Hi I have a 1989 5.0 litre 302 in F150 that has developed a serious problem in the fuel injection, which is that when I try to start it the fuel floods the engine, I seem to have isolated the major problem being cylinder number eight which fills with fuel, so much so that it locks the engine up and will not turn over, until I remove the plug and fuel pours out, I thought it was down to the injectors, which were in a bad state, they look like the originals, the engine has 170,000 miles on it but it is in good condition, so I changed all the Fuel injectors, the MAP sensor, Throttle position sensor, Oxygen sensor and Intake air temperature sensor whilst I had the top stripped down. Could it be something to do with the electrical system or maybe over pressurizing of the injection system, any input will be greatly received Thanks

 

And your fuel pressure is????
If I had to guess (& I do cause you don't know your fuel pressure), I'd guess your fuel pressure regulator is pooched. Remove the Vac hose & see if you find gas. If none, could still be pooched, but that's a dead giveaway.

All that throwing of parts (especially the sensors) doesn't guarantee you replaced the any that needed replacement or you still don't have some that need replacement. Buy one of these for $23-$30 (depending where you buy it). Didgital numeric display w/ memory. (optional cable not required)
See Link: http://www.handsontools.com/Equus-In...ol_p_5574.html