Electrical Fuel Pump Pressure Problems

[Dave WM]

I get a 2.0v drop video to follow.

I also checked by leaving the setup but rather than look for  drop (pump + term compared to Batt + term) I connected from Pump + to chassis ground. got about 10v suppled to the pump. This is with the engine not running. Typical battery voltage with the alternator working would be close to 14v so a 2v drop would supply the pump with approx. 12v.

 

Edited October 30, 2018 by Dave WM

[Dave WM]

here it is

 

[Yellow78]

 I can check again tonight but I don’t see this being an electrical drop issue I see it being just a pump that won’t pump enough pressure. 

[Dave WM]

that kind of thinking makes it hard to diagnose but its your car, go for it.

[Yellow78]

OK I did the electrical just like the video and I came
up with around a 2 V drop


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[Dave WM]

Not excessive (compared to mine, which works fine) so now we know the power supply to the pump motor is not the problem. and the amp draw is ok, this would tend to say the motor is at least drawing the correct amount of power.

Next did you ever try feeding the pump from a source other than the fuel tank? That would eliminate a fuel supply issue.

I would just get a gas can and a long rubber fuel line, set the gas can up on a chair so its about the same as the fuel tank, and hook that up to the inlet of the pump.

 

Edited October 30, 2018 by Dave WM

[Yellow78]

With the aftermarket pump that I had on the car was only giving me 26 PSI there was plenty of fuel at 26 PSI coming to the filter under the hood. Of course 26 PSI is not enough to keep the L6 running correctly. At this point I’m sure I’ve got a bad pump from the supplier, I will return it and get a different pump.

Thanking of this one:

https://zcardepot.com/catalog/product/view/id/2535/s/electric-fuel-pump-and-filter-combo-bracket-efi/category/349/


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[Dave WM]

Are you trying to support 700 hp? If not I would be wondering if that much fuel having to be regulated back to the tank would stress out the FPRegulator.

Did you say this is the second pump that is only producing 26psi? and that is with the return clamped off? You say you are sure its the pump but I don't remember you saying you tried feeding the pump as I mentioned to make sure its getting a free flowing supply. The pump is designed to push fuel not pull it thru a restriction.

Edited October 30, 2018 by Dave WM

[Yellow78]

I talked to z car depot and they said they sell these to a lot of Z owners and it’s a good price. Plus it has a nice filter before the pump. Can’t find anyone to actually tell me what BOSCH unit would work and is available was not copied crap. This is the first pump besides the stock ones. With everything hooked up correctly I got Carly 2PSI with return lines back to the tank if I clamped off I only get 26PSI.


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[Zed Head]

He also sells the Airtex pump.  https://zcardepot.com/catalog/product/view/id/176/s/electric-fuel-pump-fuel-injection-280z-280zx-75-83.html/

[Zed Head]

21 hours ago, Zed Head said:

The general spec for a stock L6 is about 30 gph at 36 psi.  Higher volume means bigger draw on the electrical system.  You don't want that on these cars, the electrical is on the weak side already. 

The Airtex E8312 is a common replacement.  I have one, it's worked great for years and many miles.

https://www.amazon.com/Airtex-E8312-Electric-Fuel-Pump/dp/B000DT7Y7K/ref=sr_1_1?ie=UTF8&qid=1540865716&sr=8-1&keywords=airtex+e8312

You only need 30 gph.  Excess volume will cause excess current draw.  You'll be upgrading your alternator next.

Good luck.

[Yellow78]

That’s the same pump that I got from a different vendor on Amazon and only get 26PSI. AirTech unit does not say how much PSI or GPH.


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