My truck is flooding when trying to start it after it has been run for awhile. If i let it set for 15 minutes, it will start, but you can smell the fuel and watch the black smoke. First thing in the morning and after is has sat for a few hours, It starts just fine. I have changed the TPS, Fuel Pressure Regulator, Idle Air valve and a number of other things and I have yet to make a difference. I have also done a complete tune-up.
'93 F-150; 5.0L; K&N Air Filter; 4 speed manual; 32x11.5 BFG A/T, Dual Flowmaster exhaust - NO CAT;
I would have guessed the FPR, but I see that you've changed that. Are you sure that you don't have an ignition problem? It could be that you're getting the proper amount of fuel, but your ignition system just isn't burning it as it should. I know that coils can go bad and still spark, but barely. The result will be a good start when cold in the morning, but after driving and warming up the truck (and coil) you'll stop in a convenience store (or otherwise), shut the truck off, and return to try to start it within a couple of minutes. You'll have to grind on it for a while, and when it finally does start you'll get a puff of black smoke (unburned fuel). You're problem may be something else, also, like a TFI ignition module or stator/coil assembly going bad, and I guess it could also be a sensor (bad coolant temperature sensor constantly telling the EEC that your engine is cold?), but I'd check out some of the ignition components next..... Hope this helps.
When the problem first arose, I replace the ignition coil and the ignition module. Still would not start. Then I noticed the strong fuel smell so I began working on the fuel system. I changed the TPS and it started up. Now it starts fine as long as its cold. It just floods when its warm.
Smell of fuel? Black smoke? Probably is a bad O2 sensor. It may be running rich because it is being told to. I think your '93 is a lot like my '92. There is 1 sensor located on the exhaust just after the left bank cross-over and before the cat. Its right under the starter. You can check the voltage from the unit but they usually only last 60,000 miles or so and will really foul up your fuel mileage when they go bad. There may be some DTC in your computer pointing to this as well. Has your Check Engine light illuminated? If you do change the sensor remember to reset you computer recent driving memory or it will take several driving sessions to re-adjust the fuel mixture.
Just looked at the bottom of your photo. Nice truck by the way. No Cat and Flowmasters. You may have a different sensor setup from my stock arrangement, but it still could be the O2 sensor. Is it (are they) connected correctly and are the connections tight? Sounds like you have worked the fuel supply side well. Only other thing is the injectors themselves, but try this first. It is much easier to work on.
High alcohol fuel will cause a hot restart problem.
The alcohol vaporises in the runners floods the cylinders.
I lessened my problem by having the injectors cleaned.
Still does it ocassionally though.
I try to stay with major brand gasoline.
Hope this helps.
Check for restriction in the fuel return line. When you shut the engine down, if the fuel pressure is to high, the engine will flood when you try to restart to soon. When you let it set for a while, the fuel slowly works it's way back to the tank, bringing the pressure back to normal. It's the easiest and cheapest place to start looking for your trouble. Also, sometimes the coolant temperature sensor signals the computer that your in cold start mode, even if your temp guage reads normal (3.8L tuarus motors were known for that little problem).
Does your truck have dual tanks? I have a '93 150 with a 4.9 , did all the same things you did...oxy sensor, fuel pressure regulator, map sensor, etc. Only difference mine would not run on cold start up, would stumble, and lots of black smoke. When operating temperature was reached, it would run except the "check engine" came on. One day it was acting up, so I switched tanks and it stopped. Finally decided I was not getting any fuel return to my back tank, it was all returning to the front tank which caused a rich condition in the fuel system. Was so bad that fuel was pushed out the filler neck and running on the ground. If I ran 50 miles on the front tank then switched to the back tank, would not have any problems. A month later I received a recall notice from Ford Motor Co. regarding the fuel pumps. Problem is caused by a check valve in the pump. I would still change the oxygen sensor if you haven't already. You said you are running dual exhaust with no cats. What kind of mileage are you getting? Is it better or worse? Without cats it's hard to keep the oxygen sensor hot enough to get good gas mileage. I lose about 4 miles to the gallon going from summer to winter. Think this because oxygen sensor is in cold air stream in the winter. Hotter the outside temp. is, better the gas mileage. Good Luck!