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wierd engine noise

D

dick seiders

Well Known Member
Ok,I am back with an old problem. A few months ago I experienced a stange noise in engine shortly after taking off and leveling out. The sound is what I would guess to be an ignition aberration ( I call it burp).. It gets your attention. I talked with VAF and most opinions were unbalanced prop. I did the whole digital level fix and long story short got the blades w/i 1 degree. In the course of this effort the engine noise did not repeat. Therefore, prop was the cause. A couple guys at my home base said it's the Soft Start Module take it off!. I didn't do that as it seemed unecessary.
Flew yesterday and got the sound back again after takeoff and turning left C.wind. Flew the pattern for awhile and it burped once or twice so I landed and looked at things. Saw nothing so took off again and engine performed well, maybe a tiny burp one time on downwind. I figued it's fine.
This am I took off (run ups normal, and getting 5030rpm wot static). I lifted off and climbed to about 60 ft and engine sound was back in full and also a slight loss from full power. I quickly looked at runway left to see if I could abort and did managing to set the 12 down with about 1500' to spare. I pulled the top cowl and checked all and found nothing. Took off again and at about 80' the noise was slight, but back, and by now I am a little unnerved so aborted again . Pulled the cowl and disconnected the Soft Start relaxed a bit and went out to try again. The field temp. was 97 degrees and while I was doing two or three run ups one of the banks of cyl temp. climbed into the red at 248. Likely I caused that with all the ground testing in such high temps. In the course of run up testing I did note that even with the throttle locked the prms would vary from 4080 to 3990 and back w/o killing either ignition. What's with that? The run up checks however were w/i 120 rpm of A & B ignitions as one would expect. Following this with the high temp on cyl I decided it was a good time to put the thing away. I don't think I have a fuel problem as tank had 16 gal. tested sump on gascolater and it was full. Carb. sync is good. I also installed a new set of plugs about a month ago when having a similar problem. Maybe I need to replace the Rotax ign. module?? Would really appreciate help so I fix this and get back to flying where I can go futher than half the runway length. Thanks in advance, (I know I haven't tried since removal of Soft Start Module, but will before changing anything else).
Dick Seiders 120093
 
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The dog is right

Dick, Next flight flip to the fuel page of your EMS and watch what is or is not happening with fuel pressure and fuel flow. But before you do that pull the data download from the problem flights and look at those two columns. Unusual aberrations there are indicative of the pump problems several others and I experienced.

Jim
#264
flying since 12/10
 
Can you both describe what the symptoms of the fuel issues were please? Ie: sound of engine, or any other noise? For what it's worth I checked fuel pressures today before flights and the Facet was 2.6 while the engine pump was 3.6. As I recall that's about what I have been seeing. On one check yesterday the engine pp. was up to 5 or 6 I believe. Wondered about that. Another thing usually when I check the gascolator I get only a couple thimblefuls. Today after the hot run ups two sump tests resulted in two half full tubes and I halted the test at the half way point as I felt I could have gotten more, but I stopped testing. Mean anything?
Dick Seiders
 
Dick,
Do a forum search on fuel pump in the RV12 forum. There is a lot of info about the fuel pump issue. A pump failure is a lot like you symptoms.
 
dick seiders said:
Another thing usually when I check the gascolator I get only a couple thimblefuls. Today after the hot run ups two sump tests resulted in two half full tubes and I halted the test at the half way point as I felt I could have gotten more, but I stopped testing. Mean anything?
Dick Seiders
Click to expand...

This by itself warrants disassembly of the gascolator. Check the screen and the bottom of the bowl for debris. Gas should flow from the drain valve on the gascolator as long as it is open. If it does not, ground the plane.

As mentioned a faulty fuel pump could induce fuel pressure variations. A partially plugged/plugged gascolator and/or debris in the carb float chamber/needle valve could do the same.

DOWNLOAD the D-180 data and look at the fuel pressure, fuel flow plotted vs. engine speed.
 
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Marty, thanks for the thought, but I just did the annual and cleaned the gascolator screen two weeks ago. (got a little wad of what looked like fine cloth remnents off of it). I tested flow of drain today with the fuel valve closed so was surprised at getting so much out of it. Could have been more I think as I stopped draining it.
DickSeiders
 
Dick, OK, the screen is clean. The crud you pulled out at annual is what everybody else is finding--a little wad of lint. Re-do the fuel flow test from your before-first-flight regimen. If you have more than the required 2 gallons in the tank, make allowances for that. What you want to confirm is that boost and fuel lines aft of gascolator are good. Once you have done this, you can focus downstream.

Didn't see on your posts that Dynon download results were analyzed. If your fuel pressure is north of 3.5 even when hot and under WOT, your pump is probably OK. However...mine would lose pressure after 30 min of flight in hot weather. So you need to confirm that FP and FF are behaving well into the flight.

On another front... I was told in no uncertain terms by Rotax that ignition modules had no intermittant failure mode.Lacking contradictory evidence, I have to believe this. Be sure the grounds for your modules are good. They ground to the RH intake manifold. If the casting roughness was not ground down properly on the bosses, you could get an intermittant loss of one mag.

Jim
 
Colin, I found a bunch of fp info on old thread. Esp. helpful was John's whose description sounds a lot like my issue.

