If the fuel is leaking, it is possible it is leaking from one of the injectors right into the intake and being burned as soon as the engine starts. Or if the fuel pressure regulator is faulty it could be going out the return line and being sent back to the tank.
I find it's usually easier to remove the bed to access te fuel tank and lines. At this age, everything near the tank is probably rusted and brittle. I wouldn't be so sure that there is a problem with the fuel pump just yet. Also, if the code reader is removed does the pump still run continuously? Does the CEL stil blink with the code reader removed?
Another step you can try is to disconnect the MAF sensor... start and run the vehicle like that. If the symptoms are gone, it's possible that the replacement MAF sensor is faulty or more likely the engine is sucking air someplace between the MAF sensor and the intake. Spray carb cleaner on the rubber intake air hose and all around the base of the intake manifold. If your idle increases then you have a vac. leak that needs to be repaired.
Hi again, I'd really like results from a fuel pressure test. Does the CEL only blink with the vehicle running? or with the engine off but the key in run??
Unplugging the MAF puts it in a sort of fail safe mode, so we should be able to rule out air delivery for now. It really sounds like a fuel problem. Enough gas to let it idle, but under load it bogs because it is running lean.
You should be able to rent a fuel pressure gauge from one of your local auto parts stores if you don't want to purchase one. Also, if you still have the tank accesible try removing the return line and checking how much fuel comes out of it with the pump running. It should have NO fuel until it overcomes the regulator pressure. If it just comes pouring out as soon as you turn the key on, then it sounds like the regulator has failed. It is cheap from Advance Auto.. less than $20.00 and looks like this:
Let me know what you find with the fuel pressure testing.
The regulator is there to regulate the pressure. By removing the return line, we were trying to check if it was doing its job. It is supposed to maintain the pressure in the rails at a certain spec... when that spec is exceeded then the regulator opens and fuel returns to the tank.
Fixing the leaky injector is definitely a start! It appears that you had/have multiple problems. Were you able to locate a fuel pressure gauge so we can take some readings? I'm going to get my reference material for this truck... be back in a few minutes.
Ok, lets try something relating to the fuel pump not shutting off....
Look in your Power Distribution Box under the hood. I believe it is on the driver side near the battery. There should be a relay labeled fuel pump in there. Remove this relay and make sure the pump does not come on with the key in any position.
Assuming the pump shuts off, try swapping the fuel pump relay with another relay and see if it now works correctly. It is possible the fuel pump relay is stuck on due to corrosion.
Let get the fuel pump constant running figured out first!
2 more items for you to do:
#1)Since you replaced the injector, you should disconnect the battery for 30 minutes to force the computer to relearn the fuel trims. It was detecting an overly rich condition from it dumping fuel in the intake and leaned out the long term fuel. Now that you fixed that, it is probably still stuck on full lean.
#2) Disconnect PCM and remove fuel pump relay. Then check continuity from the data link connector under the hood to a good ground. With both components disconnected there should be no continuity to ground. It should be a completely open circuit. I believe it is a Light Blue wire with an Orange tracer. While holding the DLC in your hand and looking at the terminal side it should be the one in the lower right corner. There should be an empty cavity next to it.
If you have continuity then you have short to ground in the wiring harness betwen the Relay and PCM. This will keep the fuel pump running all of the time. If the wire measures ok, then we will need to check inputs to the PCM.
I'm not sure why this dropped off my question list!
At this point, either the PCM is faulty or its getting a reading that tells it the vehicle is running and that is why the fuel pump continues to run as long as the key is on.
Since it is accompanied by the rapid blinking of the CEL I think you have an internal fault in the PCM.
No, because that is where diagnostics lead us?? The PCM is commanding the fuel pump on all the time. We know this because there is no short to ground on the relay control and no short to power on the fuel pump feed.
I wanted to rule out all the things that could be easily checked first.
If you have an Auto trans here are some computers you could purchase:
If you have the manual trans:
At those prices I would say that is the cheapest thing you could replace! Please remember they only part I recommend replacing was the regulator if you couldn't take a fuel pressure reading and that was because you said you could not see or smell a leak. I've tried to lead you on the best path possible to solve this problem.
Has the CEL rapid blinking also stopped?
When the pedal is pushed all the way to the floor to get it started does the engine race after that or does it just try to idle?
Also, with the amount of unburnt fuel that has run through the exhasut.... it is quite possible there is an exhaust restriction. I just scanned through all of our posts and didn't see anything relating to the exhaust. You may want to remove the exhaust pipe before the convertor to see if you now have a large exhaust restriction. Or if you have access to a backpressure gauge remove the O2 sensor and take a reading.