JE Oil pressure switch - WHY ?

[izu069]

I'm dragging up an old thread, but since someone pointed it out to me....

or you could wire it the way i originally thought it worked and that is as a safety, so if you loose oil pressure it will kill the fuel pump ..

Not if it is standard (JE) Camira, (some) Rodeo etc wiring whereby if you have zero oil pressure, the fuel pump stays on.
The engine will eventually stop but probably as a result of seizure.
The exception is if the normal fuel pump activator has failed (its relay, charge circuit, air flap etc), so it's only the oil pressure keeping it on.

Apart from the above trivial issue (except for those caught with seized engines ), Is there anyone that still does not understand why - or accept that - oil pressure should NOT be used to control the fuel pump?

[Holden202T]

Not if it is standard (JE) Camira, (some) Rodeo etc wiring whereby if you have zero oil pressure, the fuel pump stays on.
The engine will eventually stop but probably as a result of seizure.
The exception is if the normal fuel pump activator has failed (its relay, charge circuit, air flap etc), so it's only the oil pressure keeping it on.

as far as i am aware, the oil pressure switch in commodore/camira etc are wired up as a backup for the fuel pump relay meaning if the relay fails the fuel pumps will still run to get you home!

my comment above about using it as a safety means re-wire it to cut the fuel pumps if you loose oil pressure ..... and yes i know youre theory on it and my comment still stands

[izu069]

Not sure which comment still stands, but as long as people are aware that if the oil runs dry in the Camira, the fuel pump will keep operating.
(I'm not arguing that it keeps the pump running when the relay fails - that is obvious. But it is IMO flawed - better to use air flap etc since it's EFI anyway. Then there is the question - how is fuel pump relay failure alarmed? Or does the car keep running without notification>?)

The oil pressure is - as you said - a backup. It is NOT a fuel pump cutout feature. (At least not in the circuits I have seen.)

Cool. It's just that so many insist on using oil pressure control of the fuel pump. (I did, but then I learnt.)

[delcowizzid]

yes the ecu keeps the pump going as long as its seeing rpm so if you loose oil pressure its gonna keep running unless you do holden202's mods to use it the other way

[djbrooksy]

one thing i would like to know is what kind of threshold dose the switch have
how low the oil pressure has to get before the switch cuts out
and how high before it turns on

[Holden202T]

well from what i've seen it seems to die off at about 5psi in my car .... i assume it would activate at the same point as pressure comes up.

its easy to tell if you have an oil pressure gauge on your car, start the engine then stop it straight away while the oil is still cold, it takes ages to bleed down and the fuel pump still runs for that time .....

when i get home from work (approx 50 mins driving) and shut it off the pump stops within a few seconds ... when its cold it can go for 5-10 seconds.

[delcowizzid]

mine went for 70 seconds the other day after a short start to test a tune took ages for pressure to bleed down and the pump to stop when warm mines like yours second or so

[Holden202T]

70 seconds ... you got bloody gear oil in the sump or something

[izu069]

It sounds like you are still missing the point....

Oil pressure is an engine preservation issue - it should kill the engine or alert the driver.

The fuel pump cutout is a safety issue - as soon as the engine stalls, the pump shall stop.

End of story.

[delcowizzid]

it does with the oil pressure light