First Start Woes

[Chris Engler]

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!

[Michael Henning]

Why an MT governor and not the jhirosti?

[greghughespdx]

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?

[Chris Engler]

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.

[Chris Engler]

Originally Posted by greghughespdx

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.

[Bob Martin]

You have a Carb?
"fuel pressure is 4.5 - 6 psi,"

[Jesse]

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.

[Michael Henning]

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.

[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

[Bob Martin]

Originally Posted by 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