mx5cartalk.com

hey im a long time lurker first time poster!

i have a 1991 mx5 that wont start,

when i go to start it everything is working and motor is cranking over but it just wont fire, i previously thoougght i had no petrol in motor so i added some more and it did nothing, replaced the fuel pump relay and still no joy, had a look at the spark plugs and replaced then just incase and then the car started and worked fine for about 2 weeks. ive just gone to start the car again now and ive having the same issue where the motor wont fire , check spark plugs are fine and the car has plenty of fuel, and checked that there is power going to the fuel pump, so im not sure what the issue could be ? im thinking it could be the CAS from what i read up on from similar issues people have had on this forum i, just not sure how it could be as 2 weeks ago that didnt appear to be the isssue?


does anyone have anything else i should check on that could cause this issue?

what hose should i remove off intake to put petrol staright into motor to see if it fires or not?

anty help is much appriciated!

thanks charle.

I would check plug leads, if these break down they can cause all sorts of oddball problems.
If you crank the motor are the plugs wet? ie have petrol on them?
I wouldn't go pouring petrol straight into the inlet manifold.
I would check and double check all the electrical connections for the motor and its sensors.

Could also be an issue with an alarm / immobiliser

Check you have both spark and fuel first.

Okibi wrote:Check you have both spark and fuel first.

Try to start it for a few seconds then take out one spark plug. If the plug is wet then you have fuel. Reconnect a plug lead and hold the a metal part of the plug body against some metal on the engine and get a mate to try to start the car again. If you have ignition then you will see a spark arcing across the plug electrode.

Bad plugs, bad leads, bad coilpacks and bad filters don't normally make a car cut out completely, they just make it run progressively rougher. You probably have an wiring problem or a problem with a switch, relay, fuse or sensor.

If it's no spark and no fuel then it's possibly the FUEL INJ fuse (1 in the Main Fuse Block) or the MAIN or FUEL relay or a problem with the connection of the loom to the injectors and coil packs or faulty contacts within the ignition switch.

If it's just no spark then it's possibly the CAS.

If it's just no fuel then it's possibly the ST SIGN (9) fuse or an intermittent wiring connection to the fuel pump.

If the car starts and runs for just a second or two then it's probably a bad connection or internal fault in the AFM.

Swap components one by one with those from a mate's car before you decide to go and buy something expensive that you don't need.

See http://mx5cartalk.com/forum/viewtopic.php?f=18&t=59384&hilit=start for other tips, including a link to the "MSM Engine Won’t Start Diagnostic Checklist." - much of the info in it is applicable to non MSMs/SEs.

Almost forgot the obvious question. Okibi alluded to it. Has the car ever had an immobiliser fitted?

Good point about the fuse, i've had a car that started but won't idle when the engine fuse has blown.

sorry for such a late response guys! ive been flat out trying to get the thing started, and all your imput has helped out clarifying a few things...

fuel pump, fuel filter and relay are all working as normal

leads are fine , spark plugs are working

replaced the CAS

reset idle level in ecu

unplugged battery for 2 hours to reset ecu(not sure if thats actualy how to do it but its all i could find?)

was only able to remove 2 injectors and they seemed to spray a decent mist of fuel

CAR STILL WONT GO SHE JUST KEEPS TURNING OVER AND OVER AGAIN

any ideas? could a fuel pressure reg cause this issue?

as far as immobiliser goes i cannot see one connected and ive only had car for 3 months now so i cant tell if it has had one previously,

how do i test if engine fuse has blown or should i just get a newy and find out? although i didnt think the car would turn over so much if that was the issue?

is it possible that the AFM could cause this issue too?

im so amazed at the fact it wont start that i am struggling to think what i should try next?

I had this exact same issue in my NA6 once. Cranked fine and everything appeared working. Was told it was ECU. Car was trucked home by RAA. Talked to the previous owner who recalled similar happening to him - was just a slightly loose connection at the plug under the steering column to the ignition switch. Looked and felt connected and was connected enough that most things were working fine, but gave it a good push together and the car started. Held it tight with zip ties after that.

Maybe on off chance worth checking ...

Sent from my GT-I9100T using Tapatalk

I think there is some starting relay in the system that allows fuel delivery until the AFM senses airflow after the engine fires up. Maybe that relay or connection is dead. It sounds like an electrical problem.

Are the plugs wet after these start attempts?

JBT wrote:I think there is some starting relay in the system that allows fuel delivery until the AFM senses airflow after the engine fires up. Maybe that relay or connection is dead. It sounds like an electrical problem.

Are the plugs wet after these start attempts?

If the injectors are spraying fuel I assume the only way he could test that was during cranking., so that probably says its not a problem with the system triggering the fuel pump.


Sent from my iPhone using Tapatalk

Have you taken out a spark plug yet and checked that you can see a spark on the plug electrode when it's being cranked?

sailaholic wrote:If the injectors are spraying fuel I assume the only way he could test that was during cranking., so that probably says its not a problem with the system triggering the fuel pump.

Yep, I agree - and I've found it's best to assume nothing on this forum. We still don't know if the plugs are wet and there is spark.

sparks plugs are getting spark and the get pretty moist after 10-15 seconds of cranking

Are all plugs getting spark?...any other weird signs such as the taco not working?

Have you touched the plugs connecting to the ECU in the passenger foot well? I did this once (and then again ) with the battery still connected. It zapped the ignitor. The ignitor supplies current to the spark plugs. It is difficult to tell if the ignitor is stuffed. I ended up getting a follow NA6 owner to loan me his ignitor. A 2 minute job to swap it over. Car started first time.

Where are you located. Someone local to you on this forum may be willing to assist.

From (poor) memory the part is around $130 new. Super cheap can also order in a after market part, but you need to allow for a delay in the getting it.

Hope that helps.

J