"Engine Problems" Solved !

[flyguy]

Re: "Engine Problems" Solved !

Needle tip shapes to jet seat and sticks closed overnight. Not enough pressure to blow loose with short fuel head. Engine runup and and taxi out sucks fuel level down and engine stumbles/quits. With fuel level down all float weight is pulling on needle and tip is warming up. Engine shakes when it quits, needle breaks loose, and chamber refills. Engine runs ok for remainder of day on low or full fuel because it never rests on seat long enough to conform to shape and is always lubricated by fuel flow.
DC

[1938BF50]

Re: "Engine Problems" Solved !

After watching this thread with great curiosity, I am making damn sure I have a steel needle in my carb....period.

[VictorBravo]

Re: "Engine Problems" Solved !

Needle tip shapes to jet seat and sticks closed overnight. Not enough pressure to blow loose with short fuel head. Engine runup and and taxi out sucks fuel level down and engine stumbles/quits. With fuel level down all float weight is pulling on needle and tip is warming up. Engine shakes when it quits, needle breaks loose, and chamber refills. Engine runs ok for remainder of day on low or full fuel because it never rests on seat long enough to conform to shape and is always lubricated by fuel flow.
DC

Close, but I don't think so. The warmup and taxi and runup and wait for takeoff clearance process at this airport is about ten minutes minimum.

[jdoran]

Re: "Engine Problems" Solved !

Perhaps your carb fuel bowl vent is clogged. The air bubble could not escape when you turn on the gas to the carb until the engine vaccum drew it out while running, and eventually replaced it with gas.

[flyguy]

Re: "Engine Problems" Solved !

Ah. The plot thickens.
DC

[VictorBravo]

Re: "Engine Problems" Solved !

Perhaps your carb fuel bowl vent is clogged. The air bubble could not escape when you turn on the gas to the carb until the engine vaccum drew it out while running, and eventually replaced it with gas.

Good Call ! I'm going to ask the carb expert to look for this possibility tomorrow. I'm going in to have him perform a Rubber Needlectomy followed by a Stainless Needle Arthroplasty. This will hopefully prevent any further MyoContinental Infarctions or Go-itus Interruptus.

[flyguy]

Re: "Engine Problems" Solved !

So you don't ever experience the failure unless the fuel level is low and the aircraft is accelerating? I can see why you came to your original conclusion.
Verrrrry interesting.
DC

[Dano"T"]

Re: "Engine Problems" Solved !

I had a similar incident on floats with the 90HP Tcraft this summer...I was giving rides and my fuel got down to about 4 gallons...I took off...and on floats the nose pitches up quite high for a couple of seconds at full power and then it transitions onto the step...I then rotated and jumped off clibing at a rather steep angle and the engine quit...I leveled out pull the throttle back and it restarted....I landed, checked the fuel bowl for water and took off again....same thing...I landed again....dumped 2 gallons of gas in and took off again....this time it was fine.....So...I am convinced in my case it was un porting...Imagine firewalling the throttle...the nose pitches up unporting the fuel in the tank....then a few seconds at full power I rotate...but the few seconds at full power sucked my bowl clean and the engine suddenly quits...I pulll the throttle back, level the plane and slowly add throttle and it comes back to life....Unporting for sure in my case...now taxiing issues I'm not so sure...but that's just my experience.

[VictorBravo]

Re: "Engine Problems" Solved !

Darryl, yes this only usually seemed to happen with low fuel and acceleration on the ground. ONE time it happened under different circumstances and I blamed it on carb ice (see previous thread on that subject) but it MAY have been related to this instead.

AFTER the "carb ice" incident I had three failures:

First time I was taxiing uphill with only 2 or 3 gallons on bard and it quit on the taxiway at 1500 or less RPM.

Second time I was taking off with not a lot of fuel (forgot how much but between 4 and 8 I think), after a full runup, and it quit less than three seconds into the takeoff roll.

Third time I had measured 6.5 gallons in the hangar before startup, taxied out and did a runup (10 minutes), and it quit three seconds into the takeoff roll.

Never had a failure in flight outside the airport (thanks Clarence). All failures were accelerating to one degree or another on the ground. Uphill taxi incident was cured immediately with 5 more gallons of fuel. Second and third incidents were self-repairing, meaning I immediately did a couple of 100% runups with no problem, and took off/flew for a while with no problems at all.

Although saying this (after everything that has come and gone) I feel like Charlie Brown about to try and kick the football... I'm fairly sure the steel needle would solve the problem. There's nothing else it could be except that or the vent hole mentioned by Jdoran.

So, the needle gets changed Monday, and while we're at it it will have the vent hole checked, the float checked for sticking, etc.

