extra fuel when the throttle is opened quickly, like in a go around or missed approach.  It can also help during starting.
After normal plunger priming, with the Aux Pump on and while cranking the starter, pump the throttle quickly twice from cracked to full open.  On the second pump bring the throttle back to about an inch open.  The first throttle pump primes the accelerator pump.  The second will send a shot of fuel directly up into the barrel of the carb and into the intake manifold.  As long as you are cranking, the fuel will mix with air and the engine will fire shortly.  After 4-5 rotations and no firing, give it one more throttle pump. 

The Flooded Start
If at any time you see gas coming out of the cowling,  stop cranking. The engine is probably flooded.  Open the throttle.  This will let some fuel vapors into the intake manifold.  Let the engine sit a minute or until the gas stops flowing from the engine.  Crank again with the throttle open and no priming.  This will clear the intake.  Be ready to quickly reduce the throttle when it fires.

These techniques work just as well in carbureted Cessnas with accelerator pumps.  They do not work in fuel injected engines, they are primed and started differently.

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Re: Hard starting PA-28 140

Anyone who uses the accelerator pump to prime their engine should also have someone standing beside the plane with a big fire extinguisher.  These engines are equiped with primer pumps to avoid having to use the accelerator pump.  If the carb were on top of the engine so that excess fuel just ran into the engine rather than under the engine so the excess runs out of the intake system then you could get away with this procedure but if you love your plane and don't really want to sell it to the insurance company then you might want to just use the primer.

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Re: Hard starting PA-28 140

I believe Leigh is correct regarding the accelerator pump...use caution and the primer is better.

One other point:  I have found that my 140 starts much better in cold weather if I have pluged in the oil sump heater the night before.  There is a significant difference than if the engine is cold-soaked.  After pre-heating with the oil sump heater, the oil is generally 75 degrees on a cold morning, and when I check the oil level, I can feel that some of the heat has affected the cylinders as well.  My cold weather start procedure includes priming 3 or 4 times as other have indicated above, and she starts just like it was warm weather.  You might consider some method of pre-heating to assist with cold weather starts.

Gary

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Re: Hard starting PA-28 140

IF you read BG's suggestion, he only said to pump the throttle twice, and ONLY WHILE CRANKING THE ENGINE.

I too have found this technique useful when the engine just needs a pit more prime. It also provides a prime to all the cylinders (the primer doesn't). But be careful, incorrectly pumping the throttle is asking for an airbox blowing backfire.

PilotKris

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Re: Hard starting PA-28 140

Yeh, but if you read all of it he goes on to say "The first throttle pump primes the accelerator pump. The second will send a shot of fuel directly up into the barrel of the carb and into the intake manifold. As long as you are cranking, the fuel will mix with air and the engine will fire shortly."

Pull your air box, secure your plane, position yourself CAREFULLY underneath, and see what really happens. First of all, as long as the float bowl is full the pump is already primed and if a second pump is needed to discharge fuel a malfunction is indicated. More importantly, a starter isn't able to rotate the engine fast enough to atomize but a small portion of the discharged fuel and a substantial amount of it is deposited along the manifold and runs back down onto  the carb as liquid. Even when the engine is hot and fuel is evaporated quickly there will probably be wetness by the time the engine starts but it's all just "Fuel for the fire" when the engine is cold. That's what makes pumping the carb so risky and that's why they decided a primer system was needed. (No manufacturer would prefer to eliminate the weight and complexity of unnecessary systems more than those building small aircraft). Naturally, some people "get away" using the pump to start the engine without incident for a long time but most will not. Not that it validates or invalidates using the pump to start an engine and I won't say there are no planes out there with just one or two primer nozzles, but I personally have never seen one and a Cherokee 140 should have no less than 3.

BD goes on to say "If at any time you see gas coming out of the cowling, stop cranking" but how is one able to see that from the pilots seat? Even if the engine doesn't start until the following hour, day, or week the pilot should consider him or herself lucky they can't see anything coming out of the cowling because if they do, it will be smoke, flame, or both. Am I wrong?

The point is that there are no really good reasons to use the throttle to start an engine and some really good ones you shouldn't, the biggest being that fires just plain suck. In the end it comes down to a problem with the plane or a problem with the procedure if the primer won't get it started.

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Re: Hard starting PA-28 140

This works for me 90% of the time. 

I never prime even below 40 degrees.

master switch on

mixture full rich

electric fuel pump on

when fuel pressure maxes out - electric fuel pump off

throttle pump two times full open - return to one third open

hit the starter

and zing its magic

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