Hello all,

Let me first start off by saying I am a capable mechanic, I own a fuel pressure gauge, scan tool and a nice box of tools. I'm no ASE certified mechanic, but I can fix most anything without to much trouble. I have replaced plenty of fuel pumps, brakes, engines, transmissions, even rebuilt carbs on really old junk. It's enough to last me a lifetime and because of that, I am the family mechanic. I have searched these forums along with other Ford forums, have found similar problems, but no real solutions to mine. That said, here is my problem -

My brother-in-law Dan has a 2003 Expedition with the 5.4 triton, 4wd auto trans and it has a cable operated throttle body. He started it Friday morning, it ran for a minute or so, sputtered and died. After cranking on it a few times, I had him listen to the tank while key was turned on and he could not hear the pump. Told him I would be over Sat morning to check it out.

Sat morning, put the fuel pressure gauge on it, cycled the key several times and got 0 psi. Cranked engine over 3 times - 0 psi. Checked the inertia switch, 0 psi. Went to check the relay and fuse and got confused. There is no Power Distribution Box under the hood!? No bank of relays, nothing. Got out the owners manual and it showed there is only a fuse/relay center behind the right front kick panel. Found the relay / fuse list and diagram for the box. List showed R303 is fuel pump relay. Right on! But, box only goes to R203!? Checked list in book again, R303 is fuel pump relay, looked at box and diagram, no R303 in the box, only goes to R203!?!

Dan had bought the fuel pump and fuel filter Friday so I said "good place to start." With almost a 1/2 tank of fuel I was really looking forward to replaceing the pump! Replaced both items, turned the key, no pump noise and 0 psi. cranked engine a couple of times - 0 psi. Check inertia switch again, no pump noise - 0 psi, swapped relays and checked all fuses in box behind kick panel - 0 psi again. Checked PATS system by turning on key, theft light went out after a few seconds and odo read mileage, 0 psi. Cycled key several times, no noise and still 0 psi!

Here are my questions -
1. Where is R303? There are no relays under the hood that I can find and it is not in the box under the kick panel. Is it in a super secret hiding place?
2. If the anti-theft light goes out and the odo reads normal, is the key still suspect? He only has one key. Is a spare key a Ford item?
3. If a sensor or control module fails on the engine, will that cause the PCM to not call for fuel and leave the pump off?
4. Is there such a thing called something like "Fuel Pressure Control Module"? If so, where is it and is it suspect? Will the scan tool see the problem if defective or does it need to be tested by other method.
5. Is the PCM suspect?

This fuel system has a supply and return line, but does not have a vacuum operated pressure regulator. It has something that looks like a pressure regulator on the rail, but no vacuum line on it nor a place for one. There is another regulating looking device on the fuel pump unit itself too. It is inside the tank once pump is in place.

Sunday morning I plan on checking codes, breaking out the volt meter and checking for power at inertia switch and fuel pump along with any other ideas I may get here. Hopefully I will find the elusive R303 relay.

I have a Haynes manual for it, well you know, it's not really "for it". It covers 98-03 and everything in it is the older systems with statements like "newer systems similar". Yeah, right. The only thing similar with the 03 and the older trucks is they both use gas and oil. Nothing on this '03 looks like the piks in that book so I have deemed it worthless for this job. Any help and advice is greatly appreciated.

Gary

 

1. At the end of the list of fuses and relays (page 258) in the owners manual is this: "Note: Relays R301–R305 are not serviceable components; see your dealer or a qualified technician for assistance."
http://www.motorcraftservice.com/?li.../03exdog5e.pdf
2. No
3. No
4. You got me on this one.
5. No likely.

When you checked the inertia switch, do you mean the switch in the rear compartment, and did you press the red reset button on it?

 

Thanks for your response. By checking the inertie switch, I meant I pressed the button. Will check things out with a meter today. The owners manual in this truck does not have that statement and is different that the link you sent. I looked at it again feelng like an idiot, but it says nothing about them only being serviceable by Ford. No one knows where it is?

