Technical Electric fuel pump high current feed - where?

[RDS]

I am thinking of fitting a relay to control the high current feed for an electric fuel pump to replace the mechanical pump.

The idea is that the (inline fuse protected) "high current" spur feed will go to terminal 30 and the switched supply will go from terminal 87 to the pump and thence to ground.

Can anyone suggest what existing continuously live high current feeds in the engine bay are a good candidate to attach to the spur? I do not want to use the ignition switch to coil feed.

The pump is rated at 2Amp.

cheers

RDS

 

[chris3234]

Why not take the power fees direct form the battery?
And have the relay trigger feed from whatever ignition switched fees you can find?

 

[RDS]

Hi Chris

thanks for the swift reply. I am trying to avoid running the length of the car thorough the cab and out of the rear firewall - it will look untidy at the least and with the battery +ve terminal already hosting the Brown Wire Mod, the two sets of headlamp relay feeds and another item, it is getting pretty crowded there..

The source of a low current activation is not a problem in the engine bay though.

cheers

 

[Scotty1956]

Hi, for my electric pump I got +12v from the alternator big wire and used a 30amp midi fuse (because I rewired the alternator when I had a 65amp one fitted).

Aware that can be a lot of work so, you could use the power feed to the carb fan feed (which I was led to believe was not required with elect fuel pump and tidied up the engine bay).
It doesn't matter that the cooling fan +12v is battery fed power as the relay coil is ignition fed. The relay could be located in the spare tyre well, nice & dry.

The relay coil + is fed from the ignition +ve wire to the Ignition coil and the relay coil -ve is grounded via an inertia switch. The Inertia switch is for safety - a serious bump and the fuel stops flowing, useful in a crash! Can also be an added antitheft device.
I got mine from a scrapyard Ford Fiesta for £2. Almost every car has one, I just knew where the Fiesta switch was located.

Its a super mod as you can hear the pump and confirm petrol is being pumped but no way will you hear that once that engine runs!

 

[RDS]

Hello Scotty

many thanks to you too: I was interested particularly in the Alternator wire as the feed and will look more closely at that.

My reason for preferring the alternator over the carb fan relay is that I have already "jumped" that relay with a manual switch so I can activate the carb fan at will: it has proven very useful in London traffic in the summer heat.

I hear the fuel pump all the time because of the recirculation pipe for the fuel keeping the pump active, even if I "choke it down" a little. I do not mind the noise because it is reassuring to know that the fuel is getting to (or at least near to) the carb.

I fitted a generic inertia fuel cut off but it was so sensitive that pot holes activated it - where did you locate yours? Mine was on the firewall. I may have another look at one but it is one more thing to go wrong and most British sports cars I have driven over the years have had SU pumps without the inertia switch.

Cheers

RDS

 

[Scotty1956]

Inertia switch is bolted to the inside of the left hand compartment - where the fuel filler is.
It is also close to the fuel pump, I made an alloy bracket, secured onto the now disused fan mounting holes. Never had the inertia switch trip - yet.
I would fit an in-line 15amp if you are taking power from the alternator/starter cable.

 

[RDS]

thanks Scotty I can see that location makes sense if you have dispensed with the carb fan.

Good tip re the fuse: many forget to fuse new accessories.

I will monitor and see how I get along; having lost fuel delivery (see other posts) in some very difficult places, I am rather reluctant to fit the switch on this one on the basis of how the switch I purchased performed.

cheers

RDS