Need help with fuel pump or ECU problem

[90LAN]

yeah if you do that it will be constantly on
but good enough to move it for now

[GenesisEG]

About the fuses or relays, I know not. I'm really not familiar with the wiring of cars. Everything I've said so far is from my electrical knowledge in general.

If the fuel pump is powered by 12V through a relay, then something must control the relay. That would probably be the ECU.

The thing that worries me about running the 12V from the ignition is that I don't know if the pump is supposed to run on a continual 12V supply while the car is on. I'd suppose so, but not knowing how the fuel system works, I can't say for sure.

Electrically, I see no reason why it wouldn't work. If you run the ignition power from the cable that powers your cigarette lighter or something and take it down to the relay, join it on to the load cable (the one that was shorted out)... It should work. Just make sure you turn your ignition to accessory before turning the car on to pre-pressurise the fuel pump before starting the engine.

It might get you out of the poop, but I can't guarantee that it won't cause you any more grief. Sorry I can't be of more help.

If you get it started, drive it straight to an auto electrician that can do a diagnostic on the ECU.

[dancoco808]

i cant seem to find any sign of a main relay / main fuel relay at all...

with my 2jz, our fuel pumps have 2 speed operations and its a common mod for bpu supras to cause the fuel pump to constantly run at full duty. im hoping that constant 12v to the fuel pump on the civic would be okay too... (http://mkiv.com/techarticles/12v_mod/12v_mod.htm)

but anyway, i went down to try and hook the fuel pump up to the ignition 12v, and its now starting to struggle to crank and dying. i can hear the fuel pump prime and engage when the key is set to the 'on' position, which i guess is a good sign the fuel pump may not be dead.

is it possible that the battery is flattening due to all this testing? i assume that the battery is not likely to be the sole problem and that a change would not be the solution though.

1. is it okay to jump the car with the aftermarket ecu?

2. if i jump/change battery, how far would it be safe to drive with the fuel pump running off the ignition switch? (enough to say take it from southport to slacks creek/HPR?)

btw, thanks guys for all the help and suggestions, much appreciated

[90LAN]

test the battery to see if its flat with a multi meter

[grifty]

went down and poked the relay with a multimeter... still nothing but heres some results that may help diagnose.

(btw following is all with car on 2 clicks 'on', not ignition)

old relay has power


old relay, but no power to fuel pump line


new relay has power


new relay but also has no power to fuel pump line


so regardless of relay, there appears to be no power to the fuel pump line

wait if ur getting power to the relay but the relay is not closing the circuit then something is wrong with the relay or the wiring

also 11.8v seems abit low, maybe its too low for the relay to activate?

also which relay pin number are u getting power to?

[dancoco808]

test the battery to see if its flat with a multi meter

12.6v across the terminals

does the pivot volt stabilizer have anything to do with all this?

wait if ur getting power to the relay but the relay is not closing the circuit then something is wrong with the relay or the wiring/
also 11.8v seems abit low, maybe its too low for the relay to activate?
also which relay pin number are u getting power to?

thing is ive changed the relay over to a brand new one. same problem. from memory, 30 seems to be ground, 85 and 86 are other powered sources, and 87 is to fuel pump with 87a in the centre left unattached.

[grifty]

when the key is in no 2 ignition position you should be getting power at 86, if not then ur ecu is not sending the sind signal to turn the fuel pump on

[dancoco808]

when the key is in no 2 ignition position you should be getting power at 86, if not then ur ecu is not sending the sind signal to turn the fuel pump on

I'm pretty sure im getting power at 86, just nothing sent through to fuel pump (87). I'll go check the exact contacts in a sec.

Try another relay? Try another battery?

[dancoco808]

i think there may be 2 problems:

1. wiring is going to the wrong pins of the relay
2. battery is starting to flatten/weaken

on the car at the moment:
30 - solid blue w/ white stripe: 0.0 volts
85 - thin blue w/ red stripe: 9.4 volts
86 - thin green w/ blue stripe: 8.2 volts
87 - to fuel pump: 0.0 volts

according to above results, on the car atm:
30 - ground
85/86 - power/switch
87 - fuel pump.

according to the markings on the relay itself it should be:
30 - power
85 - ground
86 - switch
87 - fuel pump

so... are the pins going to the relay wrong? anyone know what the colours of constant power and switch are?

clearly my voltages are dropping also. which also might be the reason why it hasn't started even when i ran ignition power directly to the fuel pump.

i will go get a new battery and place the wires in the correct position on the relay, hopefully this works ><

[dancoco808]

okay, have new battery in and wired the fuel pump directly to ignition wire. car starts and works fine, maybe smelling a bit extra fuelly (although it doesn't have a cat). ultimately i'd like to get the relay harness up and running though. but its good to hear the car running again, and great that i can move it out of the basement carpark.

so here's what i've worked with regards to the relay:

when i had the following on the relay:
85 - ground
30 & 86 - power/switch (unsure which is which)
87 - fuel pump

car would start, idle for about 5 seconds, then turn off. after the first start, the car would no longer start again, unless i unplugged the battery then it would start once again for a few seconds before being unable to start again. i was unsure about which wire was power and switch, so reversed them with the same result.

i then tried running brand new wires (not from the ecu), directly from battery to 30, ground to 85, ignition switch directly to 86 and from 87 to the fuel pump. the same result occurred as above.

it's got me stumped, cannot figure out why the relay circuit will power the fuel pump or keep it going.

im considering making the 60km drive with constant 12v to fuel pump to take the car to the guys who did the engine swap (HPR). anyone reckon it will be okay to do this?

[GenesisEG]

So many things to reply to, so I won't reply to them all.

First, to attend to your immediate problem.

Make sure it is a 12VDC coil. If it's not, don't even think about trying to run the relay with 12V or you'll fry it. There's a chance it might be lower, if it's being controlled by the ECU. It should say the coil rating on it.

If it is 12VDC, take it to the battery, lets test it.

Connect your ground pin to ground using any wire.

Since I can't tell for sure which pin is for the coil and which is for the pump, I'll need you to do a quick test for me.

Put one probe of your multimeter on the ground, and set the multimeter to resistance.

Then put the other probe on pin 30 and then 86.

One should have a completely open circuit, the other should show the resistance of the coil. I'll assume that 30 will be open circuit and 86 will be the positive of the coil, but I need you to test to make sure before I tell you to blow up your relay...

Let me know how that goes.

I just want to eliminate one problem at a time. Once we can confirm that the relay is working fine, we can worry about everything else.

[grifty]

ok here is how u should have it wired up

30 is power going to the replay

86 is the wire from the ecu

85 is negative

87 is the wire going to the fuel pump


if you were getting power at 86 and the relay wasnt turning on that means you werent getting power to 30, id either run a new wire or try to find the fault in the existing wire.

edit: i just read the above (stupid me)

can you just check if contacts 30, 86 and 87 are getting power when you are turning the ignition on?