How would you approach this engine???

[mhorowit]

I have a friend who is thinking about a project.
It's a Tcraft on it's feet, with a mounted engine with next to no compression which hasn't been run in three years; the crank turns(that's how he know there is next to no compression ( little on two cylinders).

Would you attempt to start the engine or would you pull the cylinders to find out why no compression?

If you wanted to attempt to start the engine, how would you prepare it? - Mike

[Rick Connolly]

Re: How would you approach this engine???

I think you'd be smarter to pull it down rather than risk casuing more damage running it. If it has no compression that is a bad sign. Unless the seller claimed it was a runner three years ago. Then I would suspect it's something in the top end...

[barnstmr]

Re: How would you approach this engine???

It is most likely due to dry rings... possibly due to rusted cylinder walls. Do you have access to a borescope to look at cylinder walls? If they look good, then it might be a valve leak. When you flip the prop, can you hear air swishing thru with your ear up to the exhaust pipe? If so, exh valve leaks, probably sticking. This can sometimes be freed up by pulling the rocker cover and dousing everything good with penetrating oil or marvel mystery oil. Then "stake the valve" a time or two.
Compression #s should be taken when the engine is warm and cylinder walls and rings are oily. I would attempt to start the engine but first some preliminary maintenance.
1) Pull Spk plugs - clean
2) Pull gascolator - clean
3) Flush and fresh fuel in nose tank
4) Change the oil - clean screen. Make note of the kind of contaminants in the screen and oil. Service with 50 wt straight mineral oil with a 1/2 pint or so of marvel mystery oil.
5) Squirt a small amount of marvel mystery oil in spark plug holes.
6) Turn thru by hand numerous times.
7) Re-install plugs
8) Attempt start - warm up at 1000 rpm to 1200 rpm until oil temp stabilizes
9) Shut down engine and check differential compression (60/80 is considered airworthy). If 40/80 or better there's still hope.
10) Change oil again while it is still warm. Use 50 wt straight mineral oil. Run some more... compression may improve some more after several hours of running at fairly high power settings.
11) If all are cyl's are in the 40's ...stay on the ground and plan to run some more. If only one or two cylinders are 40 and the others are >60, plan a flight, stay local, include high power settings... climb, get the engine hot but not over oil temp redline.
12) Don't continue using mineral oil after about 5 to 10 hours. Note - use of marvel mystery oil in the fuel (mix per directions) will help upper cylinder valve train lubrication.

[mhorowit]

Re: How would you approach this engine???

[QUOTE=barnstmr]It is most likely due to dry rings... possibly due to rusted cylinder walls. Do you have access to a borescope to look at cylinder walls? If they look good, then it might be a valve leak.QUOTE]

We don't have access to a borescope.
If we did, and we saw rust, would we continue with your outlined steps or take another approach? - Mike

[barnstmr]

Re: How would you approach this engine???

That depends on how rough they look. If pitted... I wouldn't waste time trying to get rings to re-seat. If light rust.... it would be worth a shot to run it some. Then look at the inside again. Worst case is pulling the cylinder either way. I wouldn't worry too much about the crank , cam and bearings... cylinders usually rust first. Cam next.

[mhorowit]

Re: How would you approach this engine???

... trying to get rings to re-seat. .

OK - that's what we're trying to do. - Mike

[alwaysoar]

Re: How would you approach this engine???

They aren't necessarily rusty if the prop pulls through smoothly. Even though you do a compression check hot, you can still hook up a compressor and find out where the leakage is--most likely rings, but again not necessarily.

[lfries]

Re: How would you approach this engine???

Once resurrected a cherokee 180 that had sat for many years. IA annualed it and said run it hard. Lo an behold compressions came back up after 5-6 hours of good hard running. Engine lasted about 15 years 30-40 hrs per year before it quit in flight one day. (fortunately near the airport)

[barnstmr]

Re: How would you approach this engine???

Getting rings to re-seat after light rust is not usualy difficult. Hence the recommendation for straight mineral oil. If rust is heavy, you;re not likely to get compressions to come up much.

It is possible for there to be no rust. I recently bore-scoped an engine that sat for 20 years... no visible rust...looked great steel cylinders. The owner had stored it in an insulated hangar and said he would periodically turn the crank thru a few revolutions.

But the lack of compression you are feeling should be verified with the engine hot and with oil film on rings if at all possible.

[high time cub]

Re: How would you approach this engine???

7) Re-install plugs
8) Attempt start - warm up at 1000 rpm to 1200 rpm until oil temp stabilizes

7) Re-install plugs
7.5) Prime the oil pump.
8) Attempt start - warm up at 1000 rpm to 1200 rpm until oil temp stabilizes

[Guest]

Re: How would you approach this engine???

[QUOTE=mhorowit]

It is most likely due to dry rings... possibly due to rusted cylinder walls. Do you have access to a borescope to look at cylinder walls? If they look good, then it might be a valve leak.QUOTE]

We don't have access to a borescope.
If we did, and we saw rust, would we continue with your outlined steps or take another approach? - Mike

Hi Mike

FYI, you can rent a borescope from Wicks for $30 per week, Dave.

[Marv]

Re: How would you approach this engine???

Before you do much i would take the valve covers off and make sure the valves are opening and closing. If they are not, its to late now, but you probably have some push rods and tubes bent now. This happens often to Franklin engines. Marv

[Ragwing nut]

Re: How would you approach this engine???

First determine it is not valve leaks. If all compression leaks then do the following. Drain any oil that may be in it. Roll any cylinder onto compression stroke and fill the cylinder full of Marvel mystry oil and let set overnight. Drain and repeat the process until all cylinders have been done. Drain any excess Marvel that has filled the oil tank, and fill with fresh mineral oil. If everything else looks good fire it up. Compression should start coming back after a couple hours of running it. Also since it has been sitting for several years, you may need to prime the oil pump for oil pressure in indicate.

Mike

[barnstmr]

Re: How would you approach this engine???

Very good point Jim and Mike... I left out an important step... Prime the pump.

[KTW]

Re: How would you approach this engine???

I have seen valves stuck open on A65s that sat 3 years or less