engine malady

s2d · Post by **s2d** » Sun Apr 12, 2009 11:22

Friend went to pick up airplane for me yesterday. runup was good including high speed taxi and momentary liftoff. Then topped the aircraft off with avgas (previously had mixture of avgas and cargas) and when he went to depart, the engine would runup fine, but about twenty feet down the runway it would start cutting out 3-400 rpm. (field was alittle bumpy.)
any ideas ?? He is sending me the carb to go thru, but don't want to miss anything else and have another wasted trip for him
c-90 with stromberg carb.
Thanks

Post by **joea** » Sun Apr 12, 2009 11:28

Would check for debris in the carb (blocked passageways) and do a fuel flow check out of the gascolator. Have heard of hoses swelling sometimes with some fuels and could be that the carb is getting enough fuel to do run-ups and normal running but when pushed to full throttle for takeoff it runs out of fuel.

While the carb is open would also check the float level.

Joe A

s2d · Post by **s2d** » Sun Apr 12, 2009 11:44

yea, it appears to me it is starving for fuel with that little amount of extra RPM one gets between static RPM and takeoff RPM. maybe the adding of gas before it happened was just coincidental, or the extra head pressure forced a piece of crud into an opening.
Thanks

I'm going to stick it on my 85 hp Chief when I get it and see what it does, but with the little less HP of the 85, it may not duplicate it.

gusc · Post by **gusc** » Mon Apr 13, 2009 02:38

I totaled a perfectly good Stinson once with the exact same symptoms.

The fuel tank vent was blocked.

It was ok with the tank almost empty but when I topped it all my extra air space was gone and it quit on takeoff.

MikeB · Post by **MikeB** » Mon Apr 13, 2009 08:45

Gus makes a good point, although could be one of several items. That also happened to a friend of mines Champ after someone made a new cap gasket and managed to plug the cap vent. Luckily it died on the take off roll rather than 50 feet in the air over the lake. When I took the cap loose it went "whoof"

as the air rushed in. I was riding along in the back seat at the time. (Edit: guess the last sentance doesn't make sense

I took the cap loose after we stopped the plane/couldn't obviously reach it from the back seat........hard to get going in the morning sometimes

).

Mike

gusc · Post by **gusc** » Tue Apr 14, 2009 00:58

I made it to about 75' with my Stinson and then smeared it all over the end and side of the runway.

As I was sitting there feeling sorry for myself someone yelled out, "look out there is gas running out of the wing".

The vent was spurting gas from the down wing vent, this was five minutes after the crash. Mud wasps (Dirt Daubers in AR) had plugged the vent and gas had dissolved the mud while the plane was sitting with the wing tip touching the ground. There was no gas flowing right after the crash.

With this info I saved the FAA or CAB straining their intellectual powers in figuring out what caused my ruined day!