Dano, it's strange because I believe there is less un-porting on a ground acceleration than there would be in a steep nose-up climb. I've done very steep climbs (55-58 mph IAS) immediately after both of the last failures, with the same amount of fuel on board, and it did not quit in the climb. That angle HAS to be somewhat more of an un-porting risk than just an 85HP straight acceleration on the ground. or around a turn.

I greatly appreciate all of you guys applying brain time to this. It's got me really baffled as to why this can happen on such a simple system. There may be a new owner of this airplane sometime in the near future (unrelated to this issue), and he definitely doesn't deserve to have takeoff engine failures like I apparently do ! Not on my watch

[jgerard]

Re: "Engine Problems" Solved !

I took off...and on floats the nose pitches up quite high for a couple of seconds at full power and then it transitions onto the step...I then rotated and jumped off climbing at a rather steep angle and the engine quit...I leveled out pull the throttle back and it restarted....I landed, checked the fuel bowl for water and took off again....same thing...I landed again....

I had a similar thing happen to me in my F19 during a steep climb out. Turns out the float level was way off (LOW) inside the carb. That was on a Marvel carb which is a piece of cake to set the float level on. The Strombergs are much more sensitive to proper float adjustment and require some special home made tools. Make sure your carb guy knows Strombergs.

[VictorBravo]

Re: "Engine Problems" Solved !

Make sure your carb guy knows Strombergs.

Yes, thank goodness he knows them very very well.

[VictorBravo]

Re: "Engine Problems" Solved !

Guys, today I set a new record... THREE engine failures on takeoff in one day. I guess I really need some help from the group.

Last night, thanks to a very experienced Forum member, we replaced the carburetor needle. The rubber tip needle came out, looking brand new, undamaged, un-swelled, and un-cracked. The person who removed the needle said "Well, there's nothing wrong with this needle."

We installed the new steel needle from Fresno Airparts anyway, and the new seat. We set the float level to the correct height, 13/32" below the carburetor housing parting line using shims under the seat. We did a check to verify the proper function of the float, the needle, and verified strong flow coming in to the float bowl.

We reassembled it, safetied it, and I reinstalled it on the airplane. I expected to not have any further problems with engine failures.

This morning, I test-flew the airplane, doing 5 landings, and the engine ran well. This was after a full runup and mag check. No engine failures.

Later, I was going to fly with a passenger. We started up, taxied out, did another successful runup, then I did a brief full-power runup. When I accelerated down the runway for takeoff, three seconds into the takeoff roll the engine lost power.

We had about 5-6 gallons on board at the time.

I taxied off the runway, taxied back to the runup area, did three full power runups, was cleared for takeoff and proceeded to take off. We had no problems, and continued to climb out beyond the pattern. My passenger and I discussed the probability that it was fuel running back away from the outlet.

We arrived at a nearby airport and tied down. I happened to see a very well known expert on antique engines and told him about what had happened. Long story short, he said that he had personally had carb ice with these carburetors, even on warm days. Perhaps I should try the carburetor heat on takeoff or use it to make the carb warm before takeoff.

We decided to do a test. Since the engine was warm, and carb ice should not be a big probability, we would go back and take off again (we now had about 3 gallons on board). If the engine quit on takeoff it would indicate un-porting. If the engine ran right, it would indicate that we had previously experienced carb ice, but now that it was warm there was no problem.

We taxied out and did an intentional high speed taxi on the runway, with about 3 gallons and carb heat OFF. 3 seconds into the takeoff roll, it sputtered and lost power.

We taxied back, using full carb heat on the taxi, and left full carb heat on for another simulated takeoff. The engine did NOT sputter or lose power.

We taxied back a third time, left the carb heat off, and did it again, where it promptly lost power three seconds into the takeoff roll.

We taxied back a fourth time, put the carb heat ON, and did another takeoff run with NO loss of power and no sputtering.

By this time we probably had 2-3 gallons max on board.

After lunch, we put 7 more gallons in the airplane, took off using carb heat, and had NO problems. We left the carb heat on up to 2500 AGL.

It CANNOT be "un-porting" of the fuel tank because it did not un-port when we used carb heat all other factors being equal.

It shouldn't be carb ice either, because the engine was already warmed up. I had flown earlier this morning, when it was EQUALLY moist, cloudy and cold, and NOT had a failure.

[Robert Bradbury]

Re: "Engine Problems" Solved !

Guys, today I set a new record... THREE engine failures on takeoff in one day. I guess I really need some help from the group.

Last night, thanks to a very experienced Forum member, we replaced the carburetor needle. The rubber tip needle came out, looking brand new, undamaged, un-swelled, and un-cracked. The person who removed the needle said "Well, there's nothing wrong with this needle."

We installed the new steel needle from Fresno Airparts anyway, and the new seat. We set the float level to the correct height, 13/32" below the carburetor housing parting line using shims under the seat. We did a check to verify the proper function of the float, the needle, and verified strong flow coming in to the float bowl.

