EFI Fuse intermitent blow

[EvilJack]

Just over the past couple of days the EFI fuse has been blowing, i was hopeing it was a once off but its blown quite a few times now.

I havent done any wiring changes or mods since its been happening but before i go poking around tracing what could be the cause is there usually a known issue, 1 of a few things or could be numerous things?

Any help appreciated thanks

[turbo ke20]

my guess is u have to have a short somewhere. is it a standard ecu or have you put a aftermarket one in?.
check all wires for ecu harness around firewall area where it may have rubbed through or any other tight squeezes in the harness u might have.
ive seen some right behind the middle of the dash before and it took hours to find.
check the common areas first and eliminate them 1 by 1

[sideshow]

if it was wired properly u might have a fuel pum,p thats gettin bad

the efi fuse also runs power to the fuel pump thru the cop relay

so maybe yr pump is on the way

basically theres about 5 things that run of the wire that comes from efi fuse

[EvilJack]

thanks guys, i will check for any lose wires first as its a bit easy to get to than the fuel pump

i had a feeling it might be the fuel pump as i filled up from a servo that the guy next door has had problems with, basicly some new pumps went in and some crap from the bottom of the tanks has got in.

its a walbro pump and probly been in over 3 years now, have a spare one on hand

+rep

[sideshow]

one thing to do is maybe run an extra relay for the fuel pump and run a 15 amp fuse just for pump

[EvilJack]

well i dont think its the fuel pump, ive pulled code 47 which is "sub-TPS signal"

im guessing i have a short in this circuit somewhere

[Mos]

Hi,
Sub-TPS - do you have your traction contol TPS hooked up? That's the most likely cause of that error.
Out of the 4 wires in that circuit, only 1 has a remote chance of blowing the EFI fuse and that's unlikely (VCC) - the other three wires wont do anything with the EFI fuse if shorted to ground (ECU signal Gnd, VTA2, IDL2).

The factory setup makes calculations for the EFI fuse based on the components connected to it. IF you change any part of that, like the fuel pump, you have changed the calculations and the margin of error is reduced. A higher capacity/pressure fuel pump has to get the extra oomph from somewhere - the power supply - requiring a higher current in high load situations. (As the pump slows down while the pressure rises it will draw more current).

As sideshow suggested, run the separate power to the fuel pump. You will immediately isolate one of the suspects while doing things the more correct way. If the EFI fuse continues to blow it might be a short - if not, it was likely just overcurrent in certain situations.

BTW, running an additional power supply is by far the least time comsuming option

Hth.
Mos.

[EvilJack]

Hi Mos, thanks for that but i replaced all relays and re done some of the grounds and looks to be ok. I got rid of the TRC throttle body so its not hooked up.

I think the code is seprate to the fuse blowing, when i get some time i'll follow the manual here

http://mkiv.supras.org.nz/articles/engine_2_41.htm

its real strange the car has been running the same fuel setup for a few years now without a hitch

+rep for your comment

[camrygt?]

I'd probably put a multimeter temperarily where the fuse is and start the car walbros draw a lot more current than the standard pump. You may have 17 amps running through a 15 amp fuse or something and it is not unheard of for this to work for a few months then blow, especially if the fuse socket corrodes slightly and the poor connections adds a little heat to the bottom of the fuse (AKA VL commodore fuse boxes).

Sometimes a high wattage light bulb (like a few headlight bulbs in paralell) used instead of the fuse can let you move parts of the loom around to find a fault without blowing 100's of fuses (light comes on when you find the faulty area.)

[EldarO]

basically i think hes caying that the ECU runs things percentage based.

so, if you change something, like a fuel pump, or injector, if you go any bigger/smaller, the percentage the ecu is supposed to be running is all out of whack...

is this what your saying...?

Eldar.O.

[EvilJack]

well after replacing some relays and regrounding some earths its been 2 days without a blow

reset the ecu and havent had error code 47 appear again within the 2 days either

i will do the sub tps tests to make sure everything is ok from that end

cheers guys