Fuel pump relay (relays)

[MYVS5LTRUTE]

Just a quick question please. I not long purchased a VE SSV with a couple of mods.

I'm running two 325 lph in tank pumps. Should they have individual relays? At the moment they both run through one and the main power in wire is getting hot.

Any help would be appreciated..

 

[Trevor loves holden.]

Yip they should have there own separate supply

 

[Skylarking]

Disclaimer, I don’t have a VR but if the wiring is getting hot, it’s overloaded by having two pumps running off it. I’d suspect the previous owner simply put a bigger fuel pump fuse and maybe a higher capacity relay but utilising the existing wiring.

What I’d do is duplicate the fuel pump wiring, including the relay and fuse, from the battery all the way to one of the pumps. The other pump should then be able to run on the original wiring fuse and relay.

To switch on the second pump relay on, I’d use a jumper wire from the original fuel relay control pin to the new fuel relay control pin. If you’ve got space within the fuse/relay box, you may be able to integrate it to look factory.

With such an arrangement, the original wiring will carry 1/2 the current it is currently asked to cope with.

Alternative is to replace the original wiring with heavier gauge wiring, higher current relay and appropriate fuse for the wiring and load.

The whole wiring path should be able to cope with the current demands of what it feeds and the heat of the engine bay. Previous owner stretch it a little too far it seems.

 

[MYVS5LTRUTE]

Yip they should have there own separate supply

Cheers Mate!!

 

[MYVS5LTRUTE]

Disclaimer, I don’t have a VR but if the wiring is getting hot, it’s overloaded by having two pumps running off it. I’d suspect the previous owner simply put a bigger fuel pump fuse and maybe a higher capacity relay but utilising the existing wiring.

What I’d do is duplicate the fuel pump wiring, including the relay and fuse, from the battery all the way to one of the pumps. The other pump should then be able to run on the original wiring fuse and relay.

To switch on the second pump relay on, I’d use a jumper wire from the original fuel relay control pin to the new fuel relay control pin. If you’ve got space within the fuse/relay box, you may be able to integrate it to look factory.

With such an arrangement, the original wiring will carry 1/2 the current it is currently asked to cope with.

Alternative is to replace the original wiring with heavier gauge wiring, higher current relay and appropriate fuse for the wiring and load.

The whole wiring path should be able to cope with the current demands of what it feeds and the heat of the engine bay. Previous owner stretch it a little too far it seems.

The previous owner has replaced the relay and wiring from the standard with a higher capacity wiring but looks like a normal 12v relay? It's got one main power into (the one getting hot) the relay and what appears to be two power wires running out to each pump..

It all looks like it been done to a high standard but maybe the capacity of each pump has been overlooked when installing..

Thinking by separating each pump to its own relay will be a fix.. should be an easy enough job.. I just hate doing wiring jobs.. lol

On a positive I guess if I have one pump fail and they are wired separately I will still be able to drive on one to get me home!!

 

[Skylarking]

If your wiring is like:

+-----+                      +---------fuseb-------pump---earth
! BAT !----fusea----Relay----+
+-----+                      +---------fuseb-------pump---earth

The wire from the batttery to the relay must be able to cope with twice the current that the wires from the relay to the pump can cope with.

Thicker copper wires are able to can carry more current than thinner wires while insulation thickness is more than required primarily for mechanical wear reasons. Also a wire's current capacity is downgraded by some safety factor to handle environmental heat issues and some overcurrent. This gives a base current capability that the specific wire can handle. A circuit is then normally fused at level which is some margin above the needs of the device(s) you're providing power to (pump(s) in this case). The relay should also be rated at the appropriate current needed of the circuits it feeds.

For example, if each pump needs 8A, the wire from the relay to the pump should be fused at 10A. The wires from the relay to the pumps should be rated at more than 10A, probably 15A/. The wire between the battery and relay may should be fused at 20A while that wire should be rather at 30A or more which should be the current rating of the relay. Doing it this way provides some factor of safety above what is needed and the fuses will protect the relay and wiring. Anything less can't be described as professional, just neat looking despite looking neat

I find it simpler to mimic what the vehicel makes have done as its usually robust (just ignore Holen pump connectors melting in this case). As such, i'd simply duplicate the wiring from the battery to the pump itself for your seciond pump using the same wiring size and relay to what currently exists. Something like this:

+-----+
!     !------fuse------->to own pump relay
! BAT !
!     !------fuse------->to own  pump relay 
+-----+

 

[MYVS5LTRUTE]

If your wiring is like:

+-----+                      +---------fuseb-------pump---earth
! BAT !----fusea----Relay----+
+-----+                      +---------fuseb-------pump---earth

The wire from the batttery to the relay must be able to cope with twice the current that the wires from the relay to the pump can cope with.

Thicker copper wires are able to can carry more current than thinner wires while insulation thickness is more than required primarily for mechanical wear reasons. Also a wire's current capacity is downgraded by some safety factor to handle environmental heat issues and some overcurrent. This gives a base current capability that the specific wire can handle. A circuit is then normally fused at level which is some margin above the needs of the device(s) you're providing power to (pump(s) in this case). The relay should also be rated at the appropriate current needed of the circuits it feeds.

For example, if each pump needs 8A, the wire from the relay to the pump should be fused at 10A. The wires from the relay to the pumps should be rated at more than 10A, probably 15A/. The wire between the battery and relay may should be fused at 20A while that wire should be rather at 30A or more which should be the current rating of the relay. Doing it this way provides some factor of safety above what is needed and the fuses will protect the relay and wiring. Anything less can't be described as professional, just neat looking despite looking neat

I find it simpler to mimic what the vehicel makes have done as its usually robust (just ignore Holen pump connectors melting in this case). As such, i'd simply duplicate the wiring from the battery to the pump itself for your seciond pump using the same wiring size and relay to what currently exists. Something like this:

+-----+
!     !------fuse------->to own pump relay
! BAT !
!     !------fuse------->to own  pump relay
+-----+

Could not agree more with everything you have written!!! As it is now it's as the first diagram but would like to change it to be the same as the second diagram !!

The only point it looks to be getting hot is at the relay housing? there is no discoloration or evidence of excess heat anywhere else! in saying that I will still double up on relays!!

The things we do for horsepower.. and thanks for taking the time to write your post !!

 

[Trevor loves holden.]

Could not agree more with everything you have written!!! As it is now it's as the first diagram but would like to change it to be the same as the second diagram !!

The only point it looks to be getting hot is at the relay housing? there is no discoloration or evidence of excess heat anywhere else! in saying that I will still double up on relays!!

The things we do for horsepower.. and thanks for taking the time to write your post !!

That's because it needs to draw more power to operate both so the relay is working harder, you maybe able to get a higher amp relay and test but be careful on how hot the wires get, if any sings of extra heat run a new line on its own relay and remove the piggyback system.

 

[07GTS]

my twin pump setup i got uses a thicker power/earth and a relay for each pump, power and earth are direct from the battery-relay-pump x2 and the relays are triggered by the factory pump power wire so it all works as factory with safety

 

[MYVS5LTRUTE]

my twin pump setup i got uses a thicker power/earth and a relay for each pump, power and earth are direct from the battery-relay-pump x2 and the relays are triggered by the factory pump power wire so it all works as factory with safety

I will change mine to be the same as you have!! heaps better setup.

should be an easy change! just double up with relay's and the power pump wire.. have that on my singe relay set up.

Thanks for the info!