2003 Ford Expedition Fuel Pump Relay (R303) Damaged

[mggmgm1]

Please help! My 2003 Ford Expedition started randomly stalling and I would wait a few seconds and it would start up until one day it didn’t start at all. I checked the fuse box and discovered the fuel pump relay (R303) was melted above one of the pins. I soldered a new relay (R303) and removed the melted relay. The 2003 Ford Expedition worked perfectly for 5 days but then it stalled suddenly and never was able to get it started. I don’t hear the fuel pump run. If I bypass the R303 relay the fuel pump runs and the 2003 Ford Expedition starts immediately. That leads me to think the new R303 relay was damaged. This being the second R303 relay to be damaged, I am needing assistance in identifying what’s damaging the R303 relay? Also, what’s the solution to this problem?

 

[whtbronco]

The circuit board in the Central Junction Box(CJB) can be damaged or faulty as well, they can melt a bit when the relay melts down. I replaced the relay in mine, but I mistakenly used plumbing flux which ruined the board in about 6 weeks. So I had to replace the CJB entirely.

Everything you need to know is in this thread in the 2003-2006 forum:

Another fuse box replacement ....

Just replaced my '03's fuse box again. The second fuse box was installed in January 2014 due to the typical melted fuel pump relay and PCM relay. It was manufactured in November of 2013 but still had the old 15 amp Osram fuel pump relay and other micro relays just like the original '03 fuse box...

www.expeditionforum.com

 

[mggmgm1]

Thank you for your help. You suggest the cause of the R303 relay melting is a faulty circuit board? Also, do you suggest the solution is to replace the complete fuse box?

 

[Hamfisted]

Did you also inspect the PCM relay for signs of overheat damage ? It's the top right relay in the fusebox. If you see signs of melted plastic in the terminal area you can try swapping in one of the other relays ( among those 3 along the top row... they're all the same...) and see if your Expy starts. In the end though you'll end up replacing the fusebox. Make sure you order the fusebox for your specific year and date of manufacture range. Don't just go pull one out of a salvage yard and use it just because it "looks the same".







.

 

[mggmgm1]

I did switch the relays and the Expedition has the same issue. There are no signs of melted plastic in the terminal area. Do you know what is the cause of the R303 relay getting damaged? I don't want to replace the fuse box and then the R303 relay to get damaged as well.

 

[whtbronco]

My understanding is that the small relay can just barely handle the current draw for the fuel pump and after while it fails. My replacement CJB still has a 15amp relay, but as noted in the sticky thread I posted a link to above the updated CJB's have a more robust 20amp relay.

Within that sticky thread you will find other options to resolve this as well, such as installing a remote relay.

 

[IO40]

I had to replace the fuel pump relay about a year ago on my 03. It may cover this in the thread linked above, but make sure you get the updated Omron relay. I found them cheap and readily available on Ebay. Old relay: Omron F8VF-BA. Updated relay: Omron G8QN-05.

 

[Martynka]

Hi, I'm new here but had the same problem few years ago.

Do you know what is the cause of the R303 relay getting damaged?

In my opinion problem is in your fuel pump. Probably it's start to be worn and electric engine need more power to rotate. You can measure amps on work ( if you know how and have minimum 20A multimeter ).

I solved problem with this relay another way. I removed mini relay, soldered wires to relay soldering point, connected wires with external relay. Now I have big relay and easy acces to it.

 

[peeteri]

Maybe its good idea to put extra fuse between fuel pump and relay? So it will blow fuse not melt relay on PCB.

 

[mggmgm1]

Did that fix resolve this problem? Did you encounter the same issue with the R303 relay again?