63 M20C getting really difficult to start

[ragedracer1977]

Left mag has ~40 hours SNEW, right ~150hrs SNEW.  Plugs were replaced at annual ~30 hours ago. 

In the past, it's started by the 2nd or 3rd blade.  Now, it takes 20, then wait, then pump the throttle a little, then crank some more, then some more, then fires off.  

My standard starting procedure is:  Fuel pump on.  Mixture full rich.  Pump throttle twice.  Push throttle forward just a tad.  Used to be it would immediately fire off.  Temps have not significantly changed.  Would start fine in the mid 80's in the evening a few weeks ago.  Now in the mid 80's I'm worried I'm going to kill the battery.  Once it's running, it runs perfect.  Mag checks on run-up are what I would consider perfect.  Around 100 RPM drop on each mag, with each mag having an essentially identical drop.

What should I be looking at?

[steingar]

The battery. How old, when last checked.  Temps getting cold? Could be affecting power output.

[Jerry 5TJ]

Shower of sparks vibrator: If bad, hard to start but engine thereafter runs normally. 

Consider checking ignition switch to see if it is grounding correct magneto during start. 

 

Edited November 11, 2017 by Jerry 5TJ

[Andy95W]

1.) After turning on the fuel pump, the fuel pressure gauge should rise, and then stay around 4 or 5 psi.  When you pump the throttle to prime the engine, you should see the fuel pressure drop.  If it doesn't, then your accelerator pump in your carburetor needs new seals- otherwise it isn't actually priming the engine.

2.). Along the same lines, try pumping the throttle once or twice while you're cranking.

3.) Talk to your mechanic about checking the strength of the spark coming from your Shower-of-Sparks vibrator unit. He can also check that the shower of sparks is happening at Top Dead Center from the left magneto.  Filing or replacing the points is inexpensive.  As long as you don't have a 201 windshield, it is easy to get to as well.

Good luck, keep us posted on what ends up fixing it.

[ragedracer1977]

2 minutes ago, Andy95W said:

1.) After turning on the fuel pump, the fuel pressure gauge should rise, and then stay around 4 or 5 psi.  When you pump the throttle to prime the engine, you should see the fuel pressure drop.  If it doesn't, then your accelerator pump in your carburetor needs new seals- otherwise it isn't actually priming the engine.

2.). Along the same lines, try pumping the throttle once or twice while you're cranking.

3.) Talk to your mechanic about checking the strength of the spark coming from your Shower-of-Sparks vibrator unit. He can also check that the shower of sparks is happening at Top Dead Center from the left magneto.  Filing or replacing the points is inexpensive.  As long as you don't have a 201 windshield, it is easy to get to as well.

Good luck, keep us posted on what ends up fixing it.

1:  If I turn the fuel pump off, the pressure drops right away.  

2.  That's what I usually end up doing and it slowly coughs to life.

3. I have a 201 windshield.  

[Raptor05121]

Sounds like a fuel delivery issue. I had the same issue with a bad electric fuel pump. Open the left cowl flap deflector panel and the one that flanks the nose wheel doors. Check your fuel selector, fuel pump, and gascolator for leaks, although Andy might be hitting the nail on the head with the carb issue. It's not hard to get to, but its an all-day affair.

[ragedracer1977]

I'm also now wondering if the shower of sparks is working.  Just read a little on it and it says you should hear a buzz from it when you turn the key to start.  I'm not sure that I hear that.  That's one place to look.

2nd, should the pressure stay at 5psi, or close, when I turn the fuel pump off?

[Andy95W]

The shower of sparks is usually pretty much maintenance free, but when it goes it's like Jerry said.

The fuel pressure should stay up until you pump the throttle, or maybe slowly bleed down over a few minutes.  That drop is really just an indication that the accelerator pump is working correctly at the carburetor.  In your case it might mean that your internal seals on your electric pump are starting to go, or you have a leak in your fuel pressure gauge line.

I would try pumping the throttle twice while you are running the electric pump.  If the engine starts, then you'll probably need an overhauled electric pump soon, or you have a leak somewhere else.  If it still doesn't start very well, you're probably due for an overhauled carburetor- or if it was recently done, an IRAN of the accelerator pump.

Edit- I think Alex's post is also right on about checking the fuel selector, gascolator, and pump for leaks.  You will have to remove the inspection panel below the pilot's rudder pedals.  Your fuel pump, like mine, is probably on the firewall just forward of the pilot's feet.  You can probably check it by looking and feeling just above the cowl flap with the fuel pump on and checking everything else for leaks.

[ragedracer1977]

5 minutes ago, Andy95W said:

The shower of sparks is usually pretty much maintenance free, but when it goes it's like Jerry said.

