Patchy's Fawlty Towers risk management. Enter at own risk

[StanTheMan]

US O2 sensor shouldn't cause non-starting - could be the black Fuel Inj relay in the engine bay fuse box or may be the fuel pump relay under the driver side dash. But first check all the fuses are ok, especially the big fuses in the engine bay fuse box.

FWIW:

Re: engine cranks over normally but wont start-cold:
Checked the Rod's Enthusiast's Shop Manual Troubleshooting section:
Engine cranks normally, but doesn't start:
Damp sparkplug leads;
Dampness in sparkplug wells;
Sparkplugs in poor condition;
Fuel, ignition or control system malfunction (establish that plugs are sparking & fuel is reaching engine);
Very low engine compression;
Blocked exhaust; &
No fuel.
Also checked the Haynes Troubleshooting section but it doesn't really add anymore value.

Ok.

Checked the fuses all Ok.1 looks a little corroded but swapped it around with another one.
Didn't check the relay under the drivers dash.....
Will check for dampness in spark plug wells.



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[StanTheMan]

To give you the full story.
patchy started. Took her for a spin. Engine cut out suddenly. Wouldn't start again . Rolled her back to my place.

The Fuel injector relay does not click. When ignition switches on. Prolly the most likely culprit. That's the one under the dash. That's been replaced before but for all I know. It could be the same age as the original.
But why do the spark plugs seem covered in petrol? Or is that my imagination? It's been running super rich. I have a new O2 sensor on the way which will hopefully sort that out.

The relay needs to click when ignition switches on. Right?


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[gslender]

You've got fuel, and air is a given, so spark is very likely the problem. Focus on that and be sure the coil is working.


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[93_Clubman]

Relay that clicks when the ignition key is turned to the 'ON' position on the NA6 & NA8 is the black 'Fuel Inj' one in the engine bay fuse box (on NB8 this is the green EGI relay). Relay under the dash is the fuel pump relay.

If no luck worth checking earths as well.

Just going from memory here from my NA8.
In order of importance for engine grounding they are:
- coil/injector loom to rear of inlet manifold
- misc bits to bracket below front of inlet manifold
- engine block to chassis from near dipstick to firewall ledge
- PPF to chassis near rear axle
Also check all connections to alternator are clean and sound, especially the white.

Not absolutely NA6 specific, but link to USDM MazdaSpeed Miata Engine Won't Start Diagnostic Checklist is in my last post here:
viewtopic.php?f=18&t=69683&hilit=Diagnostic+Checklist

Also a couple of basic engine trouble shooting PDFs in my post here:
viewtopic.php?f=29&t=69784&start=15

[StanTheMan]

You've got fuel, and air is a given, so spark is very likely the problem. Focus on that and be sure the coil is working.


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I have spark all 4 cylinders
Fuel pump works. When bypassing relay through the diagnostics box.
Ignition relay in fuse box of engine bay clicks when ignition is turned from on to the next stage.
Fuel relay under driver side does nothing. No clicking when turning ignition on or to start. Is it supposed to?
I've checked the cam belt. It's not broken but seems a little loose.....not sure.
I will check all the earth connections next. But stopping the way it did.....not sure.
Tomorrow weather allowing I,m thinking of checking the cam belt alignment . Could a jumping o tooth or 2 on the cam belt have this effect?
Spark plugs are wet undoubtedly. Seems to get the fuel. Or am I hallucinating . Refer pic above

[93_Clubman]

Fuel relay under driver side does nothing. No clicking when turning ignition on or to start. Is it supposed to?
No. Some hear the fuel pump itself initially, but not evident on all NAs.
Could a jumping o tooth or 2 on the cam belt have this effect?
Maybe if it's jumped enough teeth.
Spark plugs are wet undoubtedly. Seems to get the fuel. Or am I hallucinating. Refer pic above.
From the pic ceramic around electrode looks more glazed than wet, ie there looks to be a unglazed or dry bit, which wouldn't expect if wet.

[StanTheMan]

Cheers clubman. It's perhaps I wiped it with my finger before taking the pic it was definitely wet.
Will check timing on cam belts & earth connections tomorrow


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[Magpie]

Get a noid light to check your injectors are firing or this tool http://www.efi.com.au/product-range/diagnostics/ignition-injection-testers/efi-quick-probe-detail

If in Brisbane happy to lend the tool I have linked.

[gslender]

How are you confirming spark? Describe exactly what happens when turning it over, does it catch at all, or just turn over as if nothing firing at all.


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[StanTheMan]

It's turning over, strongly. With no hint of wanting to fire up, or "catch"just keeps going round & round..
Spark. At this stage the battery is in great shape.
I took out each spark plug separately,Placed it on the cam cover. Turned it over standing outside to watch what happens. I have spark on each spark plug individually. Connected to thier respective leads. Leads are connected to the correct place on the Coil. ( or whatever it's called)

Since I did the cam belt only a few weeks ago.....it's a major suspicion. I've never taken a conscious check exactly how tight the belt is supposed to be. I just noticed that it seemed loose. It could also be just the way it is. I'm just not 100% sure. That's why I'm suspicious until I've checked it. I've changed the belt several times. I can do it in my sleep. Maybe that's why I'm also suspecting it. Maybe I was sleeping while doing it. The belt tensioner is not making any excessive noise. It's not much trouble pulling it down to check though .
I don't know how to check a relay. I have no skills with electronics. I don't even own a multimeter.
But at the same time I will also check the earth connection suggested earlier.

[gslender]

Seeing spark doesn't always indicate a suitably strong spark for compression. In the free air a small voltage will leap across a spark gap. In the combustion chamber, it can be very different. This is where measuring the resistance at the spark plug works - it will tell you the quality of plugs, leads and coil. Needs to be in the range of 8 to 15 k ohms.

The other area of fault can be the igniter (which drives the coils) and they commonly fail early in an mx5


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[rascal]

Seeing spark doesn't always indicate a suitably strong spark for compression. In the free air a small voltage will leap across a spark gap. In the combustion chamber, it can be very different.

I've first hand experience of this. Car wouldn't start at Sandown once.
Car turned over reasonably fast but wouldnt fire. Plugs were soaking in fuel. Pulled plugs and cleaned, checked for spark against cam cover. All sparked.
Put back in and still wouldnt fire.
Long story short, battery lead was loose and not allowing full current. Tightened lead and fired straight away.

[93_Clubman]

I don't know how to check a relay. I have no skills with electronics. I don't even own a multimeter.

While 'Fuel Inj' relay is labelled such it also affects spark. However, manga_blue & caffeine have used a temporary work around for it (piece of coat hanger wire), which might allow your car to start - just have to find the thread - here you go:
viewtopic.php?f=29&t=38526&p=535770&hilit=relay#p535770
viewtopic.php?f=29&t=49188&p=617511&hilit=relay#p617511

[93_Clubman]

Here's main relay pinout pic to go with the above link:
viewtopic.php?f=29&t=38526&p=535770&hilit=relay#p535770

MAIN Relay pinouts.jpg

[StanTheMan]

Timing belt jumped 6 teeth . Patchy is purring like a pussy cat.


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