Fuel pump relay setup.

[bansheebuzz]

When i purchased my crown majesta cut i was unaware that the system required a fuel pump ecu. After some searching without any luck i decided to work a system to run the pump.

I used a common 12v change over relay.

86 - ignition
85 - oil pressure switch or alternator L terminal
30 - to fuel pump
87 - to ignition switch start terminal
87a - to ignition

How does it work? well when you turn ign on the relay will energise and connect fp to start wire so nothing will happen. The you crank the engine and this will power the fuel pump. The engine will fire and oil pressure(or alt) will then release the relay. This will disconnect the start curcuit from the pump and switch ign power to the pump. If the vehicle stalls, the pump will stop due to lost oil pressure/alt not charging.

 

[Peewee]

Problem with this is that it will take a few seconds of cranking the engine to build up oil pressure, and then a few seconds to build up fuel pressure before she will start.

Personally I'd either get a 2nd hand Fuel Pump ECU (I paid $75 for mine), or spend $275 on a brand new one.

Another option is to use an RPM triggered relay.

 

[bansheebuzz]

95% of toyotas do not trigger fuel pump until crank. With the relay setup i have the fuel pump is powered while cranking so you have fuel pressure before oil pressure. The vehicle starts fine like this and oil pressure builds instantly

an rpm relay will do the same job as what i have acheved with a change over relay

 

[Peewee]

87 - to ignition switch start terminal

Sorry, I missed this line.

The setup you described will work perfectly.

 

[361UZ]

Most cars of the 70's and 80's with carbies and electric fuel pumps used this technique.
Some used oil pressure - which meant if the oil pressure didn't build up enough, there'd be a lag as the pump was switched off from the start circuit, and on again via oil pressure.
Others used the alternator (L terminal so it has a voltage as long as the alternator is turning) eg Holden Gemini's used this, it also powered the electric choke release.
The problem with this one is that if the fan belt breaks, the car stops, which may be an advantage but not very safe if you are in traffic and need to get off the road. In a carby system there may be enough fuel in the float bowl to get you out of trouble, but in a fuel injected system, once the pump stops, that's it!
I'd be going with the oil pressure driven system.

 

[mr2crazybyong]

this sounds like a good alternative when the fuel pump ecu fails.. thanks for sharing bansheebuzz..

 

[gloverman]

Sideshow has a tachometric relay which works very well. We have wired plenty the way you discribed but with the alternators prone to problems funny things can happen. I now use sideshows unit. Cheers