need help

[Bootlegger]

  Tried to go flying the other day, got the engine started, ran breifly, then died, I'm thinking bad glow plug.
 However when I put the driver on the plug the gage doesn't go all the way over like the driver needs charging.
  I charged it and it still shoes the same.
  Tried the driver on another engine and the indicator goes all the way over indicating it is fully charged, I'm thing bad glow plug.
   What are your thoughts???

[Tim Wescott]

I've never seen that effect before (current meters on glow plugs???), but Troubleshooting 101 says that if you swap out just one part and the problem goes away, then the problem is probably with that one part.

[Balsa Butcher]

You are correct, it is a bad glow plug. It is a misconception that the meter on the (orange) McDaniels batteries (I'm assuming that is what you are using) shows the state of the battery charge. It does not. What it does do is register the circuit continuity between the battery and the plug. When a plug goes bad the needle will not move into the green. The second engine had a good plug therefore the needle moved appropriately. The battery is charged and the needle is working like it supposed to...change the plug and keep on flying. 

[Tim Wescott]

Well...

That meter most likely measures current.  The current through the plug is going to be a function of both the plug and the state of charge of the battery.  So saying that it's a misconception that the meter shows the state of battery charge is a bit misleading -- it shows the state of the battery charge munged together with the state of the plug.

Which is why checking it on a spare plug is a good way to check the battery: you use the spare plug as a standard against which you measure your glow driver, then you can trust what it says on you plug-under-test.

You mention checking the driver on another engine.  Don't you carry spare plugs?  You should -- even if you never need to change them, you can make friends by handing them out to people in need.

[Bootlegger]

    Thanks Guy's, I appreciate the help...

[Randy Cuberly]

Well...

That meter most likely measures current.  The current through the plug is going to be a function of both the plug and the state of charge of the battery.  So saying that it's a misconception that the meter shows the state of battery charge is a bit misleading -- it shows the state of the battery charge munged together with the state of the plug.

Which is why checking it on a spare plug is a good way to check the battery: you use the spare plug as a standard against which you measure your glow driver, then you can trust what it says on you plug-under-test.

You mention checking the driver on another engine.  Don't you carry spare plugs?  You should -- even if you never need to change them, you can make friends by handing them out to people in need.

Gee, I don't know Tim I hand out plugs all the time and I still don't have any friends...

Randy C.

[dennis lipsett]

We all know that lending out plugs is a bad way to end a friendship. Especially when you need one and he says he's saving his only spare for the contest next week. Worse when you know that it's been in his box forever but he hasn't needed it because he has 'friends'. LOL

Dennis

[Larry Wong]

Yes but plug were only 75 cents, but now is up to $6.00 plus !

[Jim Kraft]

Randy, it helps if you hand out good plugs, not those that you removed because your engine would not run. LOL.

[Howard Rush]

  Tried to go flying the other day, got the engine started, ran breifly, then died, I'm thinking bad glow plug.
 However when I put the driver on the plug the gage doesn't go all the way over like the driver needs charging.
  I charged it and it still shoes the same.
  Tried the driver on another engine and the indicator goes all the way over indicating it is fully charged, I'm thing bad glow plug.
   What are your thoughts???

None of the normal failure modes causes a glow plug to draw some current, but less than usual.  A burned-out plug draws zero current.  A plug with a deformed element draws more current than usual if the coils touch each other or the body, but same as a good plug otherwise.  A plug in a flooded engine will draw more current than usual.  My guess is that it's not getting enough fuel. 

[Brett Buck]

  Tried to go flying the other day, got the engine started, ran breifly, then died, I'm thinking bad glow plug.
 However when I put the driver on the plug the gage doesn't go all the way over like the driver needs charging.
  I charged it and it still shoes the same.
  Tried the driver on another engine and the indicator goes all the way over indicating it is fully charged, I'm thing bad glow plug.
   What are your thoughts???

   If it will start and run out a prime, it's a fuel issue, as Howard notes, specifically not enough fuel. Check for debris in the needle valve, spray bar, filter, or an air leak somewhere like a split in the fuel line.

    Brett

[Bootlegger]

  It started and ran a little lean, backing the needle out it started to run better, then after about 30-45 seconds it stopped, and would not re start.
 I changed the glow plug, but haven't gotten a chance to fly again, hopefully this week end.
 
  Again thanks for all the advice...

[john e. holliday]

Went back and looked,  what engine are you talking about???   My Fox .35 Stunt never ran for more than 30-60 seconds at a time for the first dozen starts or so.   Even he old K&B Greenhead .35.   The Johnson .35 stunt was as bad.   Now todays OS LA engines if they done run right out of the box, thy are set too lean,  rarely too rich.  My Brodak .40 and .25 ran right out of the box, but had to watch that they didn't go lean and slow down  while doing some break in.   

[Balsa Butcher]

There certainly could be other causes of this problem and checking fuel, NV, etc. is always a good idea. The indications of the meter point toward a bad plug. Looking forward to an after-action report.