Discussion in 'Fuel System & Electrics' started by peter drogi, Oct 9, 2017.
SO why was the 'pump rattling'?
Ignition on somehow. Key was in off position in the ignition switch. Yet all lights on in the dash. Power was getting to coil. In turn power to fuel shut off and electric pump.
Thought fuel pump relay turned pump off unless engine is running? If I turn on ignition pump runs for a few seconds then stops unless I start the engine.
Those were the days
'Were'? still are, I drive a T3 lol
Where did you get your cut off solenoid from? I think I need to install one.
Bought it off flea bay.
Yes get a fuel cut off solenoid.and a tachometric relay to get it to open and let petrol flow when starting and shut fuel off when turning car off.
See post #23 above for Just Kampers link for relay.
I'm going to be cheeky.
I thought that's what the key did! If you have no key bypass! Okay if I'm unconscious & can't turn the key off solenoid & tachometric relay has no merit but at that point I actually don't care.
I take it that this relay/solenoid only works when you use the key? That I can't whilst unconscious.
But I'm okay if you want another level of security.
Just think it's another thing to go wrong.
Had 2 Kombi fires. None were related to this stuff.
And if you are unconscious, sleeping in the back, after a decent night out, and too inebriated to drive.......believing you are doing the right thing:
Ensure your keys are NOT in the ignition when the local ranger or police arrive to make “enquiries”.
Otherwise, you may find yourself deemed to be driving, even though you were far from the drivers seat.
Always taught my kids it was about where the keys were & their availability to you not where you were.
If you have a bingle and the engine stops one thing extra you don't need is fuel pumping everywhere! Tachommetric relay stops the pump when the ignition is on but engine not running. Cheap insurance..
I'm no brain surgeon so could you help me understand how that happens. What controls the tachometric relay? How do I get my engine to go initially with ignition on & engine not running if the fuel pump is stopped?
Electrical is my weakest field!
Relay is controlled by voltage. It understands three voltage levels:
0v, or ignition off
12v, or battery
14v, or alternator output with engine running.
These numbers are rounded off for simplicity. In its simplest form, it understands 13v. If above this it runs power to fuel pump. If below, it cuts power to fuel pump. So when disaster strikes and engine turns off, alternator stops spinning so voltage drops from 14 to 12. Relays then cuts power to fuel pump.
To start up, relay is set up (programmed) to operate for a set time, ie 5sec when power state changes from 0 to 12v. Enough to start and when alternator kicks in 14v, relay powers fuel pump.
Ahh........ Thanks Tangles.
Same for F/I?
I was struggling with exactly that concept.
Might buy one. Going to need another to wire it in tho'!
Can sleep now!
Tachometric relays rely an ignition pulses to remain turned on. if the engine stops (no pulse) the relay drops out.
One of the leads goes to the negative side of the ignition coil
Some vehicles have alternators with an extra terminal for tacho pulses which can also be used.
There are also 3 terminal oil pressure switches and latching relays that can be configured to drop out when oil pressure drops.
All FI that come standard in vehicles have devices that cut fuel pumps when the engine stops and in some cases if the vehicle tilts more than a certain angle (roll over)
If you install an electric fuel pump to feed carbies then it would be a disaster waiting to happen without a tachometric relay.
This is a good safety switch. Designed for LPG lock off and perfect for fuel
Has more than enough current capacity for pump and fuel solenoid
I think the fuel solenoid is a must as the tank and outlet is high in a bus. If the needle and seat in your carb/s start leaking you can imagine the result over night.
Well explained above. Comes with simple instructions to install. Clever little device.
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