My buddy is having a problem with fuel pump turning on sometimes and not others. So my guess is the wiring. Anyways, if i check his fuel pump on a EG, what volts should the pump be at?
Thanks

 

Battery voltage.

 

Like ee_chris said, 12 volts should be going at the pump.

fs

 

Thanks guys.

 

It's going to be approximately 12...your battery will put out slightly more or less, and then there are losses in wire resistance to consider. Besides running larger gauge wire, there is nothing you can do to avoid some slight losses, but anywhere in the ballpark of the battery voltage is good. Check the battery voltage first, then the fuel pump voltage and compare.

 

Can i just unplug the electrical connector going to the fuel pump and stick in MM testers in the connector?

 

Yes, with key on.

fs

 

IF the pump should be on, then there will be 10-14 volts.
But the ECU turns off the fuel pump relay quickly if the car is not running.

BTW a common problem that will cause this is the main relay. be sure to check that too.

 

I just went and tried to test MY car. The one without the problem and i set the MM to battery load test 12V. Battery came in a 12.4 or something. While i tried to test my connector located under rear seat that has power/ground. And the MM isnt picking up a reading from the connector with the key is ON position. I plugged back in connector and turned key again to ON...sure enough fuel pump is getting power now. So why cant the MM read from the connector that has the power/ground? Do i need to change the readout on the MM?

 

put the black lead to body ground (anywhere with a good ground), put the red led on every pin and see if u got 12v

 

Should I plug in the connectors THEN turn key to ON?
Or have it set on ON the whole time?

 

Just start the car and measure it.

If the car is running and you can't get a measurement - user error.

 

Iam trying to test the connector, so there is no way to have it connected and test it at the same time. Unless i strip some of the wire, which iam not doing on my car which works fine. But thanks anyways.

 

Here's how it works:

You turn the key 'on' and the fuel pump will prime for 2 seconds - this means its getting a voltage that you can measure - for 2 seconds.

After this 2 seconds, the next time it will have voltage is either a) by turning the key 'off' then 'on' or b) by starting the car.