bgfireman

My Feedback: (13)

Ok, So I have a G38 on a fourstar 120. It is giving me a problem I just cant fix. This is my first gasser so be easy on me. It will start and run for the first run of the day, but will not after that. All it will do is run out the prime. I have rebuilt the carb. I am also having a problem with the muffler staying tight. I used blue locktight on it, but after 1 flight it was loose again. This engine has a C&H electronic ignition and a B&B Muffler on it. The gas is fresh. The only thing I know of that could be wrong is there are a few drops coming from the needles on the carb. It is not very much, but it is the only thing I can think of. Any Ideas?
Thanks
Alan

karolh

First off if you are using as gasket between the muffler and the head get rid of it. Clean both mating surfaces and apply a thin bead of Hi Temp Red Silicone to one face and after a few minutes bolt them together using some red locktite on the muffler bolts and that will be the end of your muffler coming loose problem. With your engine willing to only burn off the prime and not run sounds like the carb is not pumping or sucking fuel. When did you rebuild the carb, after it started giving problems or before, and did you replace the pump diaphram. Check that the pulse hole from the engine to the carb is not blocked. I'm pretty sure that others will chime in with other possible solutions.

Karol

ahicks

My Feedback: (2)

Wondering 2 things here. What you are using for fuel line, and do you have ALL you fuel line connections clamped securely?

jerdavis

My Feedback: (3)

Try setting the spark plug gap at .018-.020 and let me know if it helps.

Jerry

jerdavis

My Feedback: (3)

bgfireman

My Feedback: (13)

KarolH
No gasket. I'll get some Red Hi Temp silicon and red locktight.

AHicks
No clamps on the tygon. Its so tight I cant pull it off.

JerDavis
I thought the plug came pregapped from C&H, but I can check and see if that helps.

Keep the ideas coming. I appreciate them.
Alan

jerdavis

My Feedback: (3)

Alan

OK, let me clarify about the plug gap. I think the recommended gap is more like .025 so it may be the right gap.

I ran into a situation on one of my engines where it would start and run the first flight of the day, but would not start on subsequent flights (tries). It would fire but not run, like it wasn't drawing fuel. But it would start and run OK if the plug gap was less than recommended. I suspect it was because I wasn't pushing the engine hard enough and the plug was oil fouling.
On a G38 I was using for sailplane towing, after the sailplane disconnected , I would do a steep dive for a 1000+ feet and land with the throttle closed. After that, it would fire
but not start without a lot of cranking. I suspected the plug was loading up in the long power-off dive. So I would then give it full throttle for a second on the down wind leg to clear the engine and never had the starting problem again.

Maybe If you find nothing else you could try closing the plug gap to see if things change.

Also, thanks for giving me a chance to tell a story. LOL.

Jerry

bgfireman

My Feedback: (13)

jerdavis,
Always love to hear a story. Yours may be true for mine on a long slow aproach I dont run much rpm so it maybe what you are describing is happening to me. I may start running up some rpms on it on the ground to clear it out some.

Also someone had asked about a rebuild of the carb. I got the engine used with the old magneto and converted it to EI. At that time I rebuilt the carb. I replaced everything I could with the rebuild kit.
Thanks Alan

Jezmo

In some engines a phenolic insulator is necessary between the carb and engine to keep the carb from heat soaking. When the carb gets too hot the fuel boils off and then when fresh fuel is drawn in by the pump it also boils building up pressure causing the pump to stop pulling fuel from the tank. Sometimes it's referred to as "Vapor Lock". I know my G26 did this with a custom made aluminum spacer block and I had to put the stock phenolic one back on.

Also, my MVVS 26 gasser has a phenolic spacer between the carb and adapter for the same purpose.