Been lurking for a few years and this forum has helped me keep my 93 F150 going and going. She has 450,000 miles and has never been touched other than accessories, 4.9L I6 of course. Unfortunately while she still runs OK after waiting 30 minutes for the crappy dual tank selector to prime the fuel pump that is. She is way down on power and fuel mileage and now the tranny won't switch out of first. I inherited "Big Pink" she used to be red lol from my Father in Law who bought it new, he was a contractor and I work as a Handy man myself. Big Pink served him well and has served me well for the last ten years and I have grown attached to the old gal she's never been hit the body is in relatively good shape almost rust free. I have looked at rebuilt 4.9 engines and would be willing to spend the money if that is the best solution but I also have a 99 Exploder with a 5.0 that runs pretty well that the body is rusting off of. I like the idea of the extra HP the 5.0 offers and maybe a more robust tranny to allow me to tow a small-medium sized camper with.
I am a decent mechanic have always worked on my own cars so I realize that this is more involved than just getting the new motor in the truck and would need the computer and wiring harness from the Exploder so I am looking for advice even if it is sell them both and buy a newer F250 LOL.,

 

Just reading your post, it doesn't sound like the engine is your primary issue.

It sounds like fuel pumps and transmission are your biggest issue.

It's not a big deal to do a compression test, as an *easy* indicator if the motor needs to come apart or not, but I'd be fixing the pumps, bare minimum, before I'd be pulling the engine.

 

Your ‘93 doesn’t have the “crappy dual tank selector.” Each tank has its own high pressure fuel pump. What transmission do you have? Have you checked the fuel pressure and for fault codes? The check engine light does not have to be on for there to be codes stored in the memory.

 

Cant use any of it, its OBDII, and you will need the OBDI harness, and PCM

 

Well like I said it is considerably down on power and fuel mileage and getting blowby into the block. But you are right the transmission and fuel problem are pressing problems as well. Both fuel pumps work and the selector switch works fine but the "distribution valve?" perhaps selector is the wrong terminology? pumps fuel from the back tank to the front and the check valves do not keep fuel in the lines to the fuel rail. So to get it started I have to turn the power on and let the fuel pump run until it reaches pressurization and shuts off to be able to start the motor

 

I don't think there's a valve of any sort in the fuel lines on a '93, The check valves and everything else are built into the FDM's (Fuel Delivery Modules) which are the units that are in the fuel tanks, that combine the pumps and sending units.

 

I guess it depends on your definition of crappy, Both pumps work fine but the plastic part that determines where the fuel is sent, perhaps fuel selector is the wrong term? sends the fuel from the back tank to the front tank and no matter which tank is selected the check valve allows the fuel to drain back into whichever is selected which means I have to turn on the ignition switch and let the fuel pump run until it is pressurized and the fuel pump turns off usually at least 30 minutes before the truck will start. And if you spend more than twenty minutes or so at your destination the process must be repeated. So not exactly optimal performance of it's intended function thus my personal opinion that it is indeed "crappy".

 

Hmm, every search I have done has returned the same result that there is a black plastic piece that the two supply lines and return line pass through that fails and produces the symptoms that I have experienced, and I'm not sure how it would pump fuel between the tanks without that piece, but to be honest I have not actually tried to find it since I was sure that I knew what the culprit was. I will have to try and find out tomorrow. It looks like the tanks must be dropped to change the pump module out is your understanding as well?

 

I'm not absolutely sure, but I think that only applies to the Bricknoses, 87-91, and *maybe* the Bullnose 302's in '86, I know my 87 has one, and I had to replace it. I know my '92 F250 didn't have one.

 

I think I misunderstood your comment, sorry about that. I thought you were saying the piece wasn't "crappy" when you were saying I don't have that part on my truck. I will have to try and follow the fuel lines back to front I just don't know how it would pump the fuel from one tank to the other with just a check valve on each fuel pump assembly it seems like if one or both are "open" it would never reach pressurization. So I will do my homework and try to figure it out. Thx for the advice.

 

I’m saying your truck does not have a dual function reservoir on the frame rail. Each in-tank high pressure pump has check valves in the fuel pump module to prevent fuel from flowing into the wrong tank. I’m no expert but to me it sounds like you have a problem with the fuel pump or pumps so you are not building pressure.

 

At key turned to "on" but not to "crank", selected pump should run (audibly) for 1-2 seconds then stop. If pumps run continuously, there is a problem with computer.

It will produce enough pressure on the injector rail for the engine to start & run at which time the same signal that fires the ignition will "tell" the computer to keep the pump running.

Any sort of wait period between what you're doing & the truck actually running, is coincidence & taking you away from actual problem.

 

Did the gas trucks not have a tank selector valve? I have one one my 96 as do all the other dual tank trucks I thought, at least the diesels.

That sounds like what the OP is describing. They're not cheap to replace properly, about 500. Alot of folks just eliminate it and run a single tank. Bronco tank is cheap and easy to swap in with a good capacity.

 

From his description, both pumps are shot.

Having to turn the key on 2 or 3 times to build psi, is a tell tale sign, and one pump pushing fuel to another tank is definitely a sign the pump(s) are or have failed.

He will need to either pull the bed or drop the tank and replace the pumps. No mechanical switching valve on most of the F150'S after 1990.

Time to move on to transmission problems....

 

No, the gas trucks use 2 high pressure fuel pumps. One in each tank. They both have check valves to prevent filling the other tank. It's a simple system that is easy to fix. If the check valve in both tanks are bad, then you would have a large pressure bleed. It will still run but notice the tanks fill themselves and you have to prime it... The fix would be new FDM's in both tanks, which would be about $120 each or so