Basic gascolator questions for '68 M20C

[DXB]

I got a '68 C model with bladders 5 months ago  and find that I still need to learn some really basic stuff about this plane.  Per POH preflight, I been dutifully pulling the ring by the fuel selector for each tank. But until yesterday, I never made someone else do it so I could see if and where the gascolator drains. Turns out I don't see anything draining. Further I have no clue where to find the the drain nozzle.  Per records, the MSC mechanic who did my pre-buy+annual did clean the fuel screen and change a gasket in the gascolator.

 

I'm not sure that it's related, but I had an incident 3 months ago where the fuel pressure gauge would go down to near 0 psi when I turned off the boost pump during climb above 1000agl.  It happened 3x in a row, on either tank, making me freak out and turn the boost pump back on.  Since then it's never happened again.  I wonder if a piece of partially obstructive debris ultimately broke up and plugged the drain.  

 

So my questions are:

1.  Where is the drain in the '68C?   I've learned from prior posts that earlier C models had it in the nose gear well, but I'm not sure this is true of the '68.  When I look in the wheel well, I can't identify it, but then I don't have a clue what I'm looking for either.

2.  Assuming the drain is clogged, is there anything I can do to deal with this before taking it to the shop? 

3. If it must go the shop, are the guys on my field able to handle this easily?  They know Pipers and Grummans but seem minimally familiar with the old Mooneys.  

[Danb]

I answered to the wrong post sorry...Dev I'd go over to see Dorn at Webers and have him show you the mechanics of operation of your drain only a nice little hop from Kpne...

[gsxrpilot]

HI Dev,

 

First off, I'm guessing you're not pulling on it hard enough.  You pull up until it stops, then pull it about 1/4 inch further. You'll feel it give the extra little bit. Then it will drain. The drain is just aft and just left of the front wheel well.

 

Low fuel pressure on the climb is also not that unusual. Mine has never dropped to zero, but often drops to 2. I've never had to turn the boost pump back on.

 

I doubt anything's wrong with it.

 

Just my $0.02

[DXB]

 

First off, I'm guessing you're not pulling on it hard enough.  You pull up until it stops, then pull it about 1/4 inch further. You'll feel it give the extra little bit. Then it will drain. 

 

 

Thanks- this is entirely possible.  Wondering what other details I've missed...

[Marauder]

Dev -- on my F, there is also a mechanical drain at the pump that you can use your fuel sump gizmo to pull a sample. This may be unique to my F when I switched over from the Dukes pump. I never knew it existed until a buddy with a J showed me. I had always been using the pull of the ring way.

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[jetdriven]

The J has a spot u can push the fuel drain ring up from below to get a sample. The earlier versions have a kink and you can't do that. Otherwise it's a substantially similar fuel selector / gascolator

[HRM]

Thanks- this is entirely possible.  Wondering what other details I've missed...

 

Good grief, you've only had it for five months--you'll still be discovering things five years from now 

 

Some of the discovery will relieve an annoyance (like this one)...

 

...much of it will make you gaze in awe and wonder at your plane...

 

..and some of it will cause you to utter curse words that have yet to be invented.

[Guest]

..and some of it will cause you to utter curse words that have yet to be invented.

Or use existing ones in new wonderful combinations

Clarence

[PTK]

DXB, I also think you may not be pulling hard enough.

I was guilty of that as well thinking I would break something. But thanks to Larry over at Weber's, he showed me how to do it. It's a strong spring under there that must be overcome when you pull. You can't break anything but the ring and that's nothing.

[Alan Fox]

I don't like the zero on the pressure , that is not acceptable , not even a little , Have your A&P do a pressure and volume check on the fuel pump , If you have good pressure at Idle and cruise , you may have a volume issue , perhaps dirt in the screen , perhaps a pump issue with the engine driven pump , but have it checked out , Brian at Doylestown is well versed in Mooneys if you don't already have someone , Also Bob Cameron at South Jersey Regional has Mooney specific experience.....Both very reasonable rates....

[DXB]

DXB, I also think you may not be pulling hard enough.

I was guilty of that as well thinking I would break something. But thanks to Larry over at Weber's, he showed me how to do it. It's a strong spring under there that must be overcome when you pull. You can't break anything but the ring and that's nothing.

Tried it last night.  Yup-that was it.  May future Mooney newbies be spared the embarrassment (and potentially water in their fuel systems)  by finding this thread.  

[DXB]

I don't like the zero on the pressure , that is not acceptable , not even a little , Have your A&P do a pressure and volume check on the fuel pump , If you have good pressure at Idle and cruise , you may have a volume issue , perhaps dirt in the screen , perhaps a pump issue with the engine driven pump , but have it checked out , Brian at Doylestown is well versed in Mooneys if you don't already have someone , Also Bob Cameron at South Jersey Regional has Mooney specific experience.....Both very reasonable rates....

