I have a 1994 F-150 with a 5.0 V8. I bought it used about two years ago and while it was rough around the edges it did everything I needed. I started noticing after a while that the AC would stop blowing when accelerating or under any load. Then one day at a gas station the truck just wouldn't start. I could really give it gas and it would run rough, level out a little, but the moment I put it in any gear it would die. It's just sat for a while and I decided to finally try to fix it. I'm thinking maybe it could be vacuum problem, only because of the AC issue before the real problem started. I originally thought fuel pump, but after reading I think each tank has it's own fuel pump and I here it prime when it's set to either one. Does anyone have any suggestions or advice? Thanks in advance.

 

Check for codes.

Check fuel psi.

And just to throw it out there, if you're bored, pull the PCM out and check for failing capacitors. Capacitor failure is becoming more and more noticeable as the years keep ticking by on these old trucks.
Do this last. See if there are any codes stored in the PCM.

 

I don't see any codes.

I actually got the truck to run and even drive for a few minutes early this morning, but the issue came back just a little later. I was able to test the fuel pressure, it was 38-40psi when priming before starting (using either tank), and then 32-33 psi when running (when I could get it running). Any idea if that's good or bad?

I didn't get to the PCM today. I started to, until I found a wasp nest right under it. I'm waiting for some bug spray to do it's job and may try to get it tomorrow.

Side note: when it was running I did notice the AC wouldn't change vents, so I looked and found 2 cracks in a couple vacuum lines by the heater core hoses. I fixed those, and the AC started working, but it didn't make a difference on starting.

Thanks again.

 

When you said you didn't see any codes, did you get a system pass code of 11 or 111?

Fuel psi seems good.

Wasp nests are bad! Carburetor or Brake Cleaner will kill those things dead. I love the straw on the cans as I can pinpoint my spray!

 

Well I still didn't get time for the PCM today, but I rechecked the codes, as Im pretty sure i did it wrong the first time. I was able to get the car started twice and found a video on YouTube on how to get codes when "on" and when "running"
If I did it right, the codes are:

On codes - 116 , then 111

​​​​​​​Running codes - 116, then 172, then 225

 

Well I still didn't get time for the PCM today, but I rechecked the codes, as Im pretty sure I did it wrong first time. I was able to get the car started twice and found a video on YouTube on how to get codes when "on" and when "running"

On codes - 116 , then 111

Running codes - 116, then 172, then 225

 

your a/c vacuum could be on pass. side vacuum line(white) going to diverter valve on top of blower motor, truck needs to be at operating temp before doing the KOEO(key on engine off) and then codes fixed, before doing KOER(key on engine run) or you get bad codes, chasing your tail.

 

The white vacuum line did have a crack in it and another vacuum line that came out the same way but went the opposite direction towards a t adapter closer to the engine. I replaced both with rubber hose and they worked the last time I got the truck started. How long do you think the tuck should run to be at temperature before the code tests?

 

5-8 minutes maybe, its 85* humididity(lol) feels like 92* here in bama, so 5

 

So after getting it up to temp, I still get code 116 with koeo. I wasn't able to get it started again after that. For what it's worth, it seems like each day I try I can get it started and it runs as long as it's off that first start. After it runs for a while and I turn it off, I can't get it back on. Could that possibly be some type of temp sensor maybe?

 

Here's my favorite. Pull the cap & rotor to expose the shutter wheel underneath.

Remove the 2 screws holding down the shutter wheel to expose the PIP [profile ignition pickup] sensor. (this tells the computer to fire the plugs & keep the fuel pumps running)

Blow it out with compressed air, electronics contact cleaner or a soft bristle brush.

The PIP below never set a code:

 

Well I got the shutter wheel off, but honestly I'm not sure what I'm looking for under there. I could take some pictures if it would be helpful, but I'm having a hard time finding a picture on google of a pip sensor so I know what to clean.

 

The only thing inside the distributor under the shutter wheel is the PIP.

A roughly 5 sided U shaped item with wires. The pic above is the space that the shutter wheel passes through.

The wheel breaks a magnetic field to send a signal to the computer. If it's full of crap as shown, the signal functions, but degraded.

 

I just want to make sure I have this right, is it this thing?

 

Here's the whole thing.