Hi everybody,
Does anyone know how many amps the fuel pump is using?
I took a reading of 7 amps at the red wire of the fuel pump relay, is that too much?
If it is can you suggest where I can look for the problem? Both fuel pumps have been replaced.
Thanking you all in advance

 

If anything 7 amps seems like "not a lot" to me. Is the fuse 15A or 7.5A in your book/tag. I bet it is 15 A.

 

The red wire at the fuel pump relay is not the current going to the pumps, the yellow wire is.
The red wire goes to the coil of the relay and 7 amps sounds like way too much to me.

 

7A for the signal wire? Yes, something is wrong.

 

Thanks for your reply can you tell me where to look for the problem

 

Thanks for your reply can you tell me where to look for the problem

 

First of all I think maybe you have been looking at the power relay and not the fuel pump relay.
In this case the red wire from the power relay supplies all of the solenoids and the fuel pump relay. So 7 amps for this wire would be OK.

Also I do not know what you are working on.
What year is it?
What transmission?
What engine do you have?
Is this a van or a RV?
If it is a RV what class is it (A, B or C)?

 

7 amps is not unusual -- that is less than 100w, which is not much power when it is running and moving fuel.

The critical thing --- the pump shuts off once max. pressure is reached and is not pulling 7amp all the time --- resulting in a much lower than 100% duty cycle.

It is constantly cycling on and off and that is normal.

 

The red wire does not move fuel.

Wrong, the pump does not shut off at pressure.

The pump does not shut off, it runs all the time.

 

Hmmm... well.. take your word for the red wire it since my gasser is not in service and I haven't looked at it for a while.

The OP question is about power draw for a fuel pump... and 7 amps is not excessive.

This link below shows the power draw for a Honda Passport --- 9.4A peak, 5A average for a much smaller engine.


http://autolabscopediagnostics.com/fuelpump.htm

So 7 amp is not out of line at all.

I will have to pull the specs of the gasser pump --- but typically all commonly used fuel pumps will stop once "max pressure is reached --- it may be cycling (as shown in the above link), to me that is a shutoff.


My diesel fuel pump does shut off once it "pressurizes".

 

Here are some actual traces of what current a fuel pump draws on a range of vehicles --- too bad the closest I can come to a 5.4 Ford is a 5.7 Chevy:





Fuel Pump Waveforms


Note the waveforms (up and down) that is the pump cycling on and off.

It may not appear to you that the pump is cycling on and off, but to an oscilloscope, it is obvious.

 

As I said above he was on the wrong wire or wrong relay so current draw of the fuel pump is not a factor with his 7 amps.

 

I can't speak to the wire --- as my E is decommissioned.

But the amp draw... 7amps is not too much for a fuel pump pushing fuel for a 5.4


The question is, what is the 7amps doing going through that wire?

What is its function?


Or another question... how did he measure 7amps for that wire?

If he used a clamp on meter, it could be measuring the other circuit.

 

The red wire function is to provide power to the computer, all the injectors, the fuel pump relays coil, transmission solenoids and other solenoids (IAC, TAB, TAD and so on).
Its source is the EEC/PCM power relay.

 

Well, for that function, 7A is about right.