Fuel pump Earth wires goes where? Wiper motor earth?

[anthonym]

K R500 looking at this https://www.lotus7.club/sites/default/files/images/Docs/Guides/51236ST%20Main%20harness%20stack%20K-series.pdf

if it's the correct one. 

The fuel pump does not earth directly to the chassis anywhere apparent, I gather for good reasons (which I forget or never understood), so when the 12v side of the circuit is replaced, that just leaves the earth side to fail. Strikes me when replacing the engine bay to pump section I could also replace the earth, if I can understand the requirements for this, which having heard comments about "earth switching" may be more complicated that I at first thought. 

The fuel pump seems to have two circuits, one that fires to prime the engine and another to keep the engine going once running. This would explain why on occasions the car will run until stopped, then won't start, but did not fail while the engine was running. If this is not the case, the amount of luck involved in having "broken down" recently three times but only after engine stop becomes a bit hard to believe. Wires direct to the pump are of course one yellow/green (12v) and one black (earth).

If I replace the entire engine loom, then I gather the only component of the engine that is outside the engine loom, is the fuel pump, which circuit integrates in to the chassis/main loom to access the fusebox and the pump itself.

Anthony

[revilla]

The published wiring diagram shows it earthed to a big spliced joint inside the main vehicle loom, where it joins a common earth wire for pretty much everything at the back of the vehicle (lights, fuel pump, fuel gauge sender). This in turn runs up the wiper motor bolt that you mention. This is certainly the case on much later Duractec cars as we discovered when trying to help John Vine track down some earth voltage errors with his fuel gauge sender.

[anthonym]

Great so I have understood thus far. When replacing the 12v feed, also replacing the earth from a good location, maybe the battery itself, should be safe and so separate my fuel pump from all other loom related matters. 

How did you annotate that diagram? Very nice and clear.

 

[revilla]

I just played with Paint.NET. There's an add-in tool called I think Grim Color Reaper, lets you turn all the white to transparent. So I turned the diagram transparent, added another layer underneath and filled it with white, then added another layer between them and draw yellow lines on it  

I honestly wouldn't play with the earth. You would have to further modify the main loom - having seen your photograph I think there's rather a lot on your car which is non-standard ... if I were you I would be aiming to simplify things and get back to a nice clean loom with things as they were originally designed as far as possible. I think by the time you've chopped into the earth and added extra wires you are more likely to introduce issues than you are to fix anything if it's OK at the moment.

BM me if you want to discuss ideas!

[Wrightpayne]

Andrew,

Had an idea for a mini winter project for you - I wonder if someone has an old chassis loom ideally for a K series / injection car they could donate for dissection.

It would be a fantastic resource to have documented the location of joints within the loom etc that the wiring diagrams dont convey.

If no second hand loom available I’m sure we could crowd fund purchase of a new one.

What do you think?

Ian

[revilla]

Haha yes why not! The only thing is the are likely to have changed a bit over the years. What are you thinking of, a K Series era loom?

[revilla]

I have actually found at least one error in the published wiring diagram for the main vehicle loom too. I've updated a copy here. I could maybe publish an updated one as I did for the engine loom.

[Wrightpayne]

I thought a K as we both own one ;-)

Ian

[anthonym]

I asked CC (Damien) for a new chassis loom the other day and was told there are none and won't be; then rj pointed out the engine loom so I have ordered one of the remaining three. edit: NOT to dissect it, but I suppose the old one in due course might become available, but it's not the main loom. I'd love to identify any redundant wiring.

[rj]

There's a lot of redundant wiring in the engine loom.