Greetings!

I recently acquired my first F-Series pickup, a 96 F-150 that was headed to the crusher.

It's a 96 Extended Cab, Longbed, with 302 V8 / automatic. 2WD. White with red 2-tone. 2 fuel tanks. Actually in pretty decent shape, minimal rust, wiring harnesses don't appear to have any damage to them anywhere I've looked. Couple rotten vacuum hoses, which I will take care of, and the tires, while almost brand new tread, have cracking on the sidewall, so they will have to be replaced.

I consider myself reasonably handy, have been working on various cars and trucks over the year, and presently daily a car with 365,000 miles and counting that I've done almost EVERYTHING on.

The problem at hand: F-150 has sat for 3-4 years and will not start. It was driven to the location I towed it home from. It ran when parked.

I've done my troubleshooting, and it's a fuel problem. It will start on fluid.

New battery was the first thing I did when it rolled off the trailer.

Determined the inertia switch was bad, as I would get 12 volts on one side but none on the other at KOEO. It was not 'tripped', it just had zero volts out.
I jumpered the inertia switch to get it out of the equation. May replace it at a later date.
Tank select switch was questionable, as I got 12 volts on the input leg, which is connected direct to the (now jumpered) inertia switch, but got 9V out on one tank, and 10 on the other. Replaced tank switch, and now briefly get 12 volts on the selected side of the switch at KOEO.

I *never* hear a hum from either fuel pump.
The fuel gauge never reflects anything - the needle is to the right, well beyond the 'full' mark.

I pulled C205 at the firewall to inspect the connector that takes the wiring to the fuel pumps and the connector was clean, dry and found no broken wires.

I do not know how much fuel was in the tanks, I did put a can of seafoam in each tank as well as 3 gallons of fresh premium unleaded in hopes that it would dilute whatever was in the tanks.

I have Alldata DIY and have been referencing it as I try to troubleshoot.

One question I have:

Under the operation section of fuel delivery, it indicates that

When the ignition key is turned on, the electric fuel pump runs for about one second, but is then turned off by the PCM if a Profile Ignition Pick-up (PIP) signal is not received.

How would I tell if the PCM is turning off the fuel pump? I don't ever get any codes set, as the engine doesn't start, so I'm not sure if I have any codes.

Any suggestions, feedback etc are appreciated. I need to get it started so I can start figuring out what I have to do to get it roadworthy and enjoy it. Thanks for helping!

 

Welcome. Usually when the pumps don't prime it indicates a bad PCM. Computer. Pull yours and take the cover off and see if your capacitors are bulging or leaking. There should be two or three that stand upright and have two legs.

 

Thanks for the advice.

I unbolted the cable bundle, removed the bolts at top and bottom and removed the plastic cover. The PCM slides half way out and hits the fender liner.

I just ran out of light, was trying to pull the fender liner but stopped to come inside and warm up. Is it possible to remove the PCM without removing the entire fender liner?

 

Yes. Use a broom stick or similar device and push down on the liner. Of course a pair of extra hands helps. If you have any questions about the condition, post pictures.

 

Pull the 4 or 5 inner fender screws, it slides out nicely.

 

Here are some PCM photos. It looks clean to me, but I will yield to your opinion since I am the newbie here.

I don't see any components that look burnt or charred either.

Is this something where I should replace this as a troubleshooting step? Since all the ECMs I've found were refurbished, I'm concerned I could be sending what appears to be a nice clean core back for one that has some ugly previous damage to it. Thoughts?


Part number

PCB looks clean to me. No corrosion.

Caps aren't bulging, and since it's raised up off the board, I can see it hasn't vented any electrolyte on the board.

Caps aren't bulging, and since it's raised up off the board, I can see it hasn't vented any electrolyte on the board.

There's something coating all these terminals that doesn't look great, but I expect it may be something that protects these terminals. If I had to guess, this may be how Ford updated the ECMs in the factory.

 

They certainly don't appear bloated or leaking. The one that is leaning may have a broken leg (contact) as I can't see. It also appears you have only two capacitors is that correct?

 

Only 2 electrolytics, C2 and C7
Both 105 degree nichicon caps, appear to be in good shape and no broken legs.
I do have an ESR meter, which I could try to test them with but they may not have accurate values in circuit, and while I'm very good at soldering and desoldering, I do not have a schematic for this particular PCB and with no good way to test it, I hesitate to change them out myself.

Trying to determine next steps... did a little research online and did find a place that mentioned there's an updated version available, but since this worked just fine for 150k, I don't think it's a software related problem.

 

The computer looks pretty good to me. These 1996-1997 PCMs are very robust. But looks can be deceiving.

Just like the OBD-I vehicles the PCM is programmed to energize the fuel pump relay for ~ 1-2 seconds when cycling the key from the Off to Run position. Whether that is hard wired or built into the programming was a recent debate. Since your truck is OBD-II there is no way to jumper the fuel pump relay to ground like the OBD-I trucks can do at the test port. It's a handy troubleshooting tool to test the integrity of the fuel pump power circuit.

Best advice is use a DVM to verify power is getting to the supply side of the load contacts as well as the relay coil. The computer applies a ground to energize the relay coil which in turn applies power to the fuel pump(s). Just keep in mind it is there for only 1-2 seconds.

In Post #1 you stated you did some troubleshooting the power side of the circuit, but wanted to give some details on what is going on when you cycle the key. If the fuel level is over full and no hum from the pump(s) then I suspect a bad ground for the pump/sender.

Here is the diagram for the computer interaction with the fuel pump relay and EEC/PCM relay.

 

has anyone verified the inertia switch isnt trippped

 

Yes...Post #1

 

Not that is wrong sorry, a bad PCM is indicated when the fuel pumps run constantly with the key in the run position. To me the OPs computer looks to be in very good condition.

To the OP, your problem is almost certainly dead fuel pumps, they generally don't survive sitting unused for years in stale gas.

 

Inertia switch was bad, so I jumpered it out temporarily. I just connected the input and output wires with a butt splice.

I get voltage at the tank switch at KOEO for a second or two when I turn the key in the ignition.
I get voltage at the selected output of the tank switch when I turn the key in the ignition.

Thanks!

 

Thanks for the feedback, Paul. I appreciate everyone's attempts to help here.

I did try shorting 12 volts direct to either side of the fuel tank switch, and didn't hear the slightest hum from either fuel tank so I was debating how likely it was that both would have failed at the same time. But maybe they did. The previous owner of this truck (my father) was very meticulous about it and often used to marvel at how great it was that he had 2 fuel tanks, so he could keep both of them full and not be as concerned about gas prices. So I know both worked when he parked it about 4 years ago.

I need to get a second set of hands to turn the key while I get under the truck and verify that I have 12v at the fuel pumps when selected.

This truck is intended to be used for short drives of 100 miles or less, to haul things to and from local home improvement stores, parts for my other vehicles from the salvage yard, body shop, etc. I've wondered if it makes sense to convert it to single fuel tank if the pumps are indeed bad. I will see what information I can find online regarding that process.

If the pumps are bad, I may let a mechanic change them for me. I try to limit my automotive wrenching from spring thru fall. but had to act in a hurry to rescue this one

 

OK you have our Experts chiming in now. I will let the pros help and follow the thread.