You fix one thing, something else breaks!

Hi all, got a weird issue that’s developed after I fitted the Seaflo fan but they may well be unrelated.

I’d previously fitted an electric fuel pump with on/off switch and momentary action prime switch, using SpeedyJim’s instructions. This had been working fine.

So, when I switch the ignition on the oil light comes on but no battery charge light. The on/off fuel pump has a light on it, that now lights even in the off position even though the pump isn’t working. Switch it on and the pump works straight away, which it shouldn’t do, hence the prime switch.

Engine starts and runs ok.

Then the plot thickens, if the revs drop very low or when switched off, the battery light comes on as the engine dies, then off again when it stops.

I can only think I’ve disturbed something while working on the fuse box or near it but can’t find anything disconnected etc.

Any ideas?

 

Wiring diagram for the fuel pump relay, which has a connection to the battery charge light.

 

sounds like the relay coil is dropping out, probably best to check battery voltage, charging etc.

 

Just what I’m doing now!
On the 200 ohm scale, there’s no continuity between the blue wire to the battery charge light.
With ignition on, there’s between 6 and 7 volts.

Could a faulty relay give these symptoms, even though it appears to work and switch the pump on and off?

 

is that wiring diagram correct?
if you follow the 12 volt into terminal 30, and this is drawn with power off, it then goes through the other terminal ( cant make out the number then to the positive of the pump effectively bypassing the relay?

 

whats the voltage at terminal 30

 

Ignition off, meter’s showing 0 volts

Ignition on, 5.9volts ???

 

check battery voltage next at the battery

 

Battery positive to earth strap 12.3v

 

Also checked between the new fan earth (cable off) and earth, 11.2 v Is that correct? The new fan is totally disconnected now so shouldn’t affect things, unless it’s destroyed something?

 

you have a high resistance, check all joints are tight, crimps secure etc, self tappers tight etc.

 

I see what you mean about the diagram. The idea is that if the engine stops in a crash, the pump stops working.
It doesn’t pump unless the switch is on though.

 

Will do, anywhere to start especially?
Thanks for your help by the way!

 

11.2 volts depends on the cable cross sectional area and length for volt drop

https://www.12voltplanet.co.uk/cable-sizing-selection.html

maybe add colours to the schematic as you reffered to a blue wire?

 

process of elimination, just follow all the wires work in a logical manner, maybe highlight he schematic as you go as an aide memoire

 

The blue wire is the original loom wire to the battery charge light.

 

Will do, it’s a while ago I fitted the pump. Cheers

 

5.9 volts on terminal 30 says a fuse has fallen out in the pump feed circuit.

Should be 12 volts there.

 

Ive had to dash out but will check once I’m back. Many thanks

 

Not really sure what that's trying to do there, if you've wired it as per your diagram. As shown, the fuel pump will be powered as soon as you turn the ignition on, then the pump will stop as soon as the engine fires up .

Mr Speedy Jim's diagram shows it wired correctly (although I'm not too keen on driving the relay off the alt light).