Hi all been looking through the forum and have gained a welth of knowledge. So let me first say thank you.
So I’ve a 91 reg uk mazda 1.6 loom, engine, gearbox, everything but the shell as im building a lotus style kit car. (gbs zero mazda) My problem is, well frankly it’s done me in, I’m 3 days into trying to solve the issue ive been having, ive connected all the relevant engine harness plugs and all the ground points for the car to run, but ive only got two cylinders firing 2 and 4, 1 and 3 refuse to fire. I’ve checked the ignighter the cas all the wires have continuity. I cant find a break in any wire. I know I’m only firing on two cylinders as two ports of the exhust are getting hot. Which led me to belive its either spark or fuel. I’ve tried all 4 plug leads. I have a good spark on all 4 brand new plugs again all getting a good spark. Ive ran a light from each injector plug on the harness and bingo it only pulses on 2 and 4, nothing on 1 and 3. So the ecu is not send a pulse to 1 bank of injectors. Any help would be appreciated.
Also my tach is not working but the oil and temp gauge are if that helps.
Have you got a 12 volt feed at each injector with the ignition switched on?
Yes i have all the white red wires at all 4 connectors have 12v ive traced this 12v wire and it has 12v all through the loom
The injectors fire simultaneously, 1&3 and 2&4. Have you double checked the continuity along yellow/black wire from each injector back to the ECU? I’d check for a short to ground on those wires and a short to live too.
Ive opened the ecu and check for contiunity on all the white red and both yellow and both yellow black from the plug to the ecu board i get a bell on all from my multimeter for some reason i cant get a pulse on one bank of injectors
Can i run new wires from the ecu to the bank of injectors not firing?
What else is connected to the injector circuit to make them fire?
Sorry for all the questions ive beem staring at the loom and witing diagram for 3days straight and its beaten me lol
Have you checked the resistance of the wires? I’d check the same with the ECU and injectors disconnected too. You could run new yellow/black wires in but if the wires are OK then there is not much point. There is nothing else on the yellow/black trigger wires between the injectors and the ECU. The ECU puts the trigger wire to ground to switch the injector. If that’s not happening it’s either a fault with the ECU or a fault with something else and the ECU is not being “told” to trigger the injectors. Have you run a fault code check?
Ive not ran a resistance test on the wires, what wpuld be the best way ignition on off or engine turning over?
What would be the best way to test for a short on the wires live and ground?
Ive done a diagnostic test only fault was the charchoal canister valve as that wasnt connected it is now but no more faults
Resistance checks should only be carried out on an isolated, non live circuit, you should have done your continuity checks in the same way really. Check for a short to ground by checking resistance between the each connector terminals and body ground. a simple short to live check would be to check for 12 volts on the yellow/black wire with the injector plugs disconnected and the ignition switched on.
Thank you i will try that when i get home later. The continuity check was done on non libe circuit.
Does the tach not working have anything to do with the ecu/injectors?
Right ive tested the injector plugs for resistance all 4 trigger wires (yellow and yellow black) are the same resistance ive checked the live on with ignition on to the plugs only one bank will get 12v so ive took the plug off the injector harness and checked the continuity of the yellow and yellow black wires i got a bell from.multimeter. so the ecu is not sending a ground signal to the injector wire what will cause this?
Are you getting a spark at all 4 spark plugs?
Ive ran an 12v led on the injector leads and only one bank puleses the led which is what the mulitimeter confirms. Ive got a good spark on all 4 leads and spark plugs. My ecu is just not sending the pulse signal from the board ive put the multimeter on the ecu board on the actual pin traces and i only get a pulse/12v when turning over the car on the yellow trigger wire not on the yellow black?
It’s beginning to sound like an ECU fault to me…
Agree with RR.
Is it possible that when you gave the injector plugs a 12v feed that you accidently touched the other wire in the plug which is the earth switching wire from the ECU.
The result if you did is most likely a damaged track in the ECU. (a bit like a fuse blowing).
Richard.
Before checking any of the loom or ecu i was only firing on 2 cylinders
Ive got a replacement ecu coming tuesday aswel as CAS and ignighter as a precaution
Im going to try and test the ecu board by tracing the pulse pins back through through the ecu itself see if i can find a break or broken component
Is.my rev counter not working linked to the injectors?
CAS is most likley culprit and coil packs
So the replacement ecu turned up today and im happy to report the engine fired up on all 4 cylinders woohoo, still fot no tach which im suspecting will either be the CAS or igniter i have them coming larer this week
Just like to say a big thankyou for everyones input!
I will try and compare the boards to see if i can find what component has died and if its salvagable i got aa far as tracing the injector pulse pins to a set of transistors which feed into two big plastic boxes but thats as far as i got for now