No oil Pressure with first start up

I have a 1993 Grand Caravan 3.3L V6. When I leave the van set for a couple a of days (or even overnight) and then start it, I have no oil pressure for a minute or so. After the engine has been running for about a minute or so the oil pressure finally comes up but not to normal. Once the engine has warmed up the oil pressure returns to what could be considered “normal”. After the cold start, no oil pressure problem, the engine and the oil pressure is fine for the rest of the day. Let it even set overnight though and I have a repeat no oil pressure with start up. I am thinking that there is a problem with the pick up tube not sealing properly and allowing the oil to bleed down while the engine is off for an extended period of time. So, in effect, I have to basically prime the oil pump at each start up. I haven’t noticed any leaks of engine oil anywhere, so I am thinking that this is an internal problem. Is there a check valve or O-Ring associalted with the pick up tube or oil pump that may cause this problem? Is it a fairly easy problem to correct? On this engine the oil pump is located in the front of the engine block behind the timing chain cover. (As best as I could determine from the Haynes Manual).

Are you observing the actual oil pressure on a mechanical gauge or the gauge on the dash? The oil pressure gauge sending units fail often.

You might consider a balky oil pressure sending unit as the cause (cheap) or an engine sludging issue. (not so cheap)

Sending units are cheap and easy to change so it might be worth a shot to swap it out and see what happens. Senders are normally 5-20 bucks on most vehicles.

There is no check valve in the oil pressure system. But, for many cars, there is a back flow valve in the oil filter to keep the oil from running out as it sits overnight. It could take several seconds for an oil pump to refill a side-mounted oil filter that is empty. I notice it all the time during oil changes. I use Purolater filters because I know they have this valve for my Toyota side-mounted filter.

Other oil pressure performance issues may be due to age and mileage. The truck is 22 years old. A worn pump or worn bearing journals could be contributing as well.

I agree with BustedKnuckles. I had a similar problem with my old vehicle–I would hear some bearing rattle at the first cold start of the day. Switching oil filter brands solved the problem. Try a Wix or genuine Mopar filter for your van and see if improves the situation.

Another possibility if you haven’t actually checked the oil pressure with a mechanical gauge is that the sensor is gummed up and sticks for a bit on the first cold start before it begins measuring properly.

Thought all oil pumps had relief valve for cold starts? Cold oil is thick, high viscosity. Oil pump goes into bypass mode at start to allow oil to bled off and prevent filter from rupturing. Cadillacs are known for bypass sticking and losing oil pressure.

Even an empty oil filter (faulty anti-drain-back-valve?) shouldn’t take a full minute to build pressure.
The gauge in the dash could be faulty, as well as the sender.

I thought that the sending unit was bad so i replaced it. I did check the pressure with a mechanical Guage before and it seemed like there was no problem then. While there is no pressure the engine is making a rumbling sound. As soon as the pressure comes up the noise goes away. I use wix filters on everything. It does need an oil change now that’s why i was wondering if now would be a good time to pull the pan and check the pick up tube.

A 22 year old vehicle with ?? mileage…What weight oil do you use?

The engine has around 140,000 miles on it. I use castrol edge 10w30 oil. Sorry, I forgot to mention that.

I had noisey lifters on my 2002 Chrysler minivan with the 3.3 engine using either Mopar or Fram filters. I read a tip on a Chrysler minivan forum to use a Motorcraft FL-1 filter and my lifter noise (due to low oil pressure) was gone.

Pulling the pan for a look-see would at least eliminate a few possibilities.

I know my Vics all prefer a Motorcraft Oil Filter… Other brands can produce a noisy cold start on the 4.7L OHC V8…But zero oil pressure for a minute, that’s very worrisome and probably not filter related… It’s time to drop the pan and take a look at the pump, tube and screen…

I am going to pull the pan here sometime in the next week or so. I live in Michigan and haven’t got a garage to do this in, so I have to wait for a break from the cold weather. Unfortunately, like I mentioned earlier, the oil pump is not located in the bottom of the engine, so checking that will be more difficult. I at least can change out the pick up tube to see if that corrects the problem. It’s a cheap part so I won’t be out a lot of money if it doesn’t solve the problem. I’ll try to keep everyone updated on my progress.