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Lucas fuel pump on my 72 CP


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On Steve Denton's Video where he swaps out the pump for a TRGB kit, he puts a new 20a wire from the battery to a relay in the boot. TRGB's kit has a relay to fit on the inner wing, and suggests using the existing wiring back to the pump.

are both correct or one method preferred?

 

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It doesn't really matter where the relay is situated John, providing the wiring which carries the the pump supply is suitable for the current drawn.  The original wiring should be OK for a Lucas pump but will probably need beefing up for other types. 

It is convenient to use the existing wire for the coil side of a boot-mounted relay and run in a new high -current wire for the pump side.  

 

 

Edited by RobH
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38 minutes ago, johnwill said:

On Steve Denton's Video where he swaps out the pump for a TRGB kit, he puts a new 20a wire from the battery to a relay in the boot. TRGB's kit has a relay to fit on the inner wing, and suggests using the existing wiring back to the pump.

are both correct or one method preferred?

 

That's essentially how I did it (Steve's method), but I put the relay near the fuse box. The relay is there so you can use the normal ignition to switch on the pump via a dedicated wire to take the load of the new pump.

Gareth

Edited by Mk2 Chopper
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On 5/12/2022 at 7:53 PM, RobH said:

Why is that Neil?  It's the only way to do it correctly if the car has an ammeter. 

If there is no ammeter then the alternator and battery are connected together so in that case you have no option anyway. 

Rob

But if the alternator fails then the battery will get you home 

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7 minutes ago, ntc said:

But if the alternator fails then the battery will get you home 

It will do that anyway Neil -  the current will just come the other way through the ammeter from the battery. :rolleyes:

Don't forget the ammeter is really just a piece of thick wire connecting the alternator (or dynamo) to the battery.

 

 

Edited by RobH
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13 minutes ago, RobH said:

 

It will do that anyway Neil -  the current will just come the other way through the ammeter from the battery. :rolleyes:

Don't forget the ammeter is really just a piece of thick wire connecting the alternator (or dynamo) to the battery.

 

 

Agree but with things that can and do fail I will stick with Racetorations setup relay fed from the battery 

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1 hour ago, Kiwifrog said:

I hope that with the direct wiring method that the inertia switch is still part of the circuit !

cheers 

Alan

Hi Alan

My car never had one fitted from new, but I intend to fit one as fitted to later cars within the circuit that triggers the relay. 

Andy

PS Marmite YUK!

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On 5/13/2022 at 5:03 PM, Mk2 Chopper said:

That's essentially how I did it (Steve's method), but I put the relay near the fuse box. The relay is there so you can use the normal ignition to switch on the pump via a dedicated wire to take the load of the new pump.

Gareth

To understand (I'm an ignoramus when it comes to wiring) you connect the fused 20a wire from the battery to the relay, then use a 20a wire from the relay to the pump? This effectively makes the existing white (white/green?) wire redundant?

John

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On 5/16/2022 at 6:27 PM, johnwill said:

To understand (I'm an ignoramus when it comes to wiring) you connect the fused 20a wire from the battery to the relay, then use a 20a wire from the relay to the pump? This effectively makes the existing white (white/green?) wire redundant?

John

Yes that's pretty much it.

Where I mounted my relay near the fuse box I used the connection on the fuse box that goes live when the ignition is on to switch the relay, or if you site relay in the boot you could use the existing wires to switch the relay. The only reason i didn't was if the relay went bad it isn't as easy to get to it.

You might want to add another earth wire from the pump to the body, so that's new too. 

I've now taken my 'battery' power from the alternator so it's the right side of the ammeter - and now the ammeter operates correctly again. 

Gareth

Edited by Mk2 Chopper
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23 minutes ago, johnwill said:

To understand (I'm an ignoramus when it comes to wiring) you connect the fused 20a wire from the battery to the relay, then use a 20a wire from the relay to the pump? This effectively makes the existing white (white/green?) wire redundant?

