A wee problem or two. Think they might be related?

[93_Clubman]

As a 1998 MX5 it's an NB8 (1998-2005), which we commonly refer to as an NB8A (1998-2000). If the 6 speed GB was factory fitted then it sounds like a special/ limited edition as 6 speed GB wasn't fitted across the range until NB8B (2000-2002).

Given your location is Ireland, & it sounds like the car sat for a year slowly filling with water, & you say there appears to be electrical issues, it would be worth checking over the entire electrical system, i.e. fuses (in cabin & in engine bay), earth connections (in cabin & in engine bay), battery connections, engine control unit (ECU), & relays, as the sound deadening material under the carpet acts like a wick & retains all that moisture. So, if you haven't already pull out all the carpet & sound deadening material to allow it to dry out. ECU is either located in the RHD passenger foot well or in some models/ countries behind the RHD passenger seat.

Also, given the above conditions & that you say fuel is not getting through, it's possible that the external fuel filter needs replacing, as well as the internal (to fuel tank) fuel pump sock filter. Personally, even if I wasn't changing the fuel pump filter, I'd still want to check what the inside of the tank with all that old fuel looked like given conditions. Good luck!

[bruce]

I concur. There is moisture in your electricals and will be a pain to sort out. Treat it like a flood damaged car. I would sell it, as it may never be right.

[hks_kansei]

As a 1998 MX5 it's an NB8 (1998-2005), which we commonly refer to as an NB8A (1998-2000). If the 6 speed GB was factory fitted then it sounds like a special/ limited edition as 6 speed GB wasn't fitted across the range until NB8B (2000-2002).

It's probably a Japanese RS model.

If so, the gauge cluster should have red needles instead of the normal white, the tacho should redline at 6500rpm instead of 6000rpm, and the needles for tacho and speedo should rest at 6pm when the car is off.
The tacho will also have "6 speed" written on it in red.

[93_Clubman]

Is the ECU ("is either located in the RHD passenger foot well or in some models/ countries behind the RHD passenger seat") separate from the fuse box under the steering column? Incidentally, how do I check the ECU? If it's wet, dry it? If it's dry, bin it or what?

...the fuses or relays/assys in the engine bay are copper and some of them have green verdigris on them. Are they fixable with a rub and WD40 do you think? Or is it a case of replacing them?

I know where the internal fuel filter is (under the parcel shelf) but where is the external fuel filter?

ECU is completely separate from the fuse box under the steering column.
Disconnect the battery, remove ECU, & open ECU up to inspect the printed circuit board (PCB) & its components. Ensure it is dry, clean, & there is no discolouration of the PCB, & no bubbling or burn marks on PCB. If wet see hint links below.
Re engine bay fuse box & relays, you could try cleaning them, but it's a bit like the ECU, you probably won't really know how their going to respond until you clean it all up & attempt to drive it.
External fuel filter in under the vehicle just behind the driver in a RHD MX5.

As Bruce mentioned above you probably need to treat this car as flood effected, which are often repairable write-offs for insurance purposes here in Australia at least - the term certainly also came to mind. I recall two flood effected NB8B (one standard & one SP) whose ECUs got wet:
viewtopic.php?f=18&t=46348
viewtopic.php?f=55&t=46386
viewtopic.php?f=18&t=46427
viewtopic.php?f=53&t=51079

Some hints dealing with flood effected cars:
http://www.mx5cartalk.com/forum/viewtop ... 18&t=28787
http://www.mx5cartalk.com/forum/viewtop ... 85&start=0

[93_Clubman]

Can I just pull all the individual wires out (there are around 20 wires) that connect into the green connecting block? Or do I need to cut them and buy a new block?
I'm hoping that I can pull these wires out, cut them and crimp them and slot them back into their proper place? Or are these wires permanently attached to that block and must be cut?

The wires in the NA loom ECU block, at least, move back & forth in the block. They appear as usual to be held in by a tongue of metal on each individual metal electrical connector, so you need to insert a very very fine screw driver or piece of wire into the plastic block to flatten the tongue which will then allow you to withdraw each metal connector from the plastic block.

Or does the entire wiring loom need replacing?

There's a reason that flood effected cars are often repairable write-offs, in Australia at least, & that's because of the potential amount of labour & parts, & therefore cost involved in fixing them properly. As you're discovering there's more & more of your car's electrical system that's been effected - what we're suggesting is the minimal labour & cost approach, which may not work, but at least won't cost you thousands to find out that it doesn't work. So, does the entire loom & what hangs off it need replacing? That depends - we can't see how bad it is, but it certainly doesn't sound good. But if you're prepared to put in a lot of time sealing it up, removing everything, cleaning & drying, then you might get it sorted. Alternatively, you can spend a significant amount of money on it & probably eventually sort it. Your time or your money - the choice is yours.

Another consideration is a health one - homes can be deemed unfit for occupation due to certain types &/ or extensive mould because of the spores that can be inhaled due to proximity & exposure. While you don't live in your car, you're in close proximity to the mould & exposed for various periods of time in a very small enclosed space. The use of the heater or air conditioning, if fitted, in that environment doesn't even bear thinking about.

Also, the drain plugs that I've seen people talking about, are they a solid circle about 2 inches across in the floor? How do you open these?

