I am new to this forum but any help would be greatly appreciated

Problem #1
Lost oil pressure completely so I put a new oil pump and pick up tube on my 1990 E150 Van with a 5.8L just about 1 month ago along with new valve cover gaskets. While I had the valve cover gaskets off I cleaned up some deposits around the rocker arms, and tried to clear drains. My engine has 172000 miles. When I started it back up one of the lifters wouldn't stop ticking for the longest time but eventually stopped and ran very good again with good oil pressure.

I thought everything was ok until yesterday I noticed the pressure drop to the bottom of my oil gauge everytime I stopped at a light and idled and when I give it gas I regained oil pressure. It has been about 1000 miles since the new pump was installed so I went home and changed the oil and filter last night. The filter seemed heavy when I took it off. I have always ran Havoline 10w40 in this van. Drove the van 25 miles this morning and the pressure stayed good. On the way home this afternoon it dropped again only when hot and idling. As long as I accelerate the pressure would come up well into the normal range.

Problem #2
Now to add to the list, I had to cut it off at a stop on my way home and it wouldn't start back. It tried at first but ran very rough then just turned over and over like there was no fire. It finally cranked about 45 minutes later and I drove it 20 miles on home. Turned it off after noticing the oil pessure drop. Tried to start it back and it wouldn't crank back again. Went in the house for a while and when I went back out and tried it it cranked fine and ran good. Oil pressure came up so I let it run until it reached full operating temperature and never lost oil pressure? So now when the engine gets hot and you cut it off it want start back . If you wait a while it will. Runs good as long as you don't cut it off.

Any suggestions or diagnosis. Thanks sincerely

 

Hate to say it but there's a possibilty your rod and main bearings are worn past servicable limits. An oil pump can only pressurize clearances up to certain limits and then the oil basically runs out so fast the pump can't keep the pressure up.

Hot's worse because the oil's thinner and flows thru the bearings more easily making the pump's job even harder. The reason the pressure picks up above idle is simply more rpm, but it should maintain some pressure at idle.

Thicker oil won't hurt a bit but it may only buy you some time. Try some 20/50 and see. I've run straight 50wt in racecar applications before but you need to warm it up real carefully. You can break oil pump drive parts trying to rev a cold motor on oil that thick.

Best of Luck on it.

 

I think I am going to do as pntrbl suggested and change to 20w50 oil and see what happens. When the oil pressure drops when idling, the motor doesn't make any ticking or pinging, yet.

 

How hot is the motor getting? Since you said it wouldn't start until it cooled off, that made me wonder if it's overheating.

 

Have you changed your oil pressure sending unit? Are you sure the pressure low? Might be a cheap $5 fix if your willing to gamble......fair odds....just might be!

 

Victorcharlie's advice is worth doing. For the past year or so my F250 351W 2v showed oil pressure about half scale on startup that fell to almost 0 after warming up. I figured I'd drive it till it quit then rebuild the motor. About a week ago I noticed a little oil leaking around the pressure sender when changing the oil filter. I put on a new sender and now the oil pressure shows full scale on cold startup and drops to the middle of the gauge after it warms up. Anyway it will only cost about $7-$8 and about 15 minutes check it out. That's a whole lot quicker and cheaper than starting out by checking bearings and pumps and it may solve that part of your problems.
RussA

 

I have a 1990 351 in a jeep and had similar hot run problems myself. Eventually I found 2 problems. One was a spark plug wire that had fell against the exhaust and partially burned through. the other was a cracked tfi module on the distributor. I noticed the latter purely by luck. I was adjusting my timing out of pure desperation and when I touched the tfi the motor died. Replaced both, runs great. As for the oil pressure, does the motor rattle or knock briefly during cold startup?

 

You might also check to see if the connection on the sending unit is clean, corrosion free and tight.......the more I think about it, a loose connection would cause the guage to run all over the place.