2003 Ford Expedition Fuel Pump Relay (R303) Damaged

[mggmgm1]

@Martynka I am still not understanding how I determine if the fuel pump is drawing too much current? How would I check the current it is drawing if the R303 relay is damaged? The fuel pump does work perfect when I bypass the R303 so I know it is the R303 that was damaged. Also, this is the second R303 relay that is damaged which is a 30 A relay and it was damaged within 5 days after working perfectly.

 

[mggmgm1]

@whtbronco I did isolate the issue to R303 two different times.

1. The first time, the R303 relay was visually melted.
2. I installed a 30 A R303 relay and it worked perfectly for 5 days. Then all of a sudden the Expedition stalled. I bypassed the R303 relay and the Expedition starts perfectly.

Do you have any idea of how to identify the root cause of what damaged the original R303 fuse and then the newly installed one after 5 days of working perfectly?

You suggested installing an external relay but if the root cause is not fixed, I believe even the external one will be damaged.

It might be the fuel pump drawing too much current but how would I check that?

 

[whtbronco]

You've may have a fuel pump drawing too much power for the 15amp relay to handle, motors can draw more power as they age/wear. Or there may be an intermittent short in a wire.

This video should help with how to test for current draw. You won't need an external power source, the battery in your truck will work. https://youtu.be/c9KNAIjoEYs

 

[mggmgm1]

The relay was actually a 30 amp relay and not a 15 amp relay and it was damaged in 5 days.

 

[whtbronco]

Then you have a rather serious problem if a 30amp relay didn't hold up. Test the current draw from the fuel pump. Also test and inspect the wiring for potential issues.

Another idea would be to visually inspect the circuit board the relay is soldered to. I say this because the electrical runs in it can connect over time. Or you could have messed it up while repairing it the first time, like I did. I mistakenly grabbed plumbing flux and after a little while the acid in the plumbing flux ate up the board causing an internal short.

 

[Martynka]

I am still not understanding how I determine if the fuel pump is drawing too much current?

Like this:

How to use multimeter to measure current amperes #shorts

#shorts #electrical #plc Please Subscribe to PLC Tutorials for more Videos and TutorialsPLC Programming Tutorials for beginners

www.youtube.com

but use 20A multimetr.

The relay was actually a 30 amp relay and not a 15 amp relay and it was damaged in 5 days.

We don't know how your pump works before you measure it.

Then you have a rather serious problem if a 30amp relay didn't hold up. Test the current draw from the fuel pump. Also test and inspect the wiring for potential issues.

Correct

 

[mggmgm1]

When I use a multimeter what numbers are normal and what numbers are abnormal?

 

[Martynka]

It should be few amps at idlle, but better to check it when driving because current draw is changed by temp and fuel flow.

 

[mggmgm1]

So I should be looking at amps and nothing else?

 

[Martynka]

So I should be looking at amps and nothing else?

yes. only higher amps can burn relay. High amper means:
- hard working pump
- electrical short circuit