Key position "ON" fuel pump noise

bmchi · Postby **bmchi** » Wed May 04, 2016 6:13 pm

Hey Guys,

wanting to confirm, if I have the key in the on position will this signal/prime the fuel pump? I've heard you should be able to hear the fuel pump buzzing when the key is in the on position, but have read a few times on Miata.net forum that the MX5 doesn't work that way and it will only prime when you crank it.

Reason why I ask is because I put my key in the on position and I cant hear the fuel pump buzzing. I've removed the cover and shelf carpet to hear everything and no sound until it actually starts up.

The reason why I am asking is because I think it may be a slow to work pump (a new pump I've just changed over) and takes 4-5 secs of cranking before it starts.

can anyone confirm?

Postby **NitroDann** » Wed May 04, 2016 6:21 pm

No pump until you crank.

smy0003 · Postby **smy0003** » Wed May 04, 2016 6:43 pm

What dann said. Unless you have a non standard ecu you won't hear anything before firing.

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Magpie · Postby **Magpie** » Wed May 04, 2016 7:37 pm

Can here my pump when the ignition goes to on, yes I have an aftermarket ECU.

Nevyn72 · Postby **Nevyn72** » Wed May 04, 2016 9:04 pm

Really?

It's part of my starting ritual to go to the 'on' position on the ignition, listen to the fuel pump prime the system (usually just over a second) and stop, before cranking and starting the car.....
NB: factory pump, factory ECU, NB SE.

bmchi, what pump did you install?

Roadrunner · Postby **Roadrunner** » Wed May 04, 2016 10:17 pm

Before I changed from the factory ECU I could definitely hear the fuel pump in my SE.
The pumping noise lasted exactly as long as my boost gauge took to do its start up sweep and like Nevyn72, it was part of my start up ritual.

Now with the Adaptronic it primes for longer so I just start the car :lol:

hks_kansei · Postby **hks_kansei** » Thu May 05, 2016 3:05 pm

NB8A

Pump only active when car is cranking, pump wont run with key at "ON" unless the engine is running.
confirmed with a multimeter etc when my car had issues and I suspected pump.

Worth noting that it's not triggered by the CAS like the coils are, my timing belt was stripped at the time (so cams not moving) and the pump worked while cranking.

When you turn to "on" there are other things that activate, coil relays click on and the coils start to charge, as well as some other stuff, so it's possible that people are hearing those whirrs and clicks and thinking it's the pump.

smy0003 · Postby **smy0003** » Thu May 05, 2016 3:19 pm

Good point hks, could also be the aerial deploying since its a similar sound.
Although by the sounds of it, the SE may prime the pump with the key switched to on.

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RS2000 · Postby **RS2000** » Sat May 07, 2016 11:44 am

My NB8A track car has a buzz/hum with the ignition s/w at ON & I always presumed it was the fuel pump.
After reading this topic I searched for the noise location, & it's from the intake - loudest is with my ear at the pod filter!
MAF ?

hks_kansei · Postby **hks_kansei** » Sat May 07, 2016 12:06 pm

I think the nb uses a hot wire style afm, so may just be the afm wire heating up.

bmchi · Postby **bmchi** » Mon May 09, 2016 1:41 am

I installed a fuelmiser pump which i bought from repco, its a generic to fit the mx5.

I now have an extended crank and my thinking is that the fuel pump is not primed before starting