Wiring help

[ianmayco68]

Hi all , finished installing my electric lift pump today took longer than expected as had to make a bracket due to moving the fuel filter as I've got a clutch servo fitted . But as I'm new to this wiring lark tried to fit a switch into the wiring so I can bleed the system with out the engine being on and have knackered my oil pressure switch so a trip to craddocks in the morning is called for , trucks running fine no leaks but fuel pump doesn't kick in as oil switch broke .

So what would be the best way to install sed switch ? Have the relay wired like this 

pin 30 12v from battery 5amp fuse

pin 87 power to pump

pin 85 to oil pressure switch

pin 86 earth 

would I be ok running a second live from the fuse attached to the battery then connect it to the live wire on the pump after the relay as in image below

 

any help much appreciated 

cheers Ian

 

[western]

Instead of coming off the oil pressure switch, take a 12v feed from a ignition controlled wire, there should be a White/orange wire in the loom at the multiplugs, I've used mine to power a relayfor a different job.

[ianmayco68]

Did think about doing it that way , but reading reb78’s post Tsd pointed out that the relay should really be activated via the alternator or oil pressure switch for safety reasons, ie if your in a smash the pump will cut out if the engine stops and won’t empty the tank over the road.

[Bowie69]

In a smash, if there is that much damage the megafuses will likely blow anyways. 

I personally wouldn't bother so much with diesel, petrol would be much more likely to ignite of course, for these you fit an impact sensing switch -in fact if you can get one, I would do it that way. 

So, wire to ignition live and fit this inline: https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.co.uk%2Fulk%2Fitm%2F182986429788

[cackshifter]

Back to your original question, you are basically earthing the relay coil via the oil pressure switch? Assuming you are keeping the oil light, I think you will really need to add a diode in each lead to the oil pressure switch so there can be no feed between circuits on 2 different fuses Doubtless an adult will correct me shortly but I think you need something like....

[cackshifter]

I think too I agree with Ralph better to feed the relay from an ignition switched supply, as sometimes oil pressure switches fail 'on'. That would mean you fuel pump was permanently on, so feed term 86 from the ignition.

[Scotts90]

I'd go for Bowies version with the inertia switch. Mounted on the bulkhead à la factory set up in the td5....also an ad-hoc immobiliser if need be 

[ianmayco68]

Cheers all , will go with Ralph’s suggestion on the feed and Bowie’s on the impact sensing switch , seems a better option that way as ignition feed is more reliable.

thanks for the help Ian

[ianmayco68]

Hi all , wired it up as western said , fitted a new oil pressure switch and all’s working fine  . Just need to order and fit one of them switches suggested by Bowie69 .

cheers Ian