Thanks again

 

Ok, after testing everthing, I found the problem. The elusive R303 relay (along with R301 - R305) is mounted to the circuit board in the fuse box behind the kick panel passenger side. This one is melted. I had to pull the box out of the truck ans dis-assemble it to find the relay. Going to have to find a new fuse box and figure out why it melted. I'm hoping the old fuel pump shorted and took out the relay although I don't know why it didn't burn fuse 34 first. Going to put a meter on the old pump later and see if it is shorted. According to the wire schematic, power comes from fuse 34, through relay R303, through the inertia switch and to the pump. Seems to me if the pump was shorted, the fuse should have burned, but it didn't. Instead, the relay burned. Kind of odd I think, but, it is what it is.

I found the Ford wire schematics at the library which shows how this is layed out.

Thought everyone would like to know.

 

Always!

Very nice diagnostic work.

 

I found a new relay and I'm going to replace it instead of the entire box. Believe it or not, I'm haveing trouble locateing a fuse box for it. '03 was a special year for the expedition/navigator. I could take some piks and post them if anyone is interested.

 

pics are always good

 

Ditto on the pics.

 

Give me a couple of days for piks. I'll take a few and get them posted soon.

 

Thought I'd revive this thread with some pics since nobody else did. The burned up fuel pump relay is a common failure for the '03-'04 Ford trucks. It's a lot of amp draw to pull through a micro relay. At Ford "Poor Quality is Job Security One". WTF were they thinking?
There's different fuse box part numbers for various reasons of course. Cost should be right around $300. I ordered mine through Tasca Parts for about $270. If you fuel pump quits or you hear buzzing from your fuse box, or maybe some smoke coming from it, this is your problem. You can "bandaid" it by swapping the top white relays around, that will buy you time or maybe just get you home. But in the end you're gonna have to replace the fuse box. It's pretty easy since it's modular and everything just unplugs.



-Mike


Located behind passenger side kick panel....


2003-2006 Ford Expedition, F150, Navigator fuse box, passenger kick panel... It starts with the PCM relay middle terminal showing melt damage... top right white relay is PCM relay....


Fuel pump relay 303 on fuse box circuit board, non-repairable.... gotta replace entire fuse box...


Old on the left, new on the right, comes with all new relays and fuses....

 

I have a 2003 Navigator and had the exact same problem. I bought a "repaired" fuse box of EBay and after the install the battery light came on and the notification of check the charging system came on. I did not have the problem prior the the install of the fuse box. Negative cable was removed prior to any of this work being done. I checked the battery and alternator and they are good. I also checked the fusable link (mega fuse) going to the positive terminal and the alternator. That was good as well. The battery is only reading 12.2 volts when the vehicle is running, so the notification is correct and it is not charging the system, so that makes me rule out any computer issues. I also checked the fuses and they are good.

So, I am thinking that maybe I got a crappy fuse box. Thoughts?

 

More likely a crappy alternator ....
If everything else is working fine and that's your voltage reading at the battery with the engine running it kinda leads you to the alternator.

-Mike

 

@ Hamfisted:

The alternator was checked twice at Autozone. I was expecting the alternator to be bad after doing the voltage checks, but they are telling me that it is good. Have you seen this before? Do I not trust their test?

 

I've seen alternators pass bench tests but fail in-vehicle tests. It all has to do with the alternator being hot in the vehicle and cool on the bench tester.

 

I don't understand why this is thought not to be serviceable. We replaced the fuel pump and fuel relay at same time for less than $300.00 total. I bought my fuel pump from Rockauto for around $150.00. Not the cheapest but also not the most expensive. I also bought the replacement relay from Tanin Auto Electronix for around $25 . I paid a friend $120 to change the fuel pump and did the relay myself. New relay is an OMRON G8QN 12VDC LAEA different number but looks the same. Saw some on Ebay also. It is my thinking that if the fuel pump is going bad it will pull more amperage and will cause the relay to go out. My vehicle has over 200k miles so changed both. Ran the Expedition for several hours today and did not stall once. Not recommending the vendors they are just who I used (Not complaining about them either).




Fuel Relay 303 is 3rd soldered relay in between large Ford relays




3rd relay shows burning on bottom left side




Disassembled board I took pics at each stage to be sure I put it back together correctly




Used soldering gun and bulb syringe to suck out old solder and pull relay




Reinstalled new relay took me less than 5 minutes to solder it in.