MX5Ireland

Hi all. I recently bought a non runner off a friend. Long story short the car was parked for quite some time and wouldn't start for him. It cranks, fires but won't catch/stay running. He had workshop at the dealership he works at go through it and they came to the conclusion the ECU was fried. I started by eliminating the usual stuff, no immobiliser or alarm, fuel inj relay, fuses, leads, spark,(not getting spark when tested with plugs removed but ran on easy start) fuel flow, CAS swapped, commpression fine, checked for power to the ecu (its getting power) etc. I was since told the ecu is bulletproof so long as it wasn't under water, which it wasn't, it should be fine. The fuel pump doesn't whine with the key at run position but if I bridge the GND and FP terminals in the diagnostics box under the bonnet the pump whines but still the same symptoms. It ran last night on easy start(misted into a half open throttle body) but its refusing to run on its own steam. Could it be a weak fuel pump or blocked fuel filter causing my issue or the maf as I'm pretty mechanically minded with a lot of friends in the motor trade and it's causing hair loss. Anyone had a similar issue or know where my problem lies. Symptoms again, cranks, fires, knocks off.. Keep the accelerator flat it'll crank, fire, rev out slightly and roughly and knock off. Thanks in advance for any help you can provide.

Hi,You have obviously tried all the things we spoke about but maybe fuel is de-oxiginated.How old is the fuel .Years old will be rotten.Drain the tank ( bung on the bottom) and put 2 gallons on new fuel in it.Then try fuel filer and take pipe off at engine and see if its pumping fuel to there with ignition on or while cranking over..Be careful as petrol is highly flammable.!!

Fuel drained and replaced with new fuel. Fuel working both ways flow and return, without having GND and FP bridged. Have power to the injectors, plugs when taken up are black but new, cleaned thoroughly and I do have spark consistently now across the four cylinders, was intermittent,gaps are correct. Could the CAS that was installed be faulty?, is there a bench test for checking for failure? Taking it out, plugging it in and switching the ignition to run, then passing a screw driver past the spigot side and see if it reacts was mentioned to me but I don't know how true this is.

Heres the procedure for testing the CAS :

"Test the CAS by back probing the wires at the connector with a digital voltmeter. Leave the CAS connected, but as a safety precaution disconnect coils so engine won't try to fire. With ignition on, White/Red wire should have battery voltage (12V). Black/Lt. Green wire goes to ground (0V). Turning engine slowly so you can read the voltmeter, the White wire and the Yellow/Blue wire should both fluctuate from 0 to 5 volts. One should pulse 4 times per CAS revolution, the other should pulse once. Don't remember off the top of my head which is which. Remember, you'll have to turn the crankshaft two revolutions for one CAS revolution.

If the CAS does not pass this test, remove the connector and test for proper voltages at the connector.
White/Red= 12V
White= 5V
Yellow/Blue= 5V
Black/Lt Green= 0V (ground) "

also, if it coughs and then quits, this will happen when the Air Flow Meter is disconnected/broken. Worth looking closer there to check connections after the CAS.

Thanks Steve. Spoke to Robert earlier today and he sold an AFM for one doing something similar and it cured it. I don't know if its a bit premature of me but I'd put money on it being the AFM. Tested the voltage on the AFM connector and have 12V supply there. I'll test the CAS tomorrow and see how it fairs out.

Update. I can add the CAS and AFM to the list of things it's not. CAS passed Steve's test. AFM from Robert installed and still not starting. Noticed the "GOLD" terminal on the AFM connector (the one directly beside the power supply) had an odd voltage of 0.01 with the ignition on. Is this right? Should it not be zero if inactive? Power supply there was 12.12v, everything else in the connector was zero. I may have to bite the bullet and send my ECU off for testing.

We have ecu,s and checper than posting away etc/What number is on the side as there are loads os different ones

BPF3 Robert. What sort of money we talking?

I will check now