Could L6 run well on mech fuel pump only!?

AliK

AliK

Vehicle Dating Officer
Staff member
Club Member
Dear Z knowledge bank!

This may seem like a daft question but, I was under the Z today playing and it struck me that I don't have the electric fuel pump!!! Can this be possible and the car run as well as it does?

I assume it sits in front of the fuel tank, but when I look at where it should be I see two male and two female bullet connectors. See pic ... Males in foreground females in back ground ...

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I don't hear any whirring when I turn the ignition on and I've traced the fuel lines from engine bay to tank and can't see an elec pump. The only place I couldn't see is where the fuel lines go behind the transmission.

I do have to crank for a good 15 seconds before it catches when left overnight, I had assumed it's taking air but now I'm wondering if it's the lack of elec pump causing it?

Any thoughts on this?

Thanks,
Ali
 
Well a 240Z will run ok with just the mechanical pump.

You shouldn't have to 'churn' for 15 secs if only left overnight though - if left a couple of weeks maybe.
 
Thanks chaps.

Rob, I agree it seems odd, I get an initial burst followed by cranking then it fires up. Need to investigate it.

Dave, I had read about 260s having both, was that mainly for other markets?
 
yes, 260z has wiring for electric pump, but no pump. I believe Australian market had one.
Like Rob says, it should start much quicker than that - time to check some stuff I think.
compression check? ignition advance?
 
My 260z had no wiring for the electric helper pump but then it's an early one so maybe that's why, either that or it was removed by a previous owner.

I had the same issue with the mechanical pump, I thought it was caused by a bad diaphragm inside the pump but it looked ok. I gave up trying to solve it in the end and installed an electric one instead.
 
I've experienced a faulty pump valve on the inlet side. You shouldn't be able to blow back towards the tank.
 
Mine is a bit like that, only mech pump, runs pretty well though.
Needs about 9seconds if left overnight and about 15 seconds after about 2 weeks.
But once fired up runs well.
It has always been like that as far as I can remember.
It just take a little time to get the fuel up from the tank?
I think an electric fuel pum will prime better and start quicker.
 
There should always be fuel in the carb bowls, so actually slow start shouldn't be a fuel supply problem.
As I remember mine when it was on SU and mech fuel pump, on choke it started straight away.
 
Thank all for the great input!

I thought the same about fuel in the carbs but I figured it's evaporated over night + I get an initial burst when I turn the key which I assume is a result of what is left on the carbs, then realistically about 10 secs of cranking ( longer if left for a week) .

I have two theories; 1. Need to renew fuel pump and look at carbs or, 2. Plugs fouling with oil getting past seals/guides overnight.

Head being rebuilt in a couple of weeks so I'll wait to see how that goes before changing the pump / playing with carbs.

When I get a spare hour I'll also take pump off and test as per Rob's post and let you know the outcome.

Thanks again,
Ali
 
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