Won't start - Main relay - how to check?

[goldtop]

Silver '93 NA1 is in long term storage and has been on a battery conditioner for a few months. Called the company today to say that I would collect it and they called back to say it won't start: engine will turn over just fine but it will not fire into life.

First question was about the immobiliser on it (Toad I think), but that seems to be working OK as the starter turns. (Unless there's likely to be a second immobiliser circuit that interrupts fuel/spark/etc?)

So, I just did a search here and found Kaz's excellent postings - about the main relay controlling fuel/etc and the starter being on a different circuit. And I've seen a few mentions of the relay's solder joint issues and where to find it on my non-DBW car.

The car is however, several miles away, so I'm wondering if there's any other diagnostic check that can be done with the relay in situ?

Or do I just buy a new relay, swap it in and see if it works?

Or do I swap in the main relay from my other NSX ('95) to check? Logic says that this would be an obvious idea, but I know that if there are any marginal solder joints on this one, disturbing the relay may break them and I could have 2 non-starting NSXs!

[Kaz-kzukNA1]

Hi, goldtop.

As in your post, seemed like the immobiliser was disarmed properly but no fuel to the engine.
You can ask them to do a quick check by following method.

First, you need quiet environment.
After disarming the immobiliser, turn the IG key into P2/On but do not crank the engine.

As soon as your key is in P2, you should hear faint hissing sound behind the seat for 2sec.

Every time when you turn the IG key from P1/ACC to P2/ON, the Main Relay will prime the fuel pump for 2sec resulting in this hissing sound so you can repeat the above test many times.

If you can’t hear it, it’s the main relay.

Some of the main relay on 2000 – 2002 models already started to fail several years ago and looks like the manufacture didn’t change the soldering method at all so there were several reports of new main relay failing within 2 years even after being replaced in Japan.

If you need to move your NSX urgently, I have several emergency spares that you can use for the time being.
If you can wait for a while, I can order one for you as I’m about to order GND cable and non-DBW spec Main relay for the NSX that I will be servicing next week.

You can try your 95 DBW main relay on your 93 non-DBW one but you need to somehow deliver it to the storage place and in order to get to the main relay on your 95 model, you will need extra steps.

Please note that the bracket is longer on the DBW spec main relay than the non-DBW one but the electronics circuit is the same. So, you can use it for testing purpose but you won't be able to install it properly.
If the main relay on your 95 model was never replaced, I won't be surprise for it to fail as well in the near future.

Kaz

[goldtop]

Hi Kaz. Thanks for the advice. There's no urgency, just annoyance and a new development...

I went to the storage place on the way to tonight's mini-meet in Kent, and after a few times repeating the same process, at one point, I did hear the slight whirring noise behind my left shoulder, and the car started perfectly. To the amazement of the mechanic who had been trying for an hour or more. Switched off and repeated the process 3 times- all OK.

But as I had a long trip and no breakdown recovery, I did not take the car in case the problem returned. Will definitely buy a new relay (or two) and swap them to see if I can get it 100% consistent and reliable. my day job is electronics, so I can investigate and resolder the old relay.

So yes please on ordering the relay. I will PM you tomorrow.

[WhyOne?]

........my day job is electronics, so I can investigate and resolder the old relay.



The main relay failed on Y1 (2001) a few years ago. I am certainly no electrician, but at Kaz's advice, I just used a soldering iron to melt the solder on all of the connections on the failed relay - much to my surprise and delight, this did the trick and this relay worked without fault for a couple of weeks until a new unit arrived. I retain the old 're-soldered' unit as an emergency spare.

[328]

Hi goldtop,

this happened to my car prior to our mini meet a couple of weeks ago. I followed Kaz advice and got my friend to resolderer and the engine turned over :) was an original unit from the 1990 car!

Bought two units from Kaz :)

cheers,

andy

[britlude]

as you may realise, it's a common problem, and most people have got a spare.

when i re-soldered mine it seems the relay pin corrodes beneath the solder, so slowly jacks the solder off the pin until it eventually fails!

desolder, a quick scuff up, and resolder! simples!

[goldtop]

Thanks fellas. This seems to be a well-trodden path of NSX ownership.

Wonder what causes that corrosion in this particular place? Gold plated contacts would have been over-the-top, I suppose?

[328]

Thanks fellas. This seems to be a well-trodden path of NSX ownership.

Wonder what causes that corrosion in this particular place? Gold plated contacts would have been over-the-top, I suppose?

i would guess mine was just old age! Wear and tear....but saying this at lest it lasted 23 years!

Only after did I realise everyone has spare main relays!! So I had to buy spares too :)

[WhyOne?]

You can't have too many spare main relays :)

My original only lasted 10 years before failing.

[Hondaboy]

Just resoldered my main relay on the prelude 3rd gen so it's not just the nsx that suffers this lol

yes I'm still hanging about this forum god I miss my nsx :(

[328]

Just resoldered my main relay on the prelude 3rd gen so it's not just the nsx that suffers this lol

yes I'm still hanging about this forum god I miss my nsx :(

maybe you will miss it soooo much that you will eventually get back into one :)

[NSXGB]

i would guess mine was just old age! Wear and tear....but saying this at lest it lasted 23 years!



As far as I can tell from my records mine has never been changed and is into its 21st year, I carry a spare just in case but now I have to beat 23 years!

[328]

As far as I can tell from my records mine has never been changed and is into its 21st year, I carry a spare just in case but now I have to beat 23 years!

Lol....just don't drive your car like what I did for the past couple of years and your bound to sail past 23 years!

[Nick Graves]

That'll learn me not to believe you lot!

I'd moved my cars onto the wayleave behind the house, so I could mess around with the Legend.

Finished up, started NSX and just sat there cranking. It 'caught' after turning it on and off again, so I took it for a thrash to punish it.

Just bought an unused 39400-SL0-A01 off Fleabay for £70 (Senna.C?), so it looks like serendipity is on my side today! Could've been a lot worse.

[Nick Graves]

Quick post mortem on the old relay:

Most are OK, but the current across the relays themselves seems to have met high resistance and began to melt the shellack (or whatever it is these days).