I was driving my untuned half bridgeport in fourth gear, maybe 1 psi boost, put the clutch in and the car died while I was moving. Now it will not start. When I turn it over, it cranks normally but where it seems like it should start to rev up it just back fires really loud. Every time I crank it it back fires. Can anyone help me figure out what the hell is going on here. Map sensor is still hooked up, TPS is at .66 VTA1 and 1.55 VTA2 respectively. I've tried unflooding it, but it simply turns over a bit longer and then backfires still. None of my fuel setting have been changed from before when it used to start.

 

Well we tried to push start the car, but still, once I dropped the clutched there were 3 huge back fires and it would not run. Maybe an injector is stuck open? Anyone have any ideas? I need some serious help.

 

First, your idle TPS V is a little too high!

Second, I doubt it is back firing as that would be through the intake ( a true back fire). I belive it has fuel exploding in the exhaust, would that be called forward firing or extreame late firing? So many questions, and so few answers.

You have said nothing about checking the ignition system. Trying to start with only the trailing plugs firing, can do something similar. Use the commander, and temporailly advance the IGT until it is the same as the idle IGL and try starting.
Try ajusting parameters that affect idle fuel and spark.

Also check that none of your crank angle sensor connectors came loose.

 

sounds flooded to me....

try disconnecting the fuel pump relay and clearing the engine out...then starting it again.

if that don't work, then i dunno...

 

If you ever watch OverHauling or American Hotrod, have you ever see them have problems starting some engines? The ones where flames shoot out the carb due to bad timing or mismatched spark plug leads. That is back firing through the intake. That is where the name and definition came for backfiring.

Any other use of the term is incorrect!

 

What's puzzling me is that even when we tried to push start it there were a few huge explosions (extremely loud) until the car wound down and stopped rolling. I have tried to start it again since, and it fire up briefly, popping here and there until dying. The motor sounds different than it did before, a bit raspier. Is it possible that these explosions from unburned fuel in the exhaust damaged my motor? It only has about 160 miles on it.

 

The exhaust explosions can not hurt the engine.

A Louisianna friend has a engine with a well known builder's very large port engine. It started fine and he was breaking it in and tuning cruise. Then it started acting badly and not running well. He checked everything external and all was fine.

Disassembling the engine revealed a seal snaged a port which caused a loss of compression and cross chamber contamination. Worse case senario!

 

Would this be the apex seal catching the exhaust port?

 

Mine was doing the same, but once mine is started it drives fine. Sounds like you have low compression the mixture isn't firing and then going into the exhaust where it is firing and comming out the exhaust.

 

All my friend told me was that the intake porting job was defective, and a seal dropped into it. The builder flew to LA. and rebuilt the engine for him, then flew to work on something in Florida. The builder had a helper who F***** Up the original job. Hard to get detail oriented workers.

 

I got it started today, seemed to just be very badly flooded. Drove around a bit and everything seemed normal again. However, it sounds like my wastegate is now partially open, maybe from pressure from one of the large explosions. But, the wastegate hasn't moved in almost a year and half while the car has been down so it doesn't suprise me.

BuckyFD3, so you were saying that you were having similar problems with running really rich and flooding? I need to get this motor tuned pretty bad, way too rich.

cewrx7r1 - the same thing happened with my last full bridgeport motor. I did all the porting accept the primary intake ports. Instead, to save time I had the shop (Prather Racing in KS) port those while they resurfaced my irons. They made the primary bridge too narrow, dropped all 3 of the small corners of my front apex seals into the port and shredded my motor. I just bit the bullet with them and decided never to business with them again.