Have a Poulan PR208 Stormforce snowblower that quits after 2 or 3 minutes.

Backfire is the result of unburned fuel in the exhaust igniting. I would look at the timing. Could be out enough for this to be the cause. Good starting point in my opinion. Not usually a plug issue.

Check cap, rotor and wires. Also possible is a cracked distributor housing.

Check fuel pressure at the injector rail. Could be pump is failing or filter is clogged.

coil pack is dropping fire after it heats up

Did the problem come on suddenly or was some previous action or work done......

Have it checked with a computer diagnostics. It sounds like it could be a bad sensor, quite possibly your oxygen sensor. A bad sensor could cause the computer to think your engine needs more fuel.

85 with TBI only needs 13lbs of fuel pressure. verify that the fuel filter is clean. there is no easy way to ck fuel pressure, special adapters are needed, I dont have info here at home but there should be a relay for the pump, on the firewall and the oil pressure switch also powers the pump. did you replace the pump trying to fix this problem or did you just mention it to help troubleshoot the problem? verify that the fuel pump wiring has a good ground, should have been a eyelet that bolted to the frame..when you initially turn the key on, you should hera the fuel pump power up for 2 seconds, then go off, after the engine starts, the power for the pump goes through the oil pressure switch.

sounds like the ignition module is going bad.

does it make any difference if the engine is cold or warm ? if when its warm and it starts ok your spider part is not working properly or not plugged in right check it again .. check it by using starting fluid if it starts ok its the spider part bad .. did you replace it with new ? holler if you need more Jerry

check your timing