How easy would it be to fit a fuel cut off switch that can operated from the cab? I am thinking for safety and security.
It depends on what you would consider difficult. If you can cut a fuel line, install a valve and do a bit or wiring it’s easy.
Why make it so complicated ?? I`d use the fuel solenoid on the carb. Cut into the live feed FROM the coil , run some twin-core up to a hidden switch in the cab and return run to the solenoid to cut the fuel supply. Another route would be to cut the live feed TO the coil and isolate it with a switch in the cab thereby cutting the leccy supply to the coil. Either way it`s pretty straightforward .
Shutting the solenoid on the carb will not stop the petrol flowing out of the tank should you have a leak or worse. Wire the cut off solenoid into the oil light switch circuit so it only opens once the engine is running and will shut as soon as the engine stops for whatever reason. There will be plenty of fuel in the bowl to start but you will need a bypass switch in case you forget to turn it on and run out of fuel!
are you wanting to do this for safety reasons or as a security measure? A proper fuel cut off solenoid will set you back around £40+......this would be installed immediately after the tank outlet. This could either be wired (via a relay) from the ignition switch, or on a separate switch (only live when the ignition is on) Another option is to use the +ve from the oil pressure switch so the fuel supply cuts when oil pressure drops.....the issue here is there is no facility to prime the carb (s) when cranking over the engine to start....so as @mollysdad suggested a by pass or momentary push switch would be good/required if you're running an eleccy pump.... I have a manual shut off valve just after the tank outlet.....it's a bit more of a ball ache to turn on and off, but then it's not really for security....I use it for changing lines/filters etc. I can easily lean under the bus and turn shut the fuel off as an anti theft if necessary. I'm running an eleccy pump and have used a three pin oil pressure switch from a US campmobile (1979 -1980 Vanagon)....details why here it would be an easy job to break into the +ve supply and fit a dash switch....
[QUOTE That will work if there is a fuel solenoid on the carb.[/QUOTE] Agreed - mine is a 1600 on a standard solex so not a problem .. Like the Vanorak idea of a manual jobbie though - saves having to clamp the pipe when there`s work to do .
Best to put a cutoff valve right after the tank, powered by the ignition supply. This'll stop gravity-fed fuel gushing into the engine compartment in a conflagration, which is what you're trying to avoid. The valve on the carb shuts off the idle circuit - it doesn't cut off the fuel supply from the tank. Any wiring you do put in needs to be robust - you don't want the fuel drying up when you're overtaking an artic on the motorway
Really ?? You learn something every day - alus thought it cut the supply totally , i stand corrected .... (yet again !!)
That’s why I made mine so complicated. I have Weber carbs (so no fuel cut-off) and an electric pump wired through a fuel injection relay triggered by ignition pulses but it also provides power for a few seconds as soon as the ignition is switched on to prime the carbs. The fuel cut-off valve is just after the tank outlet, before the filter and pump and is supplied from the fuel pump relay through a remote central locking/alarm/immobiliser. The ignition circuit and starter motor have relays to minimise voltage drop and reduce the load on the ignition switch to just the power required to close the relays. The ignition, starter and fuel pump relays are mounted in the engine bay on the bulkhead next to the alternator regulator. Simple.
I have a solenoid valve between the tank and the engine bay on the chassis rail, simply switched with the ignition. It has been responsible for about 10 fail-to-start scenarios. Dirt from the fuel tank has jammed the plunger on several occasions. A dodgy pre-crimped fuse holder from Halfords in series with the solenoid valve has caused or been involved in all the rest of the occasions. Putting it downstream from a metal bodied filter and replacing the fuseholder with a soldered-on version has stopped this happening.
