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Fluctuating Fuel Pressure

Old 04-23-2016, 01:47 PM
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Default Fluctuating Fuel Pressure

Hello All,

Having an issue with my fuel pressure. I'm using the FAST EZ EFI system with the stock Miata fuel pump. Some of the time I start it up and get 44 lbs. About a quarter of the time I only get 22 lbs. I'm thinking fuel pump but just wondering if anyone else has had this problem.

It will stall at red lights sometimes and will try to hunt for a air/fuel ratio. I think that is when the pressure is low.

Also, does anyone have a recommendation for a replacement pump?

Thanks,
Denis
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Old 04-24-2016, 07:25 PM
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I recommend a walbro 255 pump or an Aeromotive stealth pump.

But prior to that I'd ask if you've done any modification to the stock miata fuel pump wiring circuit? the stock fuel pump wire is very small gauge and I'd recommend upgrading the power and ground to the pump, also, the stock fuel pump relay is infamous for going out. With that said, when it does the low pressure situation check the voltage at the pump using it's own ground and see what you've got. Make sure it's battery voltage and not dropping off. If voltage is good, It would be a safe bet to assume you've got a failing pump
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Old 04-25-2016, 10:40 AM
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Originally Posted by SupaDupaSteve View Post
I recommend a walbro 255 pump or an Aeromotive stealth pump.

But prior to that I'd ask if you've done any modification to the stock miata fuel pump wiring circuit? the stock fuel pump wire is very small gauge and I'd recommend upgrading the power and ground to the pump, also, the stock fuel pump relay is infamous for going out. With that said, when it does the low pressure situation check the voltage at the pump using it's own ground and see what you've got. Make sure it's battery voltage and not dropping off. If voltage is good, It would be a safe bet to assume you've got a failing pump
Thanks for the info Dave. I haven't messed with the fuel pump circuit (that I am aware of anyways). I'll try testing the voltage when it is at 22 lbs.

Denis
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