burner and pilot blow out

[manawahouse]

coleman presidential 2--model 7700a--pilot and burner was out--I lit it and when the burner came on it ran about 20 secs and all went out--as if sucked out--I thought it was therno-couple so replaced burner and thermo couple control unit attached to burner--still same thing--flame gets some orange,seems disterbed(even more by combustion fan) burns 10-20 secs and go's out

[furnaceman]

ck roof jack for seperation, flame should be blue.
does pilot stay lite after u light it, w/o out going out. If so, when blower kicks on does the flame move alot.
its possible u may have a spider web in the pilot tube/ burner or even in the spud behing the gas valve.
Let me know what the flame does after the blower comes on, then we will go from there.
a gentlemen by the name of robert may reply to u before i get back to u, if so, pay attention, he's the ace on mobile home units

[Robert]

Hi,

Does it go out before or after the blower comes on ?



Thanks,
Robert

[manawahouse]

goes out before--burns 10-15 secs

[Robert]

Is the small booster vent motor remaining running ? It should be first thing to come on and MUST remain on throughout the cycle.


Check what furnaceman mentioned. Also be sure booster motor is running strong and it and wheel are clean.

Make sure you maintain a 24vac signal to gas valve throughout cyle as well

IF all that is ok, will need hvac tech to check gas valve operation and gas pressures next.


Be SURE the burner orifice/spud, burner tube, pilot tubibg and pilot burner are ALL clean and clear.


Thanks,
Robert