Yeah it happened literally the first time I solo'd in the plane after my transition training, on a cold winter day.  Totally freaked me out, but  the RPMs didn't drop and the engine didn't stumble - I did turn the boost pump back on before needle made it all the way down to the 0.5 psi minimum.  For the next two takeoffs, I tried it on each tank - same thing happened.  These tims I let the needle come all the way down past the red line that time (also without any perceptible engine issue) before hitting the boost pump- which I later turned off without any problem after leveling off.  Having resolved to get it looked at ASAP, I flew it a third time- and it didn't happen at all (needle goes from 5psi to 3-4psi even at WOT, no big deal), and it hasn't happened in about 25 hrs since then.   I probably should get it looked at though- something tells me that if I did it at Vx and full power, I would have the same issue.  I do drop the nose a bit now at 1000 AGL to go faster than 100mph IAS, as this is the only way I can keep CHT from shooting past 400 (around the same time I turn the pump off).  I wasn't doing this at first, and maybe this is the difference.

[PTK]

Dev, regarding your fuel pressure incident, it sounds to me like it may be your engine driven fuel pump starting to go.

Probably should have it looked at. But first speak to a Mooney specialist to be sure it's a real issue vs. something "normal" in view of the fact that you had no engine hesitation.

 

Have you consulted with Dorn at Weber? May not be a bad idea to call and discuss with him.

[mooniac15u]

The fuel pressure drop on climbout in C models is not uncommon. http://mooneyspace.com/topic/13291-fuel-pressure/  See posts 9 and 10 in particular.

[carusoam]

1) FP on Cs is pretty small...

2) FP on Cs drops to a smaller number with an increase of attitude. Really noticeable on initial climb.

3) FP at or near zero would make the engine not run or run really lean/rough.

It sounds like the old mechanical FP gauge is getting some work.

There are two pieces of information that would back up the FP gauge reading.

1) FF. Some LBs don't even have a FP gauge. They have been replaced with FF.

2) EGT.

Unfortunately, with a new-to-you plane, the single EGT with no calibration would make it difficult to use.

Something to check...

The FP gauge in the C is a line through the FW. It would be good to put eyes on every inch of the line looking for kinks or other issues.

Best regards,

-a-

[Alan Fox]

Pl;ease don't listen to Pete about this as he has no clue , the reason you are getting no performance issues is because the engine will run about 20 seconds on the fuel that is in the bowl (carb)....so when you go to zero pressure you are draining the pint or so in the carb , when that's gone the powers gone.....this is not to be taken lightly......If you were injected , you bet your bacon there would be performance issues.... NOBODY KNOWS WHAT IS GOING ON UNTIL IT IS LOOKED AT......GET IT LOOKED AT........I don't want to read about you in an NTSB report.....

[Alan Fox]

Also I read the referenced post mentioned by Mooniac , the pressure in that post is dropping to 2 PSI , that is in the Green , .5 is not and its not safe ....

[Hank]

My fuel pressure fluctuates in the climb, often down into the skinny part of the green line, but it holds pretty steady in cruise. This was a week ago at 10,000 msl, 145 mph indicated, leaned 25° ROP.

[jetdriven]

5 PSI is a heck of a lot more than zero.

My FI engine was doing something similar last year. A new mechanical fuel pump and putting fire sleeve over the main fuel line from firewall to pump fixed it.

[Marauder]

Here is my plane idling:

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[Marauder]

And in flight:

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[Hank]

Looks good. But the OP and I have M20-C with O-360 engines. If my fuel pump somehow went into overdrive and put out 25 psi, it would drown the engine!

[Alan Fox]

There is so much that it could be , pressure instrument , line to pressure instrument , Check valve in boost pump , engine driven pump , gascolator obstruction , collapsing fuel line , obstructed screen in gascolator ..... I don't like a reading below 2 PSI let alone .5......  I cant remember where the gage tap is in the system , is it at the carb , or off the pump ??

[Marauder]

Looks good. But the OP and I have M20-C with O-360 engines. If my fuel pump somehow went into overdrive and put out 25 psi, it would drown the engine! Mine will occasionally drop to around 2 psi, but it continues to run well. Note that this is still in the green stripe, just below the wide part.

Yeah, I realize we are talking about the O-360, but I suspect before too long someone will be asking about the IO-360 pressures.

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[mooniac15u]

Also I read the referenced post mentioned by Mooniac , the pressure in that post is dropping to 2 PSI , that is in the Green , .5 is not and its not safe ....