When driving down road at speed, oil pressure sometimes drops to zero. When de-accelerating or idling, pressure comes back up to normal (40 psi). Just changed oil and filter - still doing it the same, if not worse. Could this be a false reading? Or could I be in trouble? Currently driving from Lubbock to Dallas.

 

if i were you, i would install a manual guage to see what's going on....you can get a guage and enough hose at any auto parts store.
remove the pipe plug from the top of the oil filter housing, that's where to install the hose for the guage
i think it's a 1/4 pipe plug..... if your oil pressure is right, the guage should read over 40 at a cold idle.
be sure to get a guage that reads 100 psi

 

okay, but can anyone tell me why my in-dash gauge would go to zero when I am on the throttle and go back to 40 when I'm not? What can cause this?

 

The oil sending units on these things are bad about going bad and doing just as you have described. The best thing to do is as was suggested earlier to verify the problem and if the mech. gauge shows normal pressure replace the oil sending unit.

 

Ok I made it home. 180+ miles showing ZERO oil pressure.
I guess we can assume that there is a malfunction between the gauge and the engine. I'm pretty sure that engine would have seized by now otherwise. Strange though. I had to slow down for turn about 1 mile from the house and the gauge came up as it had been at low RPMs but this time stayed after getting back on the throttle. I even tried flooring it and it stayed up. But when I got home I put it in park and rev'd the engine and it would peg the gauge to zero every time.
Oh well I'll look into it tomorrow.
I'm too tired for that right now!!
Thanks for the help.

 

I would agree that since you made it home with zero pressure reading that the oil pressure sending unit would be my first guess. I completely agree with johnh...get a manual oil pressure gauge on there to really see what's happening. The reason why is my last ram, with a 360 gas, did exactly what you initially described and it ended up being sludge clogging the pickup to the oil pump. The only difference was when mine dropped to zero, I couldn't get off the road fast enough and the engine siezed. I've never seen an engine sieze up so fast...it literally took all of 15 seconds and it was done. I discovered the sludge as soon as I took the valve covers off after I pulled the engine to rebuild. The sludge was so thick throughout the engine that it buried the head bolts, clogged the oil passages to the lifters and and the oil pump pickup(which was what finally did it in). I had just bought the truck used about 2 months before this happened...ran great btw, until it siezed. The only things that survived were the block, intake, 7 of 8 rods, and the crank which had to be reground because of damage. Everything else was destroyed. This is why I'm glad that it sounds like the oil sending unit is bad, but, get a shop gauge on there to make sure.

 

I would venture to say that it's the send unit. That's what fixed mine when my oil pressure started crazy.

 

Is this the sending unit for the my gauge?

 

Yea! Replace the oil pressure sending unit and be done with it. It's been posted to death already.

 

That's my plan.
That's what this forum's for.

 

Catp.Ron

You will need to get deep well socket if you don't already have one. I can't remember the size but 1 1/8" comes to mind but I would double check on that before you buy one.

 

BE NICE!!!

 

Thanks.

Had I been sitting in the comfort of my home looking at a laptop or a PC I would have searched through the forum. Instead I was driving in the rain literally in the middle of no where trying to use a cell phone to view and post this thread. You can't imagine how nerve racking it is to watch the oil pressure swing from 40psi to ZERO just from the push of the peddle knowing the whole time that there isn't a mechanic on duty anywhere remotely close to you!!

 

Yes I can, I've been there.

 

Not sure if that is just a stock picture, but I believe that your sending unit should have three pins, not two. I thought the gauges up through ~'02 actually read the pressure, then in '02 they switched to the two pin unit that was just a pressure switch.