First off I I am not a mechanic. However, I am an electrician and do all the repairs around my house regarding carpentry painting, etc. So I’m hoping that I’ll be able to fix this using your help. I’ve owned this truck for two years. It is a 1994 F150 with a five speed manual six-cylinder. It has 135,000 miles on it and I am the second owner. The first owner was a farmer who did a lot of maintenance on his own and used a dealership when necessary. For its age, the truck is in really good shape (I think), but it is an old truck.

Prior to when I bought the truck, the front fuel tank was not always providing fuel consistently. When I would select it, sometimes it would work fine, and other times it would start to feel like the engine was not getting fuel and I would switch it back to the rear tank. this is not the problem that I am posting about however but it might be related. The other issue that I would like to try to solve is that sometimes it will not start. It turns over but will not start at all other times it starts up no problem






and idles properly. The no start action happens less than one in five times and I started noticing it about three or four months after I bought the truck. Lately it’s getting a little more consistent with not starting about every five times I don’t use the truck much accept in the summer. so that could be over the course of more than a month. I think what I have done to solve. The problem is push the car about a foot or two without it started and then I tried to start it again and it starts up. The reason I say I think is because there have been 2 or 3 times where it will start up in the situation after I switch the fuel tank selector switch. I don’t know if this is just coincidental or if this is a problem that goes along with a second problem that is affecting the trucks ability to start sometimes.

I’m wondering if my moving the truck indicates it could be a starter that’s failing and I’ve noticed that it looks like the starter doesn’t have a heat shield which I wonder if it’s contributing to the degrading of the starters ability to work. But I don’t know if this is even the problem or not. Any suggestions on how to troubleshoot?

 

You say it turns over so it can't be the starter. Since you have the dump bed which gives you easy access to the top of the fuel tanks, I say replace the fuel pump in the front tank and then run off that and see if it happens or not. Your rear pump could be failing on you but you need the front pump anyway.

 

When I turn the key to the ON position sometimes I hear the fuel pump and sometimes I do not. I think I am going to take to a mechanic because I’m not sure how to proceed.

 

I would check the wiring connections at the fuel tank selector switch, and check the switch for continuity with the wires unhooked.

Also check the ground connections at your battery, engine block and/or frame and the ground connection on the driver's side upper part of the radiator support.

Ground connections need to be clean and tight.

 

https://easyautodiagnostics.com/ford...ring-diagram-1

 

Normal operation is turn the key to "on", not start & the pump "primes" (runs 1-2 seconds) to pressurize the fuel injector rail.

If computer does not "see" the distributor spin, it will not energize the selected fuel pump.

At a time when the engine will turn over repeatedly, but not run, spray a shot of ether/starting fluid & if the engine trys to catch & run, then there is possibly a fuel delivery/pressure issue.

If it does not, then there is possibly an ignition or related issue.

 

If you turn the key to start, and sometimes the engine spins, sometimes it doesn't...

That is usually a symptom of a poor connection in electrical or a failing clutch interlock switch.

Nice truck by the way.

 

I no longer hear the fuel pump priming the line when I turn the ignition switch to the On position. When the No start was intermittent I would hear the pump prime when it did start and when I didn’t hear it prime it wouldn’t start. Now that I don’t hear it priming the line I could try and see if the fuel pump is getting power. With the dump body lifted I have easy access to the fuel pumps. Can I do this by removing the fuel pump connector and testing at the connection/pins?

 

Yes you very lucky to have dump bed easy fuel pump access and testing.

 

I doubt I'll be able to help much as I'm recently picked up a 94 F150 and I'm in a similar situation. I bought it cheap but it had not run in several years. I pulled the air cleaner lid and sprayed throttle body cleaner down the hoses and it fired up for just a second, but enough to tell me it was a fuel issue.

Sounds like yours is likely a fuel issue as well. Get a fuel gauge, lots of auto parts stores will "rent" them for free with deposit, or Harbor Freight has a cheap $15 one. Plug that onto the schrader valve on the fuel rail. These trucks run with around 35 - 45 pounds of pressure. Mine had no pressure on the fuel rail. Next I watched a video , in that video he shows how to troubleshoot. Using his method I jumped the pumps at the pump selector switch and found that the front pump wouldn't work at all but the back pump was working and after a few seconds built 40 lbs of pressure. With that pump jumpered if I turn the key it will fire right up and run fine. After removing the jumper I lose the pressure in the rail in just a couple of minutes. When I turn the key to on, it will prime the pump for approx 1 second (verified with volt meter at switch) but that hardly builds any pressure. Now I'm in the process of diagnosing where the fuel is going, likely the front pumps check valve is stuck open and it's draining into that tank.

 

Thank you for the response Bob. I will try your t-shooting suggestions. I think there are a couple of issues and this will help. It’s still running intermittently which makes it a little trickier for me.