You shouldn't need to open those up as water should not be getting into the cabin. If it still is then your priority is to stop water getting in otherwise you're wasting your time with the other work you're doing. Make it water proof first then remove everything to be cleaned & let it dry out. Then you can tackle whatever needs to be fixed. There are numerous drains in the MX5 - see here: viewtopic.php?f=28&t=35601 & here: http://www.mx5oc.co.uk/forum/forums/p/270/439.aspx#439

[hks_kansei]

The car is watertight now, it's just I'm having a bit of difficulty getting the carpet out. Water is still coming out of it so it's like leaving a huge sponge in the car while trying to dry it out. Someone said you have to cut it in half to remove it, which begs the question, how does the carpet fit in the first place or get replaced in one piece!

The carpet is installed at the factory before the dashboard/console/etc.

But, to remove it without removing the dash all you need to do is cut a small section that is only visible when you've got your head in the footwell.

Basically there's a strip that does across the transmission tunnel behind the radio panel etc. You need to cut this to let the carpet free (I can't remember the exact cuts, but if you look at it with a torch you should be able to see where it's caught.

[93_Clubman]

Thanks 93_Clubman. I thought they would come out, but I didn't want to just force them out. I think I may be able to remove them individually, snip them, recrimp them, then put them back in the correct holes. (that's the theory anyway!)

Like you, I'd be trying to clean it up first rather than replacing the loom. Think it might be worthwhile trying to clean up those loomside ECU electrical connectors which are inside the ECU plug blocks rather than cutting & fitting new ones. Perhaps there's a solution of something that they can be dipped or soaked in after disconnecting the battery.

Great to hear it's no longer leaking & that you've given some thought to the mould issue. Good luck!

[Steampunk]

Sorry I haven't read everthing clubman & hks has written (my eyes can't stand reading lengthy things on a screen) but if i got the gist correctly and you've got electrical gremlins due to water (in whatever form), then I would fix it as best you can until it runs ok again and on-sell as suggested. Unless you really want to replace the entire wiring loom.

Over the last few years I've learnt a new affliction of "capillary action" in electrical wires starting at one place then cancering to other places. Think back to primary school biology when you put a stick of celery in water with dye and it sucks it up and you can see it in the tubes of the celery.
When I first heard about this I thought "yeah right, I call bullsh*t on that" but when explained the theory, it kinda makes sense.
Water has an ionic charge, so there is a possibility for it to be "sucked up" by electrical current from one place to another.

[93_Clubman]

Agree Andrew, & OP's posts certainly point to that occurring in parts of the vehicle outside of the effected area, i.e. spreading from the interior to the engine bay.

[Steampunk]

The problem really is the actual model of the car. I also would loath selling it, it's the old heart vs head debate.

[93_Clubman]

I'm going to get a used fuel pump unit and replace the one that's in it. I'm fairly sure that's the problem for it not starting now. (here's hoping anyway...)

Ref fuel pump - have a quick look at this related issue which effects NA & NB:
viewtopic.php?f=55&t=46425

[93_Clubman]

Previously:

I put in a new battery, cleaned the spark plugs and it started first time.

Then after 20 mins it just suddenly stalled and won't start. It'll turn over alright, but the car won't come to life. It's not receiving fuel even though it has petrol in it.

Currently:

4. If I attach a battery to the pump, it works fine. Good, but have you tested the top of the tank electrical connections for continuity? See here:
viewtopic.php?f=55&t=46425
5. I've checked the electric source at the main fuses in the engine bay and there is power at all fuses. But is the Fuel Injection relay working?
6. I've attached the Fuel Pump fuse terminal to the pump and it works. Again, but is the Fuel Injection relay working?
7. I've removed the 4 wire-6 terminal, green fuel pump relay located under the accelerator pedal and connected it to a battery. It works. Good

There seems to be no power going between the fuel pump fuse and the fuel pump relay as both ends are working, but there is no power connecting the two. Might be reading this wrong, but if both ends are working then that suggests that it's ok up to & including the fuel pump relay & that the issue is between & exclusding the fuel pump relay & the fuel pump. If so, again see here: viewtopic.php?f=55&t=46425

My question is: Is there another component between the fusebox and the fuel pump relay that may have failed? Or would it be likely that a wire has suddenly broken or come loose in this section?

The car was running idle at the time of the problem, but it just stopped dead suddenly. It turns over, but doesn't fire.

Apart from what I've included above, given all the work you've done over a fairly long period of time, I'd also recheck for spark & fuel by trying to start the car a few times, then removing a sparkplug to check if it's wet, & finally with the sparkplug removed but still connected to the sparkplug lead, try starting again to confirm you're getting a good spark.

[93_Clubman]

Not saying you've fixed anything, but am saying that out of all the things you've done over a long period of time something might have changed, hence the need to reconfirm spark, or confirm spark if you hadn't previously.

To clarify there are two relays & a fuse involved - there's the 'fuel inj' fuse & the 'fuel inj' relay ('EGI' relay on the NB8) in the engine bay fuse & relay box.

And under the driver side dash there's the 'fuel pump' relay.

If you have a look at page eight of the US MY1999 NB8 wiring diagram pdf you'll see the links between the fuel pump relay, the fuel inj (EGI) relay, the fuel inj fuse, & the ECU:
http://neomiata.com/garage/Wiring%20Dia ... agrams.pdf

Page four also shows the fuel pump relay linked to the ECU, & the diagnostic box in the front of the engine bay.

So in response to your question, from looking at the wiring diagram it would appear the the issue could be in the ECU or in the wiring to the ECU from the fuel pump relay, or in the wiring between the fuel pump relay & the engine bay fuse & relay box. None of which are common issues, but then again what your NB8A has gone through isn't too common either.

[bruce]

I'd be trying swap in a good ECU (at least it eliminates one possibility).
An ECU might 'look' good but there might be damage not visble.