MX5 NB 1.8 vts sport cranks but won't start.

[ClassicTinker]

Hello all :)

So after a year of fault free driving the wife's little mx5 refuses to start! We've had the car for a year now and it's always started and ran fine...no trouble at all. Yesterday I had to pop the space saver onto the driver's (UK) front as she had a flat. The wife then drove it to the supermarket...about hmmm 1/4 mile max. It drove fine as usual but when she came back out of the shop it wouldn't start. It cranks over fine but just won't fire up.

This morning I walked around to the supermarket and did some basic tests;
With the electric aerial disconnected I can hear the fuel pump prime when the ignition is switched on.
I checked all the fuses in the engine bay and under the dash with a multimeter...all fuses are good.
I pulled the number 1 HT lead off the plug, popped a new plug into the HT lead and earthed it to the cam-cover...No spark!!!
The multimeter is showing 12v at the coil pack. (I only checked the front one)
Using Torque on my mobile with an official Bluetooth dongle there are no fault codes recorded.
The engine cranks at its normal speed.

Some history that may be relevant;
3 days ago when unlocking the car the alarm went off and I had to turn on and off the ignition then get out and relock then unlock the car to get the alarm to switch off. This has happened a few times before but only when unlocking the passenger door or the boot but this was the 1st time it's done it when unlocking the driver's door. Could the alarm be on its' way out? We only have one key, there are no buttons or secondary fob for keyless entry, we have to make do with unlocking and locking via the key.

A few months back the rear drive-belt failed, I had to pull bits of it from behind the crank pully as it had shredded and wrapped around the back of the pully. Could this have damaged or loosened the crank angle sensor??? Although the car has been driving fine until yesterday. Is there a way to test the sensor?

So, any ideas where I should start??? I'll tow the car back home at the weekend so I can take a proper look at it. I'm concerned that it's the immobiliser that's crapped out...are there any tell tales signs such as dash lights or blinking LEDs? If so is this when cranking or just with the ignition switched on?

Sorry I couldn't give more info but until I get the car back home I'll just have to try and come up with a list of possible issues lol.

Thanks in advance CT

[Mazda Mender]

I would start with the most common first, check for water under the carpet on the passenger side...then the crank sensor in case the shredded belt as damaged one of the wires or the sensor, and then the cam sensor before we look at anything else after you have ruled out fault codes which would of been top of the list to attack.
M-m

[blackyb]

Our now departed 2003 1.8 sport had a remote key fob (plus a spare) for keyless entry and the alarm. Just wondering if it was an extra or standard on ours and if the 2004 would have the same. If its a standard fitting could it be an inobilser issue.

[ClassicTinker]

I would start with the most common first, check for water under the carpet on the passenger side...then the crank sensor in case the shredded belt as damaged one of the wires or the sensor, and then the cam sensor before we look at anything else after you have ruled out fault codes which would of been top of the list to attack.
M-m

I checked for fault codes the only one recorded was for the gearbox speed sensor that sometimes looses it's signal. Nothing else in there...would a failed immobiliser, cam or crank sensor cause a fault code?

I'm townng the car home tomorrow after wifey finished work so I'll be able to start working through the possible causes. I have the cable for forscan somewhere, I'll dig it out and renew my licence for forscan as that might let me see live sensor data???

Where is the best place to source a new cam and crank sensor...normally i use fleebay but with the mx5 being a popular car I'm thinking there are probably spcialist supplies that have better quality/priced parts?

[ClassicTinker]

Our now departed 2003 1.8 sport had a remote key fob (plus a spare) for keyless entry and the alarm. Just wondering if it was an extra or standard on ours and if the 2004 would have the same. If its a standard fitting could it be an inobilser issue.

I would hope that a vts sport would have keyless entry as standard...I just assumed that the fob had been lost at some point. It would be nice to get hold of a 2nd hand fob and receiver as the door locks freeze solid in cold weather lol. I don't think the lack of a key fob is this issue with the no-start problem though as we've had the car a year now and it's always started and run spot on...although it does crank a little on the slow side and takes a few seconds to fire up. I just put that down to the skinny battery leads. I've put the battery on charge so it's ready when I get the car home but it still had 12.6v which should have been enough to start the car.

[ClassicTinker]

@MM Yep sounds sensible. I'll tow the car home tomorrow after wifey finishes work. Is there any good mx5 parts websites I should try or is it a case of using fleebay?

The only fault code was for the iffy gearbox speed sensor that sometimes drops its' signal...other than that there was nothing recorded. Would a failed IMMO, cam or crank sensor cause a fault code?

@Blackyb I'm guessing that the remote fob was lost at some point. We've just had to make do with using the key like commoners but it's never caused a starting/running issue. A 2nd hand fob and receiver would be nice though as the locks always freeze solid in cold weather.

[Mazda Mender]

Contact Andrew at Autolinkmx5 for any bits and let him know you were sent to him from here for a discount.
Let us know where you get to once you have her on the drive.
M-m

[ClassicTinker]

Will do :) I should have the mx5 back home by this evening so tomorrow I'll hook it up to the laptop and see what signals are coming from the crank and cam sensors. I have two spare engines in the garage from a racecar project so a replacement cam sensor shouldn't be hard to find lol but I'm pretty sure both crank sensors and knackered after moving the engines around. I'll pop into the garage today and remove all the shrink wrap from the engines grap a cam sensor and see if either of the crank sensors are useable. Do you have any idea where I could find a wiring diagram or even just the pin outs for the ECU would be helpful...the car is a 2004 UK market.

[Mazda Mender]

Just plug straight into the OBD 2 port, that's what is for .
M-m

[ClassicTinker]

A quick update. I was trying to check sensor data today using forscan and noticed that the led to the left of the gear stick (immobilser?) wasn't lit. Locked doors, unlocked doors, ignition on or off or engine cranking nothing causes the led to light up. I know it used to blink as it should before the no-start issue. The data I got from forscan was a bit *iffy*, it will give me the voltage to the ecu but is saying OFF for things like the fuel pump even though I can hear it run when I 1st turn on the ignition.

I will be dragging it onto the drive tomorrow so I can start checking through things properly ,so I'll start with lifting the passengers carpet and security plate and check for dampness etc. Also I found a wiring diagram for a 2003 usa market miati so I'm hoping it's not too different to a 2004 UK car lol.

[ClassicTinker]

So it looks like it's the crank angle sensor. The led next to the gear stick was part of an aftermarket alarm which I've removed. Neither Torque nor ForScan is able to give me live data for the crank or cam sensors so I bacvk probed then at the ecu (which was nice and dry by the way). The cam sensor looks likes is working ok but the crank sensor just sits at 5v while the engine cranks. When I checked the air gap it was huge...about 6 mm. I reset it to 1mm before I checked for a signal at the ecu. I#m guessing that when the belt let go it must have given it a good old wack to move it that far out of possition...I'm suprised the car ran so well lol.

I'll order a new sensor today and hopefully that will fix things. On a plus note while removing the alarm I noticed that car has a keyless entry module...are the coded to the car or just the fob? If it's just to the fob I can get a 2nd hand module and fob(s) off eBay.

[Mazda Mender]

You should be able to program one in.
M-m