Jim, I will test the pump flow and psi. I haven't done the data download as I don't know how to do it, and am concerned about screwing up my 180 as I had mega problems with it when I was starting up. Where can I find instructions for doing this? I also was advised that the ign modules don't have intermittent issues. Lockwood says they work, or not, no in between. If true then the fuel pp issue certainly looms large.

Larry, yes, that is what I found early on. The is little to no flow w/o facet on.

Thanks to all. keep the info flowing.
Dick seiders
 
Dick, Don't let the data download stuff spook you. I am reeaalllly stupid about computers and the stuff on this forum got me set up OK. Just search "Dynon Data Download".

I think you are going to discover important details about your problem in the download. You will be able to scan across all the instruments at the exact second the engine burped. If you don't have a laptop, used ones are dirt cheap if you don't want wi-fi on it. Get a serial port to USB extension cord at Radio Shack and you can set the laptop on your wing and drink a cold one while the 10 minute download happens. If you fly again without downloading, the data will be lost.

When you get the necessary stuff on your laptop, PM me and I will talk you through the process if you don't have anyone nearby.

Jim
 
JIm, thanks. I do have a laptop and a serial port connector. I will check the Dynon instructions and give it a try tomorrow. If I wind up needing a new pump what is the new pump number? Don't want to be sold the present style, and while that's unlikely it can happen.
Dick Seiders
 
Dick,
When John and I asked LEAF about the pumps I believe they said they are out of the old pumps and sold 20 some of the 25 new pumps received with their first shipment. I don't think you will get an old pump. I do believe you will have to change the hoses yourself. So, if you need a new pump get the new pump BEFORE you send in the old pump so you can change the hoses. Just remember it is an educational experience.
 
Pump replacement

I just replaced my leaking pump with the new style pump about 3 weeks ago. Lockwood has them in stock and are also helping me with the warranty paperwork. The new pump requires a drain line and clearances are tight so send me a PM with your phone number and I can describe the install.
 
Dick, You won't get an old style pump. I'm the sorry SOB who got the last of the old ones left on the shelf and I'm still waiting to see if Rotax will advance me the $150. Any of the techs at LEAF or Lockwood will know which pump you need. No way of knowing if they will honor warranty for you.

You can order it with hoses attached which ran IIRC about $450 for the old pump or just the pump. Factory clamps can be removed with a Dremel and a steady hand. Automotive fuel injection clamps are used by some for attachment; stainless bands are preferable.

You might want to hold off on the pump replacement until you see the download. Look for a high FF and low FP at the time of the incident.

Although Rotax insists that leaking is the only pump problem, I am convinced that prolonged heat and/or time of operation causes the spring to weaken, reducing FP. That or they had some bad springs. My replacement pump had a noticibly stiffer spring.

Jim
 
Jim, I have downloaded and reviewed the Dynon data. Not sure I understand all of it, but managed to sort out the basic engine data, as well as altitude and airspeed. I have checked the first three flights on the d. load, ( there are more, but I felt that was enough to compare) and then compared those results against the last two which I aborted as mentioned in an earlier post. I can see no significant difference between the five records. As the takeoff begins I am consistent in mp, oil temp, oil psi (varys a bit), fuel psi (rises with mp), voltage, amps(don't understand the plusses and minuses at all), rpm, and fuel flow. I matched these with the airspeed and altitude to be able to determine what is happening regarding flight. The difference between the numbers are consistent with the other changes in engine data. Fuel psi ranges essentially from 3.1 to 3.8, and fuel flow ranges from 1.500 up to from 5.8 to 6.4 at peak, and back down basically following mp and rpms.
During the two flights that created the question there was a change in engine sound, and I did not imagine it, and I seem to recall a slowing of speed, but did not take time to look. Don't know what to think except go try it again as nothing in this data indicates any engine issues. Could some part of the airframe be causing the sound? I love mysteries, but not when they involve airplanes.
Appreciate any feedback.
Dick Seiders 120093
 
Dick- Well, your fuel pressure numbers are way more stronger than mine were when my old pump was cratering. You did mention at one point that the FP went up with application of power. This seems contradictory inasmuch as it "theoretically" goes down as the fuel flow goes up. But the accuracy of the FP sender being what it is, sometimes my FP goes up on takeoff too.

Lacking any definitive data from the Dynon, your engine may just be practicing for the auto-rough mode it will go into when you get over open water. Seriously, I find the fixed-pitch prop and bumpy air can set up some strange noises in the 12.

If you operate off a fairly long runway, you may want to just put some hours on it and write it off as an aberration. BTW, I hate mysteries involving my plane too.

Jim
RV-12 #264
flying since 12/10
 
That's pretty much how I see it Jim so will fly tomorrow. This will be first try since removing the soft start module which is still somewhat suspect. We'll see how it goes. Thanks for your feedback.
Dick Seiders 120093
 
I put the cowl back and flew for an hour or so today with no unusual noises. The data indicated engine is operating well and it did indeed. The only change I made was disconnecting the soft start. Don't know if that had any effect. I plan to fly about 20 hrs, and if no issues will re connect soft start and fly to determine answer to that question. Thanks for the comments and interest.
Dick Seiders
 
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