The fuel pressure should stay up until you pump the throttle, or maybe slowly bleed down over a few minutes.  That drop is really just an indication that the accelerator pump is working correctly at the carburetor.  In your case it might mean that your internal seals on your electric pump are starting to go, or you have a leak in your fuel pressure gauge line.

I would try pumping the throttle twice while you are running the electric pump.  If the engine starts, then you'll probably need an overhauled electric pump soon.  If it still doesn't start very well, you're probably due for an overhauled carburetor- or if it was recently done, an IRAN of the accelerator pump.

Edit- I think Alex's post is also right on about checking the fuel selector, gascolator, and pump for leaks.  

Fuel pressure falls immediately (within a few seconds) when I turn off the pump, to zero. I don't see any fluctuation in the pressure when I pump the throttle.

I start with the pump on, always have.   

Not sure when the carb was overhauled, I don't have the logs handy (still at the IA from annual)

[carusoam]

If nothing has changed...

1) expect the weather is getting cooler...

2) if two pumps worked when warm, three or four may make it better... remember to wait 30 seconds for evaporation to occur...

3) I had a procedure for # of pumps based on OAT...

 

As Andy explained...

On my C, the fuel pressure stayed full at the top after the electric pump was turned off, it stayed for a very long time.  Pumping the throttle was nicely indicated by the FP dropping... it took several pumps(?) for it to bleed down, one pump at a time...

If the fuel pressure drops off on its own, This is a sign something else is happening to allow the leak of pressure to occur...

 

For comparison...

With the IO550/fuel injection... as the weather cools... It can be pretty important to run the fuel pump after the engine starts for a minute or two... The subtle extra fuel delivery is required to supplement the slower fuel evaporation rate...

You can hear the engine starving of fuel and dying, while you quickly try to figure out which switch to turn on.

since the carb has a bowl and a float it may not be as sensitive to fuel starvation during the time after start...

 

First things to Check...

1) How quickly the fuel pressure comes up, when the pump is turned on...  Expect just a few seconds... (pump test)

2) How quickly does the pressure drop, on its own... should stay there for quite some time... (fuel system test)

3) Can you See the pressure drop with each pump of the throttle... This is a sign the engine intake is being primed...

4) This fuel is still pretty far from the cylinder intake valves... the carb is mounted below the engine, the intake runners pass through the oil sump.  The oil in the sump won't be very warm for a while.

 

Then get on to abnormal psychology.  If you haven't checked the shower of sparks, it can get ignored for a long time...it may no longer be adjusting the timing needed for a good start.

There is a booklet related to how the SOS system works posted around here somewhere....

Definitely sounds like something is letting fuel pressure escape. Check with your mechanic for reasons why...??

PP thoughts only, not a mechanic...

Best regards,

-a-

[N601RX]

Here is the link to a video of a properly firing SOS I posted a few years ago . You need a adjustable spark gap, current meter and manual to set it up correctly. With new parts and correctly set point gap mine would barely fine.  The dwell is set by slightly bending the contact arm.  This sets the current in the coil and it will come alive when correct. 

 

Shower of Sparks-1.MOV

Edited November 11, 2017 by N601RX

[ragedracer1977]

I'm really leaning towards a fuel or spark issue.  I don't think it's temp related at all.  Upper 80's and low 90's really is not cold.  I'll spend some time at the hangar tomorrow and see what I can see

Anthony,  I definitely do not see any decrease when pumping the throttle cause the pressure is all gone already when I turn the pump off, lol

Edited November 11, 2017 by ragedracer1977

[ragedracer1977]

6 minutes ago, N601RX said:

Here is the link to a video of a properly firing SOS I posted a few years ago . You need a adjustable spark gap, current meter and manual to set it up correctly. With new parts and correctly set point gap mine would barely fine.  The dwell is set by slightly bending the contact arm.  This sets the current in the coil and it will come alive when correct. 

 

Shower of Sparks-1.MOV

Wow that's pretty impressive

[mike_elliott]

Everything you need to know about the SOS system.

ShowerSparks[2].pdf

ShowerOfSparks.pdf

[ragedracer1977]

43 minutes ago, mike_elliott said:

Everything you need to know about the SOS system.

ShowerSparks[2].pdf

ShowerOfSparks.pdf

Thanks.  Gives me a place to start.

[MIm20c]

Try “bump” starting it by getting the prop turning 3 or so blades and letting the key go back to both. If it fires up it is probably the SoS. I would also have the fuel system checked as the pressure should stay up until you push the throttle in to prime (pump should be off for priming). In 80 degrees it should take one pump. However, I don’t think fuel is the issue right now.

I had some issues with my starting my new to me plane a few months back. I think it was an issue for awhile because of all the new parts the previous owner put on. Turned out to be wired wrong and passed through a lot of well know shops with the problem. 

If the SoS system is not working it will crank forever because the mags are grounded until you move away from the start position. 

