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First Start Woes

Chris Engler

Active Member
During a first start working with the local A&P we noted a couple of issues that have us stumped. The set up is as follows:

Airplane - RV-8

Engine - Superior XP-400

Prop - WW constant speed with HRT blades, 14 inch WW spinner

Governor: MT

Ignition System - Standard mags and G3i

Issue 1: Prop Not Moving:

We've run the engine for over a 1/2 hour at various RPMs including 2000-2500 and moved the prop pitch many times....sometimes slow, sometimes fast, and can not get the prop pitch to change. We pulled the governor, confirmed the gasket is oriented correctly and there are no visible blockages/obstructions. We also confirmed that the prop shaft plug is removed.

Issue 2: Engine Coughs/Dies at High RPM

When the throttle is advanced, all is well until around 2400 RPM then the engine will cough/sputter. If the mixture is leaned (about half travel on the throttle quadrant) I can keep the engine from running rough and at full throttle and half "lean" maintain around 2550 RPM.

All EGT/CHT readings are in the green, fuel pressure is 4.5 - 6 psi, and oil pressure is fine. Fuel flow is reading 30 gph at full throttle though the Red Cube has not yet been calibrated.

The coughing is present with the G3i ignition system switched both on and off so we don't believe that's a factor. Thought possibly the stock snorkel/air filter were not providing enough air volume (we assume the "cough" is due to a rich mixture since leaning eliminates it). To test that theory, we opened the alternate air supply to provide more inlet area but that had no effect...cough still there at 2550 RPM.

Planning to call Superior and WW tomorrow but wanted to put this out to the collective wisdom of the VAF community for thoughts/suggestions.

Thanks in advance!
 
Is the oil plug installed in the engine for the governor operation? I wonder if something got missed maybe? That would be a bummer but if you are getting oil pressure without the prop cycling, it's one possibility to consider. Have you pulled the prop yet to look for signs of meaningful oil flow?
 
When I discussed with WW, they said either would be fine and as I recall, the jhirosti was back ordered at the time from WW and the MT was a bit cheaper so went that direction.
 
Is the oil plug installed in the engine for the governor operation? I wonder if something got missed maybe? That would be a bummer but if you are getting oil pressure without the prop cycling, it's one possibility to consider. Have you pulled the prop yet to look for signs of meaningful oil flow?

Greg....the A&P has thoroughly inspected and confirmed the engine set up is correct for a CS prop. We did pull the prop after a run last week and there was some oil in the hub but not as much as the A&P thought there would be (typically 2 cups or so). WW indicated a small amount of oil doesn't suggest a problem but will discuss that again with them tomorrow.
 
Next run hold the prop lever out for 30 seconds to a minute. It sometimes takes that long to get enough oil in it to cycle.

Also agree with the question on fuel pressure. Why would you have that engine setup with a carb?...I see that your signature says IO-400. You should be running 20-30PSI for that engine.
 
I'm with Jesse on holding propeller controller back for a longer period. Non-counterweighted props don't cycle as fast. I need at least 1800 rpms to cycle it, I normally do my run-up at 1900.
 
Chris

I had a similar problem with a prop that would not cycle.

Two engine pro's looked at it and could not find a solution.

I got a hydraulic pressure gauge and attached it to the governor hose. On startup it indicated about 180 psi, proving the prop was getting lots of pressure.

Had us all stumped. Where was all that pressure going?
Went back to the engine shop and looked at a case of an engine they were starting to build.
Found there was a hole in the front bearing housing that was allowing the governor oil to back in to the sump.

So, we had to split the case and install a plug in that hole.

After re-assembly the prop worked normally.

Hope this is not your problem.

Carr
 
Chris

I had a similar problem with a prop that would not cycle.

Two engine pro's looked at it and could not find a solution.

I got a hydraulic pressure gauge and attached it to the governor hose. On startup it indicated about 180 psi, proving the prop was getting lots of pressure.

Had us all stumped. Where was all that pressure going?
Went back to the engine shop and looked at a case of an engine they were starting to build.
Found there was a hole in the front bearing housing that was allowing the governor oil to back in to the sump.

So, we had to split the case and install a plug in that hole.

After re-assembly the prop worked normally.

Hope this is not your problem.

Carr
Not to ruin your day but we had a similar experiance to Carr above.
We could not get the prop to cycle.
checked the govoner like Carr.
Then tested the nose fitting by trying to pressurize it and could not.
This was a overhauled engine with 600TTSMOH on it.
The Clamshell nose bearing was out of place and allowed the oil to flow under it. Once corrected, it worked perfectly.
Good Luck
 
Similar issue with my prop. Multiple starts, RPM tests, times, could not get it to cycle. I was certain I removed the plug correctly, though that was what everyone questioned. I removed prop governor and checked gasket, etc. All good.

Finally read on here someone had similar issue and they had crud in their oil supply line from governor to prop. I removed both ends of the line and blew it out with shop air, and got out a lot of the preservative oil that was still in the line. After that, it cycled wonderfully.
 
Thanks guys...really appreciate the advice on this. To clarify, this is a fuel injected motor (completely stock IO-400). Sounds like either the fuel pressure is actually too low or I have a gauge out of calibration.

Regarding operation of the pitch lever, we've run the motor above 2000 rpm with the pitch lever advanced for a couple of minutes, cycled the prop, etc. with no joy.

I spoke with WW this morning and they are sending a governor that they bench tested and verified to be working correctly. I'll install this week and hope for an easy answer that the MT governor is somehow non-functional.

Carr - very interesting situation with the nose bearing.... we'll keep that in mind if all the other trouble shooting options don't pan out.
 
