So I was accelerating over a highway overpass and noticed my 2004 F250 6.0 stumble a bit. I recovered when I let off and I didn't think too much about it. I stopped for an errand a mile or two down the road and when I went to start it to leave, I had to crank it a bit to get it started.
I'm using Torque to monitor the vitals and everything looked OK so I headed home. At the stoplight, I noticed that the "Check gauge" light was lit and the oil pressure idiot needle was resting on the lower stop peg. It picked right up when I touched the gas, so I took it easy heading home.
I asked my favorite mechanic, Mr. GoogleWrench, and found a few different issues to check for so I picked the easiest to shotgun, the switch. Got that replaced today and cranked it to see if there was a change. It didn't start with the normal amount of cranking, and I didn't see the idiot needle move so I tried again and watched the HPOP reading from Torque. It started around 5 psi and climbed as I cranked. It slowly climbed to begine with but then jumped through the 50-500 range when it started up and idled. I drove around the block a few times and found that any RPM over 700 (it normally idles at 650) gives a good oil pressure idiot needle reading. The HPOP/ICP is around 550 at idle and when I ran it up for testing, all seemed fine if I could keep the ICP under about the 3000. Over 3000, it would bog down and the ICP would fall like a lawn dart. I recognized the bogging from the day before so the switch replacement didn't change anything. If I let off the gas, it would recover almost instantly and all was well until idle where the idiot needle would drop to 0 again.
This truck is a new to me truck with 90k on the odometer. Previous owner was a road construction company and according to the OASIS report, it must have idled a lot in it's life as they went less then a year between EGR valve replacements. I've had it for 3 weeks and it this is the first time the needle has fallen over and played dead. All I've done is clean the EGR valve and give it an oil change with Ford filters and Rotella T6 oil. And spritz the old oil over the top of the engine when I neglected to tighten the hold down bracket for the turbo oil supply line.
I found a list of causes for the low oil pressure and was wondering how to test each one.
Typical causes of low(er) base oil pressure indication:
1. Bad LPOP
2. Leaking pressure regulator on LPOP discharge (recirculates too much oil)
3. The HPOP check valve ball mentioned earlier
4. Bad oil pressure sensor
5. Open oil filter base drain valve - usually related to aftermarket filters as mentined earlier.
It would seem not to be #4 since I replaced the switch already and it's had no effect and #3 is a rather involved check and repair process. Is there a test/quick fix for the other items?
It's too new to me to tell for sure, but it seems that possibly there is an unhappy squeaking noise at the front of the engine. I've heard what kind of sounds like a bad pulley once or twice but never really narrowed down what was causing that prior to the oil pressure issue. Could that be the LPOP trying to free itself from the confines of it's housing or just my hyperactive imagination running wild?