Low oil pressure on cold start

[dyerpunk]

Hi guys, got a little problem with my 99 4.0L. just started when the nights got cold. I am getting low oil pressure and noise in the top end of the motor on startup. After a few minutes of running the noise goes away completely and the pressure comes back up to normal. The noise isn't that bad otherwise I wouldn't run it. But it is noticeable. Engine has 208k miles on it. I'm suspecting I need a new oil pump but before I go pull the engine I wanted to see if you guys know something else it might be. Thanks in advance.

 

[Bgunner]

As it gets cold the oil thickens and is harder to pump to the top of the engine causing a "Dry" start condition.

Try this:

push the gas pedal to the floor and hold it there and crank the engine over. This shuts the fuel off and allows the oil pump to start to pump oil to the top of the engine. I give a 10 count then release the gas pedal I then turn the key again and crank till it starts. This should lessen your top end noise and prevent the dry start condition you are experiencing.

Now if the engine starts with the pedal to the floor shut it off and use zip ties on the pedal end of the throttle cable to tighten it back up, they stretch over time, so that the cable pulls the throttle plate wide open again. I needed to put 3 ties on my cable to get it back to a wide open throttle but yours may vary.

A thinner oil may help during the winter as well. I run 5w/30 in winter and 10w30 summer. No mater what oil you use it will be thicker when cold which makes it harder for the oil pump to pump it on start up.




Please let us know if you still have issues after doing fuel shut off trick.

 

[dyerpunk]

Thanks for the quick response, I'll try it first thing in the morning.

 

[DILLARD000]

@dyerpunk
Bgunner's correct. I do the GasPedalToFloor PreOiling cold start routine for ~10sec when engine has not run 12hrs+.
The OilPressureSwitch & fake OilPressureGage (only an Off\On indicator) Ford used for the V6~4.0L~SOHC engines
are notoriously slow to come up to pressure when starting cold.
Considering 200k+ Miles & the engine noise during warmup you've described,
likely need to replace your OilPressurized TimingTensioners, if you haven't done so recently.
I use 0w30.FullSyn Spring+Summer then 0w20.FullSyn Autumn+Winter, but at 9000ft in a colder climate than most.
More critical than the oil weight or filter used, is that you change your oil+filter often.
Hope this helps.

More info on replacing TimingTensioners & OilChanges at

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[dyerpunk]

@DILLARD000 my 4.0 is the ohv not the sohc so the guides are different but thanks for the reply.
@Bgunner I tried the cold start method you described, same problem as before so I'm almost positive it's my oil pump now, unless you guys have any other suggestions.

 

[RonD]

If problem is recent, like from the last time oil was changed and new filter was installed, try a new filter, premium brand

Oil filters have a "back flow" preventer flap, it stops oil from flowing back into the filter after engine is shut off, so oil stays in the main passages
Maybe last oil filter installed doesn't have this or its defective

 

[dyerpunk]

@RonD thanks for the suggestion, it did seem to get more noticeable after the last oil change. I'll swing by the store tomorrow and swap it out. I'll try anything to avoid pulling that engine at this point. I'm not worried about doing it right, I know how much work it is lol