Fuel on Demand

[huzilulu]

Hi guys

I know some of you have used the FOD system to regulate the fuel pump to keep fuel cool, increase pump life, etc ... I have a few questions as I try to install mine:

1) I set it up as in the documentation, using a return style system setup - my target is to get 58psi to the rails. My issue is even after trying a few different settings, I am getting the pump to run at almost full speed: it's at 98 duty cycle and drawing 10A to maintain 58psi! I'm not sure what I'm doing wrong...
I tried FOD at 58, regulator at 60
FOD at 60, regulator at 58
Both at 58

All three give me fuel pump at almost full speed

2) the FOD shows a much different pressure than my fuel Guage that came with the regulator - almost a 10 psi difference... I'm not sure which one is incorrect so I need to get another Guage to verify - if the FOD pressure sender is bad, where can I get a replacement?

Others who run this system - what duty cycle / amp draw have you seen?

Thanks

[mt308]

I think what ia happening is that the body of your fuel pump is making an earth connection against the rear bulkhead. The FOD works by varying the current to earth. If the fuel pump body is earthed you will have the pump running full all the time. Its what mine did when I first fitted it.

Now when under moderate load it draws 3 amps or so. I've never managed to get my Bosch 044 to draw more than 6 amps or so and that's open throttle on a 700hp LS7. So the pump seems man for the job.

Good luck

Mark

[huzilulu]

That's a very helpful idea - thanks Mark..

How did you solve the body earthing issue? Or test for it?

[Steve_D]

huzilulu said:

That's a very helpful idea - thanks Mark..

How did you solve the body earthing issue? Or test for it?

Disconnect the pump then using a multimeter test for continuity between the pump negative terminal and the chassis.

If it is connected then you need to come up with some sort of rubber mounting.

Steve

[F.C.]

These:

http://www.vibrationmounts.com/

http://www.sdp-si.com/products/Vibration-Mounts/in...

Take your pick!

[mt308]

Steve_D said:

huzilulu said:

That's a very helpful idea - thanks Mark..

How did you solve the body earthing issue? Or test for it?

Disconnect the pump then using a multimeter test for continuity between the pump negative terminal and the chassis.

If it is connected then you need to come up with some sort of rubber mounting.

Steve

Yes, as Steve says. To begin with I would suggest turning off the ignition then using multimeter to test for resistance between -ve terminal and chassis, then between pump body and chassis (both will probably be the same as I think the -ve terminal may be grounded to the main pump body).

If you have (as I suspect) almost zero resistance (i.e. a connection) then I think there are 2 likely suspects - firstly the body of the pump is somehow touching the rear bulkhead, secondly a metal braided fuel hose is touching the fuel pump and in turn the rear bulkhead.

Either way you need to insulate it, using either some rubber sleeving, and/or some "spiral wrap" for the fuel hoses (I've done both).

If you have the standard Ultima set up, and are running a Bosch 044 pump, this should be mounted to the chassis on 4 rubber mountings - if so, it won't be the mountings themselves that are giving you a connection, more likely the body is just touching the rear bulkhead at the back.

Good luck!
Mark

[huzilulu]

Thanks guys.. I did check and there is no 'continuity ' between the pump body or negative terminal and chassis / ground points.. I did disconnect the wiring to test, so next I will look the FOD wiring to see if it may be grounding out somewhere, though I doubt it since the negative terminal goes to the FOD and not chassis ground..
Is there a way to test if the FOD controller is working correctly?

[mt308]

huzilulu said:

Thanks guys.. I did check and there is no 'continuity ' between the pump body or negative terminal and chassis / ground points.. I did disconnect the wiring to test, so next I will look the FOD wiring to see if it may be grounding out somewhere, though I doubt it since the negative terminal goes to the FOD and not chassis ground..
Is there a way to test if the FOD controller is working correctly?

Have you checked the set up by plugging into a laptop? There is a setting which will run the pump at full rate.

[MarkWebb]

A visual check of how much fuel is coming from the pressure regulator return is probably in order here. I would believe the electrical pressure sensor supplied with the FOD over any mechanical gauge!