94 F150 5.0 starting issues
 

I am a new member, so please advise if this should have been placed elsewhere. I did search for threads related to my problem; but, all I found were 6 cylinder engines or later model F150's. I have a 1994 F150 5.0 4x4 and recently replaced the battery and alternator. The truck has been running and starting fine; but, Friday evening I went to a store three blocks from the house, and when I got back in the truck, it would not start. I had it towed home. Today (Mon. 7/25) I reconnected the battery after charging it (ran it down trying to start it), and the truck started with no problem. I backed it up in the driveway, let it run about 15 minutes, shut it off, and tried to start it. It wouldn't start. I can hear both fuel pumps when I turn the key on, and I selected one, then the other. Is it possible I still have a fuel system issue? I've never had to touch the gas pedal to start the truck in the year and a half I've owned it, and this is the first time it's acted up this way. Any advice would be helpful and much appreciated.

It would be beneficial to start with a scan tool reading to see if any codes are stored.

I would test for a loss of spark either with an old spark plug or a spark tester when the engine is in a no start condition. Hearing the fuel pumps isn't a valid test. You could hange a fuel pressure gauge on the shrader valve located on the fuel rail. You should have 30-45 psi. You need to start by verifying which system is at fault.

Thank you, raski, for your response. That gives me a good starting point to find out what's wrong. I tried to start the truck again today, and no go. With this Texas heat, it may take me a few days to try your suggestions and let you know how it turned out since I don't have any shade over the vehicle.

With the heat and no shade, I didn't try to work on the truck today; but, I did try to start it again. It started, I ran it a few minutes then shut it off. Tried to start it again, and it wouldn't start until I switched it to the rear tank, and it was hard to start. Hopefully we'll get some cooler temps here in East Texas and I can get out and start with raski's suggestions on what to look for.

Well, I haven't gotten to work on the truck since my wife has been in the hospital twice since my last post, and I had to go to the ER myself. My daughter's boyfriend replaced both fuel pumps, the tank selector switch and I'm not sure if he changed the fuel filter under the cab or not. I'm also not sure if he used a fuel pressure gauge to see if I have enough fuel pressure or not. I do know my scan tool will activate the computer in the truck; but, it isn't receiving any codes back, so I don't know what codes may be stored, and the truck still won't start. Any ideas where to go from here would be greatly appreciated.

Start again with the basics: spark and fuel pressure verification. Computer seems to acting strangely. Make sure battery, cables and its ground are good.

Hope your Mrs. is feeling better.

Will give those a try. Thank you. And thank for replying about my wife.

Still doesn't want to start
 

Here's where I am now. Fuel pressure gauge shows no pressure until my daughter did a bypass where the code reader plugs in. The truck started with 40 psi on both tanks; but, once it warmed up, it wouldn't start again. It's like the ECU is telling the computer the fuel pumps are bad, or, possibly the ignition switch is bad and not letting the brand new pumps kick in like they should. Without the bypass, it shows 0 PSI on both tanks. We're thinking now it's either the ECU or the ignition switch. Is there a way to test either one or both? U

Still won't run
 

I've gotten both fuel pumps, the selector switch and the fuel filter replaced. The truck will start, run for a bit, then won't start again until it sits for a while. I'm getting 40 PSI with a fuel pressure tester, so, I'm not sure where to go from here. Any more suggestions and ideas will be greatly be appreciated. I'd like to get my truck up and running so I can drive it again. I am wondering about the inertia switch and/or the fuel pressure regulator. BTW, I didn't mention before; but, it's got 288K miles on it.
​​​​

It's not the inertia switch . It will kill the power delivered to the fuel pump and need your intervention to reset.. It does not reset on its own. "IF" you are getting 40 LBS of pressure AT the time the engine dies, you need to determine if ignition is ceasing to function or the injectors are not being driven electrically by the computer. You should have a constant 12v power source on one leg and the computer will ground the injector's other leg at the time it is supposed to be pulsed on.Also, the fuel pressure regulator does not act up that way. You can check it in a few seconds by unplugging the vacuum line to it to see if raw fuel comes out of the nipple after cycling the key just to rule it out. Change it only if it leaks fuel..