Fuel Pump relay wiring :(
Turbo Mini Forums

Hey guys,

yes its another wiring question from myself.


My fuel pump relay is as follows (I missed off the inline fuses and inertia switch in this diagram, but dont worry they are there):



I wired it differently to the standard metro turbo relay because I am using the megajolt as the earth switch instead. This works differently to the oil pressure switch in that it is earthed after the engine reaches 500rpm (in my case as thats what I set it to on the map)

I have double checked all connections, put a brand new relay on and double checked the MJ map, the outputs light comes on on the MJ map so I know the MJ is doing its bit.

I get fuel pump working when im running the starter motor but nothing when the engine is running :(

Any Ideas?

do you have a multimeter or voltmeter? check for 12v on teminal 85 & terminal 87 when ignition is on.

also from what you say you are wiring the earth for the coil through the megajolt for >500rpm? are you sure this contact is switching?

Maybe try putting terminal 86 straight to earth and see if it works then.

im assuming this relay doesnt have any indication as to when the coil is energised?

if i understand it right, the fuel pump runs during cranking and the megajolt will ground the relais at 500 rpm to keep the pump running.
what starter do you use? i never had one that reaches 500 rpm at the crank. so my guess is that the MJ simply doesn't pull to ground as the 500 rpm are never reached.
if it works with straight earth as said i would search in this direction

I will try with a straight earth, but the idea of the circuit is that the fuel pump run when the starter motor is running and then that will start the engine making it run higher than 500rpm so then the megajolt grounds the coil connection and thus making a circuit for when the key is on ign and the engien is running

try it and see what happens. with straight earth the pump should start by just turning the ignition on. If it still doesnt start then you need to investigate your ignition supply to the relay coil.

if it does start on ignition then theres gotta be something wrong with earthing via the megajolt. can this rpm setting be adjusted lower? i dont have megjolt (just yet) so dont know

saved this link a while ago form Richards turbo van build may be of use for you...

http://www.johnharperltd.co.uk/wiring/WiringCircuits.xls

The circuit gets its ign live from the same place as the megajolt as ive wired in an aux fusebox

Follow the link to my wiring diagrams above mate and check out the two cranking and normal running circuits. Hopefully they'll help you.

Richard.

Minivanless, but reluctantly happy living with the decision. There'll be another one day.
http://www.youtube.com/profile?user=minimadmotorman#p/u

The circuit shown should work, but there is clearly a problem with what you believe is an ign live.

Either that or the ground you are supplying.

Although that would be confusing if you are relying on a dodgy ign live to turn on the MJ in order to receive a ground.

Wire the ign live from the ign switch so there is no confusion whatsoever, or anything else in between that might affect its operation.

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

fixed it yday, was a blown fuse *facepalm*