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Hello all,

My 1990 MX5 1.6 starts first time when cold, however once it has warmed up and the idle has dropped to about 850rpm, if I turn off the ignition it won't start again.

It turns over and tries to fire but wont, even if I hold the throttle flat to the floor, it kicks but won't run

I have fuel pressure and spark but it just wont start.

Any help would be great.

Cheers

Check the cam or crank position sensor. Usually the culprit for not starting again after its been dríven.

I have replaced the cam angle sensor and the ignitor along with the ECU as I have bigger issues before.

Replace it with a new one?

Are there any mods?

New cam angle sensor, S/H ignitor and S/H ECU, the car did not start at all when I bought it and now it starts first time when cold but not once hot.

Hi.
Check your battery terminals are tight and are seated right to the bottom of the post. Also check your connections on the starter motor.

I had this problem once, it only started a few weeks later after I installed a new fuel pump and after a while I pulled out to look at the strainer on the fuel pump it was all blocked and looked like it had been crushed.

It had the same problem as well, would not start when the car is hot. Only on cold nights.

Bought a 2nd hand oem pump and put it in and starts straight away.

Thanks, that is my next job then to pull the fuel pump and check it, I replaced the ECU temp sensor today and that made no difference at all.

When I went to start the car today cold, it back fired out the exhaust so I think my problem is too much fuel when it is hot, I think some how the engine is flooding because there is a strong smell of fuel when cranking it hot and black smoke is coming from the exhaust.

I thought it might have been the TPS or that water air valve but it starts cold and idles at 1600rpm then drops to 850 once warmed up so I am assuming that side of things is working correctly?

I will try the fuel pump and see how it goes.

Cheers

Kallaroo MX5 wrote:I thought it might have been the TPS or that water air valve but it starts cold and idles at 1600rpm then drops to 850 once warmed up so I am assuming that side of things is working correctly?

I will try the fuel pump and see how it goes.

Yeah, cold initial start-up idle will be 1500ish, which should drop back to 850ish after a couple of minutes.

Given you're having a look at the fuel pump, also worth checking the inside fuel tank wiring connectors as per this thread:
viewtopic.php?f=55&t=46425

I didn't suggest this previously as if this problem is present it usually affects start-up hot or cold. Good luck!