Thread: V8 Discovery Fuel Pump Prob

Interesting read, i know mine is going to die soon, just have that feeling

UTEMAD, is your disco a 3.9 or 3.5 v8 ?

Might go and get myself a spare VN pump, ready for that day it dies

Matt.

Originally Posted by PhilipA

Thats why you have a fuel pressure regulator ( on the rail in D1 and in tank on D2) and a return line to the tank.
The pressure in the injectors is kept at AFAIK a constant 2.4 bar relative to the internal manifold pressure/vacuum .
The excess is bled off and returned to the tank. In this way the combination of ECU and pressure regulator ensures correct A/F ratio at all altitudes and atmospheric pressures.
Regards Philip A

ERRRRmmmmm yes,no maybe....

The pressure regulator will deal with a little over pressure but you have to be careful as to how much flow and over pressure your asking it to deal with...


a pump with the same pressure rating but a higher flow rate will be ok as the pump wont shift the volume of fuel once the pressure gets up to the operating range.

A pump with the same flow rate and a higher pressure rating wont raise the pressure as it cant shift the volume of fuel required to cause the pressureregulator to jam wide open and then raise the pressure.

A pump with an increase in both can achieve this. If your replacement fuel pump is over in both specs (a little bit you should be able to get away with but dont count on its reliability or economy in the vehicle) Dont use it.

on that note, if the fuel pump your going to fit doesnt list a flow rate but does list a pressure rating DONT use it. In the world of hyrdaulics pressure is created by the resistance to flow, an easy way to gain (temporarily) more pressure is to simply increase the flow rate. If you dont have a flow rate listed its probabley a cheap pump thats been tweaked to get more pressure and might fall into the higher flow rate AND higher pressure catagory.

Originally Posted by matbor

Interesting read, i know mine is going to die soon, just have that feeling

UTEMAD, is your disco a 3.9 or 3.5 v8 ?

Might go and get myself a spare VN pump, ready for that day it dies

Matt.

It's a 3.9. Still running fine.

Originally Posted by Utemad

It's a 3.9. Still running fine.

Thought so, just didn't see it anywhere.

Thanks.

ERRRRmmmmm yes,no maybe....

The pressure regulator will deal with a little over pressure but you have to be careful as to how much flow and over pressure your asking it to deal with...


a pump with the same pressure rating but a higher flow rate will be ok as the pump wont shift the volume of fuel once the pressure gets up to the operating range.

Blacknight, The context is that he is talking a VN Commodore 3.8 engine.
In my research on regulators when I put my Thor on, I believe that the Commodore regulator is exactly the samepressure and flow rate ( physically it may be a mirror image), The fuel requirements of the motor are near as dammit the same 3.8 vs 3.9 , so there is a 99% chance that the fuel pump will have a similar spec.
I wanted to KISS it.
Regards Philip A

Originally Posted by PhilipA

Blacknight, The context is that he is talking a VN Commodore 3.8 engine.
In my research on regulators when I put my Thor on, I believe that the Commodore regulator is exactly the samepressure and flow rate ( physically it may be a mirror image), The fuel requirements of the motor are near as dammit the same 3.8 vs 3.9 , so there is a 99% chance that the fuel pump will have a similar spec.
I wanted to KISS it.
Regards Philip A

and thats true enough but the warning I was giving was for someone looking for a replacement pump.... theres a hodge podge of pumps out there and physically they look the same but the regulators can vary hugely, an engine that is high in low down torque uses less fuel than one built to rev its nipples off and as the pumps are generally an On/Off setup the one with the higher fuel demand has a regulator capable of dumping more fuel as at idle they pump will be immitating a firepump and the fuel has to go somewhere....

you can get both sets of regulators and pumps to suit the various engine tunes that can be setup in a holden which I probabley should have indicated in the first posting... Sorry if that lack of info has caused any confusion..

I was facing the fuel pump saga just last week. I thought seriously about going the VL-VN route but at the end I decided it was easier and would be less problomatic to just replace it with a LAndrover product, so I did, problume solved car runs like new no pressure regulator issues and or line volume.
Just a thought!

Originally Posted by muddydigger

I was facing the fuel pump saga just last week. I thought seriously about going the VL-VN route but at the end I decided it was easier and would be less problomatic to just replace it with a LAndrover product, so I did, problume solved car runs like new no pressure regulator issues and or line volume.
Just a thought!

How much was the pump?