Well, back to the same old problem I had with my car. Although this time, its not my car - I've tried everything I can think of (considering ive had this problem 10x over, and its worked fine since) - Just thought I would post up to see if anyone had any better ideas.
Its a Mk1 with a 172 Ph1 engine, the same as mine. The ECU is from a Ph1 also, and has been fitted with an emulator to disable the immobiliser completely - This is 100% confirmed as it starts my 172 Mk1 perfectly fine, every time.
Basically - Key In. Turn to position 2. Fuel pump primes. Then go to crank it and it cranks over for as long as you hold it, just never fires up. There is no fuel pump running when cranking (no fuel comes to the rail), nor is there any injectors, or any spark (tested with spare plug and lead).
Below are the things we've tried. Every one of the sensors are 100% known working from either my own car which as we know from above runs fine, or a 172 Ph2 which is faultless.
Which consisted of - Fuel Pump Live (From ECU), Ignition live to engine loom and starter solenoid wire. Connected these up, the ECU primes the pump as it should, then touch the solenoid wire onto a battery and it just cranks exactly the same without starting - so that rules out the interior loom.
This leads me to think it is 100% engine bay related. I know the ECU earths one of the small black relays when it recieves all the correct signals from the sensors which in turn releases power to the Injectors/Lambda/Coil etc.
This relay earths fine when the ingition goes to stage 2, although it does not when cranking - Which says to me that the ECU isnt seeing something it needs to, hence not letting the engine start.
From that I had a think what might cause the ECU not to release this relay - only things I can think of which will stop it starting are the crank sensor signal and the ECU immobilser. Although, we have a known working crank sensor fitted, and a known working ECU plugged in! Which makes no sense.
I then thought what does the crank sensor actually read......the flywheel teeth. We turned the engine over by hand and inspected all the teeth via the inspection cutout to see if anything was stuck in them/damaged (which could provide a bad reading) - although they were all fine. The flywheel spins true when cranking also so its not like thats loose/wobbling etc.
From that I think its every option exhausted, and ive not really got any ideas of what to try. We're going to wire up an OBD port tommrow and read the codes from the ECU via a reader/or an RSTuner (which has worked fine on mine in the past). Im hoping this will reveal some codes, but if it does not - I have no idea whatsoever of what could be causing this.
I might have missed one or two bits out of the post as I was trying to think of everything we have tried - but any suggestions of things to try would be welcome!
Its a Mk1 with a 172 Ph1 engine, the same as mine. The ECU is from a Ph1 also, and has been fitted with an emulator to disable the immobiliser completely - This is 100% confirmed as it starts my 172 Mk1 perfectly fine, every time.
Basically - Key In. Turn to position 2. Fuel pump primes. Then go to crank it and it cranks over for as long as you hold it, just never fires up. There is no fuel pump running when cranking (no fuel comes to the rail), nor is there any injectors, or any spark (tested with spare plug and lead).
Below are the things we've tried. Every one of the sensors are 100% known working from either my own car which as we know from above runs fine, or a 172 Ph2 which is faultless.
- Crank Sensor
- Knock Sensor
- MAP Sensor
- Coolant Temp Sensor
- Throttle Position Sensor
- Lambda Sensor
- Tested ECU was getting 12V on cranking - Which it is on both the Ingition Live and Permenant Live Connections
- Checked the ECU earths for continuity, all spot on.
- Cleaned all the earths (chassis and box), and replaced box-to-chassis earth lead.
- Tried Replacement Key Barrel (In case of any issues with position 3).
- Replaced all the black relays in the engine bay (Fuel Pump, ECU, Immob)
- Checked and Replaced relevant fuses in the engine bay.
Which consisted of - Fuel Pump Live (From ECU), Ignition live to engine loom and starter solenoid wire. Connected these up, the ECU primes the pump as it should, then touch the solenoid wire onto a battery and it just cranks exactly the same without starting - so that rules out the interior loom.
This leads me to think it is 100% engine bay related. I know the ECU earths one of the small black relays when it recieves all the correct signals from the sensors which in turn releases power to the Injectors/Lambda/Coil etc.
This relay earths fine when the ingition goes to stage 2, although it does not when cranking - Which says to me that the ECU isnt seeing something it needs to, hence not letting the engine start.
From that I had a think what might cause the ECU not to release this relay - only things I can think of which will stop it starting are the crank sensor signal and the ECU immobilser. Although, we have a known working crank sensor fitted, and a known working ECU plugged in! Which makes no sense.
I then thought what does the crank sensor actually read......the flywheel teeth. We turned the engine over by hand and inspected all the teeth via the inspection cutout to see if anything was stuck in them/damaged (which could provide a bad reading) - although they were all fine. The flywheel spins true when cranking also so its not like thats loose/wobbling etc.
From that I think its every option exhausted, and ive not really got any ideas of what to try. We're going to wire up an OBD port tommrow and read the codes from the ECU via a reader/or an RSTuner (which has worked fine on mine in the past). Im hoping this will reveal some codes, but if it does not - I have no idea whatsoever of what could be causing this.
I might have missed one or two bits out of the post as I was trying to think of everything we have tried - but any suggestions of things to try would be welcome!
