Won't start

This morning all is fine, drive ten miles no issues. Eight hours later leave work turn ignition key starter engages but the engine does not fire. What I do hear is the front radiator fan running immediately I turn on the ignition. I turned it over quite a few times and would expect if petrol were being sucked through that I would get at least a whiff of it. Is there a relay stuck which might be indicating that the engine is so hot that the spark/petrol pump are disabled? There don't seem to be any fault codes as all dash light go out.
I didn't have much time to analyze but I suspect a simple (single ?) electrical fault.
The fan running is to my mind the biggest clue. Anyone got any ideas? There is plenty of fuel, it started normally this morning as soon as the key was turned and I am not aware of any solar flares. It is a first in nearly seven years as a faithful hound. 1993 no mods.

Main relay.

NSXGB said:

Main relay.

Click to expand...

Short and sweet. I hope so. And no error code?
As I am in another world (time zone) and am just about to hit the sack it will take time to confirm but I will let you know as soon as, but............... does that explain the fan running????

Won't start:
As others suggested, try Main Relay first. If your NSX is 93, it's the non-DBW type.
http://www.nsxcb.co.uk/showthread.php?6286-NSX-Health-Check-Service&p=66800#post66800

http://www.nsxcb.co.uk/blog.php?1811-Kaz-kzukNA1&s=&tag=main relay


Rad fan runs immediately when IGSW in P2:
The Fan Control Unit.
Re-solder all the joints.
http://www.nsxcb.co.uk/blog.php?1811-Kaz-kzukNA1&s=&tag=fan control unit


Kaz

The fan running is likely a symptom of a separate unrelated problem - a failure in the fan control unit (typically caused by the dreaded leaking electrolytic capacitors). Perhaps you are just noticing the fan now because of the absence of engine sound?

The high probability candidates for the non starting problem are the main FI relay (as already suggested) and given the age of your car, the fuel pump if it is original. There is no error code for a main relay failure. The quick test is you want to listen for the operation of the fuel pump during the fuel pump prime cycle. This occurs if you switch the ignition key to run; but, not all the way to start. The pump should run for about 2 seconds to prime the fuel system. Have someone listen down by the left rear wheel for the sound of the pump. If you don't hear the pump sound, then likely the main FI relay has failed or the pump has failed. Get a copy of the service manual (you can find them on -line) and check out the procedure for testing the main relay (or if you like to spend money you could just replace rather than diagnose). If the main relay tests good, then it is likely the fuel pump.

The other 'tell' for a failed main relay is that the MIL / check engine light may not light up during self test cycle when you first turn the ignition key to run. Of course, that could also be a sign of a dead ECU which would also cause non operation of the fuel pump. However, dead ECUs are infrequent, failed main FI relays not so infrequent.

If the fuel pump is going through its 2 second prime cycle and the engine does not start, then the problem is more complex and opens up a much larger selection of possible and perhaps more expensive causes.

The main relays can usually be repaired if you are so inclined. Failure is typically caused by fracture of the soldered connections on the circuit board inside. Reflowing the solder with a soldering iron usually provides a fix.

Are you sure it's the rad fan or the AC fans? I can't remember off the top of my head if they would run with switch at P2, if the AC unit was on.

Spot Prize

And the winner is...the Main Relay, I think, in fact I hope it is.
Firstly I have to apologize for the red herring (s). As I have a straight through (no cat) exhaust with a Comptech box on the back I will admit this was the first time I ever heard the A/C fan running, my bad. Also my description of no mods was a tad incorrect, an aftermarket immobiliser is wired to the Main Relay (of course) with two relays hanging out of it. It's a bit of a mess so I am not certain whether it is relevant. The immobiliser cuts the feed to the starter.... grovelling complete.
I took the Main Relay out and on inspection (see attached) it looked perfect apart from some discoloration of the conformal coating. I went ahead anyway and re-soldered all the joints and all is well. If I had been on my own I wouldn't have dreamt of resoldering as I saw no evidence of any dry joints or cracking. Just goes to show what forty years in electronics has taught me. One observation to anyone reading; I noticed in one of the tagged discussions that there was a suggestion simply to reflow the contacts. If you have access to a soldering iron you should be able get hold of a solder sucker as they are invaluable for the likes of this job. Fresh solder costs nothing.
Many thanks for speedy responses and I appreciate now that it was on hindsight a fairly obvious first port of call but as Eddie Jordan once said,'Hindsight is foresight to a gobshite', which is a bit like what I felt last Thursday. Thank you all who came to my rescue and revival of my faithful hound(a).

My main relay had to be re-soldered and I now keep a spare in the glove box.

I've heard that there are aftermarket options that plug and play with no mods that are superior. Anyone heard anything?

BATMANs said:

I've heard that there are aftermarket options that plug and play with no mods that are superior. Anyone heard anything?

Click to expand...

Are you talking about the main relay? If so, RockAuto sells a couple of aftermarket drop-in replacement options. Can't comment on whether they have better long term durability.