1999 Mx5 won't start

jet244 · Postby **jet244** » Wed Oct 19, 2016 9:54 pm

I have a 1999 nb8a that wont start. Spark is good in all cylinders and the coil packs, plugs and leads are all new. Ive also replace the crank position sensor. Fuel pressure was tested at 42 Psi. Im not sure what it should be though. I was suspecting the fuel pressure to be too high as the plugs all come out wet and the engine sounds like it wants to start when you have your foot flat to the floor which i believe is a method of purging the cylinders. Ive also used an led to check that the signal to the injectors is switching. I tested this with the loom unplugged from the injector loom. Lastly i removed the rocker cover and the timing is correct atleast between the cams. Im not sure what else to do and any help would be appreciated.

mx5madness · Postby **mx5madness** » Wed Oct 19, 2016 11:17 pm

Does it crank when you turn the key? or is there nothing? if there's nothing when you turn the key, It's most likely an issue with the immobiliser

jet244 · Postby **jet244** » Wed Oct 19, 2016 11:24 pm

yeah it cranks over fine

Postby **Okibi** » Wed Oct 19, 2016 11:46 pm

Do you have spark?

jet244 · Postby **jet244** » Thu Oct 20, 2016 12:05 am

jordan.k · Postby **jordan.k** » Thu Oct 20, 2016 1:31 am

Had a similar issue on my old e36

The fuel pump decided to kill itself.
Can you physically hear the fuel pump priming?
If not it's probably a relay or fuse or the fuel pump it's self

Good luck

Odd · Postby **Odd** » Thu Oct 20, 2016 8:10 am

Perhaps the New crank position sensor isn't fitted correctly....have you checked timing?

Postby **Okibi** » Thu Oct 20, 2016 9:23 am

If you have fuel and spark then I doubt it's an immobiliser issue. Recheck your fuses. Then consider Cam angle sensor / Crank angle sensor / AFM ... handy if you have a mates NB you can swap bits across from.

Was it running fine before it stopped or did you modify anything?

bigdog · Postby **bigdog** » Thu Oct 20, 2016 10:13 am

Did you replace all these items because it wouldn't start, or did it only not start after you replaced them. If it's the latter, I always work backwards and double check what I might have have done wrong in these situations. If it's the former then either the Timing belt has jumped a few teeth or the cam angle sensor is crook.

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forcedfive · Postby **forcedfive** » Thu Oct 20, 2016 10:26 am

Check that the crank sensor is correctly adjusted. If it is just a bit out it may not be picking up the crank. The air gap between the sensor and the projections on the pulley plate is supposed to be 0.5 - 1.5mm. If that is as it should be and still no luck and you have the old sensor, maybe swap it out to confirm the new sensor is not the issue. Good luck.

StanTheMan · Postby **StanTheMan** » Thu Oct 20, 2016 10:26 am

He sais the timing between cams is right. unless the timing has jumped on the crank sprocket. Not sure how common that is. But surely not impossible

hks_kansei · Postby **hks_kansei** » Thu Oct 20, 2016 10:48 am

StanTheMan wrote:He sais the timing between cams is right. unless the timing has jumped on the crank sprocket. Not sure how common that is. But surely not impossible

Certainly possible, esp if the belt tension is wrong.

On mine the crank pulley stripped all the teeth off the timing belt. (Thanks Chinese belt)

93_Clubman · Postby **93_Clubman** » Thu Oct 20, 2016 10:49 am

Certainly can happen STM:
viewtopic.php?f=29&t=72825&p=891448&hilit=timing#p891448

jet244 · Postby **jet244** » Thu Oct 20, 2016 11:17 am

forcedfive wrote:Check that the crank sensor is correctly adjusted. If it is just a bit out it may not be picking up the crank. The air gap between the sensor and the projections on the pulley plate is supposed to be 0.5 - 1.5mm. If that is as it should be and still no luck and you have the old sensor, maybe swap it out to confirm the new sensor is not the issue. Good luck.

I gapped the sensor to 0.9 mm at all for teeth. The car wasnt sparking consistently before i replaced it and now the spark seems good

jet244 · Postby **jet244** » Thu Oct 20, 2016 11:21 am

bigdog wrote:Did you replace all these items because it wouldn't start, or did it only not start after you replaced them. If it's the latter, I always work backwards and double check what I might have have done wrong in these situations. If it's the former then either the Timing belt has jumped a few teeth or the cam angle sensor is crook.

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I actually got the car not running. The previous owner replaced a bunch of parts in an attempt to fix it. I personally replaced the crank angle sensor because he had put one in too close and the teeth sawed into it. He said he had replaced the cam sensor and it looks new but im not sure how to test it. The timing belt may have jumped a tooth on the crank but id rather rule out everything else before i pull that apart