Grassstrippilot wrote:Probably.


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Part number is stamped on the data plate on top of the valve, any number of shops should be able to do an overhauled exchange, I've had good experiences with Quality Aircraft Accessories, they have overhaul exchange $425.00 plus $300.00 core charge on their website. You could also send yours in for overhaul or repair if your mech doesn't want to repair it..

I would still recommend opening it first to confirm....

So there are a lot smarter guys on here about these sort of issues, but I was having a similar problem with my Bo when I first bought it and my mechanic adjusted the mixture veneer and the problem was solved. It would burp a little and putter when I pulled the mixture. He adjusted it and the problem went away.

Just a thought.

Jim

Hi Cory,

You know I bought Rich's old motor for my plane. We did a top overhaul and installed earlier this year. Initially had problems with the motor not wanting to start without bumping the high side boost pump to keep it firing and it did not want to shut down cleanly just like you are describing. My mechanic had opened up the "spider" and made sure it was clean during initial install. We took it off and sent the spider to Mikes Aircraft Fuel Metering Service in Tulsa, OK.

Their tech called me up and quizzed me about symptoms and absolutely pegged the situation. Apparently the diaphragm can get stiff and not work correctly. Anyway, I think the rebuild and check out on the flow bench was about $350. Completely fixed the issue. I highly recommend Mikes - they did good work and were quick.

Awesome! Glad things are going well for you. I knew you bought his engine. Thanks for the info and recommendations. Drop me a pm with your contact info. It would be good to stay in touch. I'm anxious to get back next week and get this resolved.


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I pulled one of my TCM IO360 manifold valves apart. It was dead simple. I recorded the disassembly but I don't think it is worth posting. There are only two things that could cause your problem that I can see: 1. The spring that pushes the diaphragm down and closes off fuel flow has gone bad. 2. The valve seal is leaking allowing fuel to continue to flow. To me it looks like if the diaphragm was leaking you'd have trouble with the valve not opening because it wouldn't build enough pressure to compress the spring. On my manifold there is a small orifice that fuel would flow out if the diaphragm was leaking.

Manifold Valve
Untitled by Jon Whee, on Flickr

Disassembled
Untitled by Jon Whee, on Flickr

Diaphragm and valve shaft(?).
Untitled by Jon Whee, on Flickr
When the fuel the pressure lifts the diaphragm the hole in the shaft is raised above the seal and fuel flows through the center of the shaft. With not fuel pressure the hole is blocked by the seal and no fuel can flow.

Valve seal
Untitled by Jon Whee, on Flickr

Untitled by Jon Whee, on Flickr

Inside with diaphragm and seal removed
Untitled by Jon Whee, on Flickr

Thanks whee. I appreciate you posting those. I won't be back until next Monday so it won't be until at least then before I can start working through this.

I went out yesterday. Here are some pics of my distributor. The outlet marked vent has a hose hooked to it that disappears down between two cylinders. I didn't have time to grab a mirror and flashlight, but where does this go? I couldn't see or feel anything obvious.



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Cory, the vent line just dumps below the engine out the cowl or just below the oil sump. Some have lines hooked to them, some don't. If the diaphragm tears the fuel will leak out of the vent line. Also, inside the shaft is a spring and needle type valve and seat, look through the hole and make sure there is nothing keeping it from closing all the way. If you decide to replace parts yourself, I recommend buying the diaghram assembly, it's tricky to remove the diaghram from the valve (shaft) without scoring it, you can use two punches or rod to keep it from turning. Don't try and grab onto it with anything because if you scratch it, it won't fit properly when you go to put it back into the housing. I would send it in and have it tested and overhauled if necessary, by the time you have your guy pull it apart inspect and replace parts, you will probably have more time in it than it would be just to exchange or have yours sent out.

That's what I thought but I couldn't see where it reemerged from the bottom. I'll have more time to look around when I get back next week. Thanks!


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Hmmm...I went back through the logbook today because I thought I had seen something about the fuel flow divider and fuel control valves being overhauled. Sure enough. Just under 200 hours ago. I've emailed the previous owner to see if I can get some more info on how long it was acting this way.

I've also got a game plan in place to do some troubleshooting next Monday and Tuesday. I'll let you know how it goes.




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So, an update. I went out and started the plane and did two shutdowns on a cold engine, one from idling 650 and the other from 1,000 RPMs. Both shutdowns were normal. I also verified that the idle settings were correct and the same as before. They were.

