Engine suddenly quits running ?????

[fastj22]

Well I wrapped and insulated the fuel line and gascolator , put cowl on and 14 min later it burped once , and then I raised the rpms to about 1800 and it burped a few times and stalled once , , all the temps looked good , egt , cht , oil temp , I have no idea what to do with it , I refuse to take a chance flying this , I fly out of class d So it's pretty busy and no place to put it down in the event the engine quits I am ready to give up on it ,.....grrrrrrrrrrrrr, for sale best offer lol possibly ,

Before you throw in the towel...
Have you ever been able to do extended cowl on ground runs? 15 minutes is a long time for the engine to run without a lot of air being forced through it. Internal cowl temps might rise sufficiently that no amount of insulation will keep it from vapor locking. And with our gravity fed fuel systems and no circulation of fuel through the system and back to the tank like fuel injected systems have, that fuel will just sit in the lines and heat soak. Add to that the fact your fuel consumption is very small on a ground run so you really aren't moving much fuel through the line. Burp tube might help. I have one on my bench I've been meaning to install to solve the burps on touch and goes.
I do understand your concern, but I'm not sure your problem is really a problem we all might experience if we did extended ground runs.

[SonexN76ET]

I know this has to be frustrating for you.

You say the RevMaster engine runs fine with the cowling off, but burps and quits with the cowling on after 15 plus minutes of ground running. Is this ground running at high RPM? If it is at high RPM, you are probably experiencing vapor lock that any of us would encounter after extended high RPM ground running. The engine needs to be moving through the air in the sky to properly cool while running at high RPMs.

Now, there are a couple of more things for you to check, however.

1) Make sure your fuel line is not within 1 1/2 inches from the exhaust with the cowling on (put half the cowling on and push the bottom up to where it would be with the other side on and make sure the cowling is not pushing the fuel line closer to the exhaust).

2) Make sure that the fuel line goes upward from the gascolator to the RevMaster RevFlow without any intermediate high points that can collect vapor. Again make sure this is so with the cowl on.

3) Make sure your fuel line is as short as possible and follows a direct path straight from the gascolater/firewall to the RevMaster/RevFlow.

4) Make sure your outlet on the bottom of the cowling is big enough to allow adequate airflow to cool your engine.

Good luck! Be careful with the extended high RPM engine ground running as those are not good for the engine because of the high heat generated. In WWII and the Korean War, the Navy used prop driven airplanes on the decks of the aircraft carriers to generate thrust to move the carriers to and away from piers. They had to strictly limit the amount of high RPM ground running so they would not destroy the aircraft engines. When aircraft engine manufacturers test engines on the test stand, they pump high pressure air into the engine's cooling baffles to simulate flight conditions.

Bottom line, however, is safety. Don't fly until you are confident you have everything right. If you are not confident, find an EAA Technical counselor or experienced Sonex builder nearby to help you check things over and make sure it is ready for flight. When you fly, even though you are at a towered airport, request to stay in the pattern and make your test flight when other traffic is minimal.

[Sonex541]

I ended up have my buddy make a new stainless braided hose to replace the Rigid line and change the routing of the line so it is a bit farther away from exhaust , everything seems ok , goin to stay around the pattern a few more times Tomorow ,
Adam Simmons

[Xenos50]

Hello Adam (Sonex541). I am building a Xenos (kit #50) with Revmaster-2300. Would you share details of your fuel system (at least how it goes from gascolator to carburetor)? Details like what exactly fittings/sizes and what hose and its size you used and where you bought it. I just bought today Aeroquip hose fittings and hose from the Aircraft Spruce store working with a clerk there and showing him the Revflow carburetor I brought. Now at my garage I am realizing that the ID of the hose is 3/16, but Revflow document I got with my Revmaster says that "Main system hose ID should be a minimum of 5/16-3/8". Interesting, but the carburetor intake is 3/16. I don't know, maybe there is a reason why the requirement for the hose is that it must have bigger ID (5/16-3/8). Anyway, I would really appreciate any details you can provide since you already have a working system.
Thank you!
Sergey Demin

[wlarson861]

You will want an AN-6 hose or AN-6 metal tubing. AN-6 is 3/8 in inside diameter. Check to make sure the fitting on the carburetor is sized for an AN-6 flare fitting. You can make your own hoses by buying braided hose and the fittings from a number of sources such as Wicks Aircraft, Aircraft Spruce or I have found them on Amazon. Also I purchased fittings and hose from the local automotive Performance shop, the hot rod builders and race car builders use the hoses for brake and fuel lines. You can order pre-made hoses in various lengths but the cost is much higher than building your own. I built all the hoses for my plane, it is simple and quick.

[9GT]

You cannot beat this company for custom fabricated fluid lines. Super fast service, high quality, and pressure tested at a VERY reasonable price. The RV gang uses Tom's services quite often for custom fuel and brake lines. https://www.tsflightlines.com/

[GordonTurner]

I am hearing some talk of rigid tubing in the firewall forward fuel system. Is this a generally approved practice? Actually, I have seen this in production turbine aircraft, but it is always stainless tubing.

As far as the fuel lines, perhaps the 3/8 ID reslts in reduced drag in the flow, where the 3/16 ID inlet still let's plenty of fuel in?

Gordon

[Xenos50]

Thank you wlarson861, 9GT, and GordonTurner. I've ordered AN-6 hose together with AN-6 fittings, and will get them soon. I checked the carburetor's intake, it is AN-4, that's why I guess I was originally given AN-4 hose and fittings at aircraftspruce. To fit AN-6 into AN-4 I've also ordered an adapter, so I am good now. Will update once done. Thanks!

[Xenos50]

Last week I started the engine for the first time and had similar problem. I have Revmaster R-2300. The cowl was on. It ran ok for the first 10 minutes, but then started behaving funny, dropping the rpm for a second or two, then revving up for a couple of seconds, and then running normally for a few minutes. Then this cycle would repeat. This happened whether idling or at 1500 – 2000 rpm (I did not run it above 2000 rpm). While the engine was getting hotter and hotter, this cycle would repeat more and more often. After 24 minutes of running it just stopped at one of those rpm drops. I read this thread and others about the vapor lock and though that increasing air flow over the gascolator might help. I measured the “in” air area (together with oil radiator intake) and “out” area and found that the “out” area was about 10% less. I knew that the “out” area should be about 20% more, not less, due to the hot air expansion. I decided to cut out the portion of the cowl right beneath the gascolator and make the total “out” area 20% more than the “in” area. It worked pretty well. Yesterday ran the engine for 30 minutes with cowl on – no burping issue, was running smooth and stable. All the temps were somewhat less than before. After stopping the engine the gascolator was warm in touch, but not hot. Probably around 100 F. I did not fly my Xenos yet, so this was just ground run.

[Msing48]

This sounds like exactly what would happen if the fuel tank vent was partially or completely clogged. I've had it happen just like that with outboard motors when I forgot to open the tank vent.