Hi, I am having a problem with my truck, and can't figure out whats wrong. It is a 2wd 1994 F150 with a 4.9L 300ci straight 6. Fuel injected. My problem is that there is gas not getting burned, and is leaking out of the exhaust. Becuase of this, I am getting about 7mpg(it was getting about 18+ before the problem) It also has a loss of power and runs/idles rough. I ran a diagnoses on it myself the way it says in the manual. The only useable code I got said to check the EGR valve and the EGR Vacuum solenoid valve(or EVR valve). I checked the both of these to the best of my ability and they appeared to be good. Cleaned them up,put them back on, and the gas seems to have stopped leaking out the exhaust, but the mileage hasn't improved. Also changed out the TPS(throttle position sensor) and the engine light turned off, but as soon as the motor warms up(about 5-10 minutes on cold mornings) it comes back on.Brought it into Shucks for a free diagnosis, but they couldn't figure it out. Any ideas you have would help.
Thank you in advance for any help

 

Pull the vacuum hose off the fuel pressure regulator and check for gas in it. if there is then that could be it.

 

When's the last time you did a tuneup... If you're fuel isn't burning I would think you've got an ignition problem.

 

I agree the Fuel Pressure Regulator is the most likely cause of this problem.

 

Been there, done that. If it's smoking like a locomotive (black thick smoke), FPR is probably shot. Isn't expensive, and fairly easy to put on. Dunno how accessible it is on the 4.9, but on the 5.0, ya kinda do it by feel-a-vision. Can't really see the screws, but they're allen heads, and metric if I remember correctly. But, before you start throwing parts at it, check the fuel pressure. Either buy a gauge, or find someone that has one you can borrow. On your I6, (someone correct me on the numbers) your idle pressure should be around 45 PSI, and WOT pressure up around 65 PSI. Easiest way to check WOT pressure, is just turn on the ignition, and jumper the fuel pump test connection to ground. Engine not running (0 vacuum) is the same as WOT. If you can get your hands on a hand held vacuum pump, at 20 in. Hg, you should have idle pressure. This might save you some time and a few bucks if you can borrow the tools. The fuel pressure gauge and hand held vacuum pump will cost you more than the FPR, but you'll have them next time you have a fuel delivery issue.

If you want to test for a leak before you replace it, the simplest method is to use the fuel pump test input. Remove the vac line at the manifold, jumper the test point, and see if fuel comes out the hose to the vac tree. If it does, gotta have another FPR. Best to use a rag or something to trap any drips, otherwise you now have a nasty fire hazard next time a spark occurs. Do this on a cold engine to keep from creating vapors that can flash.