Increased Fuel Consumption $HELP$

pablo · Post by **pablo** » Wed Aug 31, 2005 18:17

The A65 in my Champ has always burn 4.5 gals/tach.hr. Then recently it started to flood by itself: so the needle was changed, but then started to drip fuel from the airbox. So the BendixStromberg was overhauled:
"Replaced main metering jet (49 JCT), smoothed out scratched mixture control plates, installed missing gasket from top of Mixture Control Shaft, and float levels were checked at 13/32 and new primer was installed" (as by eng.log entry= chinese to me!). But now burns 5.2 gals/tach. hr.
and minimal black smoke from the R exhaust pipe (stalk?). I think that the fixed mixture is too rich, but nobody seems to know how to lean it.
Any suggestions?
Thanks,
Pablo

MikeB · Post by **MikeB** » Wed Aug 31, 2005 19:32

Pablo: shot in the dark here, but let's assume for the moment that the carb was rebuilt/adjusted correctly, you might check that the 'flapper' on the carb heat box is opening correctly. If it were slightly closed (or being pulled closed by vacuum once the engine is running) that would cause a over rich condition and increased fuel consumption. I just mention it because it's necessary to remove it in order to get the carb off and often they get pulled out of adjustment. The primer would also be suspect but appears they replaced it (?).

Those with more experience on the old carbs might chime in here with other suggestions. It's a fairly simple (crude is a better word) system so it shouldn't be that difficult to solve.

Looking at the condition of the spark plugs also might give some indications, although auto fuel covers up a lot of sins.

Ron Babos · Post by **Ron Babos** » Wed Aug 31, 2005 20:21

Pablo: The mixture control plates could be thrown away with no effect on the normal mixture. Check this...... Turn fuel on and see how long it takes for the carb to drip, if it drips at all. A drip every two seconds or so may be anouying but will not cause your problem, as the engine will burn it faster than the drip, so no difference in consumption will be seen. If the drip is excessive, take the carb back to the guy who rebuilt it. Ecessively high float setting or needle and seat fit no good.
My next check would be the primer. After the engine has warmed up, disable the primer line from the spider , or under the tank and cap it so no air leaks occur. Not much else will cause your condition for extra fuel burn.
Ron

Paul Agaliotis · Post by **Paul Agaliotis** » Wed Aug 31, 2005 22:28

Pablo, I learned from racing sprint cars that you should change things one at a time. So the first thing I would do is plug off the primer and recheck your fuel burn. If it doesn,t help then I would head back into the carb. As Ron pointed out the mixture control is not going to cause an increase in fuel burn. It only causes the float level to drop by altering the vent diameter. Its called a back suction mixture control.
The float level will cause an increased fuel burn, if too high. This can be from a needle seat that is loose in the housing, or needle leakage. One other item could be the wrong seat. The proper seat for your carb should be #383911 assuming it is gravity feed. Paul

Nathan K. Hammond · Post by **Nathan K. Hammond** » Thu Sep 01, 2005 00:07

To answer the your question about how to lean it, you move the mixture lever to the right. That changes which diameter hole lines up with the back suction hole. But like others have said, the whole mixture control idea is almost usless.

Now to the problem:

You could make the mixture leaner, but that may not be the correct solution. Yes it may cause the engine to run better, but first you need to find what caused it to flood and burn more fuel.

Dripping when not in use indicates the needle isn't seatting. A fix is to lap the needle into the seat using really fine compound, something like tooth paste. (FYI: Check which needle you have. Each needle has it's own seat (as in part number) so make sure they match up. Neoprene (black) are not used any more because they swell causing an excesive lean mixture, obviously not your problem. So it's either the milky colored Delrin or Steel needle. If it's the Delrin, weight must be added to the float to work properly.)

Even the manual is skechy as too how to fix the flooding issue. It list possible conditions including
1) Sticking float
2) high fuel pressure
3) Improper installation of float needle
4) Wear on the Fulcrum Pin
5) Improper Float Level

If it were me, I'd check the float level again. If it's right, then I'd check the needle for propper seating.

Start with the easiest first. My 2 cents.

nkh

mike newall · Post by **mike newall** » Thu Sep 01, 2005 17:53

Find a Marvel Carb - problem solved !

I had all sorts of problems with Strombergs on my A-65, mainly dripping. There are guys around with a good reputation for overhauling them, mostly though it would be cheaper in the long run to swap carbs.

pablo · Post by **pablo** » Sat Sep 03, 2005 16:56

Thank you, very much for all your suggestions. I have printed them and taking them to my mechanic. I will keep you posted of any progress.

Nathan:
Your airplane and mine are first or second cousins: My 7AC is N2126E.

Pablo

Nathan K. Hammond · Post by **Nathan K. Hammond** » Sat Sep 03, 2005 23:27

Holy Cow!! We'll have to get them together for a reunion some day.

nkh