excessive fuel consumption

I fly a 180 cub that we tow banners with. The fuel consumption has jumped by about 2 gph over the last few flights. It went from 7 gph to 9 gph at 2200-2300 rpm and it has gone from 10 gph to 12 gph at 2400-2500 rpm. We have checked the timing and it is set at 25 deg. Do y'all have any ideas on what it could be?

Carburetor. Check the enrichment valve, accelerator pump.

Gas

Mayb a bad Gas Cap gasket ?

My PA-12 fuel consumprion recently jumped from 7.5 gph to over 9 gph. It turns out the 4 screws that hold the two halves of the carburetor together were loose. The locking tabs didn't lock. The carburetor jiggled ever so slightly, but enough to suck in extra air into the middle of the carb and pull extra fuel.

check oil screen?? maybe its taking that much more power to spin it....

really sucks when you leave this check till last and can barley get the screen out cause its packed in there so tight with the metal stuff....

2 examples..
first week helping out on airplanes, Eddie King in naknek had me pulling engine off a beat up yellow -12 to swap to his blue -18, oil screen housings were different, so pull it off(good engine) and it was packed!.... walk in all shy with it, ask 'this isn't good is it?'.... end of that swap......

one time our 185 went to flat pitch in cruse... pilot put it down on a blow by Becharof... we go down with a governor pulled from other plane, look see clamp loose & tighten- test fly it... bang flat pitched again... so we find something else & try again...same bang flat pitch... so we swap governor.... well this time on takeoff it does it big time, over 3000 rpm stretches and throws alternator belt, shakes bad...... stepfather was quite happy to be back on the ground, taxi up said tie it down.... he walked up and grabbed the prop and said YUP, broke the crank... could barley get the oil screen out by then it was so packed with metal...

what had happen was, crank was cracking in a spiral through the oil transfer collar hole... and that crack would open up at different times and reduce the oil going to the prop-hence the SUDDEN flat pitch.....

of course we had bought this plane in a hurry after our pilot flipped the new to us a week old beautiful 185 with new everything, engine,inside & outside and the tide got it...

this one with crank issue had 'lost' engine logs, at less than 10 hrs of our use we had to put 6 jugs on(previous ash damage), then this 180 hrs and a month or so later... ugggg think that logs were lost due to a prop strike record

Ok guys, we are still having the same problem. Here is what all we have done. We ave put another (older) engine on the plane, new gascolator, another carb, new intake gaskets and checked the fuel cap gaskets. Really everything firewall forward has been changed except the prop.

While towing I can pull the mixture out about a half inch or so and the rpm's will jump up about 100 rpm or so (where they should be) but the cht's get hot. With the mixture full rich and down on power the cht's are about normal, 350-375 deg.

Any off the wall suggestions or something we have overlooked? It is starting to drive us crazy.
:help

Muffler blast tube going bad.

Glenn

cubdriver2 said:

Muffler blast tube going bad.

Glenn

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Forgot to mention the stock exhaust is gone and we now have a sutton exhaust on.

Possibly a leaking primer...

Vickie

gauges?

Sounds like it's running rich>> You didn't mention air filter.?? Did it start suddenly or come on slowly? Make any changes before it starDid you leave the tail parachute out?? ted?? Off the wall enoug??

qsmx440 said:

Sounds like it's running rich>> You didn't mention air filter.?? Did it start suddenly or come on slowly? Make any changes before it starDid you leave the tail parachute out?? ted?? Off the wall enoug??

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Does a 3,000 sf banner count as a parachute? If so then I did leave it out. The problem was noticed over 1 or 2 flights.

Not 100% sure about the air filter, but I have a new one that I will put on.

The only change that happened, and it right after it started, was a cylinder went down so we changed it. But that was the flight after the fuel burn was noticed. That is the only change that was done within 300 hours or so before the problem.

Possibly a leaking primer...

Vickie

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We thought that and so we took the primer off to eliminate it from the problem.

gauges?

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The fuel flow is calculated after the flight. We rely on fuel flow figures from previous flights and not the gauges, for the most part.

banner tow pilot said:

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gauges?

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The fuel flow is calculated after the flight. We rely on fuel flow figures from previous flights and not the gauges, for the most part.

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I was kinda meaning the other engine gauges .....??

mike mcs repair said:

banner tow pilot said:

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gauges?

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The fuel flow is calculated after the flight. We rely on fuel flow figures from previous flights and not the gauges, for the most part.

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I was kinda meaning the other engine gauges .....??

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Could be, I guess. The CHT's go up to 425 or so when I lean it out to get full power, so I go back to full rich to keep it as cool as possible.

More off the wall: You said "nearly everything" fwf. Besides prop what wasn't included in "nearly"? Did you try different carb heat box? Cable to same acting up somehow? Same problem with two different (old) carbs? Anyway to exchange your parts (one at a time) to a good performing 180? Now into twilight zone: someone stole and exchanged your prop, competiter sneaks across runway and "adjusts" carb to obtain competitive advantage, density altitude problem, wet banner (did you try banner on another aircraft) ? Bush's fault (blaming him can make the problem magically go away, look how well that has worked for the economy :lol: ), What is plug "color" on all 4 plugs?

qsmx440 said:

More off the wall: You said "nearly everything" fwf. Besides prop what wasn't included in "nearly"? Did you try different carb heat box? Cable to same acting up somehow? Same problem with two different (old) carbs? Anyway to exchange your parts (one at a time) to a good performing 180? Now into twilight zone: someone stole and exchanged your prop, competiter sneaks across runway and "adjusts" carb to obtain competitive advantage, density altitude problem, wet banner (did you try banner on another aircraft) ? Bush's fault (blaming him can make the problem magically go away, look how well that has worked for the economy :lol: ), What is plug "color" on all 4 plugs?

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Carb heat box is the same box that has always been there. Everyone that looks at it says it is fine. Cycles fine and no play in it. Yes, we have tried both carbs on both engines.

I think the carb heat box and prop are the only things the same fwf.

Any chance the tach or the pilot are lieing to you? 8) Sounds like you need to start over. Everything again only more careful and with a second set of eyes. 30 years ago troubleshot a 4 cyclinder 4 carb bike engine that ran rough warm. Low compression on one cylinder. Hotshot mechanic kept finding nuance things. All new rings then valve job (16 valves) etc. finally on third teardown, (he said it needed a cam), I was walking through my shop and glanced down at the box of parts on my way out the back door and continued outside. Something made me stop . Didn't know what it was. Went back in and looked more closly at the collection of parts. The carbs were mounted on a "rack" to coordinate their operation. As I looked closer I noticed one choke closed on one carb. Damn a 15 cent pin cost m e a fortune. It's always fun when you find the problem. Last thought on this, plug color seldom lies about mixture. I "feel your pain" Good Luck!

Re: Gas

Bill Ingerson said:

Mayb a bad Gas Cap gasket ?

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Had not read this guys idea but it's a good one, (especially if the plugs look good) or a leak/siphon upstairs somewhere?