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VS Fuel Pump Test - How To Bridge the Relay

RUN415

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= VS Fuel Pump - Test + Diagnosis - How To Bridge the Fuel Pump Relay =


Take out the FP relay (in the engine bay) and bridge (connect) the appropriate pin slots with some thickish electrical wire.
(On my 95 VS Exec (Dual Fuel), it was the first two slots, nearest the firewall (or back of the car) - CHECK the wiring diagram on the actual relay to be sure!)
Now concentrate...as there's power to one of these slots ALL of the time.
CAUTION: Be careful to avoid sparks...if you're sloppy you may blow the 15A Fuel Pump fuse found next to the relay you're working on.
This bridge will give you constant power to the pump (even if your car keys are in your pocket) - so the pump should run continuously.


HINTS:
The trick is to get the right bridging wire...skinny enough to go in...thick enough to make a good connection.
Make sure the relay box is well lit...you don't want to be fumbling around down there.
Some peeps rig up a little device to make things easier...like a wire with pins or electrical connectors/blades.
I put nodules of solder on my wire and filed them to a point for easy insertion. (Saves twirling the ends all the time.)


This is a great test...and to me, quite mandatory if you're having probs.
It may even get you going if you're stuck somewhere...
...as it overrides the relay and will give a failing fuel pump a darn good kick in the guts!
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RUN415

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= TESTING OUTCOMES + DIAGNOSIS =

When the RELAY BRIDGE is enabled and assumed to be working...

1 - If the pump DOES NOT run when you bridge the relay
Check the 15A Fuel Pump fuse highlighted in the above pic --->[first post - 01relay.jpg]
Check the 4 pin plug (and wiring) that connects to the fuel tank.
Test pin 4 of that plug for a good steady 12 volts - use a test light (should be very bright) or a multimeter for an exact reading.
(There should also be a dim voltage at pin 2 - this is for the fuel gauge)

2 - If there's NOT 12 volts at the fuel tank plug...
Work your way back towards the battery to see where the power is failing
This includes checking that positive relay slot for a steady 12 volts. (See pic below)
...which will help you confirm that your bridge connection is viable.
Also check the 15A Fuel Pump fuse highlighted in the above pic --->[first post - 01relay.jpg]

3 - If you ARE getting 12 volts from the fuel tank plug...
Refit the plug and wriggle all the wires around there, push the plug around in different directions.
(Mine was very dodgy here...I could turn the pump on and off simply by pressing this plug on one side : )
Also try banging the bottom of the tank (gently?) with a rubber mallet...sometimes it's enuff to get the pump going.
If the wiring and plug seem ok...and the pump still won't run...it's most likely your fuel pump is stuffed
...or possibly (less likely?) the wiring/plugs inside the tank. (eg. on the sender arm assembly itself)
ICK!!! Either way...worst outcome...time to crack open that fuel tank...and lose all your fuel : -(
=================

Taking the drivers side back wheel off will afford better access but it's not entirely necessary.

*** SEARCH the forums for 'fuel pump' - there's stacks of threads on it...
...and some good info about changing your pump.
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Cava454

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Nice. I like
 

RUN415

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=================
Reasons for doing this...

Negates the 2 sec prime ---> Fuel pump runs all the time ----> easier diagnosis
Negates the FP Relay ----> which may be causing problems
Negates the Oil Pressure Switch ----> which is part of the circuit and may be causing problems.

Also, pretty much mandatory for testing fuel pump electrical connections...
...makes things heaps easier...especially if you're by yourself.

You can do this to test the fuel pump and/or its output on a car that won't start...
...which is somewhat difficult to do when it only primes for 2 seconds.

Again, I reiterate...
This is a great test...if you're having problems.
It may even get you going if you're stuck somewhere...
...as it overrides the relay and will give a failing fuel pump a darn good kick in the guts!

============
 
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Cava454

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Good for draining tank too ;)
 

aussie4life11

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used this method to drain my vr tank when my vy was low on fuel on an off pay week lol. However i used another method. I have a standard 4 pin relay which i have taken the cover off of. Also good for diagnosis as you can manually close the circuit.
 
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