where's the one way valve in the oil supply?

[jcasey007]

The first start of the day or following a stop of over 5 hours, on startup I have started getting a delay in getting oil pressure of about 3 seconds, I know it doesn't sound long but it's not right!

Any other time the oil pressure shoots up instantly on cranking.(hot or cold)

Oil pressure generally is very good, it doesn't waver from a rock steady normal from idle through to 5000 rpm. Engine sounds sweet when running. She only uses 1/2 litre every 6000 miles (every oil change)

I've changed oil and filter (in previous cars the filter had a one way valve in it to stop oil draining from the galleries) this has made no difference. New filter was a FRAM

Any idea where the non return valve is located (if it has one) or any other causes.

cheers

Jim

 

[2000StreetRod]

Oil pressure switch

The reason your oil pressure doesn't vary with engine rpm is because your "gauge" is driven by an oil pressure switch instead of a variable oil pressure sending unit. I suspect anytime the oil pressure exceeds about 10 psi the switch is activated causing the "gauge" to read normal.

The only check valve I'm aware is in the external oil filter. It prevents the filter from draining when it is not mounted in a vertical port up position.

Sludge accumulates in the port to the oil pressure switch since there is no actual flow. The switch also becomes erratic with age. The replacement part is inexpensive but not easily replaced on the SOHC V6. I suggest that you replace your switch before suspecting a weak oil pump.

 

[jcasey007]

what's the point of having a guage when a light would do the same job better.
Looking at the wiring diagram there is a resistive shunt on the instrument cluster that sets the needle at the centre point when the oil switch is closed and grounded (i.e. when the pressure is greater than 10 PSI

Does anybody know if a functioning (pressure reading) guage was every fitted to an explorer, it feels like if I can get the correct variable sender, I would be able to remove the shunt from the instument and read actual pressure.

Any info anybody?

cheers

Jim

 

[2000StreetRod]

Indicator & shunt

There are threads on the forum about doing what you're considering. It could only be done in the early year models because on the later models the shunt is internal to the indicator and not accessible. I chose to add a sending unit and additional gauge. To me a real oil pressure gauge is essential for engine monitoring.

 

[budwich]

although the oil pressure "thing" is "switched based".... it still reads some form of pressure. However, it will be basically "0" if the pressure is less than a "preset" to activate the switch. Hence, your problem is probably a "sticky switch" resulting in "no response" during the initial start. As far as the "pressure jumping around" when you hit the "gas" (which some seem to want), that has nothing to do with whether you have a "pressure switch" or a "pressure sender" per se... its got to do with implementation of the "gauge system"... ford has chosen to send the output from the pressure switch to be "biased" with the "antislosh" module which is done to reduce the "wavering" of the gadge.

 

[briwayjones]

The check valve is in the oil filter. And from what I've always heard Fram filters don't have check valves. People always say stay away from Fram filters.

 

[jcasey007]

thanks all for info

I do believe that accurate instumentation is a must so that is why I feel cheated on the oil pressure gauge.

After all I have installed an air/fuel ratio gauge and thought I had a full suite of instruments so I recon I will have to modify it.

Wth respect to the start-up pressure it is not instrumentation as I can hear a difference in the sound of the engine when oil has pumped through. That's why I want to sort it.

So I'll get a Ford oil filter from the dealer tomorrow and loose the FRAM. I thought FRAM was a decent make....live and learn

cheers all

jim

 

[budwich]

"accuracy" is one thing, "reaction" is another. Many "instruments" don't measure "instantaneous results" for various reason (ie. no value to the operation, improper output, system response, etc). A stuck switch is a problem but whether your oil pressure "bounces around" may not be of much value... kind of like having your gas gage go to full (or empty) pulling away from the light... probably not of any value in the on going operation of your vehicle.