Main relay function

[PROBLEMATIC]

What if I run my car without the main relay? I wanna know the m/r function or purpose, because my car have few cables jumped where the m/r is supose to be and the fuel pump activates with a switch. Is this dangerous? Please help. Thanks.

[visualpoet]

It sounds like you have a basic manually activated relay that someone has built in to replace a faulty main relay. It's not dangerous; if it's working and you're not having problems, I'd leave it alone unless you really want to repair it.

[PROBLEMATIC]

The question is because I heard that the proper function of the fuel system needs the m/r to stop the fuel pump (or gas flow) when the system is full of gas and starts again when it need the fuel, All that while the engine is runing. With the switch the pump keeps working unless you turn the switch off, and I turn it off when I stop the engine. On google, a page says that the ECU needs the m/r too. Is all this correct?

[ravenexi]

I cant say on the the ecu part, But I can say this. when you first turn the key on the relay will cut power to the fuel pump after a couple seconds. this is to prevent fuel loading in a cylinder if you have a leaking injector. Once the car is running the fuel pump stays engaged full time. excess fuel pressure is sent back to the tank by the fuel pressure regulator. Only non return style systems turn the pump off and on to maintain proper fuel pressure.

[PROBLEMATIC]

I cant say on the the ecu part, But I can say this. when you first turn the key on the relay will cut power to the fuel pump after a couple seconds. this is to prevent fuel loading in a cylinder if you have a leaking injector. Once the car is running the fuel pump stays engaged full time. excess fuel pressure is sent back to the tank by the fuel pressure regulator. Only non return style systems turn the pump off and on to maintain proper fuel pressure.

Thanks. I heard something like that.
Sometimes, when I push the gas pedal all the way down repently, my car sounds like choke, like with fuel excess. And if I turn off the switch with the engine running, increases the rpm 2 or 3 secs before the engine stops.

[F22BPR]

I have the same situation and need help soon!!!

My car doesn't have the main relay, just a few wires connected. The wire that goes to the ECU is gone, there are just the ground, the ignition, the power and the one that goes to the fuel pump connector. No need the switch, because it turns on with the ignition. Now, my car spends too much gasoline. I don't know if it's because the main relay deleting or another cause. There are a brand new fuel filter, newq fuel regulator, the car is almost stock (just a 2.25 pipe and resonator, a SRI.), there's no fuel leaks, I've applied seafoam to it to clean the system, I've tried to don't push the pedal viciously, etc.

I have a f22b1 on a 90 accord. Do you thing that my car must have the main relay to economize fuel or it's the same without it?

[deevergote]

The relay basically just activates the fuel pump. I don't believe it does very much while the car is running (though I may be wrong.)

[F22BPR]

The relay basically just activates the fuel pump. I don't believe it does very much while the car is running (though I may be wrong.)

So, I've asked myself: why is a main relay there and not some wires connected? something like my car does....

I don't have idea why is spending a half tank in 2 days? I'm just about 30 min of my job and I travel @ 4am. There's no traffic at that time, maybe when I return to my house...

[flatrex]

This link should give you some insight on what the main relay does

http://techauto.awardspace.com/mainrelaydetails.html

[deevergote]

So, I've asked myself: why is a main relay there and not some wires connected? something like my car does....

I don't have idea why is spending a half tank in 2 days? I'm just about 30 min of my job and I travel @ 4am. There's no traffic at that time, maybe when I return to my house...

Your fuel consumption issue is most certainly not related to the main relay. Please stop mentioning it in every post. That's not what we're discussing in this thread.

The main relay is what would shut the fuel pump off in the event of a crash, or if you ran out of fuel (rather than letting it run dry and burn itself out.)
Apparently it also has another relay for the injectors, according to flatrex's link... which makes a lot of sense (but is news to me.)

Hook the fuel pump up to wires, or up to a switch, and your pump won't shut off if you crash. You'll run a much greater risk of fire.

[F22BPR]

Your fuel consumption issue is most certainly not related to the main relay. Please stop mentioning it in every post. That's not what we're discussing in this thread.

Nice. but I've just post 2 times about the m/r, don't try me like if I've post like 5 or 6... I appreciate your responses and respect your posts but I want the same threat for mines even if there are not too smart ones. Thanks Deevergote.

I've to ask it on this thread because it's refer to the main relay and my question is about it. I don't wanna make another thread about m/r.

[F22BPR]

This link should give you some insight on what the main relay does

http://techauto.awardspace.com/mainrelaydetails.html

Good info... Thanks.