So, I decided to fly it around the pattern and get it warmed up. After several laps in the pattern, I came in and shut it down from 750 RPM, which is where it idles with the mixture leaned out for taxi. All appeared normal and then, around 300 RPM, it started to diesel again. Nuts! I brought it back to life and this time ran it to 1,000 RPMs and let it sit for a minute. Then I shut it down from that setting and it was a normal shutdown. I did 4 more shutdowns from 1,200 RPMs and all were normal. So, Michael Pearson and the others that suggested it, thanks!

The game plan going forward is to fly it and get some hours on it and see what happens. If it rears its head, we will continue to the manifold valve and fuel control unit. Otherwise it ran flawlessly today.


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I think it was already linked earlier in this thread but there's a section in this Kelly Aerospace PDF that specifically addresses troubleshooting for a "dieseling" continuous flow injection engine.

http://www.kellyaerospace.com/articles/ ... usFlow.pdf

Look for the section titled "manifold assembly" where he goes on to blame a scored mixture valve.

I also wondered if your fuel pump is set high on the low end. I don't know enough about engine driven pumps to know if they're pressure-adjustable or if there is a separate pressure regulator but the diaphragm in the manifold is opened with a threshold fuel pressure.

Perhaps coming down in pressure from 1000 rpm to shutoff is better seating that valve than easing it in from 750?

/spitballing

Thanks Zane. I'll check that out.

We adjusted the high and low end pressures when I bought it. Then while we were troubleshooting the week before last, we hooked the hoses up again to verify that they hadn't changed. They were still spot on.

For discussion sake, here is what Mike sent me when I asked for more insight on why shutting down from a higher rpm would help:

"I usually use about 1200rpm for a minute while I check 121.5 for ELT, etc., leaned out to help keep the plugs from fouling. When you pull the mixture from there, it should be way too lean to run. At <600rpm at higher density altitudes, you'll be a lot closer to a stoichiometric mixture as you pull the mixture control because you aren't asking for as much air at that low of a power setting. It's one of those things I've been doing for 30 years back from my primary training."


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Dunno if it's due to the same sort of issue or not, but several times I've seen round-engine guys run the rpm up for a minute before shutting down.

Not to thread jack- The radials are runup a bit before shutdown to scavange the oil out of the case to reduce oil in the bottom cylinders after shutdown. - We return you now to regularly scheduled programing. -Carry on...

If that hose happens to be connected up into your intake system it will cause the issues you are talking about. it needs to go to free air!

Grassstrippilot wrote:Thanks whee. I appreciate you posting those. I won't be back until next Monday so it won't be until at least then before I can start working through this.

I went out yesterday. Here are some pics of my distributor. The outlet marked vent has a hose hooked to it that disappears down between two cylinders. I didn't have time to grab a mirror and flashlight, but where does this go? I couldn't see or feel anything obvious.



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Thanks Trent. When I get up to the airport next, I'll verify where it goes.


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hummm...interesting corey...my old 470 would do that occasionally too...must be a continental thing maybe...my LYC. 540 never does it.....

Update: I finally had some time to see where that hose went to. Ends up it Ts into the manifold drain line that exits out by the cowl flap. I pulled the hose off the manifold and zip tied it so it wouldn't flop around and so the manifold vent went to free air and, guess what!?!? Three normal shutdowns, 2 on a cold engine, one from a hot engine. All from idle throttle and a leaned out mixture.

So, I'll get a few flights in and see how it goes.

The T to the manifold drain.


The hose removed and secured so that the manifold vent goes to free air.



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My understanding is that fuel distributor drain should never drip any fuel unless there's a hole in the rubber diaphragm in the fuel distributor manifold. If fuel does drip out of it, and was being sucked in through the induction manifold drain lines, then you've found your problem, but you're not done fixing it yet.

The induction manifold drain lines drain any fuel that pools after shut down, or excess fuel that has flooded the engine in a failed start. While the engine is running, they are a vacuum leak. A known leak that is compensated for when you set up your idle mixture, but none the less, a leak. Fuel leaking from the distributor drain line would definitely have been invested while idling.

I've never seen the fuel distributor drain plumbed to the manifold drain, and not seen it illustrated that way in any parts or service manuals. It looks like a field mod. Not a horrible idea, but I think you've discovered a good reason not to do it.

If it were me, I would extend the fuel manifold drain line, and possibly try to route it to a temporary bottle to see if you truly have a leak, or at least out the cowl flap so you can witness is there is a drip of fuel present. If it is leaking, as I suspect, it's a fire hazard as is. I wish it had been designed and plumbed by Cessna to be as visible as an electric fuel pump tattle tale drain tube.

Good work on finding the problem! Thanks for sharing.

Good thoughts and ideas. I wish I had a picture of how my last plane was plumbed. I'm certain it wasn't plumbed like this one, but I wonder how it was vented.

Anyone else care to share how there's is vented?


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