Ctennis - excellent idea.....we'll pull the oil line and confirm.

Carr - follow up question....was you engine a Superior as well?
 
As to fuel pressure, check the part number on the pump. It would not be the first time an engine was shipped with a low pressure pump on a injected engine or vice versa.

Bob burns
Rv-4 n82rb
 
Chris

Sorry I didn't back to you sooner. (out of town)

My engine was a Lycoming 0-360 A1A.

Did you solve your problem?

Carr
 
No worries Carr ? I know how that business travel has a way of getting in the way of airplane fun!

Yes, happy to report that the prop mystery is solved though a bit embarrassed by the simple solution. The XP 400 has a small ?set screw? type plug in the back of the hollow section of the crank and sure enough it wasn?t there (it is now and hence the prop is working flawlessly).

This was one of those self-induced problems. The engine shipped set up for a CS prop and early in the build was going to use the ground adjustable Sensenich prop so had the A&P remove the set screw and install the forward seal in the crank. As the build progressed, decided to go CS and when we re-converted, pulled the front seal and forgot the rear plug.

During the trouble shooting process, I was working with Whirlwind on possible solutions. I want to acknowledge their outstanding customer service throughout the process. I was on the phone with them a couple of times a day and they even shipped out another governor for me to try to eliminate that as one of the variables (all at no cost). Fortunately I didn?t need to do the swap governors since we found the missing plug first. These days it's hard to find customer service that includes an actual person answering the phone when you call and knowledgeable staff personally committed to helping work through issues and going the extra mile?BIG thank you to WW!

Now that the prop is working, I?m focusing on the second issue ? engine cough at high RPM:

The engine starts quickly and things are smooth until 2450 RPM then it sputters and coughs hard with mixture full rich. I can lean to about 2/3 rich mixture and advance the throttle fully and it smooths out but the RPM never gets above 2500. This is all with the prop at low pitch.

At this point I don?t think it?s fuel related as the fuel delivery system has been thoroughly checked as follows:

1. Fuel flow test to the inlet of the fuel servo ? just under 60 gph delivered with the electric pump running.

2. Pulled screen to the inlet of the fuel servo ? no sign of debris.

3. Spoke to the folks at Precision Aeromotive (the servo is a EX-5VA1) and they suggested the following to confirm fuel delivery system: Just before coughing starts (2450 RPM) with mixture full rich, lean to peak and just past. Should be a 150 rise in EGTs to peak which it is. Per Precision, that suggests that mixture is neither to rich or too lean prior to coughing. At that RPM setting, EGT spread is 60 degrees or so hottest to coldest across all 4 cylinders so it doesn?t appear to be a fuel servo/injector issue.

The only ?modification? to the fuel system since delivery from Superior is that I rotated the fuel servo 180 degrees to get the orientation of throttle and mixture levers were I needed them for the cables. I?ve confirmed with Superior and Precision that this is fine/not a factor.

Based on the above, my main focus is the ignition system. I?m running slick mags modified for the G3i ignition system. So far love the system as hot and cold starts are super easy and the engine runs very smoothly below 2400 rpm. At 1000 rpm, turning the system on and off results in a 20 rpm increase/decrease (system on +20) and can feel the engine run smoother as compared to the ?straight mag? mode. My theory is there is an ignition issue at the high RPM setting and that when I lean, I?m matching the fuel delivery to the max RPM the ignition system will allow which is why it smooths out but RPM doesn't increase. Just a theory and I have very limited knowledge regarding the slick mags.

I?ve had the A&P check timing (and rechecked again yesterday) and it?s spot on. I?ve seen a reference to an ?internal timing? and not sure if this is the same thing the A&P is checking or something else. I also read that a bad condenser in the mag can be attributed to these symptoms. The cough is present regardless of the G3i being switched on or off. In the ?off? mode, operation should be ?mag only?.

Any thoughts/advise would be much appreciated.

Thanks!
 
If you get a chance, try this simple test. Run the engine for a couple minutes to let it warm up. Do a full power run up at FULL RICH until the engine starts coughing. Bring the engine back to idle and then shut it down. Pull the top plugs after it cools and let us know if you see any difference in them.

I've seen this symptom once personally with an engine swinging a FP prop but I'm not sure if it would act the same with a constant speed. It's hard for me to believe you'd have the same issue but since this is a new engine it's possible.

If all the plugs look the same disregard this post.
 
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The engine starts quickly and things are smooth until 2450 RPM then it sputters and coughs hard with mixture full rich. I can lean to about 2/3 rich mixture and advance the throttle fully and it smooths out but the RPM never gets above 2500. This is all with the prop at low pitch.

I am an FP guy, but it was my understanding that max RPM is set via an adjustment on the prop (limits how fine of a pitch is allowed). Have you performed the adjustment? Overly limiting the fine pitch would create the symptoms your seeing. I would assume that the factory would ship with a conservative setting to help people from inadvertently over-speeding prior to adjustment. I don't believe that ignition issues would limit your RPM to 2500 without showing other symptoms as well. I can produce well over 2500 RPM on only one mag. That said, bad coils demonstrate that behaviour at times. However, you can usually feel the strange nature and in your case should see diverging EGT readings across your cylinder pairs.

Larry
 
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It's funny I'm at the airport now and just finished up a call with Thomas at g3i. We had exactly the same thought that the governor setting on the fine pitch is to course to allow the engine to spin up to 2700 RPM. I did confirm the fuel flow continues to increase even as the engine is coughing indicating the injection servo is doing its job and feeding more fuel as the throttle advances. If the governor is holding the prop back to less than 2,700 we would see the flooding symptoms that we have including coughing and black smoke. Hopefully this is the cure!
 
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