Engine turns but fails to start šŸ˜£

Technical Area Engine, Transmission, Exhaust etc
1
  1. My model of MX-5 is: Mk1 NA 1.6 (1992)
  2. Iā€™m based near: Seaford, East Sussex
  3. Iā€™m looking for technical help or recommendations on: how to fix my issue

I came back from a 3 day break from the New Forest, parked up in front of the garage to unload, came back to reverse her in and she wouldnā€™t start. There was a bit of coughing and spluttering but she refused to fire/start so I pushed her in and left her overnight. The following morning she still wouldnā€™t start, turns over freely and quickly but no sign of a cough or splutter at all.
I had no issues with her at all while in the New Forest, she didnā€™t miss a beat.
I have since checked for a spark at the plugs and there is one. I even bought new plugs, fitted those but still no firing.
I tried the wire across Ground & Fuel Pump on the diagnostic port under the bonnet and could not hear the fuel pump at all when I turned on the ignition. Do you think this is my issue? If so, do I go for an eBay replacement from a breaker or new from say MX5Parts, although these are in excess of Ā£300 :persevere: whereas Iā€™m looking at Ā£40 from a breaker.
Can you suggest any other checks I should perform first?
Any assistance/advice is appreciated :wink:
The car has been ultra reliable, even with its ME221 ECU and Fast Road Conversion from Skuzzle Motorsport.

2

First question, does your car have an immobiliser? Iā€™ve been caught out by this before. Thought it was a wiring fault but was a faulty immobiliser.
Check for 12 volts at the connector on the top of the pump. If 12 v there, with the link in and ignition on and youā€™re sure the pumps not running ( they can be quite quiet ) replace the pump. I would get a used one from a reputable dealer myself. If 12 volts not present check the fuel pump relay ( under the dash on the drivers side ) and go from there.
Good luck.
D
Edited: Should have read " If 12 volts not present "

3

The basics are spark, fuel and compression.
Looks like youā€™ve eliminated spark, its unlikely to be compression so suddenly, so that leaves fuel.
If you turn the rngine over and remove a plug, can you smell fuel?
If not, you have to investigate why not and go for the simple, cheap options first, such as fuel pump relay.
Relays are electro- mechanical and can be subject to corrosion, both internally and connectors.
They are also cheap and easy to replace.
Fuses could be worth checking too.
If a fuse has gone, why has it gone?
Fuses are there to protect the circuit. If a fuse has gone, then something has overloaded the circuit, probably the fuel pumpā€¦
Debris or water in the fuel is a possibility. Have you just filled up, did you run the tank down more than usual?
Wires can break too. My Ducati fuel pump failed because the wire inside the insulation broke, leaving the insulation layer intact.
Good luck.

4

As mentioned before Iā€™d go for the fuel pump or relay. I run a NA with ME221 on a normally aspirated engine and you can definitely hear the fuel pump priming when you turn the ignition on.

5

Thanks and yes, she does have an immobiliser but Iā€™ve not had any issues throughout my 13 year ownership. She also coughed and spluttered when trying to start when hot and I think that might have been residual fuel. When cold, nothing and plugs appear dry with no fuel smell either. I think itā€™s fuel pump or blockage somewhere. I appreciate all your advice, thanks so much :+1:t2:

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Donā€™t know if this works on a fuel injected car but a drop of petrol in the throttle body and see if it starts briefly, others may advise against it possibly if they do then take their advice !! Good luck Dave

7

look at the relay

8

Yes, I think I need to look at the relay first. Apparently you can bypass it with a wire (seen YouTube video) so will look at that. At least if I hear the fuel pump prime I know itā€™s okay.
Many thanks :pray:t2:

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9

Guys, Iā€™ve confirmed itā€™s the relay as when I bypass it she fires into life :partying_face::partying_face::partying_face::partying_face::partying_face:
So I guess thatā€™s a new relay required. Now the search starts for a new one. Not sure about cost either. Iā€™ll keep you all posted :+1:t2::pray:t2::+1:t2:

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10

MX5 parts donā€™t have the relay in stock so Iā€™ve ordered a used one from eBay for Ā£12. Should get it next week. Iā€™m so happy :smiley:

Thanks guys for all the support and guidance :+1:t2:

11

Yay, well done.

Relays are generally pretty universal things.
Your local motor factors should have one and for less than Ā£12.00 at that.

12

Mazda ones donā€™t always conform to the usual DIN standard for relays.

13

By-passing the relay does not confirm 100% that itā€™s at fault, all youā€™ve done is by-pass the switch element of it, the primary winding may not be getting switched on by the ECU. Just something to think about if the replacement relay doesnā€™t fix it. You can fully test the relay with a 9 volt battery and an ohm meter if you need to.

14

Okay Robbie, understood. Letā€™s keep everything crossed that it is the relay then. It was strange that one minute it was fine and the next not. Something has ā€œfailedā€ and hope itā€™s just the relay. My ECU is an ME221 and only been on the car 2/3 years. Iā€™ll keep everyone posted on how it goes.
Thanks again :+1:t2:

15

When my Mk2.5 stopped, and the fuel pump wasnā€™t going, it turned out to be a faulty crankshaft sensor.

16

Just fitted the new (used) relay from Suffolk Mazda and I could immediately hear the pump priming before she fired into life - result :+1:t2:

Thanks for everyoneā€™s help & support :smile:

4 Likes
17

Great news

18

Wish iā€™d seen this post earlier, I could have performed a lookup on the relay, we sell relays for peanuts.

19

Never mind matey, I thought Ā£12 to sort the problem was pretty good. I had visions of having to get it towed somewhere to be looked at and that would have been pricey!

Thanks for taking the time and trouble to post. Appreciated :+1:t2:

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