LUVTruck.com

how do you tell if your fuel pump relay is bad?

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76 mikado project,mean green

Check your fuses first. Then with a test light probe the fuel pump line at the pump, next the power input line to the relay. Next have someone turn the key on while the probe is probing the input wire to the relay. A wiring schematic will help.

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The light at the end of the tunnel, may just be a train coming!

is it either bad and not working,or good and working with no in between?

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76 mikado project,mean green

LUV trucks have a very strange way of energizing the fuel pump relay because the only time this relay is supposed to be on is when the charging system regulator sends a signal to the relay, or when the starter is engaged! So the only way you can check it is to (1)either have someone crank the engine or (2) have the engine running and the alternator charging. I believe the white wire with a red tracer is the one going back to the fuel pump from the relay. A lot of guys disconnect this wire and run power to it directly from the key switch and this works fine, but a safer way is to install a oil pressure switch (available from Summit) so that the engine oil pressure turns on the pump. That way if you should get into an accident the fuel pump won't continue to run after the engine is off. Hope this helps, if not drop me a line and we can go from there?
scjconv

You can also use the op switch from a vega.

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The light at the end of the tunnel, may just be a train coming!

Hi Rob,

Excuse my ignorance, but what is a Vega op switch?
I had to learn the hard way about the clutch starter switch and the fuel pump relay the hard way back in 76!
I lost a fan belt and of course the fuel pump wouldn't run, and I couldn't even move the truck out of the traffic lane with the starter because the starter wouldn't engage unless the clutch pedal was depressed! One of the first things I did when I finally made it home was to disconnect the clutch switch and wire the fuel pump wire direct!
Always glad to read your messages, you are a wealth of information, especially about the early days of Luv V8 swaps. Bet you have a lot more stories to tell, like to hear them sometime!

dusty

OP = Oil Pressure. The vega's had an electric pump on them and the switch will cut off the pump if the op drops too low like after the light comes on.

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The light at the end of the tunnel, may just be a train coming!

Right! I should have put the two together, op for oil pressure switch, duh!! Do you remember the thread size of this switch, 1/8" pipe or?
Just for information.
Thanks again,
dusty