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Cubes

By Cubes,
in General Automotive Discussion

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Cubes Grand Master

Cubes

Posted
Posted (edited)

Hi ppls,

A little while ago I ran a direct volt feed to my fuel pump.

I used a Jaycar 60amp relay.

My usual routine is to turn the key to the on positon, wait for the fuel pump to raise fuel pressure then auto turn off, I then start the car.

Occasionally the fuel pump stays on and keeps priming and priming and priming. :O

The only way to stop it is to pull the earth from the relay.

Is it possible the relay is some how getting stuck?

I run the std fuel pump volt feed through the relay then straight to the chassis as its earth.

Could this be the problem? Kind of like connecting a negative and positive without anything inbetween using some power?!? big sparks and not good. :O

I'm not that electrically minded so I really am not sure where to start looking?!?

Edited by Cubes
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MANWHOR3 Proficient

MANWHOR3

Posted
Posted

Cubes, if you have a look inside a relay, it's a very simple device. It's unlikely that it will get stuck open. Relays do not need much power at all to trigger. Your ecu might still be supplying a small amount of power after priming is finished.

My advice would be to change the relay anyway, in the rare case that it is faulty. They're cheap anyway.

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Cubes Grand Master

Cubes

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Posted (edited)

Space Ghost...

Great idea.. I'll give that a shot.. lol So simple.. :O

Next time it does it, I'll jump out with my trusty multimeter and measure the volts running from the ecu.

If it is small amounts as the MANWHORE has suggested then its resistor time.

If not, new relay. :O

Edited by Cubes
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Cubes Grand Master

Cubes

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Posted (edited)

90% of the time the relay works as its should.

Only occasionally it locks on, unsure if thats still possible with a fused relay?

I also observed the relay tends to leak voltage.. The constant feed from the battery see's 0.02v, even with the trigger feeds disconnected.

Edited by Cubes
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Abo Bob Grand Master

Abo Bob

Posted
Posted

I've seen them stick on and I've seem them fuse together but the latter is permanent.

It might just be the ECU though. Mine does a similar thing and it is wired in the stock manner. I didn't notice that it stayed on sometimes until I put a GTR fuel pump in because I couldn't hear it before but now I can.

When I say similar... without the engine on it only primes for about 2-3 seconds but it's when it's started that it can go on and on or not depending on it's mood.

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paulr33 Grand Master

paulr33

Posted
Posted

i too have since similar results since putting a bnr33 pump in my gtst + powerfc. normally when it first starts the pump runs flat out even at idle, sometimes the only way to make it stop is to tap the accel pedal and the revs jump a tiny bit then back down again and the pump goes off

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Cubes Grand Master

Cubes

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Posted (edited)

Interestering...

Since I fitted the AP PowerFC the fuel pump constantly runs on high, prior it would run on low at idle then once you touch the accelerator it would run on high.

All though prior to the wiring mod I never had it get stuck on while priming.. Only since after the wiring mod.

Which makes me suspect the relay, or a small amount of voltage still passing that is activating the relay.

The wiring mod was definitely worth wile.. Its much louder as it sounds like its spinning so much harder, it also no longer vibrates the floor pan causing it to be noisy in the car. Now you can only hear the buzz/surge/bubble or what ever type sound it is from the outside once the fuel gets really warm on a hot day with little airflow movement.

Edited by Cubes
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RB30-POWER Mentor

RB30-POWER

Posted
Posted

It should be setup something like this.

85 (-12V GND from ECU fuel pump terminal)

86 (+12V IGN switched)

87 (+12V to the fuel pump terminal)

30 (+12V supply from battery with fuse/fusable link)

So what will happen is, when the ecu switches the pump on (nissan usually ground relay for pump) it switches the low current coil in the relay, allowing high current from battery from pin 30 on the relay through to terminal pin 87 into the pump.

when the ecu turns the pump off (opens pin 85) the relay will open and stop pumping fuel.

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SKYBEE Collaborator

SKYBEE

Posted
Posted

you need to get a diode protected relay or install a diode in the earth wire on the relay that will stop the relay from engaging they require milli amps to engage thats the beauty of a relay little current to trigger put a relay on it and woohoo your fixed unless your relay is shgged in the contacts catchya !

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Cubes Grand Master

Cubes

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Posted
I hope you sort out your electrical gremlins ASAP.

The idea of the pump time out is in case of accident, you don't want fuel pumping everywhere even though the engine may have stopped.

If you've had an engine fire fed on 50psi fuel, you'd have the fear believe me.

Regards.

Indeed, the thought is scary. :P

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BHDave Grand Master

BHDave

Posted
Posted (edited)

60amp is a big relay for a fuel pump. The 044's only pull about 15-20amps max.I'm running a 40amp on mine as i had one lying around.

I've noticed that the bigger amp fuses (EDIT Should have said relay here but i had fuses on the brain) have a diode built in (typically 30amp up) as mentioned by SKYBEE.

Something else worth considering is the way the relay is mounted. A 60amp relay has a (relatively) heavy set of contacts. If it isn't mounted upright they can stick easily due to gravity.

I've seen this problem with the factory relays located next to the ecu in the footwell as they were mounted upside down. Turned them 90 degrees and the problem went away.

Edited by BHDave
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SKYBEE Collaborator

SKYBEE

Posted
Posted

relays are sprung so any way they go doesnt matter when not in use tehy wont fall down unless spring has sprung its last spring :D cheaper relays cheaper springs cant beat the bosch 150 relay so many uses so versitile even has a lug so you can screw it down

thast my experianc

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