OS 91 FS stops running at low rpm  
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All Forums >> Glow Engines, Gas Engines, Fuel & Mfg Support Forums >> Glow Engines >> OS 91 FS stops running at low rpm
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OS 91 FS stops running at low rpm - 8/8/2007 8:02:42 PM   
3 for 3


 

Posts: 34
Joined: 8/12/2004
From: Flint, MI, USA
Status: offline 		Hello,
Symptom: at or below 4k rpm engine stops running. It does not go rich or lean. It is as if it was a gas engine and the ignition is turned off. It just stops running

Troubleshooting- used different test tank, no air bubbles. Engine is at 90 degrees. When a brand new OS "f" plug is used I can get the idle down to 2800 rpm with no problem and it will idle for 5 minutes. After one flight, slightly rich top end, the symptom returns. The engine will not idle for more than 20 seconds and dies.

Have checked valve lash, replaced intake o-ring, checked back plate. I believe that I have eliminated fuel delivery issues by substituting a different fuel tank. Compression is good. This has does not have a pump and is not a surpass. It has the silver valve cover.

Any suggestions?

thanks in advance
rcs
       Post #: 1

RE: OS 91 FS stops running at low rpm - 8/8/2007 8:18:38 PM   
Campgems


 

Posts: 2094
Joined: 2/18/2006
From: Arroyo Grande, CA, USA
Status: offline 		I was having a similuar problem with my Mag 91. I had moved over to Cool Power from Omega, both 15%. I decided to go back to the Omega and when I went to swap jugs, the pick line on the tank curmbled. The line, above fuel level had turned to a very crumbly mess. It broke off when I lifted the top out of the bottle and when I fished what was left out, it broke off twice, dropping back into the jug both times. When I finally got the pickup out, the tubing was fine below fuel level, but about it, it was a mess. I replaced the pickup line, fuel, and a fresh F plug and the engine is running like a swiss watch again.

This may have nothing to do with your engine, but the fact that it runs OK for a part of a tank with a fresh plug sounds like fuel contamination of some sort. One of the guys in our club used to be tech support for Norvel engines. They found that some of the rubber in the bulb fillers was causing to glow plug to "glaze" over and causing the engine to die. I am blamming the fuel as I had run at least six gallons through my pump setup and the problem didn't show until the day after I went to the cool power, acnd cleared after going back to the Omega. Previous to that, I had only run Omega through it. It's worth looking at. My fuel lines came from some old stock I picked up, so I don't know the brand.

Don

(in reply to 3 for 3)
       Post #: 2

RE: OS 91 FS stops running at low rpm - 8/8/2007 10:01:41 PM   
broke_n_bummin



Posts: 838
Joined: 3/17/2006
From: Kershaw, SC, USA
Status: offline 		sounds too lean on the low speed needle, or the tank is too low.

_____________________________

I may have to give up R/C Airplanes and Golf ... They make my Torrets act up...

(in reply to Campgems)
       Post #: 3

RE: OS 91 FS stops running at low rpm - 8/8/2007 10:06:10 PM   
Edwin


 

Posts: 3431
Joined: 2/8/2002
From: Leander, TX, USA
Status: offline 		Whats this engines history? How old, was it running good then suddenly bad or just taken out of storage. A few years ago my OS.91fs suddenly started quiting as I got down to idle. Turned out to be carbon build up around the valves. Cleaned up and good as new.
Edwin

(in reply to broke_n_bummin)
       Post #: 4

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