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Matt, Mechanical Engineer
Category: UK Car
Satisfied Customers: 21881
Experience:  BEng hons Mech engineering, in auto industry 22 years
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C max non start

Customer Question

c max non start
Submitted: 1 year ago.
Category: UK Car
Expert:  Matt replied 1 year ago.


If the car's not cranking then first check it can turned over by hand so double checking for any mechanical issues

If OK then check that the main battery cables are on tight and the terminals are clean and bright. Do the same for the engine / gearbox earth strap.
Then follow the main positive lead back to the engine and down to the starter motor, and check the connection at this end as well.

There should also be a small wire to the motor which should have 12V when you're turning the ignition switch to crank. If the 12V isn't there, check back along this wire for damage to the insulation or corroded connections

This 12V feed comes directly from the ignition switch so this may be faulty and need replacing

Check the resistance of the main positive lead that runs down to the motor as anything more than a few ohms and it should be replaced

Don't forget to try a jump start from another car / battery as its possible the battery is poor, if you have a voltmeter a healthy battery should read 12.7+V

also try substituting the battery for another as I've known a very flat battery to drag down the system voltage too far even with jump cables

one other thing to consider is that the immobiliser is faulty and preventing the starter from being enabled - however if the dash / ignition lights are on then this usually means that its off

If this is all OK then its possible the car needs a new starter motor

Customer: replied 1 year ago.
You have do better top guys needed
Expert:  Matt replied 1 year ago.

can you tell me what you have tried from my list?

bear in mind I can't see or hear the vehicle and rely on your feedback to solve the issue

Customer: replied 1 year ago.
This is a high spec problem bsi can fault etc all said before fine for the good old days so far I think wireing harness as u like Peugeot etc bsi don't lose it maybe ecu as moved when doing clutch ?
Expert:  Matt replied 1 year ago.


I'd agree a wiring fault is the most likely, this is why I say to check if the starter motor is recieving the 12V signal to the solenoid/

as if the fualt is on the low current , swithcing side then its a case of checking if the ECU connection is good as you say and if the body control module has power , and if the low power earth connections onto the engine have all been replaced and are tight and corrosion free, as these are used to get the ECU functioning correctly

Customer: replied 1 year ago.
Code reader is dead red light on no crank and dash readout said fault the ecu is not firing up I say due too 1. Gem unit not sending correct 2 wiring fault between gem and ecu 3 ecu its self. I belive it could be ecu. As if you leave it a bit then try red light goes out and it turns over well till fires then stops and red light back on and no turn. You would think the gem and wiring ok as it's done its part getting ecu fired up. when ecu try start running engine it fails.
Expert:  Matt replied 1 year ago.

thanks for the extra information

OK if there's no code reader communication, then either the ECU isn't getting power, or its not connected properly , or its faulty

I'd 1st check the ECU fuses, then disconnect the battery and check the ECU connection, disconnect and re-connecting checking for bent or corroded pins

if this is all OK then I'd say its time to send the ECU off for testing / repair

both these firms are good

Customer: replied 1 year ago.
I agree what you say only problem its got bolt with no head fixing plug into ecu don't think can be fuse as does turn over after leaving I will check and clean the earth wires try moving harness around if that don't work will send ecu for testing its just a pain as all done it clutch thanks for help
Expert:  Matt replied 1 year ago.


the bolt holding the ECU plug in place should be a normal 6 point 10mm AF hex, and they often have a phillips head star in the centre too so you can use a screwdriver as well as a 1/4" drive thin wall socket to undo it