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?
2003 Ford Expedition Fuel Pump Relay (R303) Damaged
- Thread starter mggmgm1
- Start date
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whtbronco
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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:
www.expeditionforum.com
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
Hamfisted
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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".
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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
Full Access Members
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.
Within that sticky thread you will find other options to resolve this as well, such as installing a remote relay.
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.
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Hi, I'm new here but had the same problem few years ago.
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.
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.
If you ask me - yes, it help and I use standard 30A relay, not "mini 20A" ( in my opinion 20A is overrated for this relay to work long time )
On my profile I have a question:
"Hello. I was just curious why you think the problem is the fuel pump?"
Because your relay is rated for 20A. Fuel pump need to work about 15A. If your pump's motor starts to seize and has greater resistance, then the pump's power consumption increases. If rise above 20A can destroy your relays. If relays is melted after 20 years it can be because overheating, but after few days ?? For me it means:
- too much current flow through the relay
- factory damaged relay
- damaged/overheated relay solder pads
"Is there a way to check if the fuel pump is causing this issue before replacing the fuel pump?""
You can measure pump power consumption with multimeter device with 20A current probe possibility. You need to connect the meter probes in series with the pump power cable from the relay and start engine. You will see power consumption of your fuel pump. It will be good to drive and observe. Sometimes current rise with temperature and it need time.
If you observe that high current is not your problem, check solder pads on PCB. Look on my photo with pin description and remember:
- PIN 30 ( main power sypply ) is solder to circiut from bottom side
- PIN 85 and 86 ( relay coil supply ) are solder to circuit from bottom side
- PIN 87 ( pump power supply ) is solder to circuit from upper side - it means that you need to use more tin and heating time to make good contact. If you don't do it right, the pump will not start or stop working. Maybe this is your problem.
I use 30 amp relay because it is standard car relay ( normal size ).
My fuel pump workf fine. Power consumption is lower than 20A.
I wrote you why I think that it can be fuel pump... but first need to check current for pump, and soldering new relay on PCB.
You can check it with engine off and broken relay.
You need to bypass battery + with power supply for fuel pump. Now I don't have electric diagram but try to find.
whtbronco
Full Access Members
You can put in a temporary wire, jumper, to provide power to the fuel and circumvent the fuel pump relay. If the fuel pump runs you have isolated the fault to the factory relay. Run a wire from a constant or switched power lead to the output wire from the relay. The output wire is green with a yellow stripe, the below pic has a wire inserted into the connector.
External relay:
https://www.amazon.com/APIELE-Water...xvZ0NsaWNrPXRydWU&th=1&tag=expeditionforum-20
Here's the circuit board relay connection points once you get the old fuel pump micro relay out of the way.
The info and pics above are from ExpeditionForum threads.
External relay:
https://www.amazon.com/APIELE-Water...xvZ0NsaWNrPXRydWU&th=1&tag=expeditionforum-20
Here's the circuit board relay connection points once you get the old fuel pump micro relay out of the way.
The info and pics above are from ExpeditionForum threads.
As an Amazon Associate we earn from qualifying purchases.
whtbronco
Full Access Members
You need to find "dark green/yellow" wire. It is wire from relay to the Inertia Fuel Shut off switch and from switch to the pump.
Because on junction box you have "few" wires and is not to easy located "dark green/yellow" one, the simpliest way to check fuel pump is use "Inertia Fuel Shut off switch". It is switch in trunk on left side behind plastic cover. it is connected to "dark green/yellow" wire from relay side and "pink/black" from fuel pump side.
If you take long wire from battery + and connect for one of this wire pump start to work. If you have current metter you should connect one probe to the battery, second to one of this wire. Pump will start and you can read power consumption.
If you prefer to use wire from junction box, I can go to the car and check where is connected.
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