John

Dont forget the collision switch though.

Stuart

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36 minutes ago, stuart said:

Dont forget the collision switch though.

Stuart

Errr… ok.. 

is that wired too?

(just got the car, and haven’t looked at these items yet)

Edited by johnwill
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6 minutes ago, johnwill said:

Errr… ok.. 

is that wired too?

(just got the car, and haven’t looked at these items yet)

What year is your car? 

Gareth

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2 minutes ago, johnwill said:

1973 CR

John

So you should have the inertia switch that cuts power to the pump as a result of an accident. You must make sure it's still wired into the new set up so it still does its job should the worst happen. 

Gareth

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1 minute ago, Mk2 Chopper said:

So you should have the inertia switch that cuts power to the pump as a result of an accident. You must make sure it's still wired into the new set up so it still does its job should the worst happen. 

Gareth

I must watch Steve Denton's video again. Can't recall if he mentioned that.

Thanks

John

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13 minutes ago, johnwill said:

I must watch Steve Denton's video again. Can't recall if he mentioned that.

Thanks

John

Early cars don't have them, I don't recall what age car he fitted it to. 

Gareth

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2 hours ago, Mk2 Chopper said:

Early cars don't have them, I don't recall what age car he fitted it to. 

Gareth

Regardless they are still an essential fitment.

Stuart

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Hi John,
mine came from Revington, but there are others available, there was a post a couple of years back about it.

Waldi

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On 5/13/2022 at 5:02 PM, RobH said:

It doesn't really matter where the relay is situated John, providing the wiring which carries the the pump supply is suitable for the current drawn.  The original wiring should be OK for a Lucas pump but will probably need beefing up for other types. 

It is convenient to use the existing wire for the coil side of a boot-mounted relay and run in a new high -current wire for the pump side.  

 

 

My TR came with a 17 ACR alternator from new and the pump became very noisy when lights, indicators were on including heater blower, wipers made it even worse, when waiting to turn right or left.. If you blipped the throttle the pump would make less noise. The local Lucas Distributor told me if you change the alternator to a 18 ACR all that problem will go provided you up grade the pump supply wire through a switched relay through the ignition switch. I used 3mm sq. wire , rated at 27.5 amps, to guard against volt drop. Earth wire was also increased in size. I did this mod. 47 years ago and have not regretted it. Pump noise gone indictors do not reduce flash rate when waiting!

Bruce.

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4 hours ago, John Morrison said:

Any recommendations for hwich Inertia switch,

anyone fitted someing other than the original spec, I'm thinking all cars now have them?

John.

Landrover type is favourite. Red one here.

Stuart.

 

IMG_4959 - Copy.JPG

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Perfect timing on this thread as I'm just about to do the very same job having run a Prestige set up on original wiring for the last several years and have been chancing my arm and suffering a noisy pump at times. I'm also thinking of re-siting the assembly into the wheel arch a la the Revington and TRGB set ups but that's for stage 2. 

I like Gareth's idea of running the new pump feed off the back of the alternator so that ammeter stays true and I'll probably sit the relay in the boot so to use the original wiring and keep the inertia switch in play.

Otherwise what do folks to with the original feed wire in the boot? 

In his video Steve Denton just runs a new earth for the pump to a fixing on the tank.

Others on the forum have run a completely new earth wire all the way back to the battery. Any advantage in that?? 

Cheers, Nick 

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47 minutes ago, nickw71 said:

Otherwise what do folks to with the original feed wire in the boot? 

In his video Steve Denton just runs a new earth for the pump to a fixing on the tank.

Others on the forum have run a completely new earth wire all the way back to the battery. Any advantage in that?? 

Cheers, Nick 

If you are siting the new relay in the boot, you may as well use the original feed wire and earth to switch the relay. Then add a new earth wire for the pump along with your new pump feed wire. I chose to earth the pump in the boot, I don't see any advantage to running one back to the battery. 

Gareth

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