I guess I just can?t trust me.

I hang my head in shame before you all to let you know that I’ve reaffirmed what I know to be true about having others go over your work.

Over the past few weeks I’ve been running a thread about some problems I’ve been having with my brand new motor. From first start it hasn’t been running right and I’ve tried a lot of things trying to solve it.

I ended up with two problems. One, the motor was running rough. But not always. It would run fine at maybe 1700 RPM, and after several seconds it would choke and shutter for a bit, then start running fine again for several seconds and repeat. The other was low pressure from the mechanical boost pump.

I explored some of the ideas that came in from the VAF brain trust. I verified the mechanical pump was indeed the high pressure model required for fuel injection. I ran the motor with the red cube bypassed; I ran the motor with the mechanical pump bypassed. I checked the fuel lines for a loose fitting or b-nut, I checked the fuel filter for debris along with all of the fuel lines FWF and found nothing. I even removed the fuel pump and tore it apart looking for something wrong in there. Still nothing.

I had plenty of fuel pressure with the boost pump on and the engine still ran rough so I assumed I had 2 separate problems. I surmised that for sure the mechanical pump was bad at least, and that I had a separate problem that still needed discovery.

Well I finally fixed it all last Sunday and the problem was me. 

When I made up and assembled the fuel lines from the fuel selector through the filter and boost pump, I torqued all the b nuts and put a dab of torque seal on them, so, when “many” others on this site suggested I might have a loose fitting, I checked every one of them…….that didn’t have torque seal on them.

So last Sunday, after unsuccessfully fiddling with things for what I’d determined was the last time, I was going to pull the fuel pump back off, send it out to be tested/overhauled and shelf my motor problems until spring. I then decided I would go through all the fittings one more time, starting at the tanks and going all the way through to the injectors but this time, I’d check even those I “knew” to be tight.

You would be surprised how well that motor ran after I found that loose nut! You know, the one with the torque seal on it? Sheesh! What a dummy.Incredibly the mechanical fuel pump is producing 20 psi at idle and more at higher speed, and the motor isn’t stumbling and choking anymore! Idling real smooth now too!

So the moral of the story is the same one that is preached here all the time, and I hope I’ve learned it well. ALWAYS have 1 or more people put a wrench or screwdriver on EVERY nut, bolt, screw, etc. on the airplane!

Hope I’ve taught me a good lesson!

As long as we continue to wrench on airplanes we will lead ourselves down the wrong path from time to time. I've been a wrench for most of my life and I still do it now and again.

The important thing is that you went back to basics and found the problem. Laugh it off and move forward with the knowledge that you are a little smarter today than you were yesterday.

Don't fell too bad Jesse. I did something very similar. After filling the fuel tanks in the -10 for the first time doing the W/B and an exciting first engine start the same day, I shut every thing down, did a cursory search for any leaks on the ramp, and put the plane back into the hanger and headed home to pack up to leave for a week at the lake house. I remembered as we were packing that I did not shut off the Andair fuel valve and that it was worth the 40 minute diversion to go out of the way to the hanger on the way up north "just in case". To my surprise I found a very large puddle of 100LL formed under the plane and a steady drip from both wing roots. After cleaning up the fuel and airing out the hanger, I found that I failed to tighten the fuel supply lines at the fuel selector valve from both tanks,,,,and I also marked them with the torque seal!

Good examples of why I (and you) should ignore torque stripes when doing inspections.

Jesse--I dont think there is anyone on here that hasnt had an 'oh oh' moment. Most of the time we catch them so they are non-issues. Thats the way we like them, BEFORE the plane is in the air and has an issue that could be bad.
Good man to admit to THIS crowd that he overlooked something. Best part is, you found the issue, learned from it, as well as alot of us here too.
I finished my 7A tail, and had several eyes on it. And before if goes on the fuse (whenever that is purchased) it will have several more eyes on it. I'm not great on airframe stuff, but am learning. We all can learn from threads like this.

Agreed, I have learned that no nut, bolt, fitting goes on hand tight. I always leave it off or tight, no in between.
Honey, I thought you tightened the lug nuts-- do not ask.

Walt said:

Good examples of why I (and you) should ignore torque stripes when doing inspections.

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One of the things I learned early on from Walt is "you can't inspect stuff by just looking at it. You've got to put a wrench on it!"

Congratulations!

Good news that you found the root cause. Don't beat yourself up, though, it does not matter how much experience one has (or does not have) this happens. Just be glad you found it and your best bud didn't come by and casually put a wrench to the offending nut and accidentally "fix" it for you without a thought!

Better news is that you are now an expert on your fuel system and can help others. Maybe ME.

engine

Jesse, Good to here you got it sorted out. Ron

Rick_A said:

One of the things I learned early on from Walt is "you can't inspect stuff by just looking at it. You've got to put a wrench on it!"

Click to expand...

I'm still learning that lesson. When I did my first annual after buying my plane (we get to do that in Canada - no repairman's certificate needed up here) I eyeballed most of the nuts and bolts. This year I hired a young mechanic to help me, and she "put a wrench" on everything. She also found 3 slightly loose nuts that I missed I'll follow her example next time!

There, but for the grace of God, go I

Thanks for sharing your experience ... though you might be kicking yourself, you're kicking us, as well, to pay attention to everything. I'm currently obsessing about sealing my tanks, so I'm way away from running an engine, but, I'm filing it away for later. I'm sucking down as much VAF wisdom as I can.

I'm very happy that you found your bug! And that you have added to the wisdom store.

Bill,

That was kind of the intent. I'm not necessarily into self flagellation.

I find that the more of stuff like this that I read makes me realize I'm not alone in making an occasional dumb mistake and feel I can take a bit of embarrassment to put an idea out there again. Thanks.

And Ron, thanks. It feels good to have that behind me so I can move onto some of the remaining items. I'm really itching to fly it now though!

Torque seal = absolutely worthless. Perfect example of why. All it does is try to convince you its not necessary to check a fitting, when you should be.

....... interested in learning how this caused engine prob

Thanks for your post Jesse,

Just interested in the logical explanation why this caused your engine problem. Was it pulling air into the fuel lines but not leaking fuel externally and thus causing fuel starvation?

Cheers, Greg

Exactly Greg,

The loose fitting was on the suction side of the electric boost pump so it never saw positive pressure, only suction.

The electric boost pump was able to suck enough fuel through it even with the air to produce 30 PSI, but the mechanical pump was not. In addition, the mechanical would have to pull harder to overcome the additional friction losses of the fuel through the electric boost pump and the red cube as well.

Even with the electric boost pump showing 30 PSI, it was pulling enough air through the system to make the engine stumble.

Only the greenest of newbies have not had an experience like you describe. The rest of us just smile, and go, "Yep, been there; done that."
Above all, glad you found the problem!!!

Confession is good for the soul...And for the rest of us mere mortals

Did the same thing Jesse when first hooking up the fuel lines to the engine. Thanks for sharing!