Thread: Replacing mechanical fuel pump with electric on 2.25 petrol engine

Originally Posted by Timj

Here is a link to one of the LPG safety switches, more expensive than I though they were, but this is exactly what I had for the electric pump and the 2.25 with a Zenith carbie.

https://www.ebay.com.au/i/1529531814...EaAndDEALw_wcB

Thanks Tim, much appreciated. I suppose the other thing I could try is power the electric pump from the "start" position of the ignition switch ??

Cheers,
John

Well yes, but the problem is that if you stall the engine, if you have an accident etc the ignition is still switched on so you still have a pump running and pushing petrol through the lines. You have to stop the fuel pump when the engine stops, not when the ignition is turned off. This is usually done through one of these switches or through one that runs off oil pressure, either one will work fine and you just use it as part of the trigger for the fuel pump relay. That's where those Tachymetric ones are interesting because they combine the switch and relay which may ultimately be cheaper than buying the two items seperately. The discos have an inertia switch which does a similar job but will only stop things if you hit something.

Cheers,

TimJ.

Actually just reread your post and definitely not from the start position, that should only be selected when you have the starter motor going so you definitely don't want the fuel pump off that.

fit a T and secon oil presure switch (or just rely on the one to do both jobs.

set up a self latching relay cofiguration that requires

1. oil pressure to be low (engine not running
2. ignition to be on
3. a button to be pressed to start the fuel pump

turn on the ignition, push the button and the relay flips and latches running the pump until you crank the engine and the oil pressure comes up breaking the earth and stopping the pump.

in rough ascii


oil pressure switch ------ Relay coil ------T---Fuel pump
......................Normally open contact...+ Push button switch--|
Ignition source-Common contact........................................... |
......................Normally closed contact.--------------------------|

Originally Posted by Timj

Actually just reread your post and definitely not from the start position, that should only be selected when you have the starter motor going so you definitely don't want the fuel pump off that.

Why not ? as the mechanical one will take over once engine is going - true ?

Cheers,
John

Here's another fuel cut out relay that might do the job : Fuel pump wiring kit 12V 40Amp TYCO relay with wired base | eBay

Cheers,
John

G'day All,
Attached 2 JPEG files regarding the Holley single pole,double throw safety switch wiring, running from the engine oil pressure line.
Very simple and does the functions talked about in the thread.
This safety switch has a 1/8 NPT thread. You may have to make an adapter to fit the 1/8 BSP threads used on early LandRovers.

Chris

Originally Posted by JohnboyLandy

Why not ? as the mechanical one will take over once engine is going - true ?

Cheers,
John

That's right, but you said you were replacing the mechanical one, not giving it additional boost just while the starter was running .

I changed my mind Tim, I'll set up the mechanical and electric pumps in parallel :-)

So given that, do you see any issue running the fuel pump off the "start" line from the ignition switch to started solenoid ?

Thanks
John