I could use a little advice and possibly some help here. Some of you may remember my oil pressure problems from a few weeks ago. It would drop a little on the highway, only while I was in the throttle though. I thought it was an electrical problem, but it appears that it may not be.

This evening, I was running some errands and when I got home & parked the truck, I looked down and at idlle my oil pressure had dropped completely to zero. If I gave it some throttle, it would pick back up (at about 1400 RPM), but drop to zero again as soon as it went back to idle. I tried jiggling the sensor wire and connection, but nothing - thus possibly eliminating the electrical problem. I shut the truck off and immediately pulled the top plug on the HPOP resivoir to see if it had oil...it was full.

The truck ran fine, idled fine, and no strange noises. The oil is fresh as of last night, using Schaeffer's 9000. It's got all of 20 miles on the oil, so the oil can't be bad. I've got to drive across the state tomorrow, and it looks like I won't be taking the Powerstroke since I don't want to be stranded if the oil pump fails, if it is indeed the oil pump that is going out.

Any other ideas what it might be before I go ordering an oil pump and water pump? I figure I may as well replace the water pump if I'm in there, with 160K on the stock one.

If I do have to replace the oil pump, any suggestions as to where I should order the oil pump from...IH, NAPA, Orielly's, somewhere else? Any special or extra parts needed? I know I'll need a fan tool, and a special tool to pull the crank pulley, but anything else besides that?

This really sucks. I'm hoping it's not the oil pump, but I don't know what else it could be. I appreciate any advice.

 

well, to start off, make sure it's not the sensor acting up, showing you an inaccurate pressure. if you have a way, (and a fuel pressure gauge under the hood) cap off the line to the gauge, and put a gauge coming out of the rear oil cooler header plug, and see what pressure is at idle. if that wouldn't work, somehow find out the oil pressure at idle.

what makes me think that it's just an electrical gremlin is the fact that the truck will still run. with no oil pressure, the oil would not have the ability to climb up to the HPOP reservoir. in a few seconds, the HPOP (two pumps takes half the time) will eat up the reservoir capacity, and either pump air, or stall the motor. when the gauge drops to zero, let the truck idle for 15-20 seconds, or as long as you feel comfortable looking at that needle on the low end of the range. if it doesn't stall, chances are you have oil pressure.

oh, and if you need a oil pump, ITP diesel has Melling direct-replacement pumps for $69. http://www.itpdiesel.com/store.php?c...on=show_detail

 

Wow, Jeremy that's a bummer! I know it drives you crazy not being able to find the problem. Have you called Brian and asked him if he has any advice?? Heck, his shop isn't that far from you is it?? Good luck!

 

Thanks Kris. I just don't understand how it can be electrical. Unless you're thinking it's just the sensor/sending unit itself that has gone bad. Any way to test that sensor while it's still in the truck?

Edit: Jason, I tried to call Brian, but they're closed for the day. No answer there. I'll call on Monday to see what Brian says. He's not far, but it's still 4 hours away.

 

JT what is your idiot gauge doing if anything? Certainly if it went critical I would think the idiot light would light up too but probably too late. I don't think you are experiencing 0 PSI at idle. Like Kris I would think the gauge may be faulty, possibly electrical but also mecanincal. Maybe some crud or something impeding a reading, I don't know.

 

I believe these stock oil pressure guages are just an indicator of pressure and not an actual pressure guage. In other words it only has two readings - in the middle or zero, whereas a real guage would read all points in between or actual pressure, ie lower at idle and higher as the rpms go up. Mine never deviates from the middle until you shut down the engine. JT you said yours dropped when you were in the throttle, that's when it should go up.

 

In other words, that is what I was getting at. If he was showing 0 PSI at idle and there truly was no pressure, even the idiot setup would note this.

 

Tenn, the factory gauge is what I'm going off of. I don't (yet) have a real oil pressure gauge. True, it is basically just an idiot light. My light does come on as well. The oil pressure gauge has now dropped under two different instances. The first was when you would get into the throttle at highway speeds, while I was already cruising. It would never drop to zero there, just fall to the bottom of the range. Now, today it started the second thing, where it drops to zero at idle, and I do mean zero, not the bottom of the gauge...it looks like the truck is shut off. Two different ways of oil pressure dropping, both related to throttle position. One, when oil was in high demand, the other when the engine was not turning very many RPM. The highway problem would go away when oil demand went down, aka I let off the throttle, and the new problem would go away when I gave it enough RPM to seemingly bring oil pressure up. My stock gauge used to never leave the middle position either, until just recently.

Since the stock gauge is basically all or none, I'm thinking that oil pressure may be dropping below the point of it showing anything. There is some there, enough to make the truck run, but not enough to make the gauge come up.

It's the fact that the indicated pressure drop is related to engine RPM and oil demand that makes me think it's a mechanical problem. At this point, I'm thinking I may just replace the oil pump and the sending unit both. It certianly won't hurt anything to replace them both, and I'll have peace of mind that the oil pump is in fact in good working order. The oil pump is only $70, and I've got the time to replace it next weekend. I need my truck to haul some cars the following weekend, so I'm unfortunately not in a position to be able to take a chance.

 

do the sending unit first then check it. If all is well you found the problem and then you can change the pump if that's what you want to do.

 

I'll bet money that it's the oil pressure sending unit. the exact same thing happend in my old f-150 . I went to buy a new oil pump and ran into a friend that made me feel real stupid when he told me it was the sending unit. I bought the unit and it was all better. I would try that first. I know it's human nature to think the worst but that aint always the case

 

If it is the sending unit, and I haven't ruled it out yet, I just don't understand why it wouldn't do it all the time? I would think that it would behave the same way whether hot or cold. Another thing that I thought about is it only does it when it's cold. It takes some driving for the highway thing to happen, and the oil pressure was fine today until the truck got warmed up. I'm just trying to completely rule out the oil pump.

My time crunch is another problem. I'm leaving tomorrow, so I'll be out of town this weekend and can't work on it. Work during the week leaves little time to work on it as well. So, that basically leaves next weekend. If it is not the sensor, I don't have time to wait on an oil pump to get ordered. That time constraint is another thing I'm considering. I'll probably go ahead and order the oil pump, change the sensor out on Monday since it's easy, and if that does turn out to be the problem, send the oil pump back. I just have to be prepared in case it is the oil pump to change it next weekend.

 

as the oil heats up it thins thus the sending unit has a harder time reading the pressure value. try it first it's a cheap alternate to a oil pump and if thats not it you're not out of much and if it is the problem you'll be pleasently releaved and have more money for other mods

 

Whoopsie. My bad. I remember some time back looking through your gallery and then making the comment that I was surprised that you didn't have a gauge for your differential. I thought you had an aftermarket OP gauge and was referring to those readings.

I think you have a good plan based on your circumstances.

 

the 'truck warm sensor bad' points even more to the sending unit. It is an electrical part and when it warms up something inside opens up giving you a false reading.

 

I honestly hope it's just the sensor. That would be much easier and cheaper. I wish I had the time to try it first. But, given my time crunch, I've pretty much made up my mind I'm going to order the oil pump just in case. I have to have my truck in a couple of weekends, and I can't chance it. I should know by the middle of the week if it's just the sensor unit or not, after I get a chance to install it on Monday and drive it some.