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180 fuel flow issues

I had a similar scenario with my 58'180. Turned out to be a piece of rubber, I think was sliced, when the hose ends were installed. The small flap of rubber was 3/16" wide and maybe 1/4" long and would allow fuel to flow normally for days at a time, then do the power reduction bit at the worst possible time. When I finally figured it out and made a nice new hose from gascolater to carb...it was an "Aha!!!" moment.

Since this seems like you are getting down there towards the bottom of the barrel as to single point system failures...I figured I'd throw that in for consideration.

Steve
 
The kicker to me is apparently successful static runup vs faltering acceleration during early takeoff. If something can move to make things worse, then acceleration could do it. Fuel can move aft...same for internal check valve parts....and anything internal in the plumbing that can move to restrict fuel flow.

Gary
 
Gary,
I agree. I'm thinking out on the edge of logic, but it seems possible that you could have blown something up or down into a fuel line, that could be lodged somewhere and is moving with fuel flow and acceleration. I guess my immediate thought is the fuel valve. Something that came dislodged and is stuck in a particular direction, as to impede or not, the flow of fuel.

While a pain in the butt to remove and inspect...I tend to think there's only a few places a piece of a bug, or rubber, or something really dumb like a pencil eraser (which I removed from a gascolater bowl once) can actually hide or migrate to...I also tend to think things you can un-bolt and examine and test on the bench are appealing consideration points.

The valve is one of those pieces.

I think to prove the point, it wouldn't be hard to remove the valve and bypass for diagnosing purposes.

Steve
 
If mine:
Confirm all fuel lines are debris free from tanks to carb. Confirm fuel valve and vent check valve(s) as well.
Remove fuel filter to carb line at carb and flow fuel to confirm.
Remove fuel filter from system and flow fuel between fuel valve and filter.
Remove fuel lines at tanks and back flow air to confirm. Then finger screens as well.
Remove check valves and confirm vent system is free of goobers and dead offspring of critters.

But that's me not A&P saving my ass from partial loss of power. The rate of which we add power determines the rate of fuel demand, another thought.

Gary
 
Sturgill said:
It falters when the airplane accelerates from a stopped position. Within a second or two of brake release or full application of power.
Click to expand...
You sure are making us put on our thinking caps. I interpret your statement of faltering as: while you are pushing the throttle with the brakes off and the airplane accelerating and before the throttle is wide open the engine slows a bit before continuing to pick up rpm. When it slows (falters) what does it sound like? Just a power reduction or is there a misfire sound as well? Does it sound as though you pulled the throttle back momentarily? How long does the falter last before the rpm picks up?

Consider this: There is a crossover balance tube in the front of the engine intake system. This tube has a drain in the bottom. There should be a drain tube from this drain. Is this tube blocked? If fuel drips down when the engine is not running it can collect in this cross tube. When you accelerate, it is possible for any fuel in this cross tube to move back and be sucked into the cylinders providing a momentary over rich condition.

It is possible that a bug found a home in the drain tube while the airplane was stored.

You likely didn't notice any EGT change during the faltering?
 
All good thoughts. The engine is momentarily being starved for fuel. It is not getting enough flow to satisfy the demand of the carburetor. It does not misfire.

I had already planned to examine the flex hose for a “flap” of cut rubber. We will also examine the balance tube.
 
Finger screens in the tank outlets are clean and nothing floating in the tank? Venting is good? Had a clipped winged J3 with an O-200 do this. Was some kind of sealing compound floating around in the tank and on some take-offs it would cover the fuel pickup in the tank.
 
To be clear...my thought on something blocking, is pretty likely to end up being "something" floating, or nearly so...and the fuel reduction, is due to the higher fuel volume and flow sucking the "something" into blockage mode.

This makes it very difficult to find...anyway....I think you're on the right path!!!


Steve.
 
I'd also bypass the fuel flow sensor to eliminate it's effects, if any. Good luck with your project.

Gary
 
skywagon8a said:
.....There is a crossover balance tube in the front of the engine intake system. This tube has a drain in the bottom. There should be a drain tube from this drain. Is this tube blocked? If fuel drips down when the engine is not running it can collect in this cross tube. When you accelerate, it is possible for any fuel in this cross tube to move back and be sucked into the cylinders providing a momentary over rich condition.....
Click to expand...

My 53 C180 does not have that drain ("sniffle valve"?) in the induction crossover,
nor do other 180's that I've looked at.
I believe this is a thing for the IO520 engine in a 185, but not the 470 engine in a 180.
 
hotrod180 said:
My 53 C180 does not have that drain ("sniffle valve"?) in the induction crossover,
nor do other 180's that I've looked at.
I believe this is a thing for the IO520 engine in a 185, but not the 470 engine in a 180.
Click to expand...
Is there a fitting with a plug in it in the crossover tube?

Where does the primer connect? If there is a leaky primer, perhaps that could be a source of extra fuel which could bog the engine down momentarily? Sturgill doesn't mention any popping sounds which would indicate a lean mixture. Too much fuel could cause a faltering and the faltering could cause the F/F reading to be lower.
 
