Fuel pump

[Alan Whitaker]

Hi All
I have a low pressure fuel pump supplying a 4 litre swirl pot with a tank return, I have this wired up through the oil pressure switch. I have a bosch 044 on the high pressure side to the fuel rails with tank return,

question
Do I have to use the ls400 fuel ECU to control the 044 pump or can I link it into the oil switch as well.
I am still fitting the engine so has not been run yet so any help appreciated.


Alan

 

[5020Chris]

Hi Alan, I never fitted a swirl pot on my truck and have never had any fuel problems in the 15000 miles that I have done. I am not saying this is the correct way but I have not encountered any problems, I "think" it was sideshow who gave me this info when I was doing my Hilux conversion.
Hope this helps,
cheers Chris.

 

[cribbj]

Alan, just a couple comments:

1. If you've linked either or both pumps through your oil pressure switch instead of the fuel pump ECU, how are you going to start the car when there's no oil pressure to enable the circuit to the pumps?

2. The fuel pump ECU does the initial fuel system pressurisation, and it also turns the pump off in case of a collision or a rollover. It could be argued that anything that cuts the engine off, would turn the fuel pump off too, if it were linked through the oil pressure switch, but I guess I'm not that trusting.

3. The fuel pump ECU also reduces voltage to the pump at engine idle and cruise, which reduces the recirculation of excess fuel during low demand conditions. Recirculating fuel is a bad thing because it heats it up and causes loss of density (energy) and excessive vaporisation.

 

[Alan Whitaker]

Hi
Thanks for that, will look for a ecu and do it that way.

Alan

 

[Alan Whitaker]

Hi.
I have a ls400 fuel ecu on its way, which leads me to ask the following,
As I don't have a ls400 tank or pump do after market external pumps work the same way from the ecu,


Alan

 

[cribbj]

Alan, I think two pumps are probably going to overload the ECU.

You should probably slave a good quality relay off the ECU and drive the low pressure pump from that relay. Make sure the relay will pick up with voltages as low as 8 or 9 volts, because the ECU will cut the voltage down to that level at idle. If you can't find a conventional relay that picks up that low, you may need to consider a solid state type, which picks up as low as +5.

The Bosch pump could be run from the ECU itself.

Why the double pumps and swirl pot? Is this a racecar and is it boosted (turboed?)

 

[Alan Whitaker]

Hi
Trackday, may turbo later after running, I know I will have to run another ECU if I turbo

Alan

 

[Alan Whitaker]

Hi All
Ok I now have the LS400 fuel pump ECU, I have all the wires sorted from the engine ECU.
Question is

The green out from the fuel pump ECU to the pump, this controls the fuel pump so at idle it lowers the voltage to the pump and increases it as the load is required.
Can I piggy back a solid state relay onto this for my low pressure pump, the relay will operate as low as 2.2 volts.

I have not got the loom sorted out to try so I am asking anybody know the voltages from the fuel pump relay at Idle and full load


Many Thanks

Alan

 

[cribbj]

IIRC, the fuel pump ECU doesn't go any lower than 8.5v. Depending on the year, it could be a simple voltage divider, or it could be a PWM setup. The later PWM setups work better, as the voltage dividers are very inefficient and generate a lot of heat.

Your SSR should work fine, assuming it's the 30a variety. If you don't have it heat sinked, you'll have to derate it significantly - probably at least 50% to be safe. So for a 30a SSR, I wouldn't run it much over 15a.

 

[stevechumo]

Using the correct size of the fuel pump is important. There's no need to have dual pumps if the hp doesn't exceed the pump capacity. There're some pumps out there that can handle 500 rwhp by itself.