 

[ragedracer1977]

Just now, MIm20c said:

Try “bump” starting it by getting the prop turning 3 or so blades and letting the key go back to both. If it fires up it is probably the SoS. I would also have the fuel system checked as the pressure should stay up until you push the throttle in to prime (pump should be off for priming). In 80 degrees it should take one pump. 

I had some issues with my starting my new to me plane a few months back. I think it was an issue for awhile because of all the new parts the previous owner put on. Turned out to be wired wrong and passed through a lot of well know shops with the problem. 

I'll try that. I'm confident that it's some part 'going bad'.  In the past it always fired up by the 2nd blade.  

[ragedracer1977]

Ok, I believe I found the vibrator.  In the hardest, most impossible place to reach.  See photos.  One is from underneath, the other is with the autopilot controller pulled out.  It's in there.  When I turn the key to start, but don't push in, I hear no buzzing nor can I feel anything if I have my hand on it when the key is rotated.  I tried the bump starting thing and no joy.  Fuel pressure video also attached.  Pressure goes up and then drops immediately when the pump is turned off.  Where would you go from here?

 

[MIm20c]

Yep, that’s it. You might not hear it over the starter. You could (mechanic) pull the signal wire off the starter solenoid and listen for it. Or just have them troubleshoot and test it properly. 

Any leaks coming from around the engine when the fuel pump is on?

Some ignition switches do not have a separate output for the SoS. It is combined with the starter solenoid signal wire output meaning you have to push/turn the key to activate. So the only way to isolate it is to pull the wire from the solenoid. 

[ragedracer1977]

Ok, I realized something else.  It very well might be the electric pump or related.  Still troubleshooting.  However, in the past, the fuel pump I could hear pumping and as it got up to pressure, i could hear it slow down.  Now, it sounds the same the entire time.  Never slows down

[MIm20c]

11 minutes ago, ragedracer1977 said:

Ok, I realized something else.  It very well might be the electric pump or related.  Still troubleshooting.  However, in the past, the fuel pump I could hear pumping and as it got up to pressure, i could hear it slow down.  Now, it sounds the same the entire time.  Never slows down

I’d look for leaks with the pump on. If not start the plane with the pump on as it is still providing plenty of psi to the gauge/carb. 

My guess is the mag connected to the SoS, the SoS or the wiring which includes the ignition switch (the SoS output passes back through the switch) and grounds. 

Good luck!

[ragedracer1977]

Shower of sparks is working like a champ.  It doesn't engage til you push the key in.  See video.

 

 

Definitely leaning towards a fuel issue

[bonal]

Like others have said after turning off the pump my fuel pressure holds and I get about a pound drop with each pump of the throttle also it gives me about 4.5psi and yours looks to be maxed at 2.5 I'm not certain but the accelerator pump in the carb if working properly should supply fuel as long as there is fuel in the float bowl based on you videos I would be looking for a fuel system issue. However you did mention that your mags were recently overhauled always the possibility something was done incorrectly there.

[ragedracer1977]

Well, I don't know what to think.  Tested the fuel pump and it's moving a lot of fuel quickly.  There's no leaks to be found anywhere.  Fuel pump is a bendix type (appears to be made by facet now, Part 476087).  I did find a service bulletin just now (http://www.mooney.com/en/sb/M20-81A.pdf) that says the strainer should be cleaned at 50 or 100 hours or "when fuel pressure is low". From looking at the pump, I would hazard a guess that the strainer hasn't been cleaned in a LONG time.  The outside of the pump is lightly corroded (it's steel) and the strainer cover doesn't look like it's moved for who knows how long.  

Now, the Part 476087, I can find at multiple locations, however---none of them are aircraft houses.  They're all marine or automotive.  Save one.  Chief Aircraft carries it, but it's sold for experimental aircraft only.  

So, here's my conundrum.  If I pull the cover to clean the strainer, I'm supposed to replace a gasket.  Don't know where to get the gasket.  A new pump is $75 but is labeled for experimental. 

Next, after I did all of the troubleshooting, I put the plane back together.  I turned on the pump, pumped twice, and the plane fired right up.  By the 2nd blade again.  The only difference was I was aggressive on the pumps.  Normally I pump slowly, like 2-3 seconds to go from full out to full in.  This time, I moved the throttle almost as quickly as I could.  

[carusoam]

Seeing the fuel pressure disappear so quickly...

And it not leaking out anywhere...

I get the feeling, there may be a lot of fuel going to the engine that is not being accounted for...

 

up for trying something different?

Turn on the ignition before turning on the fuel pump...

 

It is possible that the engine is getting flooded by dumping what is about ten pumps + of the throttle to the engine...

An ordinary engine mechanic with knowledge of our carbs should be able to make the proper adjustment or fix the seal that must be leaking... 

Would definitely want to know what is not working before flying it, as it could get worse...

 

PP thoughts only, not a mechanic..

Best regards,

-a-