Multiple ignition cycles after replacing inducer motor

[CraigM]

I recently had the inducer motor replaced on my Goodman gas furnace. About a week later, the furnace began running through the ignition cycle 2-3 times before staying on. I called the installer out and he mentioned something about removing excess gasket material that was protruding into the heater box. He left and the heater worked for about 3 days and then returned to the same problem. I looked into it and found that when the gas ignites, the burner furthest from the ignition source does not have a consistent flame. The flame sensor is located at that last burner and dutifully shuts down the gas when it senses insufficient flame. The ignition cycle repeats and eventually the burner stage ignites normally and the normal heating cycle is achieved. At this point I don’t have a lot of confidence that the installer can resolve the problem. Is it caused by mixing too much air, too little air, a bad gasket, the wrong inducer motor, or something else?

[HayZee518]

two things come to mind - 1 the gas pressure isn't sufficient and 2 the gas valve isn't opening all the way or is sluggish in operating. the air-gas mixture should produce a blue flame with small yellow tips. a cappillary flame detect senses temperature while a cad eye senses the infrared off the flame and feeds it's signal to the lockout relay.

[CraigM]

Thanks for the response HayZee518. I'm reluctant to think it is a gas supply problem since I had no problem of this kind until I had the inducer motor replaced. The motor installer also did not mention a gas supply problem. He was convinced he did something wrong during the install. The gas supply comes on quickly once the igniter is glowing and the gas ignites immediately. It's just that last burner. The flame comes and goes like something is blowing on it. I am hoping you HVAC guys have seen something like this before and can point me in the right direction. If not, I will take it up with the installer and hope for the best. Thanks again.

[HayZee518]

is the air flow measured in cfm's the same? are the motor rpm's the same?

[CraigM]

Good questions. Except the installer took the old motor with him. I think I will continue this discussion with him and see if I can get it resolved without any more coming out of pocket. Thanks.

[HayZee518]

i looked at the goodman site. the draft inducer you speak of is of either the 90% or 80% type with a blower speed of 3400 rpm. also they speak of a black plastic bonnet that in their opinion cracks over time and should be replaced or carbon monoxide can be vented back into the living space creating a hazardous condition. i couldn't find anything that describes the number of burners off the main gas valve.

[CraigM]

The furnace is a model GMP100-3 (4 burners). I looked at the replacement motor and it is a Jakel C-frame type that runs at 3000 rpm. I found the data sheet on the Jakel site, but the transition cowling is different. In fact it looks like the motor was mounted to the original transition cowling of the Goodman furnace. I'm thinking this could definitely be a matching problem that would affect furnace performance. The plastic bonnet looks good plus I have a carbon monoxide detector nearby.