Took my PU and trailer to town today and coming down the hill I down shifted to slow down and it backfired... Then it started occasionally missing... then when I got on the highway it started running REALLY crappy. I was getting low on fuel so I stopped to fuel up and it sputtered and stalled at low RPM and I coasted to the pump. Well the truck and trailer are still at the station! The 440 only has about 500 miles on it with new distributor, ECU, etc. I have good spark but it seems to be flooding? I can get it to start but only briefly. and if I try to rev it up it just backfires and dies. I pulled the TQ off and opened it up but everything appears to be fine. No sediment or water and the bowls don't seem to be over full. I REALLY need to get this truck and trailer out of the service stations parking lot! Any suggestions?

Check the timing.

Jumped timing chain

Possibly a float stuck or needle stuck open. Clean it with some carb cleaner and check adjustments. If after reinstalling it still runs crappy & backfires I'd agree with timing issues. Don't forget to check your dizzy too!

My first thought is fuel but reading that you've opened the carb & the fuel level appears normal...

BTW You do know about the "O"rings on a Tquad right?

FWIW I typed this out so I'm leaving it..

Pinch off the supply line between the frame & the fuel pump.. Start the engine & keep the RPM's up.. BTW if it doesn't want to start hold the throttle wide open the extra air should allow a A/F ratio that will burn...Obviously as soon as it starts get out of the throttle but keep the revs up some.... With the fuel line pinched it may now idle.. That would be an indicator of a stuck float... What I would do is have one person keep it revving 2,000-2,500, have a second person using needle nosed pliers to pinch that fuel supply.. As the fuel in the float bowls starts to run out the engine will show plenty of signs.. At that point release the pliers, the inrush of fuel will often flush what ever debris has been holding the needle off it's seat causing the carb to flood...

At this point I'm also thinking you need to check the timing

Check the metering rods....sometimes a good backfire can cause them to hang up. Make sure the metering rod tree moves up and down freely.

If the metering rod tree hangs up, it will put too much fuel into the carb...

Update: Okay this if freaken wierd! When I replaced the distributor with a new one I hand turned the crank to 5deg. before TDC and popped the distributor cap to make sure that the rotor was pointing at #1 and the pickup and reluctor were in perfect alignment (and it was). Then I replaced the distributor, cap and rotor with a new one and re-aligned the rotor, pickup and reluctor. It didn't start again so I assumed it was something else but after everyone was saying timing I put a timing light on it and it is not firing any where NEAR 5deg. before TDC!!! [Edited by Moparts - Keep it clean]!!! And I found out the previous owner had the same problem with this truck (wouldn't start/run). I just assumed the motor was bad! What could possible cause such a change in the signal from the time it leaves the distributor to the time it returns to the distributor? Could a wire be grounding out somewhere between the distributor and the ECU or between the ECU and the coil and cause this type of delay?

This is wierd sh#%! Time for a Petronics...

I wouldnt look at the carb or a fuel problem, I would go over the ign. sys. FIRST THING I WOULD DO IS CHECK FOR A POOR GROUND!!!!! on ecu box to frame and a good ground strap (engine to frame).

Balancer timing reading could be wrong.

There was an era of MP distributors that had the reluctor improperly indexed....if you are running a MP dist., might wanna check it out.

Stock distributor. Checked for proper grounds on ECU and Block to battery and frame. I initially thought about grounding so I removed ECU and sandpapered behind where ECU and mounting bolts contact. Motor is new (less than 500 miles and when I installed I made sure all grounding points were clean. I think it's in the stock wiring somewhere past distributor. Maybe in the ECU plug??

Sounds like a poor connection. I would then hook up a voltmeter. With ign in run pos. watch volt's as you wiggle the harness around......check ign sw the same way.
Sounds like the old owner had the same problem with the truck.
Make shure all connectors are clean and the right volts are there. look inside the harness connector for scale in the plug of the ecm.....Mine would do that all the time.