On a V8 110 I am going to put a switch in the feed to the fuel pump so that I can switch it off when running on LPG. I'm a great believer in keeping things simple. I'm not bothered about having it switch off and on "automatically" when I change fuels.
Can I simply wire in an in line switch or do I need to go to the hassle of putting a relay in?
Thanks.
Gerald
Idris uttered summat worrerz funny about:
Depends on the switch but a half decent switch should be fine.
Lee D
The only times you really want a relay is if you are switching high current, switching lots of cables around, or having the switching done by electronic as well as manual control. So in your case, you'd gain nothing with a relay so a straight switch will do. As long as it's only breaking the current electrical feed so you can't turn off the ignition and find the fuel pump still running ;-)
Thanks for the replies, that confirms what I thought but its reassuring when others agree.
Gerald
hasnt your lpg changeover switch got a feed built in for controlling the fuel pump? mine has and i use that to switch a relay which turns the petrol pump on when it is supposed to be.
adding a relay isnt especially complicated!
No the switch doesn't have. I know how to install a relay I just don't want to go the expense and the time unless I have to and with a lot of off roading its just another thing to get wet or fail.
Gerald
I had the problem with my RRC that when it was running on LPG with the fuel pump off, the carbs had so much vacuum ,that still some petrol got into the carbs, spoiling the LPG mixture. So an electrical cut-off valve in the fuel line to the carbs solved the problem. You can check it when running on LPG, disconnect the pipe to the LH carb, when there's petrol it will show immediately on the connection. Btw I've a relay mounted in the electrical feed to the fuel pump, it's mounted high under the bonnet, no probs at all.
Kees
On or around Fri, 1 Jun 2007 13:49:21 +0200, "k.w" enlightened us thusly:
On carb systems the correct approach is to kill the petrol supply (off the pump and/or a solenoid valve), run 'til the carbs get empty and only then turn the gas on.
On an injection system you want relays to interrupt the injector signals. Turning off the fuel pump is an optional extra.
Be aware that if you turn off the fuel pump on either system, especially with a manual switch, you've got a noticeable time lag before you can get it back onto petrol. One day that will jump up and bite you - LPG will be running low, you'll be in mid-overtake with your toe down and it'll not pull and you'll not be able to switch back to petrol in a hurry.
On injection engines in particular, leaving the pump running but cutting the injectors gives you more or less instant switch back to petrol. Cutting the pump means you have to wait for the pump to build pressure in the injection system.
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