Tracing an electrical problem
Discussion
I have been trying in vain to fix an issue with my race car and before I give up, I wanted to see whether anybody smarter than me had some good suggestions.
The car has a fuel sample valve that can be manually operated in order to drain the tank (which is useful seeing as the fuel gauge is next to useless). In my car, somebody has wired the redundant horn switch into the fuel pump circuit to enable this (from the factory - it's a Ginetta - you can get an additional switch that plugs into a connector in the engine bay).
Last time I used it it suddenly stopped working, almost as if a fuse had gone. I've checked the fuses and the relays and all are good. I'm now left looking for a short or maybe a duff ground.
The issue is, I have no f**king idea how the previous owners have wired this manual fuel pump switch. I assumed that they had simply used the horn circuitry to bypass the fuel pump relay behind the dash but there is no sign of any meddling here. I must therefore conclude that they had done the bypass somewhere further down.
The engine bay is a rats nests of wires and redundant connectors so I have no way of knowing what is supposed to go where.
How can I trace this fault? Where could I try looking (have they done something clever that I'm not seeing)? How on earth can I fix this (could I for example, just bypass the fuel pump relay and forget about whatever they have done)?
Any help/thoughts/ideas/moral support greatly appreciated.
The car has a fuel sample valve that can be manually operated in order to drain the tank (which is useful seeing as the fuel gauge is next to useless). In my car, somebody has wired the redundant horn switch into the fuel pump circuit to enable this (from the factory - it's a Ginetta - you can get an additional switch that plugs into a connector in the engine bay).
Last time I used it it suddenly stopped working, almost as if a fuse had gone. I've checked the fuses and the relays and all are good. I'm now left looking for a short or maybe a duff ground.
The issue is, I have no f**king idea how the previous owners have wired this manual fuel pump switch. I assumed that they had simply used the horn circuitry to bypass the fuel pump relay behind the dash but there is no sign of any meddling here. I must therefore conclude that they had done the bypass somewhere further down.
The engine bay is a rats nests of wires and redundant connectors so I have no way of knowing what is supposed to go where.
How can I trace this fault? Where could I try looking (have they done something clever that I'm not seeing)? How on earth can I fix this (could I for example, just bypass the fuel pump relay and forget about whatever they have done)?
Any help/thoughts/ideas/moral support greatly appreciated.
Edited by LennyM1984 on Tuesday 8th July 21:20
I'd start by checking if the switch still actually works as a switch.
My personal approach to checking "continuity" is to get a fine sewing pin and connect it to your voltmeter. You can then make your way along the wire, poking the pin through the insulation to contact the metal inside and see if there's any life. With a bit of luck the pin holes are so small you don't need to fret about them afterwards when, hopefully, you've found the break in the circuit.
My personal approach to checking "continuity" is to get a fine sewing pin and connect it to your voltmeter. You can then make your way along the wire, poking the pin through the insulation to contact the metal inside and see if there's any life. With a bit of luck the pin holes are so small you don't need to fret about them afterwards when, hopefully, you've found the break in the circuit.
My theory on these things is that it's generally easier and less stress to just make a new circuit than try to figure out what bodge was done before, I always end up ripping the bodge out anyway and doing it properly.
Just disconnect the circuit and make a new one, you could have done it by now
Just disconnect the circuit and make a new one, you could have done it by now
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