The elephant problem is at what point in this saga can both the engine and fuel supply be deemed airworthy? It may be that either or both are not.

Edit, as an example: "When this originally occurred as a problem, we found that the static flow was way low. We solved it by blowing backwards through the system to the tanks. I felt like we probably dislodged some restriction, and I figured it was in the tanks, blocking the finger strainers. That got the static flow back up to normal." If the "some restriction" was in the fuel system before the tank finger screens, how would it pass through the screens back into the tank? Wouldn't the fuel lines at the screens have to be removed for that to depart? Just wondering.

The times I've had a loss of power on application was from either a defective accelerator pump (C-90), or sticking exhaust valves (O-320). That valve deal soon ended up in a spalled cam and overhaul.

Gsry
 
Last edited:
Sturgill said:
I have grounded the airplane for now. I bit the bullet and ordered a new fuel valve. I feel that we have eliminated everything else. I will be very curious to see what I find.
Click to expand...
Can't you disassemble it in the airplane, at least enough to look inside?
 
Farmer, you are right. It is embarrassing to admit that I have two. But I can’t bear to sell either one, and my kid pretty much has claimed the early model.

The valve has never worked right. I would have rebuilt/replaced it anyway if the cost wasn’t so high. This issue has forced my hand. It’s probably for the best. My IA(me) will be happy with the new one.
 
My son pulled the fuel valve yesterday in preparation for exchange. What he found was the the o rings inside were way off in size. The gentleman who I purchased this plane from had done a lot of “creative” maintenance, and I suspect this is more of his work. The rest of the valve appears to be in very good shape, so I have cancelled the order for the new valve, and have an overhaul kit on the way.
 
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Had a similar issue with a customers Supercub last year. Engine would backfire and try to quit about 200’ agl on takeoff. After finding fuel valve plugged with insect debris, owner (rancher) finally confessed that when operating on skis last winter he had fueled from gas can that was probably dirty, da!. Replaced fuel valve , flushed tanks and blew out all lines, cleaned finger screens and inlet screen. Problem solved. Fuel flow only became an issue at full throttle (takeoff) if throttle was reduced, engine ran fine. Hope your problem is resolved as well.
Ray
 
Our fuel delivery problems stopped after we rebuilt the original valve. The correct parts made it work perfectly. My son is now flying it a lot and giving dual for other 180 pilots. I told him that it’s part of the lesson about buying planes that have sat. It can take a while to find and fix the issues that are hidden. We are doing the second annual currently, and haven’t found any new problems.
 

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Hi Guys,
I assume not to start a new thread because I am facing very, very similar problems - hope it is ok…

My Cessna C180 1955 O-470-J have faltering problems during the initial phase of the takeoff. Problems are not possible to simulate on the static run up or on the concrete/asphalt runway. She falters only when you hit any bump (on a bumpy grass runway), when you get of - it goes smoothly and no problems ocured. No problems in the air, no problems on the ground, no problems on the smooth surface like concrete. Just on the bumpy runway during initial phase of takeoff - and not every takeoffs…

In order to solve problem I went through those steps with no positive result :-/
- static fuel flow before carburetor - 110l/h (29gal/h)
- no difference on avgass or mogass
- new fuel hose from gascolator to carburetor (together with fuel metering system)
- new carburetor installed one month ago
- all vents checked
- it is same if you ran on left or right magneto

Could you please share you opinions and tips were to start again? There are not so many experienced mechanics here in CZ…

Many thanks for any tips.
Michal
www.skywagon.cz
 
MichalW said:
Hi Guys,
I assume not to start a new thread because I am facing very, very similar problems - hope it is ok…

My Cessna C180 1955 O-470-J have faltering problems during the initial phase of the takeoff. Problems are not possible to simulate on the static run up or on the concrete/asphalt runway. She falters only when you hit any bump (on a bumpy grass runway), when you get of - it goes smoothly and no problems ocured. No problems in the air, no problems on the ground, no problems on the smooth surface like concrete. Just on the bumpy runway during initial phase of takeoff - and not every takeoffs…

In order to solve problem I went through those steps with no positive result :-/
- static fuel flow before carburetor - 110l/h (29gal/h)
- no difference on avgass or mogass
- new fuel hose from gascolator to carburetor (together with fuel metering system)
- new carburetor installed one month ago
- all vents checked
- it is same if you ran on left or right magneto

Could you please share you opinions and tips were to start again? There are not so many experienced mechanics here in CZ…

Many thanks for any tips.
Michal
www.skywagon.cz
Click to expand...
my experience with my 58' 180, was very similar to this, as outlined somewhere above and it turned out to be a pencil eraser...or at least I think it was...which had made its way into the fuel on off valve ( assuming from the tank...only after removing the valve completely from the aircraft for replacement, did the offending chunk fall out on the floor of the shop. That airplane was purchased damage and repaired and had not run for 4 years, so there was plently to troubleshoot. You are likely looking for something very odd, so I just was decided to go through everything, piece be piece before getting it flying. In this case, replacing lines, valves and pretty much everything including the carburetor seemed prudent. After that, it was as solid as could be.

I hope that helps,

Steve.
 
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