[Poppy]

Fuel pump relay switches, and other relays are similar to the starter solinoid, in that they make a high amperage connection through a switched low amperage connection.

Below is my fuel pump relay.


There are two smaller connections, and two larger connections.
TO test it, apply 12v to one of the smaller connections, and ground the other smaller connection.
(I used to small aligator clipped jumper wries separated by a small piece of cardboard to keep them from shorting against each other.)

You should hear it click. Then check for continuity between the two larger connections.
Now remove the power from the smaller connections and recheck continuity between the larger connections.
With power, one should have continuity, without power it should be an open circuit (no continuity).

[Boghog]

That relay checking procedure may have been ok back in the 80's,but since then different relays styles have come out and more up to date procedures. Here what should be used.

I have attached a more detailed explanation and testing methodology for testing different types of relays.I have also attached a brief tutorial on how to use a multimeter or DVOM as it is also called along with a picture and instructions on how to build connector wires to test the relay while it is still in the circuit.

To build the connector wires (you may need 4 or 5 depending on what type of relay you are testing),you'll need the following parts available at any auto parts or electronics store.

You'll need 2 ft of 16-18 gauge wire, a package of male insulated crimp terminals, a package of female insulated crimp terminals, a crimping tool and some 1/4" heat shrink tubing.
Start by cutting the wire into 2-3" sections.Strip off about 5/16" of insulation from each end. Take 2 wires and insert the striped ends into a female terminal and crimp together.Tug on the wires to make sure you have a solid crimp.Then crimp a male terminal to one end and a female terminal to the other end. I add a 1" piece of shrink tubing to the center female to protect the test lead from shorting against ground.

Once you have these made you connect them from each terminal to the corresponding terminal in the harness.Now all you have to do is probe the terminal in the center with your multimeter to test most relays.
I also added a segment on how to read a wiring diagram.

You Tube

You Tube

[Kingfish]

Originally Posted by Boghog

That relay checking procedure may have been ok back in the 80's,but since then different relays styles have come out and more up to date procedures. Here what should be used. I have attached a more detailed explanation and testing methodology for testing different types of relays.I have also attached a brief tutorial on how to use a multimeter or DVOM as it is also called along with a picture and instructions on how to build connector wires to test the relay while it is still in the circuit. To build the connector wires (you may need 4 or 5 depending on what type of relay you are testing),you'll need the following parts available at any auto parts or electronics store. You'll need 2 ft of 16-18 gauge wire, a package of male insulated crimp terminals, a package of female insulated crimp terminals, a crimping tool and some 1/4" heat shrink tubing. Start by cutting the wire into 2-3" sections.Strip off about 5/16" of insulation from each end. Take 2 wires and insert the striped ends into a female terminal and crimp together.Tug on the wires to make sure you have a solid crimp.Then crimp a male terminal to one end and a female terminal to the other end. I add a 1" piece of shrink tubing to the center female to protect the test lead from shorting against ground. Once you have these made you connect them from each terminal to the corresponding terminal in the harness.Now all you have to do is probe the terminal in the center with your multimeter to test most relays. I also added a segment on how to read a wiring diagram. Wiring Diagram How To Video - YouTube

Wow, this is great !

[Poppy]

Here is a picture of a professional set of jumpers by Mac tools, but a bit more expensive than the set that Boghog created above.