Master Relay Again?

[jpspringall]

Hi,

The other day after driving to my parent's house, and leaving the NSX for about 1 hour before setting off again, I had the dreaded refusal to start on first try.

It did splutter into life at the second attempt, but this was very reminicent of when my Master Relay started going about 18 months ago, which was duly replaced.

I'm just wondering if it could be on its way out again, that quickly?

The other thing i noticed was that the Volt Meter on the dash only registered ~13 Volts rather than 14, though this did return to normal after about 5 minutes of driving.

It's going in for its MOT next thursday so i can get it looked at then, so any ideas or pointers would be great, as i really dont fancy getting stranded again!


Cheers

James

[nobby]

Not being as techie and experienced as others on here I would check the simple things like battery life, ur terminal connections etc.

Aside from the main relay replacement there is also a recommendation to replace the fuel pump rectifier as well (wee square metal box on rhs of engine hatch). Could be this maybe fuel pump issues or indeed a faulty relay unit. Due to the age of our cars things like this will need replacing etc

Just hope u get sorted ... Keep us posted on diagnosis

[jpspringall]

I had the battery replaced about 2 months ago, so might be worth getting them to check the terminals.

[Hagasan]

Wiggle your ignition key a little too. They can play up a bit as well when the internal contact get "dirty"

[Kaz-kzukNA1]

Hi, James.


It will help if you can provide further information on exactly what happened
when you tried to start the engine but failed.


Did you feel the cranking speed was fairly fast and similar to the normal operation?

Did the engine catch briefly but died immediately or no fire up at all?

Do you normally wait for about 2sec after turning the IG switch into ON position and
listen to the fuel pump before cranking? If so, did you hear the pump priming the system?



One thing for sure, if you are saying that your voltage reading was ~13V immediately after starting the engine,
it's not right unless you were draining so much current by switching on many electrical components such as
the rear defogger, brake lights, max speed A/C fan, head lights, etc.

Once the engine starts, the volt meter is monitoring the IG1 voltage regulated by the IC Reg at the ACG so
should be around 14.5V with no major electrical load.


You may have loose battery connection.

As mentioned above, IG SW is one of the weakest point.

Watch the volt meter fluctuating when I wiggled the IG SW in the following video.





Original Blog here; http://www.nsxcb.co.uk/entry.php?599-Preparation-01



Hope you will find the cause of issue soon.
I won't say it's impossible but the Main relay won't fail in such a short period.

Kaz

[jpspringall]

Hi Kaz,

On the first try the engine cranked, but never caught
On the second try the engine cranked, and the spluttered into life.

I think i'll get honda to check the connections etc when it goes for it's MOT.

One thing i've noticed though is the volt meter reading on the dash has never been much above 14 volts, so if you are saying it's meant to be nearer 14.5 volts then i hope it doesnt signify a more serious issue.

James

[jpspringall]

Hi,

I've had all the connections checked by Honda, and they appeared to be OK.

The only thing they did notice, that there is a relay behind the ECU/Bose Speaker on the passenger side that might be sticking.

It does the following:

1. Clicks once on crank
2. Clicks again once it's started
3. 3 more clicks in very quick succession, as if it were sticking.

Just wondering if anyone knows what this is, and more importantly if it's normal?

Cheers

James

[duncan]

If you mean the amp/speaker in the passenger footwell, it's not unknown for security units/ immobilisers/ hands free units to be stuffed behind/ above/ and around this area.
Lift the carpet, remove the 3rd amp/speaker and have a look.

[Kaz-kzukNA1]

Hi, James.


Not sure what you mean by ‘behind the ECU/Bose Speaker’ but if it is the relay behind the left side seat next to the TCS module and near the centre speaker between the two seats, then it’s the Fuel Pump relay.

Not so common to fail like the Main Relay but still enough to be labelled as ‘watch out’ item together with the Radiator Fan control unit nearby.
They are normally stocked at NSX specialists in Japan due to their failure rate.

It’s just a power relay bypassing the fuel pump resistor at cranking or high rpm/wide throttle region.

If you can recreate the same issue repeatedly, you can monitor the fuel pressure or you can bypass the fuel pump resistor by thick gauge wire and see whether you can start the engine without any issues.

Having said this, it’s not that expensive and being as ‘known to fail item’, just replace it as preventative service.

Same power relay is used for different methods on our NSX.
I think you have early model NSX so it’s the 39797-SE0-003.

As a side note, the fuel pump resistor can also become faulty and cause intermittent connection which will result in difficult to hold idle rpm or even worse, it could become open circuit and in this case, you can fire up the engine but almost immediately loose fuel pressure and the engine will stop.

Kaz

[jpspringall]

Hi,

Well the conclusion is that there is no conclusion...
In that Honda couldnt find anything wrong, it's also quite difficult to prove that there is anything wrong as they cvouldnt recreate the problem.
I still think it's the master relay but there's no way of proving this, and Honda dont want to replace it for the sake of replacing it.

James