Gday,

Ive got an issue with my MTX-8s. The fuel pump relay trigger (green wire) that switches to earth to energize the relay coil and pull the switch across isnt doing its job anymore. I put a multimeter on it and its showing as around 3volts when the ignition is on but im pretty sure its meant to switch to earth isnt it to complete the circuit? The other side of the coil is ignition 12v. It used to work when i first started the car but now ive got no fuel pumps initiating at all.

Can someone please help?
E? E? Can you help please mate.

Cheers,
Blayne

try the microteh web site
they have been very helpful to me in the past
( please insert your own smart comment about searching the links section in this forum here)
http://www.microtechefi.com/

you may have a knackered transistor in the ecu.
Probably best to get it checked out by a technician...
Nick.

thanks for the replies,
yeah it turns out the bloke who owned the computer before me fried that circuit at some point. i spoke to microtech and they said they can replace the transitor and any circuitry that is damaged. so all is good, ive just got the pumps running on the cars ignition circuit at the moment which is safe according to them.

Blayne
Yer its real easy to fry that fuel pump relay pullin circuit in the ecu.
Its a no-brainer to get fixed but a nuicance to have the ecu out for a week or so.

Interestingly, that circuit in my MT-8 does the opposit to most. The relay pulls as normal in but it never switches off the pump when the engine is off after 5 seconds or so.
Been like that for years!

L8tr
E

thanks E,

yeah everyone keeps saying its easy to fry that circuit but how do i stop it from happening? is it an earthing problem do you think? I dont want to get it fixed then have it fry again in a weeks time or something haha that wouldnt be fun.

Yeah the MT (when working properly) will prime the system then once the engine is running keep the pumps going non stop like normal is this what you mean? i thought that was how it was meant to work?

autronic...

autronic... = $$$$$$

I love the blythe "Autronic" reply from some snoozer as a quick fix for a dodgey fuel pump wire......
Yeah,,,, riiiiight M8, unload a couple of large just to make the fuel pump relay work correctly.....sure thing sport!
Kinda same as "hey, I have a handling issue with my P510"....
Reply?
"Ferrari"
Good night sweetheart, back to bed.

Blayne.

The ECU is supposed to control the fuel pump/s independantly of the ignition switch.

In event of the engine not being started after switching the key on, or the engine stopping and the key left on, the ECU is supposed to switch the pumps off after blah seconds.

Ummmm.. I got told once why that circuit gets fried...........its a very basic thing...... I just cannot remember exactly why tho.......... Its something to do with the power supply on the other side of the pump relay pullin coil which would usually be the pink wire.....**** M8.... I just cannot remember exactly but it fries a diode on the motherboard of the ecu.
Its a very basic wiring mistake made by many new players and most of them usually just dont use the green pullin wire at all and wire the fuel pump direct to the cars ignition circuit as a workaround.
A certain dude down her in Tassie who fits Microtechs for other people for beers specialises in rooting this circuit and claims the ecu's are faulty.....all of them.
he wont admit hes incorrectly connected them up.....all of them.........

As an aside with mine, If I stop the engine and wait, the fuel pumps continue to run, but the engine will not restart after, say blah seconds.
I have to switch the ignition OFF to kinda "reset" the ecu and then all is well???
Its always done this tho and I just live with it until the time comes to actually get something done to the ECU or it fails.

L8tr M8
E

I used to have problems with ECUs and electronics and if piece of mind and a reliable car cost a couple grand then i'd say it's money well spent. My car runs...
Needless to say i don't have these problems anymore - ever.
you get what you pay for
It was just a suggestion - I'm sorry i didn't mean to offend. Blayne could be a millionaire, you never know. Are you, Blayne?
Apologies again.

I'll ignore anyone who doesnt actually sign in as a registered user and stays annonymous.

E, yeah ive been hearing that this circuit is being fried by every tom, dick and harry aswell. Id like to know how to wire it correctly so it doesnt keep happening, do you know?

Ive decided on buying a brand new wiring harness and starting from scratch and really spend some time getting it right, dont care if the car is off the road for a month or so aslong as i can get some results. Microtech supplied me with a wiring diagram which got the car running but i think theres probably someone that can give me some extra hints to stop these problems from reoccuring?

So that's why my old D5 wouldn't power my fuel pumps years ago.

Oh well, I just ran the pumps off the ignition full time and never had an issue. Just couldn't listen to music with the ignition off though.

Blayne
Yer its a no brainer M8.

The pink wire is really just connected to the ignition switch via the Microtech loom so no secrets there.
12v+ive from the key and this also powers up the ECU.
It goes to one side of the relay pull in coil terminal 85.

The green wire is the earth return via the ECU and goes to the other side of the relay pull in coil terminal 86.

I have a vague and sneaky feeling some guys connect one side of the relay pull in say 85) to ground and the other side (86) to green and perhaps this is what cooks the diode in the ECU.
Then again, i could be well pissing in the wind!

Its an easy mistake to make but the wiring diagramme is quite clear on what colour wires go to what terminal.

L8tr
E

Please report back what exactly was wrong with yours when you find out.
Transistors are similar to a relay and stuff up every now and then, sometimes related load but if you wire them incorrectly then...
Nick.

Thats what I dont get, I wired it correctly according to the diagram from Microtech and it cooked the circuit. At first before the circuit blew in the ECU I was getting alot of heat in the fuel pump relay and the inline wedge fuse was melting then blowing. Sounds bad i know but i had to drive it like that to get all the rego done, then finally she gave way

what size fuse and cable did you use and how long was the cable run?
Did you check the voltage at the pump whilst it was running?