We reassembled it, safetied it, and I reinstalled it on the airplane. I expected to not have any further problems with engine failures.

This morning, I test-flew the airplane, doing 5 landings, and the engine ran well. This was after a full runup and mag check. No engine failures.

Later, I was going to fly with a passenger. We started up, taxied out, did another successful runup, then I did a brief full-power runup. When I accelerated down the runway for takeoff, three seconds into the takeoff roll the engine lost power.

We had about 5-6 gallons on board at the time.

I taxied off the runway, taxied back to the runup area, did three full power runups, was cleared for takeoff and proceeded to take off. We had no problems, and continued to climb out beyond the pattern. My passenger and I discussed the probability that it was fuel running back away from the outlet.

We arrived at a nearby airport and tied down. I happened to see a very well known expert on antique engines and told him about what had happened. Long story short, he said that he had personally had carb ice with these carburetors, even on warm days. Perhaps I should try the carburetor heat on takeoff or use it to make the carb warm before takeoff.

We decided to do a test. Since the engine was warm, and carb ice should not be a big probability, we would go back and take off again (we now had about 3 gallons on board). If the engine quit on takeoff it would indicate un-porting. If the engine ran right, it would indicate that we had previously experienced carb ice, but now that it was warm there was no problem.

We taxied out and did an intentional high speed taxi on the runway, with about 3 gallons and carb heat OFF. 3 seconds into the takeoff roll, it sputtered and lost power.

We taxied back, using full carb heat on the taxi, and left full carb heat on for another simulated takeoff. The engine did NOT sputter or lose power.

We taxied back a third time, left the carb heat off, and did it again, where it promptly lost power three seconds into the takeoff roll.

We taxied back a fourth time, put the carb heat ON, and did another takeoff run with NO loss of power and no sputtering.

By this time we probably had 2-3 gallons max on board.

After lunch, we put 7 more gallons in the airplane, took off using carb heat, and had NO problems. We left the carb heat on up to 2500 AGL.

It CANNOT be "un-porting" of the fuel tank because it did not un-port when we used carb heat all other factors being equal.

It shouldn't be carb ice either, because the engine was already warmed up. I had flown earlier this morning, when it was EQUALLY moist, cloudy and cold, and NOT had a failure.

If your going to check the carb inlet screen do a fuel flow test at the same
time. Some older fuel lines have been known to swell over time and even break
down. This would check all systems from the tank including the finger screen
fuel valve all piping and rubber hose to the carb. I cannot remember from
memory what is the correct flow for a 3/8 hose but this can be found in
the builders bible AC43.13 if I recall .

BTW, it seems to me that low fuel, unporting and steep angle, or a combo of
both are the root cause of most failures . I guess as we have already been
told, do not take off with less than at least reserve, do not do steep climbs if low and when we are getting low in flight, get your ship on the ground and add some more fuel .

I normally refuel the nose tank after every flight so when I go again I'm topped up .

I will admit to talking off at one point on floats at a ridiculous angle showing off to a buddy taking pictures from the shore. Climb out was a crazy angle then back to the cottage and in the hanger she when not 10 minutes from my pals cabin. I decided for some reason to check the reserve amount in the tank to be correct since the wire was now bottomed out. What I got out of the tank was 1 gallon guys . I had just taken off in a steep climb on floats with a C90 with less than 1.5 gallons on board. Turns out the cork that came with the ship was set up wrong. Then I get nervous and start checking everything else where I discovered my oil dip stick was wrong as well . When I thought I had 4-5 quarts I only had 1-2 . This was a certified overhauled
engine .

Robert

[Dan Michaels]

Re: "Engine Problems" Solved !

A C150 will get carb ice after a long cross country on downwind just by going below green arc. Carb ice can form at 70 deg. Try your experiment again using carb heat just before takeoff but not during. (Run up 2200) using carb heat until smooth then no carb heat during takeoff.

Dan

[Robert Bradbury]

Re: "Engine Problems" Solved !

A C150 will get carb ice after a long cross country on downwind just by going below green arc. Carb ice can form at 70 deg. Try your experiment again using carb heat just before takeoff but not during. (Run up 2200) using carb heat until smooth then no carb heat during takeoff.

Dan

I fly in conditions that are for the most part ripe for carb ice ,though, I have
never had a problem. I have a carb temp guage installed and I am always in
the danger zone. On my C90 is a 0-200 carb , M.S., with mixture control that
I only use for lean cut off or to prevent fouling during the long taxiing necessary for float operation on water.

But, as you said a few C150 have gone down around here due to carb ice .
Maybe it has something to do with the C150 air induction system .

I still routinely check for carb heat though by pulling on the carb heat once
in a while. I have never had the engine run rough though .

Robert