mazda mx5 - mx5 not starting | Technical matters | Back Room Forum

Sat 9 Jul 2011 19:07

mazda mx5 - mx5 not starting - James_dbrz

Hi, my mums mx5 has recently developed a problem. First the car cut out on her way home from work, my dad noticed the connect was loose on the item beside the coil pack on the end of the cam against the bulkhead. (grey connector 4 wires).

Everything was fine for 2 week then the same happened again. this time the rac wer called and found nothing wrong but wiggled a few wires on top of the engine then it started but only lasted around half a day until it died again. Today we have had been all over the engine bay looking for problems but can't find any.

When the car is trying to start only 2 cylinders spark. I have seen that these cars have weak coils but when the electrical connectors are swapped on the coil the other 2 cylinders fire so it would appear the pack is fine.

We have checked for continuity on all parts we can trace in the engine bay and all seems fine, are there any suggestions as to what the problem may be?

Reply | Report as offensive | Link

Sat 9 Jul 2011 22:44

mazda mx5 - mx5 not starting - James_dbrz

just reset ecu, no difference.

Pulled plug 1 to see if it runs on 3, only runs on one.

Swapped coil packs over and ht leads. Still no fire on 2 and 3.

Running out of ideas going to pull ecu tomorrow to see if that makes a difference.

Reply | Report as offensive | Link

Sat 9 Jul 2011 23:23

mazda mx5 - mx5 not starting - unthrottled

It would be helpful if you gave a year. I take that it utilises semi sequential injection and ignition? So cylinders 1 and 4 spark simultaneously on one revolution and cylinders 2 and 3 spark on the next. So if components work on cylinders 1 and 4, but not 2 and 3 then it would point to camshaft sensor is used to time the ignition/fuelling.

Reply | Report as offensive | Link

Sun 10 Jul 2011 14:26

mazda mx5 - mx5 not starting - James_dbrz

hi its a 1994 eunos import

can you use the sensor from a 1.6 on a 1.8?

Reply | Report as offensive | Link

Sun 10 Jul 2011 15:57

mazda mx5 - mx5 not starting - unthrottled

I've no idea. There are often seemingly myriad changes between a manufacturer's engines, not just bore and stroke. A Heynes manual will make this a lot easier. Secondhand, they are very cheap-the local library might eve have one!

Reply | Report as offensive | Link

Sun 10 Jul 2011 21:29

mazda mx5 - mx5 not starting - Mx5 mk1 wayne

hi there

i have the same problem with mine mx5 mk1 1992 import

i have had the aa out to mine today and he found only 1 coil was working when u tried to start the car spark plugs 2&3 not firing ( but the second coil is ok he tested to see if both worked with he machine he got )

he also found that the fuel injectors on crank was only giving one pulse then nothing after that

he checked the ecu for water damage everything was ok with that(he did no test on the ecu only looked for water)

at the end of his report hes put one coil not triggering and injectors not triggering

so i dont know what to do now or look for

PLEASE HELP ANYONE

thanks wayne

Reply | Report as offensive | Link

Sun 10 Jul 2011 22:32

mazda mx5 - mx5 not starting - unthrottled

Since the cam turns at half crank speed and cylinders 1 and 4 fire and fuel simultaneously, and cylinders 2 and 3 do the same but 360 degrees out of phase with 1 and 4, and the components work when swapped, it points to the camshaft position sensor.

Reply | Report as offensive | Link

Mon 11 Jul 2011 21:01

mazda mx5 - mx5 not starting - James_dbrz

thanks for the replies so far i have just used the led trick in the diag port and it tells us that the cam position sensor is gone along with the MAF. i am looking at getting one from ebay and hopefully she will live again

Reply | Report as offensive | Link

Sun 17 Jul 2011 20:41

mazda mx5 - mx5 not starting - James_dbrz

just changed the cam sensor and now have good spark on all 4. need to adjust the timing now to sort out engine running.

Reply | Report as offensive | Link

Sun 17 Jul 2011 20:54

mazda mx5 - mx5 not starting - unthrottled

You mean the spark timing? How do you adjust that?

Reply | Report as offensive | Link

Sun 17 Jul 2011 21:11

mazda mx5 - mx5 not starting - James_dbrz

there is a slot cut into the cam sensor. you then rotate the sensor to get optimal timing. can use a strobe of the older fashioned by ear method.