Fuel pump fuse keep blowing..... HELP!!!

[Andrew]

Chaps,

I’m having a few gemlins with my 'bought built' Tornado ’40, the latest is it keeps blowing the 20amp fuse that the fuel pump(s) run off.

It all started the last time I took the car for a spin, I hit a bump (possibly coincidence) the car started to splutter and I eventually ground to a halt, got recovered home, traced the blown fuse and replaced that, the pumps sprung into life, happy days I thought! Alas no, the pumps prime, I turned the key and the engine cranks and then the fuse blows. I ran out of 20 amp fuses so tried a 25amp….the engine cranks and doesn’t fire, the fuse gets super hot so I pulled the fuse and called it quits.

Anyone shed any light on maybe there to start looking? I’m afraid electrics are black magic to me, I’m more a fabricator!

Many thanks! Andrew

 

[Bill Kearley]

Number 1, don't try and overcome the problem with a larger fuse.
A few questions first.
What kind of pump are you using ?
What are the spec requirements for the pump ? Look it up!
Fuel injection, yes or no ? Higher fuel pressure will require more amps
Look for intermittent grounding in the circuit.
In most cases the fuel pump is run of a relay, and an inertia switch.
When looking at this check wire size vs current requirements.

 

[Andy Green]

Hi Andrew,
If I recall correctly, this is John Cohen's old Tornado and is carb-fed and the Tornado supplied loom.

As Bill said find out what the pump should be drawing and what else is on the same fuse. Try putting a temporary separate feed from the battery to the pump via the rated fuse and see if that works and also make sure its got a good earth direct to the chassis. John originally had dash wiring issues as there were earth lines missing

Hope this helps

Regards,
Andy

 

[Andrew]

There's thankfully been some forward progress on this issue resulting in narrowing the problem down to the dash loom. Cue pulling the dash out and roping in a friend who's a very skilled electrical engineer to dissect the entire loom and make good / better / rework / upgrade where he can. He's found a bad earth and a couple shorted wires caused by poor routing & subsequent chaffing.

I'm glad the fault(s) have been found so onwards and upwards! Looking forward to getting the dash back in a week or so