Throttle switch fire

[bluemm]

I may have found the cause for my mysterious flooding problems. I discovered that the switchbox on the bottom of my throttlebody was not screwed down allowing it to rotate with the butterfly valve, and also the wiring harness and switch cover is badly burnt. I have two questions about this. First, I understand that the normally open set of contacts in this switch box are for full load enrichment. What is the normally closed set for?
My second question is about the fire that occured in this area of the engine compartment. I have heard that stepping on the gas while trying to start the engine could cause a backfire through the intake system. This fire appears to have been very serious. Wires are melted, the heat shields are burnt and the flap in the air metering box was wiped out. Is it possible that this was a backfire, or the result of starting fluid, or something else? Any help would be greatly appreciated.

[Dave at Pelican Parts]

The two switches in the L-jet TPS (I wasn't sure which FI system you had until you said "air flow meter") are for telling the FI when the throttle is closed (idle) and when it is at WOT. I believe they are both moved by a cam arrangement inside the TPS.

The fire could have been caused by just about anything. Backfires usually are just a pressure wave, though if there was a whole lot of fuel vapor in the intake that could have caught on fire. Starting fluid, or a high-pressure fuel leak, or just about anything else flammable could have fed the fire.

A warped flap in the AFM is Very Bad News. The warped flap usually sticks somewhere, meaning the mixture can be quite rich or quite lean. That could easily be one of the causes of your mysterious flooding problem.

--DD